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Determining the effect of an invasive species on enzootic pathogen dynamics is critical for understanding both human epidemics and wildlife epizootics. Theoretical models suggest that when a naive species enters an established host–parasite system, the new host may either reduce (‘dilute’) or increase (‘spillback’) pathogen transmission to native hosts. There are few empirical data to evaluate these possibilities, especially for animal pathogens. Buggy Creek virus (BCRV) is an arthropod-borne alphavirus that is enzootically transmitted by the swallow bug ( Oeciacus vicarius ) to colonially nesting cliff swallows ( Petrochelidon pyrrhonota ). In western Nebraska, introduced house sparrows ( Passer domesticus ) invaded cliff swallow colonies approximately 40 years ago and were exposed to BCRV. We evaluated how the addition of house sparrows to this host–parasite system affected the prevalence and amplification of a bird-associated BCRV lineage. The infection prevalence in house sparrows was eight times that of cliff swallows. Nestling house sparrows in mixed-species colonies were significantly less likely to be infected than sparrows in single-species colonies. Infected house sparrows circulated BCRV at higher viraemia titres than cliff swallows. BCRV detected in bug vectors at a site was positively associated with virus prevalence in house sparrows but not with virus prevalence in cliff swallows. The addition of a highly susceptible invasive host species has led to perennial BCRV epizootics at cliff swallow colony sites. The native cliff swallow host confers a dilution advantage to invasive sparrow hosts in mixed colonies, while at the same sites house sparrows may increase the likelihood that swallows become infected.

The cliff swallow (Petrochelidon pyrrhonota) could play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. Cliff swallows nest within colonies and their nests are occupied year-round by swallow bugs (Oeciacus vicarius), hematophagus ectoparasites that feed primarily on cliff swallows. These parasites are likely exposed to WNV while feeding on infectious blood of nesting cliff swallow adults and nestlings and thus, if competent vectors, could contribute to seasonal elevations in WNV transmission. In addition, swallow bugs remain within nests year-round and therefore could provide a potential overwintering mechanism for WNV if persistently infected. To test the hypotheses that swallow bugs are competent vectors and become persistently infected with WNV, we experimentally inoculated cliff swallow nestlings, allowed swallow bugs to feed on these birds during the acute phase of infection, and then exposed naive cliff swallow nestlings to the same swallow bugs. In addition, a subset of swallow bugs that fed on infectious swallow nestlings was maintained through a simulated overwintering period. Although swallow bugs ingested infectious blood (up to 10(6.8) plaque-forming units of WNV/mL serum) and subsequently blood-fed on naive swallows, no WNV transmission was detected, and all bugs tested WNV negative after the simulated overwintering period. Although many ecologic scenarios exist beyond the present study, our results suggest that swallow bugs may be unlikely to serve as competent biological vectors for WNV during active transmission periods or to reinitiate seasonal transmission.

The offspring of caring parents may evolve specialized traits uniquely adaptive during their dependence on parental care. For example, the mouths of passerine nestlings are often bordered by enlarged and colorful rictal flanges expressed only during the nestling period. Although these traits are commonly hypothesized to act as visual signals during begging, non-communication functions for the specialized mouth have been proposed as well. To test the hypothesis that nestling flange colors have evolved largely or exclusively as visual signals, I compared the reflectance of flange tissue that would be visible to parents during begging to that of flange tissue not exposed during begging in nestling house sparrows Passer domesticus and cliff swallows Petrochelidon pyrrhonota. Specifically, I tested the prediction that both condition-dependent color parameters and those associated with visual conspicuousness would be expressed more intensely in tissue displayed during begging. Consistent with this prediction, flange tissue exposed during begging was brighter (reflected more total light), more UV-rich, and had more intense carotenoid-based coloration than hidden tissue. These differences do not exclude a non-signaling function for flanges, but are consistent with the hypothesis that flange colors have evolved as visual signals.

We quantified the impact of nesting and roosting House Sparrows (Passer domesticus) on nesting success of Cliff Swallows (Petrochelidon pyrrhonota) in colonies in western Arkansas in 2007 and 2008. Two sections of a large swallow colony under a bridge with House Sparrows were compared in 2007 to two sections with little House Sparrow usage. Nesting success of Cliff Swallows (percent of nests yielding at least 1 chick) was 61% in sections with low House Sparrow activity, significantly higher than the 30% in sections with high House Sparrow activity. House Sparrows defended a broad zone surrounding their nests from Cliff Swallow nesting attempts. We compared the proportion of nests used, clutch sizes, and brood sizes of Cliff Swallows in two colonies in 2008, one with and one without House Sparrow activity. In the colony without House Sparrow activity, 48% of old and new nests were used by swallows versus only 8% in the colony with House Sparrows. Swallow clutch sizes were similar in the two coloni...

Alphaviruses (Togaviridae) infect wild birds, but clinical illness and death attributable to virus in naturally infected birds is rarely reported, particularly for small passerine species or nestlings. Buggy Creek virus is a unique alphavirus in the Western equine encephalomyelitis virus (WEEV) complex that is vectored by the cimicid swallow bug (Oeciacus vicarius), an ectoparasite of the colonially nesting Cliff Swallow (Petrochelidon pyrrhonota) and the introduced House Sparrow (Passer domesticus). While sampling birds for Buggy Creek virus (BCRV) during the summers of 2007 and 2008, we discovered large numbers of clinically ill or dead House Sparrow nestlings. Ill nestlings exhibited ataxia, torticollis, paresis, and lethargy. Histologic examination revealed that encephalitis was the most common finding, followed by myositis, myocarditis, and hepatic changes, but pathology was highly variable. We isolated BCRV from brain tissue in most of the ill or dead nestlings, and from blood, liver, kidney, spleen, lung, feather pulp, and skin in some birds. To our knowledge, this is the first report of clinical illness, gross pathology, and histopathology for a WEEV-complex alphavirus in a field-collected passerine species.

Most arthropod-borne viruses (arboviruses) show distinct serological subtypes or evolutionary lineages, with the evolution of different strains often assumed to reflect differences in ecological selection pressures. Buggy Creek virus (BCRV) is an unusual RNA virus (Togaviridae, Alphavirus) that is associated primarily with a cimicid swallow bug (Oeciacus vicarius) as its vector and the Cliff Swallow (Petrochelidon pyrrhonota) and the introduced House Sparrow (Passer domesticus) as its amplifying hosts. There are two sympatric lineages of BCRV (lineages A and B) that differ from each other by >6% at the nucleotide level. Analysis of 385 BCRV isolates all collected from bug vectors at a study site in southwestern Nebraska, USA, showed that the lineages differed in their peak times of seasonal occurrence within a summer. Lineage A was more likely to be found at recently established colonies, at those in culverts (rather than on highway bridges), and at those with invasive House Sparrows, and in bugs on the outsides of nests. Genetic diversity of lineage A increased with bird colony size and at sites with House Sparrows, while that of lineage B decreased with colony size and was unaffected by House Sparrows. Lineage A was more cytopathic on mammalian cells than was lineage B. These two lineages have apparently diverged in their transmission dynamics, with lineage A possibly more dependent on birds and lineage B perhaps more a bug virus. The long-standing association between Cliff Swallows and BCRV may have selected for immunological resistance to the virus by swallows and thus promoted the evolution of the more bug-adapted lineage B. In contrast, the recent arrival of the introduced House Sparrow and its high competence as a BCRV amplifying host may be favoring the more bird-dependent lineage A.

Researchers commonly collect blood samples from wild birds, and most workers assume that blood sampling has no adverse effect on the birds' survival. Few studies, however, have done controlled comparisons among bled and non-bled individuals and estimated survival using modern statistical methodology. We used a data set on Cliff Swallows (Petrochelidon pyrrhonota) that included 2,945 bled and 7,822 non-bled birds captured at the same times and sites in southwestern Nebraska from 1986 to 2006 to estimate annual survival and recapture probabilities of each group. Blood was collected with brachial venipuncture in amounts varying from 0.3% to 1.2% of the birds' body mass. Apparent survival of bled birds was lower than that of non-bled birds: bled birds experienced a 21–33% reduction in average survivorship, depending on amount of blood taken and whether the individuals were resident at a fumigated (parasite-free) or non-fumigated colony at the time of sampling. The percent reduction in annual surviva...

Multiple isolates of an alphaviruses within the western equine encephalomyelitis-serocomplex that were related closely to Ft. Morgan and its variant Buggy Creek virus were made from swallow bugs, Oeciacus vicarius Horvath (Hemiptera: Cimicidae), collected from cliff swallow (Petrochelidon pyrrhonota) nests at the Stone Lakes National Wildlife Refuge, Sacramento County, CA, during the summers of 2005 and 2006. This virus (hereafter Stone Lakes virus, family Togaviridae, genus Alphavirus, STLV) was the first record of this viral group west of the Continental Divide. STLV replicated well in Vero and other vertebrate cell cultures but failed to replicate in C6/36 cells or infect Culex tarsalis Coquillett mosquitoes. STLV failed to produce elevated viremias in adult chickens or house sparrows and was weakly immunogenic. In addition, STLV was not isolated from cliff swallow nestlings nor was antibody detected in adults collected at mist nets. We suggest that STL and related swallow bug viruses may be primarily infections of cimicids that are maintained and amplified either by vertical or nonviremic transmission and that cliff swallows may primarily be important as a bloodmeal source for the bugs rather than as an amplification host for the viruses.

Alphaviruses (Togaviridae) rarely have been found to be vertically transmitted from female arthropods to their progeny. We report two isolations of Buggy Creek virus (BCRV), an ecologically unusual alphavirus related to western equine encephalomyelitis virus, from field-collected eggs of cimicid swallow bugs (Oeciacus vicarius Horvath), the principal vector for BCRV. Ten percent of egg pools were positive for BCRV, and we estimated minimum infection rates to be 1.03 infected eggs per 1,000 tested. The results show potential vertical transmission of BCRV, represent one of the few isolations of any alphavirus from eggs or larvae of insects in the field, and are the first report of any virus in the eggs of cimicid bedbugs. The specialized ecological niche of BCRV in swallow bugs and at cliff swallow (Petrochelidon pyrrhonota Vieillot) nesting sites may promote vertical transmission of this virus.

Arboviruses have seldom been found overwintering in adult vectors at northern latitudes in North America. Buggy Creek virus (BCRV; Togaviridae, Alphavirus) is an ecologically unusual arbovirus vectored principally by the cimicid swallow bug (Oeciacus vicarius Horvath). The ectoparasitic bugs reside year-round in the mud nests of their host, the cliff swallow (Petrochelidon pyrrhonota Vieillot). We report successful overwintering of infectious BCRV in bugs at a field site in western North Dakota, where mid-winter temperatures routinely reach -11 to -15°C. Approximately 21% of bug pools were positive for virus in early spring just before the cliff swallows' return to their nesting colonies; this proportion did not differ significantly from that in summer at active cliff swallow nesting colonies in the same study area. Fewer of the isolates in early spring were cytopathic on Vero cells, and those that were infectious showed less plaque formation than did summer samples. The results show that infecti...

We sampled 100 Cliff Swallows (Petrochelidon pyrrhonota), just after arrival in Nebraska breeding areas, to ascertain if migrating birds re-introduce Buggy Creek virus (BCRV; Togaviridae) to north-temperate localities in spring. Most birds sampled were previously banded and were known to have used parasite-free nesting colonies in past summers and/or were seronegative to BCRV; thus, they were unlikely to have been previously exposed to the virus in their breeding areas. None of the birds had evidence of viral RNA in blood, as measured by RT-PCR. These results are consistent with other studies that have shown little evidence that migratory birds re-introduce arboviruses to temperate localities between years.

One probable cost of dispersing to a new breeding habitat is unfamiliarity with local conditions such as the whereabouts of food or the habits of local predators, and consequently immigrants may have lower probabilities of survival than more experienced residents. Within a breeding season, estimated daily survival probabilities of cliff swallows (Petrochelidon pyrrhonota) at colonies in southwestern Nebraska were highest for birds that had always nested at the same site, followed by those for birds that had nested there in some (but not all) past years. Daily survival probabilities were lowest for birds that were naïve immigrants to a colony site and for yearling birds that were nesting for the first time. Birds with past experience at a colony site had monthly survival 8.6% greater than that of naïve immigrants. All colonies where experienced residents did better than immigrants were smaller than 750 nests in size, and in colonies greater than 750 nests, naïve immigrants paid no survival costs relative to experienced residents. Removal of nest ectoparasites by fumigation resulted in higher survival probabilities for all birds, on average, and diminished the differences between immigrants and past residents, probably by improving bird condition to the extent that effects of past experience were relatively less important and harder to detect. The greater survival of experienced residents could not be explained by condition or territory quality, suggesting that familiarity with a local area confers survival advantages during the breeding season for cliff swallows. Colonial nesting may help to moderate the cost of unfamiliarity with an area, likely through social transfer of information about food sources and enhanced vigilance in large groups.

Cliff swallows (Petrochelidon pyrrhonota) and cave swallows (P. fulva) were sampled during the breeding season at several locations in the Rio Grande, Texas, to evaluate the potential effects of environmental contaminants on P450 aromatase activity in brain and gonads and DNA damage in blood cells. The tritiated water-release aromatase assay was used to measure aromatase activity and flow cytometry was used to measure DNA damage in nucleated blood cells. There were no significant differences in brain and gonadal aromatase activities or in estimates of DNA damage (HPCV values) among cave swallow colonies from the Lower Rio Grande Valley (LRGV) and Somerville. However, both brain and gonadal aromatase activities were significantly higher (P < 0.05) in male cliff swallows from Laredo than in those from Somerville. Also, DNA damage estimates were significantly higher (P < 0.05) in cliff swallows (males and females combined) from Laredo than in those from Somerville. Contaminants of current high use in the LRGV, such as atrazine, and some of the highly persistent organochlorines, such as toxaphene and DDE, could be potentially associated with modulation of aromatase activity in avian tissues. Previous studies have indicated possible DNA damage in cliff swallows. We did not observe any differences in aromatase activity or DNA damage in cave swallows that could be associated with contaminant exposure. Also, the differences in aromatase activity and DNA damage between male cliff swallows from Laredo and Somerville could not be explained by contaminants measured at each site in previous studies. Our study provides baseline information on brain and gonadal aromatase activity in swallows that could be useful in future studies.

Summary An account is given of the geography and ecology of the Mollendo district, Southwest Peru, followed by a systematic list of the species recorded there over a period of 16 years' residence. The following species are recorded, apparently for the first time, from the south coast of Peru:Pachyptila belcheri, P. desolata, Florida caerulea, Butorides striatus, Bubulcus ibis, Plegadis chihi, Himantopus himantopus, Micropalama himantopus, Chaetura pelagica, Petrochelidon pyrrhonota, Riparia riparia and Pheucticus chrysopeplus.

We performed experimental inoculations of house sparrows (Passer domesticus) with Buggy Creek virus (BCRV), a poorly known alphavirus (Togaviridae) vectored primarily by the swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius) that is an ectoparasite of the cliff swallow (Petrochelidon pyrrhonota) and house sparrow. Viremias were detected by plaque assay in two of six birds on days 1-3 postinoculation; viremia was highest on day 2. Viral RNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in blood of six of 12 birds ranging from day 1 to day 15 postinoculation. Infectious BCRV was detected in nasopharyngeal swab samples from two birds by plaque assay. Three control birds that were housed with viremic individuals showed evidence of BCRV RNA in blood (by RT-PCR), suggesting possible bird-to-bird transmission of this virus. Viral RNA also was detected by RT-PCR in brain and skin tissue of six birds on necropsy at the end of the 16-day experiment. Introduced house sparrows are apparently a competent amplifying host for BCRV, and their presence year-round at cliff swallow colonies may facilitate persistence of the virus locally, especially when cliff swallows abandon a site temporarily. The findings that BCRV can be shed orally, that it persists in bird skin, and that control birds could apparently be infected by conspecifics suggest that this virus may be transmitted from bird to bird in the crowded conditions of many cliff swallow colonies.

Determining the degree of genetic variability and spatial structure of arthropod-borne viruses (arboviruses) may help in identifying where strains that potentially cause epidemics or epizootics occur. Genetic diversity in arboviruses is assumed to reflect relative mobility of their vertebrate hosts (and invertebrate vectors), with highly mobile hosts such as birds leading to genetic similarity of viruses over large areas. There are no empirical studies that have directly related host or vector movement to virus genetic diversity and spatial structure. Using the entire E2 glycoprotein-coding region of 377 Buggy Creek virus isolates taken from cimicid swallow bugs (Oeciacus vicarius), the principal invertebrate vector for this virus, we show that genetic diversity between sampling sites could be predicted by the extent of movement by transient cliff swallows (Petrochelidon pyrrhonota) between nesting colonies where the virus and vectors occur. Pairwise FST values between colony sites declined significantly with increasing likelihood of a swallow moving between those sites per 2-day interval during the summer nesting season. Sites with more bird movement between them had virus more similar genetically than did pairs of sites with limited or no bird movement. For one virus lineage, Buggy Creek virus showed greater haplotype and nucleotide diversity at sites that had high probabilities of birds moving into or through them during the summer; these sites likely accumulated haplotypes by virtue of frequent virus

To evaluate mercury (Hg) and other element exposure in cliff swallows (Petrochelidon pyrrhonota), eggs were collected from 16 sites within the mining-impacted Cache Creek watershed, Colusa, Lake, and Yolo counties, California, USA, in 1997-1998. Nestlings were collected from seven sites in 1998. Geometric mean total Hg (THg) concentrations ranged from 0.013 to 0.208 microg/g wet weight (ww) in cliff swallow eggs and from 0.047 to 0.347 microg/g ww in nestlings. Mercury detected in eggs generally followed the spatial distribution of Hg in the watershed based on proximity to both anthropogenic and natural sources. Mean Hg concentrations in samples of eggs and nestlings collected from sites near Hg sources were up to five and seven times higher, respectively, than in samples from reference sites within the watershed. Concentrations of other detected elements, including aluminum, beryllium, boron, calcium, manganese, strontium, and vanadium, were more frequently elevated at sites near Hg sources. Overall, Hg concentrations in eggs from Cache Creek were lower than those reported in eggs of tree swallows (Tachycineta bicolor) from highly contaminated locations in North America. Total Hg concentrations were lower in all Cache Creek egg samples than adverse effects levels established for other species. Total Hg concentrations in bullfrogs (Rana catesbeiana) and foothill yellow-legged frogs (Rana boylii) collected from 10 of the study sites were both positively correlated with THg concentrations in cliff swallow eggs. Our data suggest that cliff swallows are reliable bioindicators of environmental Hg.

Predicting the spatial foci of zoonotic diseases is a major challenge for epidemiologists and disease ecologists. Migratory birds are often thought to be responsible for introducing some aviozoonotic pathogens such as West Nile and avian influenza viruses to a local area, but most information on how bird movement correlates with virus prevalence is anecdotal or indirect. We report that the prevalence of Buggy Creek virus (BCRV) infection in cimicid swallow bugs (Oeciacus vicarius), the principal invertebrate vector for this virus, was directly associated with the likelihood of movement by cliff swallows (Petrochelidon pyrrhonota), an amplifying host for the virus, between nesting colonies. The prevalence of BCRV in bugs was also directly correlated with the number of swallows immigrating into a site. Birds that move into a site are often transient individuals that may have more often encountered virus elsewhere. These results indicate that the magnitude and direction of daily bird movement in a local area can accurately predict transmission foci for this virus and provide rare quantitative evidence that birds can play a critical role in the dispersal of certain vector-borne viruses.

When blood-feeding parasites increase seasonally, their deleterious effects may prevent some host species, especially those living in large groups where parasites are numerous, from reproducing later in the summer. Yet the role of parasites in regulating the length of a host's breeding season—and thus the host's opportunity for multiple brooding—has not been systematically investigated. The highly colonial cliff swallow ( Petrochelidon pyrrhonota ), a temperate-latitude migratory songbird in the western Great Plains, USA, typically has a relatively short (eight to nine week) breeding season, with birds rarely nesting late in the summer. Colonies at which ectoparasitic swallow bugs ( Oeciacus vicarius ) were experimentally removed by fumigation were over 45 times more likely to have birds undertake a second round of nesting than were colonies exposed to parasites. Late nesting approximately doubled the length of the breeding season, with some birds raising two broods. Over a 27 year period the percentage of birds engaging in late nesting each year increased at a colony site where parasites were removed annually. This trend could not be explained by changes in group size, climate or nesting phenology during the study. The results suggest that ectoparasitism shortens the cliff swallow's breeding season and probably prevents many individuals from multiple brooding. When this constraint is removed, selection may rapidly favour late nesting.

We present the first detailed phylogenetic analysis of Buggy Creek virus (BCRV), a poorly known alphavirus with transmission cycles involving a cimicid swallow bug ( Oeciacus vicarius ) vector and cliff swallows ( Petrochelidon pyrrhonota ) and house sparrows ( Passer domesticus ) as the principal avian hosts. Nucleotide sequences of a 2,075-bp viral envelope glycoprotein-coding region, covering the entire PE2 gene, were determined for 33 BCRV isolates taken from swallow bugs at cliff swallow colonies in Nebraska and Colorado in the summer of 2001 and were compared with the corresponding region of BCRV isolates collected from Oklahoma in the 1980s. We also analyzed isolates of the closely related Fort Morgan virus (FMV) collected from Colorado in the 1970s. Phylogenetic analysis indicated that BCRV falls into the western equine encephalomyelitis complex of alphaviruses, in agreement with antigenic results and a previous alphavirus phylogeny based on the E1 coding region. We found four distinct BCRV/FMV clades, one each unique to Nebraska, Colorado, and Oklahoma and one containing isolates from both Nebraska and Colorado. BCRV isolates within the two clades from Nebraska showed 5.7 to 6.2% nucleotide divergence and 0.7 to 1.9% amino acid divergence, and within these clades, we found multiple subclades. Nebraska subclades tended to be confined to one or a few cliff swallow colonies that were close to each other in space, although in some cases, near-identical isolates were detected at sites up to 123 km apart. Viral gene flow occurs when cliff swallows move (bugs) between colony sites, and the genetic structure of BCRV may reflect the limited dispersal abilities of its insect vector.

The cave swallow (Petrochelidon fulva) was first discovered breeding in caves and sinkholes in Texas in 1915. Within the last 50 years, it has colonized new breeding sites in western and southern Texas, and colonization has been attributed to the presence of highway culverts and bridges. We examined published observations and breeding bird survey (BBS) data, and surveyed selected culverts in western and southeastern Texas to determine the rate and extent of colonization by cave swallows. From 1957 to 1999, the breeding range of the cave swallow increased by approximately 898%, with an average annual rate of increase of 6% per year. Based on BBS data, cave swallow populations are increasing 10.8% per year, and our survey indicated that cave swallows occupied >90% of the culverts surveyed in western Texas. Range expansion is likely to continue, and additional data are needed to determine how an expanding cave swallow population might affect local barn swallow populations.

Animals often cope with adverse events by releasing glucocorticoid hormones, which in turn promote increased energy assimilation. In captive animals, crowding also leads to increased glucocorticoid activity, probably because of increased levels of social competition. We investigated how group size and ectoparasite infestations affected endogenous levels of the glucocorticoid hormone, corticosterone, in colonial cliff swallows, Petrochelidon pyrrhonota, in southwestern Nebraska, U.S.A. Parasites were removed from some colonies by fumigating nests. Baseline levels of corticosterone in breeding adults varied significantly with whether parasites were present, colony size (measured by total number of active nests at a site) and nesting stage. Across all analyses, birds from fumigated colonies averaged significantly lower baseline levels of corticosterone. These levels in adults increased with colony size at nonfumigated sites, especially during the period when nestlings were being fed, but no relation or the opposite one was found for birds in fumigated colonies. Baseline corticosterone levels were unrelated to sex, age, body weight or testosterone levels in adults. Corticosterone concentrations tended to increase during a bad-weather event when food was scarce. Patterns in nestling and recently fledged juveniles were consistent with those in adults. The increased baseline levels of corticosterone in birds of larger colonies appear related to the larger number of parasites there. Higher levels of corticosterone probably facilitate increased allocation of time and energy to foraging and greater energy assimilation during challenging events such as bad weather, parasitism by blood-feeding bugs in large colonies and the period when young are becoming independent of their parents.

One hypothesis to explain the extensive variation in colony size seen in most taxa is that individuals sort themselves among groups based on phenotypic characteristics that correlate with their performance in groups of different sizes. We investigated how baseline levels of the steroid hormones, corticosterone and testosterone, were associated with choice of colony size and the likelihood of moving to a different site in later years in colonially nesting Cliff Swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, USA, in 2000-2004. We sampled hormone levels of birds caught at colonies and, using mark-recapture, monitored their movement and choice of colony size through subsequent years in the study area. Maximum likelihood estimation and multistate model fitting (with program MARK) revealed that birds with baseline corticosterone levels above the average for the colony and time of sampling were less likely to choose a colony of the same size or larger in a later year than were birds with corticosterone levels below the average. This result held for Cliff Swallows in both fumigated (parasite-free) sites and colonies naturally infested with ectoparasites. Relative baseline corticosterone level was unrelated to the likelihood of movement between different colony sites, and corticosterone level measured after birds were held for 60 minutes was unrelated to either colony-size choice or the probability of movement. Males whose testosterone levels were above the average for the colony and time of sampling were more likely to choose a colony of the same size or larger in a later year than were ones whose testosterone levels were below the average, but the opposite pattern was found for females. The results indicate that steroid hormone level is a predictor of whether a Cliff Swallow will settle in a relatively small or large colony, and support the hypothesis that variation in colony size reflects, in part, a distribution of birds

The phylogeny of swallows was reconstructed by comparing segments of three genes, nuclear β-fibrinogen intron 7 (βfib7), mitochondrial cytochrome b (cytb), and mitochondrial ND2, in a variety of combinations using maximum likelihood and Bayesian methods. βfib7 was sequenced for 47 species, cytb for 74 species, and ND2 for 61 species to yield comparisons among 75 of the 84 currently recognized swallow species. The family Hirundinidae was confirmed to consist of two clades, Pseudochelidoninae (river martins) and Hirundininae (typical swallows). The Hirundininae is further divided into mud nesters ( Hirundo sensu lato ), core martins ( Phedina , Riparia , and New World endemic genera), and basal relicts ( Psalidoprocne , Cheramoeca , and Pseudhirundo ). We did not resolve the hierarchy among these three hirundinine groups, but discovered many relationships within them. Mud-nesting genera have the following relationships: ( Hirundo sensu stricto , Ptyonoprogne ), ( Delichon , ( Petrochelidon , Cecropis )). Core martins have the following topology: ( Phedina , Riparia cincta ), ( Riparia sensu stricto , Tachycineta , (( Stelgidopteryx , Progne ), (Neotropical endemic genera))). Interspecific relationships among the Neotropical endemics were resolved completely; Atticora and Notiochelidon are paraphyletic, and all Neotropical endemics probably should be lumped into one or two genera. The final group of hirundinines, the basal relicts, consists of a sister pair, the Australian Cheramoeca and African Pseudhirundo . The African saw-wings ( Psalidoprocne ) are their likely sister group.

The hormone corticosterone is an important part of animals' response to environmental stress, modulating short-term adaptive changes in behavior and physiology. The hormone testosterone is also critical, especially for males, in regulating the expression of sexual behavior and parental care. These hormones can have costly consequences, how- ever, and within populations individuals show variation in endogenous levels of both cor- ticosterone and testosterone. We studied how annual survival varied as a function of natural levels of these hormones in colonially breeding Cliff Swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, USA, in 2000-2003. We sampled hormone levels of birds caught at colonies and using mark-recapture, monitored their survival through subsequent years in the study area. Maximum-likelihood estimation and model fitting (with program MARK) revealed that birds sampled for corticosterone in colonies of all sizes late in the season had curvilinear survival; individuals with very low and very high levels of corticosterone had lower survival than those with intermediate levels. Annual survival of birds sampled earlier in the season, however, generally declined with increasing corticosterone level. More birds than expected, given the survival functions, had the very low corticosterone levels in nonfumigated colonies later in the year, suggesting perhaps a compensatory benefit unrelated to survival for very low corticosterone levels. In a more limited analysis, testosterone appeared to have little effect on annual survival, although some evidence suggested that females with endogenous testosterone levels below the mean for a given date might have survived better.

We investigated how annual reproductive success, as measured by the number of nestlings surviving to day 10 and the percentage of nests that were successful, varied with colony size of the Cave Swallow Petrochelidon fulva in south central Texas. We also studied whether Cave Swallows chose colonies, in part, on the basis of reproductive success at a site the previous year. Neither measure of reproductive success varied significantly with colony size for either first-wave or second-wave nestings. Mean clutch size per colony did not vary significantly with colony size. Mean nestling body mass, an index of parental foraging efficiency, was unrelated to colony size, except for broods of five, in which nestling mass declined significantly with colony size. Colony size was not significantly affected by reproductive success at the site the previous year, although sites with more successful nests during the first wave declined less in size during the second wave within the same season than did sites that had fewer successful first-wave nests. Unlike the closely related Cliff Swallow Petrochelidon pyrrhonota , Cave Swallows did not use breeding performance of conspecifics in choosing nest-sites, because they did not preferentially aggregate at sites that were the most successful the previous year. Coloniality in Cave Swallows did not appear to have a net negative effect on annual fitness, suggesting that colonial nesting was not solely a response to nest-site limitation, but the benefits of breeding colonially (if any) were unclear.

Cave swallows (Petrochelidon fulva) and cliff swallows (P. pyrrhonota) nest in numerous colonies throughout the Texas portion of the Rio Grande along the U.S. border with Mexico. We collected swallows during 1999 and 2000 from eight locations along the Rio Grande to determine if delta15N and delta13C values could be used to predict 1,1-di-(p-chlorophenyl-)2,2-dichloroethene (DDE) and selenium (Se) contaminant burdens in insectivorous birds nesting across a geographic gradient in the Texas-Mexico border and to discern if stable isotopes could help discriminate between local versus nonlocal acquisition of contaminants. We analysed delta15N and delta13C in liver and muscle and DDE and Se in swallow carcasses. Within individuals, delta15N was higher in liver than in muscle of both species by an average of 1.34%, whereas delta13C was 0.145% higher in muscle than in liver. Significant differences occurred among locations in delta15N and delta13C values in liver and muscle of both species. Cave swallows from three locations in the Lower Rio Grande Valley were more enriched in delta15N than swallows from other sites. In general, swallows nesting in more northern latitudes along the Rio Grande had lower delta15N and delta13C values than those nesting farther south. Concentrations of DDE were significantly greater in swallows from El Paso, Llano Grande, and Pharr than in those from Brownsville, Falcon Lake, Laredo, Del Rio, and a reference site outside the Rio Grande. All swallows (n = 21) from El Paso, Llano Grande, and Pharr had DDE concentrations > or = 3 microg g(-1) wet weight (ww), a value three times greater than the estimated threshold in avian prey that could cause potential reproductive failures in raptors. Concentrations of Se also were significantly greater in El Paso and Del Rio than at other locations. Most Se concentrations were not of concern for direct effects on birds or their predators. Principal component analysis indicated some positive correlations between delta15N and delta13C values in tissues and contaminant concentrations in carcass; however, analysis of covariance suggested a stronger effect of location on concentrations of DDE and Se. At the local level (Llano Grande and Pharr) there was a significant positive correlation between delta15N in liver and DDE concentrations in swallow carcasses; however, Se concentrations were not significantly correlated with isotopes even at the local level. Our results provide a good database of delta15N and delta13C values for insectivorous birds nesting along the Rio Grande. Similar ecologies for cave and cliff swallows and their abundance and wide distribution along the Rio Grande make them ideal indicators of environmental pollution of this portion of the Texas-Mexico border.

Although it has been documented that wildlife in the Rio Grande Valley (RGV) contain increased concentrations of organochlorine (OC) contaminants, particularly DDE, little has been published on residues of toxaphene throughout this major North American watershed. In this study, 28 liver composites from adult swallows (Petrochelidon spp.) collected along the Rio Grande from 1999 through 2000 were analyzed for toxaphene residues using congener-specific gas chromatography-electron-capture negative ionization-mass spectrometry. Estimated total toxaphene concentrations ranged from 12 to 260 ng/g wet wt and were highest in samples from the lower RGV near Llano Grande Lake in Hidalgo and Cameron counties (Texas). Toxaphene congener profiles were relatively invariant throughout the watershed and were dominated by 2,2,5-endo,6-exo,8,8,9,10-octachlorobornane (P-42a or B8-806) with lesser amounts of several other Cl(7)-Cl(9) compounds, many of which remain unidentified. Petrochelidon spp. liver profiles appear to be intermediate in complexity between those in invertebrates and fish (more complex) and mammals (less complex) and differs somewhat from those reported for other avian species. In addition to other legacy OC contaminants, toxaphene residues were most concentrated in the lower RGV and accumulated at up to hundreds of parts per billion in these insect-eating birds, underscoring their utility as avian bioindicators of persistent organic pollutants.

The "challenge hypothesis" states that increases in testosterone levels of male animals during the breeding season are directly related to the extent of intrasexual competition for resources or mates that they experience. Although often tested in territorial species, the challenge hypothesis has not been evaluated for colonial animals that live in groups of different sizes and that thus experience different intensities of intrasexual competition. We measured circulating testosterone levels of male and female cliff swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, where these birds nest in colonies of widely different sizes. Males had significantly higher testosterone levels than females, as expected. For males especially, there was a seasonal rise in testosterone levels early in the nesting cycle, corresponding to the period when birds were establishing nest ownership and egg laying, and then a fall as they switched to parental duties. Testosterone levels varied significantly with colony size; for both sexes, birds in larger colonies had higher levels of testosterone than those in smaller colonies when controlling for date. Age and body mass were not related to testosterone levels. Higher levels of testosterone for birds of both sexes in larger colonies probably reflect greater competition for matings, often extra pair, in the more social nesting situations. The results support the predictions of the challenge hypothesis.

While epidemiological models have suggested that the spread of parasites and infectious diseases often depends critically on the extent of movement by infected individuals between populations, there is little empirical information for any organism on the frequency of between-group parasite transmission or how it varies spatially. The trans- mission of parasites between discrete social groups or populations may also help determine a host's total parasite or pathogen exposure. We measured the introduction of parasitic bugs (Oeciacus vicarius) into colonies of Cliff Swallows (Petrochelidon pyrrhonota) by transient birds from outside each group. The transmission of bugs increased strongly as the size of a nesting colony increased. More total transients visited the larger colonies, and the direction of change in transient numbers and the numbers of bugs introduced at a site from week to week tended to vary together. Transients at large colonies were more likely to have pre- viously or subsequently visited other large, infested colonies. The greater likelihood of parasites being introduced into larger colonies by transient birds contributes to an increase in parasite load with increased colony size in Cliff Swallows.

By using a sample of over 800 male cliff swallows (Petrochelidon pyrrhonota) that died during a rare climatic event in our Nebraska study area in 1996, we investigated how testis size was related to body size, age, parasite load, a bird's past colony-size history, and spleen size. Testis volume increased with body size. After correcting for body size, testis volume was lowest for birds age 1 and 2 years but did not vary with age for males 3 years old or more. Birds occupying parasite-free (fumigated) colonies had significantly larger testes than did birds at nonfumigated sites. Testis volume increased significantly with the size of the breeding colonies a bird had used in the past. Testis volume had no relationship with spleen volume after correcting for body size. The results show within a species that larger testes are favored in more social environments, probably reflecting a response to increased rates of extrapair copulation (and thus sperm competition) among cliff swallows in large colonies. The presence of ectoparasites, by inflating levels of plasma corticosterone, may in turn reduce testis mass. These data provide no support for the hypothesis that large testes, perhaps by producing more testosterone, are immunosuppressive and thus costly for that reason. Copyright 2003.

We measured the abundance of mosquitoes [primarily Aedes vexans (Meigen) and Culex tarsalis Coquillett] at cliff swallow (Petrochelidon pyrrhonota Vieillot) colonies of different sizes in southwestern Nebraska in 1999. Using CO2 traps placed inside and outside of colonies, we found that total mosquito abundance increased significantly with the number of active cliff swallow nests at a colony site. We found no effect of date or weather conditions on the number of mosquitoes caught it the different sites. By classifying the landscape from aerial photographs within a 2-km-diameter circle centered on each colony site, we found no significant relationships between habitat type near a colony site and cliff swallow colony size or mosquito abundance. Proximity to livestock could not account for our results. Culex tarsalis was proportionately more likely to be caught inside a colony than at traps 30 in away, but the proportion of C. tarsalis inside a colony did not vary with colony size. Our results cannot be explained by date- or weather-related sampling artifacts or by differences in habitat between sites. Most likely, mosquitoes, especially A. vexans, are attracted to the vicinity of large cliff swallow colonies.

Cliff Swallows (Petrochelidon pyrrhonota) are highly maneuverable social birds that often forage and fly in large open spaces. Here we used multi-camera videography to measure the three dimensional kinematics of their natural flight maneuvers in the field. Specifically, we collected data on tandem flights, defined as two birds maneuvering together. These data permit us to evaluate several hypotheses on the high-speed maneuvering flight performance of birds. We found that high speed turns are roll-based, but that the magnitude of the centripetal force created in typical maneuvers varied only slightly with flight speed, typically reaching a peak of ~2 body weights. Turning maneuvers typically involved active flapping rather than gliding. In tandem flights the following bird copied the flight path and wingbeat frequency (~12.3 Hz) of the lead bird while maintaining position slightly above the leader. The lead bird turned in a direction away from the lateral position of the following bird 65% of the time on average. Tandem flights vary widely in instantaneous speed (1.0 to 15.6 m s-1) and duration (0.72 to 4.71 s), and no single tracking strategy appeared to explain the course taken by the following bird.

We review the extralimital occurrence of Cave Swallows (Petrochelidon fulva) in the United States and Canada since the 1960s. Nineteen (29%) of 65 occurrences not associated with an incursion in late autumn 1999 have been verified with photographs or specimens. Spring specimens of the West Indian subspecies P. fulva fulva are from Alabama and Nova Scotia; the subspecies of a Cave Swallow salvaged in Mississippi in spring is uncertain. Autumn specimens of the southwestern subspecies P. fulva pallida are from North and South Carolina. Cave Swallows measured and photographed at Cliff Swallow (P. pyrrhonota) breeding colonies in Arizona and Nebraska were P. f. pallida, as well as one bird photographed at a Cliff and Barn Swallow (Hirundo rustica) colony in Louisiana along the Mississippi line. Photographs of Cave Swallows in spring at California and in late autumn at New York were P. f. pallida. Subspecies could not be determined for six other records verified by photographs. Most of 46 sight observa...

The percentage of otherwise successful nests containing ≥ 1 unhatched egg in Cliff Swallows (Petrochelidon pyrrhonota) varied inversely with colony size in southwestern Nebraska. Colony-site characteristics other than colony size had no significant effect on egg hatchability. The incidence of unhatched eggs at a colony site did not vary significantly with year, mean date of first egg laying, mean incubation period, extent of ectoparasitism, or mean body mass of nestlings or adults. This suggests that increased hatching failure in smaller colonies was unrelated to ectoparasitism by fleas and cimicid bugs, foraging success, or egg inattendance. Furthermore, because reproductive interference and incidence of brood parasitism do not increase in smaller colonies, these variables seem unlikely to account for the relationship between egg hatchability and colony size. More frequent matings between genetically similar individuals and reduced opportunities for females to seek extrapair fertilizations with ...

An unusually long period of cold weather in May 1996 caused extensive mortality among insectivo- rous cliff swallows (Petrochelidon pyrrhonota) in the northern and central Great Plains. We analyzed how via- bility selection affected spring arrival time in a migratory Nebraska population by comparing capture histories of survivors with those of birds known to have died and by documenting how arrival time changed in the year fol- lowing the selection event. Surviving birds had signifi- cantly later first-capture dates (an index of arrival time) in the years prior to selection than those that died; a sig- nificant selection differential suggested directional selec- tion for birds that arrived later. Colony sites were occu- pied significantly later following the selection event, and the distribution of first-capture dates in the season after selection was significantly shifted toward later arrivals. Offspring of the survivors tended to arrive later than birds of the same age prior to the selection event. While major weather-caused mortality events of this magnitude are rare in the study area, spells of cold weather severe enough to cause limited mortality are frequent in April and early May. At least 25 probable mortality events of varying severity were identified in the last 50 years based on climatological data. Periodic weather-mediated selection against early arrival constrains the cliff swal- low's breeding season and may partly prevent directional selection for earlier nesting.

Summary 1. One way that animals may select breeding sites is by assessing the reproductive success of conspecifics in one season and settling the next year in those habitat patches where success collectively had been greatest. This sort of habitat assessment may promote the formation of colonies at high quality sites. 2. We examined whether cliff swallows, Petrochelidon pyrrhonota, in south-western Nebraska used conspecific breeding performance to choose colony sites. 3. Reproductive success at colony sites varied spatially within seasons and between seasons, and was autocorrelated at a site from one year to the next, but not over longer time intervals. Cliff swallows thus met the conditions for potential use of information on conspecific breeding performance. 4. Among sites re-used in consecutive years, those with highest collective success in one season showed the greatest rates in colony growth the next season, including the greatest influx of immigrants. 5. The probability of colony-site re-use in successive years increased with collective reproductive success and average breeder body mass (a measure of individual condition) the previous season. 6. Cliff swallows probably use conspecific breeding performance in selecting colonies. This mechanism is one component of habitat selection that also includes attraction to conspecifics and assessment of an individual's own success.

Suitable nesting sites created as a result of construction of concrete bridges in southern Arkansas have allowed cliff swallows (Petrochelidon pyrrhonota) to extend their breeding range southward. During spring 2007, several locations in the Gulf Coastal Plain physiographic province of southern Arkansas were being used for nesting. These observations expand the known breeding range from the Red River drainage in southwestern Arkansas (and one location in the Ouachita River drainage) across the Gulf Coastal Plain including the Ouachita and Saline drainages of southeastern Arkansas.

We report measures of annual reproductive success and survival probabilities of adult and offspring Cliff Swallows (Petrochelidon pyrrhonota) associated with clutches of different sizes in southwestern Nebraska from 1982 to 1997. Clutch size 4 was the most com- mon (47.6% of nests). Mean clutch size varied among years, mostly through differences in the proportions of clutch sizes 3 and 4. Temperature and rainfall during egg laying were unrelated to mean annual clutch size. Incubation period declined slightly with clutch size, suggesting no incubation costs associated with larger clutches. Fledging success increased with clutch size. Ectoparasites lowered fledging success significantly in clutch sizes 3 and 4 but not in smaller or larger clutch sizes. First-year survival probability was unaffected by clutch or brood size when ectoparasites were removed, but under natural conditions survival probabilities varied among years and differed significantly among birds reared in brood siz- es 1 to 2, 3 to 4, and 5. Birds tending clutch size 4 produced the highest number of young recruited as breeders in four of eight years; in the remaining years, birds tending clutch size 5 apparently did best. Fitness associated with clutch size 5 varied significantly with tem- perature during brood rearing, being lowest in warm years. Averaged over all years, the highest fitness was conferred at clutch size 5. Parental survival did not differ among clutch or brood sizes for birds under natural levels of ectoparasitism. Body mass of nestlings at 10 days did not vary among clutch sizes in nonfumigated nests and was significantly higher for nestlings in fumigated nests only for the intermediate clutch sizes (2 to 4). Classical life- history tradeoffs probably cannot account for the observed distribution of clutch sizes in Cliff Swallows. Climate and ectoparasite load vary enough annually and are unpredictable enough that Cliff Swallows apparently pursue the risk-averse strategy of laying smaller clutches on average than they can sometimes raise. Ectoparasitism accounted for much of the risk associated with producing clutch size 5, but Cliff Swallows did not adjust their clutch sizes in response to levels of ectoparasitism. Clutch size in aerial insectivores such as swal- lows may also reflect energetic constraints associated with egg production early in the breed- ing season when food is often reduced by cold weather. Received 12 January 1998, accepted 21

I present the first published record of a foraging association between Nearctic-neotropical migrant bird species during the austral summer in South America. I observed Barn Swallows (Hirundo rustica) and Cliff Swallows (Petrochelidon pyrrhonota) in February 2005 repeatedly foraging on aerial insects flushed by flocks of Bobolinks (Dolichonyx oryzivorous) settling onto soybean plants (Glycine max). Additional observations would be needed to distinguish this behavior between an opportunistic association and a commensal relationship.

Extreme climatic disturbances provide excellent opportunities to study natural selection in wild populations because they may cause measurable directional shifts in character traits. Insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern Great Plains must often endure periods of cold weather in late spring that reduce food availability, and if cold spells last four or more days, mortality due to starvation may result. We analyzed morphological shifts associated with viability selection, and how patterns of bilateral symmetry were affected by survival selection, during a four-day period of cold weather in 1992 and a six-day period in 1996 in southwestern Nebraska. Birds that died during the cold were compared to those still alive when the severe weather ended. The event in 1992 killed relatively few birds, but the cold spell in 1996 killed thousands of cliff swallows and reduced their population by about 53%. Climatological records suggest that mortality events comparable to that of 1996 have occurred in only one other year since 1875. Larger birds were favored in the 1996 event. Selection was more intense in 1996 than in 1992 because of more stressful conditions in 1996. Directional selection gradient analysis showed that measures of skeletal body size (tarsus length, culmen width and length) and wing length were targets of selection in 1996. Survivors had lower wing and outer tail asymmetry, and wing and tail asymmetry were targets of selection in both events. Mortality patterns did not differ by sex, but older birds suffered heavier mortality; morphological traits generally did not vary with age. Nonsurvivors were not in poorer apparent condition prior to the weather event than survivors, suggesting that selection acted directly on morphology independent of condition. Selection on body size in cliff swallows was more intense than in studies of body size evolution in other bird species. Larger swallows were probably favored in cold weather due to the thermal advantages of large size and the ability to store more fat. Swallows with low asymmetry were favored probably because low asymmetry in wing and tail made foraging more efficient and less costly, conferring survival advantages during cold weather. This population of cliff swallows may have undergone relatively recent body size evolution.

Two common alternative reproductive tactics are intraspecific brood parasitism and extrapair mating. Understanding the evolution of these traits requires estimation of fitness for individuals that do and do not exhibit diem. We analyze fitness components associated with brood parasitism and extrapair mating in cliff swallows (Petrochetidon pyrrhonota). Annual survival probabilities for females known to be parasites, hosts, and nonparasites/nonhosts differed significantly, with highest survival (0.761) for parasites and lowest (0.289) for host females parasitized by egg laying. Survival probabilities did not differ among males paired to females of different status. First-year survival probabilities in die absence of ectoparasitic swallow bugs (Otdocus vicarius) were 0.546 for young raised in die brood parasites' own nests versus 0.354 for young from all other nests; first-year survival probabilities in die presence of swallow bugs were 0.223 for young raised in host nests versus 0.132 for young from nests not brood parasitized. Males that engaged in extrapair copulation attempts had an annual survival probability of 0.413, signficantly lower than die 0.614 estimated for males that were not seen engaging in extrapair mating. Annual reproductive success, measured as recruitment to breeding age, was greatest for brood parasites and similar among other classes of birds in die absence of swallow bugs and was greater for hosts than for birds not brood parasitized in die presence of swallow bugs, likely because hosts occupied less infested nests. Estimated lifetime reproductive success was highest for parasites and their mates. There were no apparent long-term effects of brood parasitism on survival of adult hosts or offspring from host nests, both because hosts did not have enlarged broods and because clutch and brood size did not affect cliff swallow survival. Brood parasites have greater fitness than hosts and nonparasitized birds, probably because parasites are superior individuals in good condition to start with. That males who participated in extrapair mating had lower expectation of survival suggests that extrapair copulations in cliff swallows are perpetrated by inferior males, and females should probably avoid diem. Key xuords: alternative reproductive tactics, brood parasitism, cliff swallows, coloniality, extrapair copulation, fitness, life history, Petrochelidon pyrrhonota, reproductive success, social behavior, survival. [Behav Ecol 9:158-171 (1998)]

Summary An estimated 80 million birds are killed by colliding with vehicles on U. S. roads each year [1], and millions more die annually in Europe [2] and elsewhere. Losses to vehicles are a serious problem for which various changes in roadway design and maintenance have been proposed [3]. Yet, given the magnitude of the mortality reported for some species [4], we might expect natural selection to favor individuals that either learn to avoid cars or that have other traits making them less likely to collide with vehicles. If so, the frequency of road kill should decline over time. No information is available for any species on whether the extent of road-associated mortality has changed [2]. During a 30-year study on social behavior and coloniality of cliff swallows ( Petrochelidon pyrrhonota ) in southwestern Nebraska, we found that the frequency of road-killed swallows declined sharply over the 30 years following the birds' occupancy of roadside nesting sites and that birds killed on roads had longer wings than the population at large.

Invasive species often display different patterns of parasite burden and virulence compared to their native counterparts. These differences may be the result of variability in host-parasite co-evolutionary relationships, the occurrence of novel host-parasite encounters, or possibly innate differences in physiological responses to infection between invasive and native hosts. Here we examine the adaptive, humoral immune responses of a resistant, native bird and a susceptible, invasive bird to an arbovirus (Buggy Creek virus; Togaviridae: Alphavirus) and its ectoparasitic arthropod vector (the swallow bug; Oeciacus vicarius). Swallow bugs parasitize the native, colonially nesting cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that occupies nests in cliff swallow colonies. We measured levels of BCRV-specific and swallow bug-specific IgY levels before nesting (prior to swallow bug exposure) and after nesting (after swallow bug exposure) in house sparrows and cliff swallows in western Nebraska. Levels of BCRV-specific IgY increased significantly following nesting in the house sparrow but not in the cliff swallow. Additionally, house sparrows displayed consistently higher levels of swallow bug-specific antibodies both before and after nesting compared to cliff swallows. The higher levels of BCRV and swallow bug specific antibodies detected in house sparrows may be reflective of significant differences in both antiviral and anti-ectoparasite immune responses that exist between these two avian species. To our knowledge, this is the first study to compare the macro- and microparasite-specific immune responses of an invasive and a native avian host exposed to the same parasites.

Ecologists often use mark-recapture to estimate demographic variables such as abundance, growth rate, or survival for samples of wild animal populations. A common assumption underlying mark-recapture is that all animals have an equal probability of detection, and failure to meet or correct for this assumption–as when certain members of the population are either easier or more difficult to capture than other animals–can lead to biased and inaccurate demographic estimates. We built within-year and among-years Cormack-Jolly-Seber recaptures-only models to identify causes of capture heterogeneity for a population of colonially nesting cliff swallows (Petrochelidon pyrrhonota) caught using mist-netting as a part of a 20-year mark-recapture study in southwestern Nebraska, U.S.A. Daily detection of cliff swallows caught in stationary mist nets at their colony sites declined as the birds got older and as the frequency of netting at a site within a season increased. Experienced birds’ avoidance of the net could be countered by sudden disturbances that startled them into a net, such as when we dropped a net over the side of a bridge or flushed nesting cliff swallows into a stationary net positioned at a colony entrance. Our results support the widely held, but seldom tested, belief that birds learn to avoid stationary mist nets over time, but also show that modifications of traditional field methods can reduce this source of recapture heterogeneity.

A new species of Carpoglyphidae, Carpoglyphus nidicolous, (Acarina : Astigmata) is established based on specimens collected from the nests of cliff swallows (Petrochelidon pyrrhonota Vieillot) and barn swallows (Hirundo rustica Linnaeus) in Oregon, U.S.A.

Construction of man-made objects such as roads and bridges may have impacts on wildlife depending on species or location. We investigated songbirds and small mammals along the Ohio River, WV, USA at a new bridge both before and after construction and at a bridge crossing that was present throughout the study. Comparisons were made at each site over three time periods (1985-1987 [Phase I] and 1998-2000 [Phase II] [pre-construction], 2007-2009 [Phase III] [post-construction]) and at three distances (0, 100, 300 m) from the bridge or proposed bridge location. Overall, 70 songbirds and 10 small mammals were detected during the study. Cliff swallows (Petrochelidon pyrrhonota) and rock pigeons (Columba livia) showed high affinity for bridges (P0.05). Combined small mammal abundances increased between Phases I and II (P0.05), but did not differ between Phases II and III (P0.05). Species richness and diversity for songbirds and small mammals did not differ before and after bridge construction (P0.05). We found that most species sampled did not respond to the bridge crossing, and believe that the bridge is not causing any measurable negative density impacts to the species we investigated. The new bridge does provide habitat for exotic rock pigeons that are adjusted to man-made structures for nesting.

Fledgling cliff swallows were cared for at a rehabilitation facility when clinical signs of ocular disease, characterized by conjunctivitis, epiphora, and hyperaemia of palpebrae and nictitans, were recognized. Treatment consisted of topical and oral antibiotic therapy and one topical steroid administration. However, one cliff swallow died and three were killed due to poor therapeutic response. Conjunctival swabs were obtained ante-mortem from the three cliff swallows and were submitted for mycoplasma culture and molecular diagnostics. Heads of the three birds were fixed in 10% neutral buffered formalin and submitted for histopathologic examination of oculonasal tissues. Mycoplasma cultures and molecular evaluation of isolates identified Mycoplasma sturni, but not Mycoplasma gallisepticum, from each specimen. Histopathologic examination revealed lymphoplasmacytic conjunctivitis, rhinitis and infraorbital sinusitis with follicular lymphoid hyperplasia, epithelial hyperplasia, and protozoal stages compatible with Cryptosporidium spp. arranged in and along the apical surfaces of epithelial cells. Identification of concurrent M. sturni and Cryptosporidium spp. infections in these cliff swallows demonstrates an alternative infectious condition that can produce gross and microscopic lesions comparable with those commonly observed in M. gallisepticum infections of house finches and other passerine species. Conjunctivitis associated with M. sturni and Cryptosporidium spp. in cliff swallows may represent an emerging disease risk to a naive, high-density and colonial species such as colony-nesting cliff swallows.

Wild birds are rarely found with active arbovirus infections, and relatively little is known about the patterns of viremia they exhibit under field conditions or how infection varies with date, bird age, or other factors that potentially affect transmission dynamics. Buggy Creek virus (BCRV; Togaviridae, Alphavirus) is an arbovirus associated with colonially nesting Cliff Swallows (Petrochelidon pyrrhonota) and transmitted by its vector, the hematophagous swallow bug (Oeciacus vicarius), an ectoparasite of the Cliff Swallow. Introduced House Sparrows (Passer domesticus) that have occupied swallow nests at colony sites in peridomestic settings are also exposed to BCRV when fed upon by swallow bugs. We used data from 882 nestling House Sparrows in western Nebraska from 2006 to 2008 to examine seasonal variation and age-related correlates of virus infection in the field. Over 17% of nestling House Sparrows had active infections. Prevalence was higher in 2007 than in 2008 when birds from all colony sites were analyzed, but there was no significant difference between years for sites sampled in both seasons. Buggy Creek virus prevalence was similar in early and late summer, with a peak in midsummer, coinciding with the greatest swallow bug abundance. Nestlings 10 days of age and younger were most commonly infected, and the likelihood of BCRV infection declined for older nestlings. Average viremia titers also declined with age (but did not vary with date) and were high enough at all nestling ages to likely infect blood-feeding arthropods (swallow bugs). Length of viremia for nestlings in the field was ≥4 days, in agreement with an earlier study of BCRV. Nestling birds offer many advantages for field studies of arbovirus amplification and transmission.