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Fire ants adjust their digging behaviour when building underground nests, depending on the size and dampness of the material they are working with.[illus. 1] Daniel Goldman and his colleagues at [...]

Circulating sex steroids levels of estradiol, testosterone and progesterone were monitored in the green turtle Chelonia mydas during different phases of nesting which included emerging from the sea, digging the body or the nest chamber, abandonment related to nest selection; and after nest completion (post-nesting) which involved oviposition and burying. The study was conducted at Ras Al-Hadd Reserve-Oman (1999-2002). Blood samples for the hormone study were taken from the cervical sinuses. Progesterone levels were significantly higher in turtles that had completed their nesting than in their emerging, excavation and abandonment phases. It is possible that ovulation may take place shortly after oviposition as luteinizing hormone (LH) begins to rise earlier than has been previously reported in other studies, and thus triggering ovulation and corpora lutea formation, which may cause a dramatic rise in progesterone levels. There are no significant differences in progesterone levels between nest digging, emerging from the sea, or nest abandonment. Testosterone levels were low throughout nesting, and there was no significant difference between the nesting phases. Estradiol levels were below the detectable levels in all of the phases. Monitoring the steroid levels at different phases of nesting may be of value in understanding the significance of hormone dynamics during the nesting process.

We studied duck nests on 1 natural island and 21 constructed islands on the J. Clark Salyer National Wildlife Refuge (NWR), North Dakota in 1982-83. We found 286 nests of 7 species; mallard (Anas platyrhynchos), gadwall (A. strepera), and blue-winged teal (A. discors) represented >90% of all nests. The mean annual nest density was 8.7/ha with a mean Mayfield-adjusted nest success of 24%. Islands on which the most ducks were produced were 335-1,085 m offshore, surrounded by [is greater than or equal to] 150-200 m of open water, and contained tall, dense, brush or forb cover. Three islands with these characteristics held 37% of the nests and produced 55% of total ducklings. Although gadwalls and mallards formed dense nesting concentrations, blue-winged teal showed little nest-clumping behavior or nest cover preferences. Other factors influencing production rates included a seasonal decline in nest success and between-year variability. To be cost effective, islands located in wetlands with large mink (Mustela vison) and raccoon (Procyon lotor) populations should have adequate spatial isolation and/or predator control.

We described nest tree and site characteristics of 53 nests of the northern race of the white-headed woodpecker (Picoides albolarvatus albolarvatus) from the central and southern Sierra Nevada, California. We located nests in a variety of habitats and in most tree species, although 89% were in pines (Pinus spp.) and firs (Abies spp.). Nests were located near the ground (x = 3.0 m above ground level). The mean diameter breast height (dbh) of nest trees on 2 mapping grids, where some of our nests were located, did not differ (P > 0.80, P > 0.20) from random samples of snags on the corresponding girds. Most snags used for nest cavities were in a moderate state of decay. Existing snag-management policies of the U.S. Forest Service (USFS) in California will probably provide sufficient snags of the right diameter classes for white-headed woodpeckers, provided interactions with other cavity nesters does not limit their use of nest sites.

When common loons (Gavia immer, pictured) settle down to breed, they pick sites similar to the ones they hatched in, even if better sites are available. As part of a [...]

Experiments by Hoi, et al. have misinterpreted their data on nest choice in the penduline tit, calling to question their conclusions. Nest building is incorrectly described, and its continuity during the incubation period has been ignored. This continuity in building explains the larger size of the nests with incubated eggs. A correlation exists between the number of pair-days and the number of the eggs laid. A female may desert a nest only for polyandrous mating purposes. The explanations for different nest types are questioned.

Marbled Murrelets (Brachyramphus marmoratus) nest primarily in trees, except in treeless or nearly treeless areas of Alaska where they are known to nest on the ground (Mendenhall, Proc. West. Found. [...]

The nests of Helmeted Honeyeaters were measured during their breeding season. Results show that external diameters ranged from 78 mm. to 110 mm. while external depths ranged from 62 mm. to 102 mm. Wall thickness at the rim and base also declined as the breeding season progressed. Early nests were dense with deep linings while later nests showed less density and lining. It is believed that nests are thicker early in the season because of the cold weather.

City-dwelling sparrows and finches incorporate the butts of smoked cigarettes into their nests, seemingly to ward off parasitic mites. Isabel Lopez-Rull and her colleagues at the National Autonomous University of [...]

The role of early life stages (eggs, neonates, and juveniles) for population persistence in long-lived organisms is thought to be minor. However, few long-term data sets are available to test this assumption. Variation in vital rates over space and time and the potential for the success of early life stages to shape adult reproductive behavior evolutionarily suggest that more thorough consideration of these life stages is necessary. In particular, the impact of climatic variation on early life-stage recruitment is not well understood. Furthermore, predation occupies a significant role in theoretical models of population dynamics, but its impact on populations through variable vital rates of early life stages is unknown. Maternal nest-site choice, an important component of nesting ecology, may influence many offspring traits and respond to selection to optimize offspring success. Overall, we have limited information regarding the long-term patterns of natural fluctuations in the nesting ecology and hatchling recruitment of populations of long-lived organisms. The research site for this ongoing long-term project is on an island in the Mississippi River near Thomson, Illinois, USA. Painted turtles (Chrysemys picta) have been studied extensively at this location since 1989 to examine the ecology and potential demographic consequences of nest-site choice and depredation, with the aim of understanding the evolution of maternal nesting behavior and its effects on offspring phenotype. We monitored the site every day of the nesting season each year to record nesting and depredation events. The data presented here include nesting phenology, nest vegetation cover, total number of nesting events, clutch size, depredation, and hatchling survival. Portions of this data set have been used to address related questions in ecology and evolutionary biology. In particular, climatic variation influences the probability of nest depredation events. Such events are typically nonrandom, primarily occurring adjacent to habitat edges. Because habitat edges may have atypical vegetation composition and vegetation influences nest temperature, such nonrandom depredation could influence offspring recruitment and, hence, population structure. Given the unique scope and accessibility of this data set, researchers and teachers should find it to be a valuable empirical resource for exploring important facets of nesting ecology and hatchling recruitment in a wild population of a long-lived species. Key words: demography; early life stages; fluctuating environments; maternal effects; nesting behavior; predation; temperature-dependent sex determination; turtles.

The nesting physiology of the loggerhead sea turtle (Caretta caretta) was studied on two Georgia barrier islands from 2000-2005. Nesting activity was monitored from early May until early August on Blackbeard Island and Wassaw Island. All nesting females observed were measured, double flipper tagged and given a PIT tag in the right flipper. Blood samples were collected from nesting females for hormone analysis each season and the reproductive status of a subset was determined by ultrasound. Nesting chronology based on tag information was correlated with hormone and ultrasound results. Testosterone and estradiol levels showed gradual decline across the course of the nesting season. Progesterone levels fluctuated as observed in other species. Corticosterone levels increased towards the end of the nesting season. Females nesting in Georgia have been documented to lay up 7 clutches of eggs during the nesting season. Yearly variation in nesting and movements between barrier islands have made accurate determination of fecundity difficult. Our results demonstrate that females are laying 5.4 nests per nesting season. This represents a 20% increase in fecundity over that previously reported in the literature for this species. Seasonal nesting patterns and fecundity measures will be discussed.

Coloniality has been suggested to have both costs and benefits. A potential cost of living in a group is high infection rates of ecroparasites. One prediction of this hypothesis is that when group size increases, ectoparasite load will also increase. Several studies have suggested that such a relationship exists. We used barn swallows to examine the relationship between ectoparasite load, group size, and nest density across eleven sites in Pennsylvania. We measured group size by counting active nests and calculated density from average nearest neighbor distance. Ecroparasites were detected by standard methods in each active nest throughout the entire 2005 breeding season. The proportion of infected nests was regressed against group size and group density Ecroparasite load was not dependent on either nest density or group size a finding contrary to other studies on colonial passerines. These results suggest that chance events and/or density independent factors are important in determining ectoparasite prevalence.

We compared nest-site selection in two widely separated populations of dusky flycatcher (Empidonax oberholseri), one located in the eastern Sierra Nevada of California, at Tioga Pass (37[degrees]N), and one near Atlin, British Columbia (59[degrees]N). Both populations utilize subalpine habitats of similar vertical structure and plant composition (subalpine willow, aspen and lodge-pole pine) with seasonal changes in nest-site selection that reflect concomitant changes in environmental conditions such as snow depth and local canopy characteristics. In both populations, aspects of nest-site selection such as nest height, nest-site substrate and surrounding vegetation are largely reflective of plant species abundance and vegetative phenology, with one notable exception. Lodgepole pine forests, which are abundant components of dusky flycatcher breeding habitat in both the Sierra Nevada and in northern British Columbia, are frequently used for nesting in the Sierran population but never in the Atlin population. We evaluate the importance of predation and weather as selective factors influencing behavioral characteristics such as nest-site selection at the population level and speculate on the importance of these mortality factors in shaping phenotypic plasticity in substrate preferences.

Advances in molecular techniques allow investigators to assess quantitatively the physiological condition of free-living organisms. For example, avian serum proteins may be separated by gel electrophoresis into five distinct classes (pre albumin; albumin; alpha-, beta-, and gamma globulins) and their relative quantities calculated by densitometric analysis of electrophoretic bands. Total serum protein concentration and levels of each protein class often differ between healthy and diseased individuals, making them potentially useful in assessing health status. Immunological assays have also been developed to assess robustness of both innate and adaptive aspects of immune function. We used these techniques to test the hypothesis that female condition is positively correlated with nestling condition, immune response, and survival until nest-leaving in house wrens (Troglodytes aedon) breeding in central Illinois. As measures of adult and nestling condition, we used body weight, hematocrit, total serum protein concentration, and levels of individual serum protein fractions. We determined total protein concentration of serum samples by Lowry assay and serum protein profiles by electrophoresis and densitometry. Cell-mediated immune response in nestlings was assessed by measuring wing-web swelling resulting from a subcutaneous injection of phytohaemagglutinin (PHA). We also injected other nestlings with the T-cell dependent antigen, tetanus toxoid, to activate the humoral immune system. Humoral response was measured as antigen-specific antibody production by ELISA. The results of this study are discussed in the context of technique efficacy and diagnostic potential.

Basic knowledge of the natural history of species is essential to our understanding of reproductive biology. Our understanding of tropical bird natural history is particularly poor. Tropical obligate ant-following birds track army ant colonies foraging from arthropods flushed by their raids. However, many of these birds nest close to the ground, thereby risking nest predation by army ants. Here we evaluate whether Ocellated Antbirds nest purposefully away from the range of army ant colonies and provide the first description of behavior at the nest for this species. Six nests were found at La Selva Biological Station, Costa Rica, in 2004-2005. All nests were below one meter from the ground, between buttress roots of trees, supporting the only other published description of a nest of this species. Parents brought an overabundance of prey from swarm raids to the nest, when fair weather allowed ants to forage, and stashed excess prey in the nest cup. This observation suggests that reproductive success can be determined by the birds ability to find raids actively flushing abundant prey. The nests were located significantly away from the reach of nearby army ant colonies, i.e. more than 100 m, but a colony in non-nomadic phase was no farther than 200m from each nest. Nesting close to a sedentary colony may decrease nest predation by nomadic raids because army ant colonies apparently avoid each others chemical trails. We also found that the nests were closer to trails and streams than what chance would predict, suggesting that such visual landmarks may be used in navigation. We propose that the location of army ant colonies and visual landmarks may be important factors in nest site selection of obligate army ant-following birds.

The sex of most turtles, including that of painted turtles (Chrysemys picta), is determined by incubation temperature. Because of this unusual mechanism of sex determination, the choice of nest site is important for determining the sex of the offspring, which ultimately influences the sex ratio of the population. Recent field studies have shown that female painted turtles choose nest sites based on the thermal microclimate at a particular location and that individual females choose thermally similar sites during each nesting event. The repeatability of this behavior suggests that there may be a quantitative genetic basis underlying nest-site choice. A preliminary test of this hypothesis was conducted by combining assays of molecular and phenotypic variation for 95 females from the focal population. We quantified overstory vegetation cover of nest sites and two highly variable microsatellite DNA markers for each female. Although more microsatellite loci and females remain to be examined, preliminary results indicate that the actual variance of relatedness (Var(r)) is positive but the heritability of nest-site choice is low ([h.sup.2] = .000171). These initial results suggest that, although related females return to nest in the same geographic area, the turtles do not inherit microclimate nesting preferences from their mothers via substantive quantitative genetic factors. Thermally-based nest-site choice is therefore unlikely to serve as an evolutionary mechanism to ensure balanced sex ratios in this system

Research is presented concerning the use of arboreal termite nests by Trogons and Parakeets nesting in the Peruvian Amazon. The selection of termitaria sites for nesting by the different species of birds is discussed.

Female Black-capped Chickadees (Poecile atricapillus) solicit extrapair copulations (EPCs) from neighboring high-ranked males, and these EPCs result in extrapair young. Females might choose to locate their nests near the territory boundaries of attractive males to facilitate access to EPCs. Other hypotheses might also explain choice of nest site, namely: (1) habitat characteristics, (2) prey abundance, and (3) previous experience. We tested these four hypotheses in 1996 and 1997. Out of 27 habitat characteristics measured, we found only one that was significantly different between nests and control sites in both years. The abundance of large trees was lower at nest sites than at control sites in each year and when years were pooled. Relative prey abundance did not differ between nests and control sites for either year of the study. We found no difference in interyear nest placement based on female experience; experienced females nested farther than 60 m from their previous nest sites in both years of the study. In 1996, females whose neighboring males were higher ranked than their social partner located their nests significantly closer to territory boundaries than did females whose nearest neighbors were lower ranked than their social partner. In 1997, all pairs nested near territory boundaries. We conclude that choice of nest location in Black-capped Chickadees is influenced by conspecific attraction based on mating tactics.

Research focusing on black skimmers and gull-billed terns, and to a lesser extent on least terns, in the Atchafalaya Delta, the only actively building delta in the northern Gulf of Mexico, has established that shell substrates play a significant role in reproductive success. Nests of black skimmers and gull-billed terns are harder to find on shell than on fine-textured dredged materials, thus making them less vulnerable to predators. Black skimmers have no preference for substrates, but this does not mean that the presence of shell has no impact on this species.

Acorn Woodpeckers (Melanerpes formicivorus) at Hastings Reservation in central California prefer to nest in dead limbs in large, dead valley oaks (Quercus lobata) and California sycamores (Platanus racemosa) that are also frequently used as acorn storage trees. based on 232 nest cavities used over an 18-year period, we tested whether preferred or modal nest-site characters were associated with increased reproductive success (the 'nest-site quality' hypothesis). We also examined whether more successful nests were likely to experience more favorable microclimatic conditions or to be less accessible to terrestrial predators. We found only equivocal support for the nest-site quality hypothesis: only 1 of 5 preferred characters and 2 of 10 characters exhibiting a clear modality were correlated with higher reproductive success. All three characteristics of nests known or likely to be associated with a more favorable microclimate, and two of five characteristics likely to render nests less accessible to predators, were correlated with higher reproductive success. These results suggest that nest cavities in this population are built in part to take advantage of favorable microclimatic conditions and, to a lesser extent, to reduce access to predators. However, despite benefits of particular nest characteristics, birds frequently nested in apparently suboptimal cavities. We also found a significant relationship between mean group size and the history of occupancy of particular territories and the probability of nest cavities being built in microclimatically favorable live limbs, suggesting that larger groups residing on more stable territories were better able to construct nests with optimal characteristics. This indicates that there may be demographic, as well as ecological, constraints on nest-site selection in this primary cavity nester.

Concealment at the nests of three old-field songbird species was investigated to determine the influence of time and nest-site characteristics and differences in concealment in parasitized, nonparasitized, depredated and fledged nests. Nests ultimately lost their concealment after some time. Mean and minimum concealment was not related to the occurrence of predation or brood parasitism for any of the three bird species.