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The variable response of wild mice to Yersinia pestis infection, the causative agent of plague, has generated much speculation concerning their role in the ecology of this potentially lethal disease. Researchers have questioned the means by which Y. pestis is maintained in nature and also sought methods for managing the disease. Here we assessed the efficacy of a new tool, the sylvatic plague vaccine (SPV), in wild-caught northern grasshopper mice (Onychomys leucogaster) and commercially acquired Sonoran deer mice (Peromyscus maniculatus sonoriensis). More than 40% of the animals survived a subcutaneous Y. pestis challenge of 175,000 colony forming units (over 30,000 times the white mouse 50% lethal dose) in both vaccine-treated and control groups. Our results indicate that SPV distribution is unlikely to protect adult mice from plague infection in field settings and corroborate the heterogeneous response to Y. pestis infection in mice reported by others.

La variación de las condiciones fisicoquímicas del mar puede influir en la distribución y la abundancia de las aves marinas al afectar la estructura trófica del ambiente pelágico. Por ello se pretendió evaluar la asociación entre la abundancia de tres estados de desarrollo (pollos, juveniles y adultos) del Piquero Café (Sula leucogaster etesiaca) y la variación de la temperatura superficial del mar (TSM) y su anomalía térmica (ANOM) en isla Gorgona, Pacífico colombiano. Estas tendencias fueron evaluadas por medio de correlaciones cruzadas y modelos lineales generalizados. En cada estado de desarrollo la abundancia presentó una tendencia diferente ante la variación de la TSM o ANOM. Se sugiere que dichas tendencias se deben a que el incremento de la temperatura del mar podría estar asociado con una menor abundancia y disponibilidad de recursos presa. Bajo estas condiciones, los adultos tienden a disminuir el esfuerzo invertido en el cuidado parental e, incluso, reducen el suministro de alimento a juveniles dependientes y pollos para aumentar su propia supervivencia. Es posible que estas tendencias hayan estado asociadas con un régimen reproductivo que les permita a los volantones alcanzar la independencia de los padres durante el periodo con mayor disponibilidad de alimento.

El conocimiento de la avifauna en México, es el resultado de muchos años de exploraciones en áreas es-pecíficas, sin embargo a pesar del esfuerzo realizado, en algunas regiones de México aún se desconoce su composición y distribución; tal es el caso de los humedales continentales, los cuales representan sitios de invernada y de paso migratorio para una gran variedad de aves acuáticas y terrestres del Neártico, así como sitios de reproducción para especies residentes. Se destacan observaciones realizadas en el Sitio Ramsar Laguna de Sayula, resultado de un estudio avifaunístico a largo plazo con muestreos mensuales durante cinco periodos de migración. Se reportan seis nuevos registros para el humedal y algunos para el interior del estado (Dendrocygna autumnalis, Branta canadensis, Sula leucogaster, Pelecanus occidentalis, Pluvia-lis squatarola y Charadrius semipalmatus) y se informa la presencia de Anser albifrons y Anser rossii con pocos registros publicados para la zona

Marine debris is pervasive worldwide, and affects biota negatively. We compared the characteristics of debris incorporated within brown booby (Sula leucogaster) nests throughout their pantropical distribution by assessing the type, colour and mass of debris items within nests and in beach transects at 18 sites, to determine if nests are indicators of the amount of debris in local marine environments. Debris was present in 14.4% of nests surveyed, with the proportion of nests with debris varying among sites (range: 0-100%). There was minimal overlap between the type or colour of debris found in nests and on adjacent beaches at individual sites. This suggests that brown boobies do not select debris uniformly across their distribution. We propose that the nests of brown boobies can be used as a sentinel of marine debris pollution of their local environment.

Identifying associations between phenotypes and environmental parameters is crucial for understanding how natural selection acts at the individual level. In this context, genetically isolated populations can be useful models for identifying the forces selecting fitness-related traits. Here, we use a comprehensive dataset on a genetically and ecologically isolated population of the strictly marine bird, the brown booby Sula leucogaster, at the tropical and remote Saint Peter and Saint Paul Archipelago, mid-Atlantic Ocean, in order to detect phenotypic adjustments from interindividual differences in diet, foraging behaviour, and nest quality. For this, we took biometrics of all individuals of the colony breeding in 2014 and 2015 and tested their associations with nest quality, diet parameters, and foraging behaviour. While body size was not related to the foraging parameters, the body size of the females (responsible for nest acquisition and defence) was significantly associated with the nest quality, as larger females occupied high-quality nests. Our findings suggest that the small breeding area, rather than prey availability, is a limiting factor, emphasizing the role of on-land features in shaping phenotypic characteristics and fitness in land-dependent marine vertebrates.

Sexual segregation in the behaviour, morphology or physiology of breeding seabirds can be related to divergent parental roles, foraging niche partitioning or sex-specific nutritional requirements. Here, we combine GPS tracking, dietary and nutritional analysis to investigate sex-specific foraging of Brown Boobies breeding on Raine Island, Great Barrier Reef, Australia. We observed sex-specific segregation in: (1) foraging location: females undertook longer trips, foraging at more distant locations than males; (2) foraging time: male activity and foraging occurred throughout the day, while female activity and foraging increased from midday to an afternoon peak; and (3) prey type, females mostly consumed flying fish, whereas males consumed equal proportions of flying fish and squid. Brown Booby diets contained five tropical prey species that significantly differed in their nutritional composition (Protein, Lipid and Water, wet mass). Despite this variation we found no differences in the overall nutritional content of prey caught by each sex. The observed sex-specific differences in prey type, location and time of capture are likely driven by a combination of a division of labour, risk partitioning and competition. However, Brown Boobies breeding on Raine Island, and other populations, might flexibly partition foraging niches by sex in response to varying competitive and environmental pressures. In light of such potential foraging dynamism, our inconclusive exploration of nutritional segregation between sexes warrants further investigation in the species.

The Western Whipbird (Psophodes nigrogularis) has a highly disjunct west–east distribution across southern Australia. Earlier morphological analyses recognised four subspecies in one species: P. n. nigrogularis and P. n. oberon in south-west Western Australia, and P. n. leucogaster of the Eyre and Yorke Peninsulas and the Murray Mallee, and P. n. lashmari, restricted to Kangaroo Island, both in eastern Australia. Later morphological analyses elevated P. n. nigrogularis to monotypic species rank, and placed the remaining western and two eastern taxa as three subspecies of a second species P. leucogaster. Initial mtDNA analysis questioned both arrangements but could not include all taxa. We used mtDNA sequence data from all available specimens of the entire group (DNA extracted from cryo-preserved tissues, toe-pads and feathers; holotypes excepted) to derive a more stable view of species limits. The samples fell into two strongly divergent but geographically structured groups, completely reflecting ...

Anthropogenic debris has been affecting fauna in different ways. We investigate the frequency of anthropogenic material in nests of a brown booby (Sula leucogaster) colony in the Saint Peter and Saint Paul Archipelago (SPSPA), Rio Grande do Norte, Brazil in February 2015 and November 2016. The items were classified according to type (threadlike plastic, sheet plastics, hard fragments, foamed synthetics and miscellaneous) and color. In 2015, a total of 30 anthropogenic items were found in 20.4% of the nests. In nests containing debris, miscellaneous items were found in 73.6% of nests. White/clear was the most common color, 52.6% of nests containing debris had items of this color. In 2016, 45 anthropogenic items were observed in 13.3% of the nests. Threadlike plastic was found in 59.2% of nests. Blue/purple was the most common color (55.5%). Even far from the Brazilian coast, the S. leucogaster colony has been affected by marine pollution.

Seabirds collect debris primarily nearby breeding sites, and thus they may be used to monitor these pollutants in the ocean. This study aimed to investigate the prevalence of marine debris used as nesting materials by the brown booby (Sula leucogaster) and to test the species selectivity to debris type and color in two coastal islands of Brazil. We found marine debris in 61% of the brown booby nests on both islands. Fishing gear and hard plastic were the most frequent types of debris. Higher prevalence of fishing gear was found on the island with greater fishery activity. Similarly, hard plastic was the most frequent type of debris in nests and adjacent beach environment. The frequency of debris in brown booby nests can be a potential indicator of the abundance of specific items in surrounding marine waters. Monitoring debris in brown booby nests in a long-term may provide a better understanding of the species⿿ selectivity for specific debris. Furthermore, the impacts of debris in seabird nests at population level remain an overlooked threat that may reduce the quality of nesting habitats. We showed that brown booby nests are widely impacted by marine debris and that these organisms are exposed to this form of pollution from the beginning of their life.

The Brown Booby Sula leucogaster is a seabird with a pantropical distribution across a wide variety of oceanic environments. Sexual size dimorphism in Brown Boobies has been proposed as an explanation for intersexual differences in foraging, but results have been inconsistent. We investigated whether there is context-dependent foraging behaviour driven by local environmental conditions. In this study, we evaluated (1) inter-sex differences in foraging behaviour (by capillary tubes, temperature and depth recorders, and diet) at two colonies in the Gulf of California: Isla San Jorge (ISJ) and Farallon de San Ignacio (FSI) and, (2) intercolonial and interannual differences in foraging behaviour, and (at ISJ) their relationship with local-scale environmental variation, using 5-day composite images of sea surface temperature (SST) and primary productivity (PP) as proxies. Inter-sex differences were few and inconsistent between years, and smaller than overall differences between years and localities. At ISJ, Br...

In the present study, I monitored nests of the White-bellied Sea Eagle Hialiaeetus leucogaster from September 2012 to September 2013 every two weeks. Maximum 40 adults and 4 juveniles were counted during this study. The 75 nests present here are categorized in five groups: Not occupied (63 %), occupied with low potentiality (12 %), with medium potentiality (20 %), reserved (4 %), and active nest (1 %). Successful breeding was observed only in one nest that raised the problem of nest occupancy and this problem is discussed in this article.

Leg-loop harnesses for the attachment of telemetry devices have been used for over two decades in terrestrial bird research. Recently, the technique has been extended to waterbird applications. An equation exists for predicting the dimensions of correctly fitting leg-loop harnesses in terrestrial bird research. This equation appears robust to the varied life histories of terrestrial birds. Yet, the applicability of this equation for waterbird research has not been tested. Here, we present the dimensions of leg-loop harnesses fitted to Lesser Frigatebirds (Fregata ariel), a sexually dimorphic seabird species. For both sexes, measured harness spans were shorter than those predicted by the terrestrial bird equation. Additionally, leg-loop harnesses trialed on Brown (Sula leucogaster) and Masked (S. dactylatra) boobies were unsuitable and hence unsuccessful. Morphological and behavioral features of species suited to leg-loop harness attachment are identified.

The Great Barrier Reef supports significant breeding populations of tropical seabirds; however, recent evidence has indicated declines in seabird populations across some of the most important breeding sites. Evidence for the cause of these significant declines is lacking but is generally thought to result from inadequate food supplies caused by warmer sea surface temperatures associated with climate change. This paper provides the first detailed investigation into the foraging behaviour of Brown Boobies (Sula leucogaster), a species considered to be more susceptible to climate change impacts due to reduced foraging ranges. Fifteen complete foraging trips were recorded from five individuals (three males, two females). Adults typically foraged in shallow inshore reef waters and the mean foraging trip duration was 6.8 ± 2.8 h with a mean foraging range of 14.5 ± 10.1 km and the total distance travelled being 49.5 ± 30.3 km per trip. While most foraging trips occurred during daylight hours, five (33%) trips recorded periods spent at sea at night. The preliminary results presented here suggest that further research across widely dispersed breeding sites and different species investigating the potential drivers of seabird declines in the Great Barrier Reef is warranted.

Cannibalism is the total or partial consumption of a conspecific’s body or eggs, and it has been reported for many bird taxa, particularly carnivorous, colonial species, and those species that ingest fragmented prey. Here we report cannibalism by Brown Booby ( Sula leucogaster ) at Saint Peter and Saint Paul Archipelago, offshore Brazil. We discussed possible causes for this behavior such as opportunistic feeding, colony sanitation and space competition for nesting places.

The ecological adaptations of parasitoids associated with bark- and wood-boring insects, i.e. saproxylic insects, are presented principally from examples of Ichneumonoidea but also other families of saproxylic parasitoids typically associated with insects inhabiting dead wood. Morphological adaptations to hosts living in wood, behaviours related to parasitism of the host and life strategies of saproxylic idiobionts and koinobionts are characterised. From the example of Doryctes leucogaster (Nees) (Doryctinae, Braconidae), details of searching behaviour and the oviposition process are described. Brief summaries of the main “saproxylic” subfamilies of Ichneumonidae and Braconidae followed by Stephanidae, Aulacidae, Ibaliidae and Orussidae are included. Habitat requirements of saproxylic ichneumonoid parasitoids in boreal and temperate forests are presented in relation to forest successional stage and the type and position of woody substrates. The potential role of saproxylic parasitoids as indicators of saproxylic habitat quality is discussed, and the lack of ecological knowledge for most saproxylic parasitoid taxa, especially from tropical zones, is indicated.

Despite many biotic, physical, and political challenges for place-based conservation in open ocean environments, conservation of discrete oceanic regions by designating pelagic marine protected areas (PMPAs) has gained considerable traction. In the oligotrophic central Pacific, a patchy and dynamic ecosystem, a robust network of PMPAs has recently been established. However, evaluations of PMPA efficacy in providing appropriate habitat coverage for pelagic species are lacking, particularly in the tropics. Here, we used high resolution GPS tracking and home range analyses of tropical boobies to determine the distribution and foraging habitat use of three sympatric species (Sula sula, Sula dactylatra, and Sula leucogaster) in two PMPAs that varied substantially in size and shape. At each site we characterized the extent and use of foraging habitat inside and outside the PMPA that surrounded each breeding colony. We found profound variation within and among species in foraging behavior and habitat use across the two sites; this was partially explained by variation in bathymetry. Yet, despite variation both in PMPA size and shape, and in foraging behavior of the birds, we determined that the PMPAs each encapsulated more than 85% (n = 216 trips) of foraging habitat for each species, indicating that these PMPAs provided important habitat coverage for highly mobile tropical species. While this study highlights the challenges in effectively designing PMPAs even for relatively well-studied, central place foragers, given strong variation in foraging ecologies across sites, it also suggests that PMPAs do provide meaningful habitat coverage for at least some pelagic species.

Levels of trace elements were investigated in feathers of 51 adults and 47 eggshells of brown boobies Sula leucogaster from one bird colony in the Marine National Park of Currais Islands, Brazil, between December 2013 and October 2014. Average concentrations (μg g−1, dry weight) in feathers and eggshells, respectively, were Al 50.62–9.58, As 0.35–2.37, Cd 0.05–0.03, Co 0.38–2.1, Cu 15.12–0.99, Fe 47.47–22.92, Mg 815.71–1116.92, Ni 0.29–11.85, and Zn 94.16–1.98. In both arrays, the average concentration of Mg was the highest among all the elements analyzed, while the lowest was recorded for Cd. As and Ni presented levels at which biological impacts might occur. Zn concentrations were higher than those considered normal in other organs. Levels of Al, Fe, Cu, Zn, and Cd were higher in feathers, whereas higher contents of Mg, Co, Ni, and As occurred in eggshells. The comparison between the elements in eggshells collected at different seasons showed no significant difference (p > 0.05) due, probably, to the lack of temporal variation on foraging behavior and/or on bioavailability of trace elements. Metals and arsenic in feathers and eggshells were mostly not correlated. Future studies on Parana coast should focus on the speciation of the elements, especially As, Ni, and Zn, which proved to be a possible problem for the environment and biota. It is necessary to investigate both matrices, shell and internal contents of the eggs, in order to verify if the differences previously reported in other studies also occur in eggs of brown boobies in the Marine National Park of Currais Islands.

Diving abilities of fledging Brown Boobies (Sula leucogaster) were characterized during the transition to independence period, and potential inter-sex differences (females are larger than males) were evaluated. Mean and maximum diving depths and mean dive duration increased gradually following the fledglings' first flights. The diving rate and the proportion of active dives (U type) increased notably between days 21 and 25 after first flight. However, maximum dive duration was not influenced by time since first flight, and none of the dive variables evaluated was influenced by sex. In Brown Boobies, acquisition of diving abilities by juveniles is a gradual process, and this can be an important driver of their extended post-fledging parental care.

The current study describes the chewing lice community associated with seabird populations resident at the Sao Pedro and Sao Paulo Archipelago in the Atlantic Ocean in Pernambuco State, Brazil. Adults of three species of seabirds were captured using hand-nets for the collection of biometric data and specimens of ectoparasites. In total, 320 birds were examined (120 Sula leucogaster (Boddaert), Brown Booby; 120 Anous stolidus (L.), --Brown Noddy; and 80 Anous minutus Boie, Black Noddy) of which 95% were infested with 8,625 chewing lice, representing eight species of the genera Actornithophilus, Austromenopon, Eidmanniella, Pectinopygus, Quadraceps, and Saemundssonia. On S. leucogaster, Pectinopygus garbei (Pessoa & Guimaraes) was more prevalent and had a mean and median intensity of infestation significantly greater than those recorded for Eidmanniella albescens (Piaget). On the two Noddies, the species of Actornithophilus and Quadraceps were significantly more prevalent and abundant than Austromenopon atrofulvum (Piaget) and Saemundssonia remota Timmermann Most of the louse species had a highly aggregated distribution, with k exponent of the negative binomial distribution ranging from 0.04 to 3.06. A weak but significant correlation was found between the abundance of chewing lice and morphometric variables (body weight, wing, beak, tail, and tarsus lengths). It is possible that high rates of infestation have a negative effect on the morphological characteristics of the hosts, including the health of the plumage. All the lice species collected--except for P. garbei (ex S. leucogaster)--were reported for the first time from Brazilian populations of these seabird species.

Northern grasshopper mice (Onychomys leucogaster) have been implicated as a potential reservoir for plague, which causes local extinction of black-tailed prairie dog (Cynomys ludovicianus) colonies. To identify mechanisms by which grasshopper mice could facilitate plague spread, we measured burrow use, movements, and flea burdens of mice in colonies in northern Colorado. At the microhabitat scale, powder-tracked mice (n = 41) used both prairie dog mounds and burrows extensively, entering an average of 5.3 burrows per 100 m traveled. Burrow use did not differ between active and inactive mounds, or vary with mouse age, sex, or reproductive status. Radiotracking revealed that mice occupied larger ranges (X = 3.84 ha) than reported off colonies, which we estimated would overlap 12–23 prairie dog coterie territories. Mice also harbored high flea burdens (8.1 fleas/mouse), including fleas associated with prairie dogs, which we attributed to their frequent use of burrows. Our results support the conten...

The Moleques do Sul Archipelago has great importance for seabirds on the Brazilian coast as it houses breeding populations of various species. This archipelago represents the southern limit for the breeding colonies of the brown boobies ( Sula leucogaster ). In order to verify the influence of environmental factors on the abundance of adults and nestling of a Sula leucogaster population, we collected population data of this species in the archipelago between 2002 and 2007 for comparison to climatological data of the region. We generated seven multiple regression models to confront sex, age, number of nests and specimens, as well as adult and offspring mortality, to temperature, relative humidity, precipitation, atmospheric pressure on sea level and wind speed. Results showed that adults were positively related to average wind speed and negatively related to atmospheric pressure. Pressure also negatively influenced offspring, whereas number of nests was negatively affected by average wind speed. Adult and offspring mortality could not be explained by the variables. The correlations found in this study corroborate literature information for other researches on seabird in islands. Keywords: brown booby, climate, islands.

Stereotypic behaviour, such as territorial calls and songs, is thought to be evolutionarily conserved, and therefore useful in discerning systematic relationships. We examined vocalizations of several species of Peromyscus and Onychomys, a monophyletic group of rodents (Peromyscini). We report stereotypic vocal signals occurring in both sexes of the deer mice Peromyscus californicus, P. eremicus, P. leucopus, P. melanophrys, P. polionotus, and the grasshopper mice Onychomys arenicola and O. leucogaster. The stereotypic vocalizations of P. eremicus, P. leucopus, and P. polionotus are confined to frequencies greater than 20 kHz, unlike those of Onychomys, which are clearly audible, or P. californicus and P. melanophrys, which generate lower frequency vocalizations than the other Peromyscus. We did not observe stereotypic vocalizations in P. aztecus. Intensity, context and consistency suggest that these vocalizations serve an announcement function. Distribution of spectral energy distinguishes genera and mos...

Social behaviour has been implicated in the natal dispersal of several small mammal species. We studied social interactions within groups of bushveld gerbil Gerbillhcus leucogaster mothers and their weaned offspring in captivity. We examined groups (n = 8) over several weeks to assess whether mothers and juveniles tolerate one another beyond weaning, and to investigate behavioural influences surrounding the onset of dispersal. Each group was placed in a series of interconnecting tanks, allowing juveniles free movement between tanks but restricting the movement of the mother. In two of the eight groups the mother produced a second litter during the study; mothers in these two groups appeared to be less tolerant of their first litter compared to mothers in the remaining groups. The remaining groups showed very high levels of tolerance throughout the study, both between mothers and their offspring, and between siblings. Juveniles began showing independence from the mother around weaning, but although indepen...

We report records for eight species of tube-nosed bats, Murina, from Laos. Murina cyclotis is the most widespread in the region, although DNA barcodes of specimens currently identified as M. cyclotis suggest high genetic diversity within southeast Asia with the possibility that the form found in Indochina is not the same as that from the type locality on the Indian subcontinent. We recognize M. peninsularis from peninsular Malaysia and Borneo as distinct from M. cyclotis. Murina huttoni is known from only one locality in Laos but has been reported from scattered localities elsewhere in southeast Asia including Vietnam and Thailand. Specimens previously reported as M. tubinaris from southeast Asia, including Laos, were recently recognized as a distinct species, M. cineracea; however, we suggest M. feae is the appropriate name for this species, based on examination of the holotype from Myanmar. Specimens formerly reported as M. aurata from Laos are now referred to the recently described M. eleryi from Vietnam. A specimen from northern Laos matches the description of M. harrisoni in morphology, while genetically it matches M. tiensa. Comparisons with additional material from Vietnam, as well as DNA from both type specimens, suggest that M. tiensa is a junior synonym of M. harrisoni. We also report M. harrisoni from Thailand and Myanmar, based on specimens originally published as M. leucogaster. The latter species is not otherwise known to occur in Thailand or Myanmar and should be removed from those countries' lists. The recently described M. walstoni is here reported for the first time from Laos. Two additional species from Laos do not match any currently described species, and are here described as new; both are also reported from Vietnam and one from Cambodia.

Recent theoretical and empirical research suggests that statistical models based on coalescent theory can improve both phylogeographic and phylogenetic inference. An approach that involves elements of both statistical phylogeography (e.g. Isolation with Migration analyses) and multilocus phylogenetic inference (e.g. *beast) may be particularly useful when applied to populations with relatively old divergence times. Here, we use such an approach in the globally distributed brown booby (Sula leucogaster). We sampled 215 individuals from all major breeding areas and genotyped them at eight microsatellite and three nuclear intron loci. We found that brown booby populations were highly differentiated and that colonies can be grouped into four major genetic populations (Caribbean Sea, Central Atlantic Ocean, Indo-Central Pacific and Eastern Pacific). These populations apparently diverged in the absence of gene flow and, with one exception, currently exchange few to no migrants. The Eastern Pacific population diverged from all other populations approximately one million years ago [90% highest posterior density: 330,000-2,000,000 years ago] and exhibits a distinct male plumage, relative to other populations. However, recent gene flow from the Indo-Central Pacific into the Eastern Pacific appears to have occurred, suggesting that approximately one million years of genetic isolation and divergence in male plumage colour are not sufficient to prevent interbreeding. Gene flow following secondary contact of the Indo-Central Pacific and Eastern Pacific populations was not detected in previous mitochondrial DNA (mtDNA) studies, and the contrast between the mtDNA results and our current results highlights the advantage of a multilocus phylogeographic approach.

The post-fledging dependence period is extremely important because it allows young birds the opportunity to develop behavioural skills required for later life. We raised 12 hatchling Brown Boobies Sula leucogaster and attached a miniaturized GPS logger to each bird to examine how flight improves after fledging. The Boobies made daily trips and increased the maximum distance, total distance travelled each day, trip duration and flight speed. Young Boobies seemed to gradually acquire flight skills towards independence.

To test the hypothesis that both physical and ecological barriers to gene flow drive population differentiation in tropical seabirds, we surveyed mitochondrial control region variation in 242 brown boobies (Sula leucogaster), which prefer inshore habitat, and 271 red-footed boobies (S. sula), which prefer pelagic habitat. To determine the relative influence of isolation and gene flow on population structure, we used both traditional methods and a recently developed statistical method based on coalescent theory and Bayesian inference (Isolation with Migration). We found that global population genetic structure was high in both species, and that female-mediated gene flow among ocean basins apparently has been restricted by major physical barriers including the Isthmus of Panama, and the periodic emergence of the Sunda and Sahul Shelves in Southeast Asia. In contrast, the evolutionary history of populations within ocean basins differed markedly between the two species. In brown boobies, we found high levels of population genetic differentiation and limited gene flow among colonies, even at spatial scales as small as 500 km. Although red-footed booby colonies were also genetically differentiated within ocean basins, coalescent analyses indicated that populations have either diverged in the face of ongoing gene flow, or diverged without gene flow but recently made secondary contact. Regardless, gene flow among red-footed booby populations was higher than among brown booby populations. We suggest that these contrasting patterns of gene flow within ocean basins may be explained by the different habitat preferences of brown and red-footed boobies.

We determined egg concentrations of organochlorines and thickness of eggshells from brown boobies at eight colonies ranging from the northern Gulf of California to southern Mexico. The only common residue was that of DDE, which was found in almost all eggs. DDE content apparently reflected pre-1990 DDT use in nearby agricultural areas and, at one site, intensive mosquito control for high-end tourism development. There were no inter-colony differences in eggshell thickness, and variation in this variable likely reflected individual bird characteristics and/or individual feeding source. This variable was not a good proxy to DDE exposure of brown boobies, under current DDE levels in the brown booby trophic chain. In the northern Gulf of California, eggshell thickness has recovered to pre-DDT conditions. Our data indicate that the Gulf of California and southwestern coast of Mexico have a healthy near-shore marine environment, as far as organochlorines are concerned.

Commensal associations between Guiana dolphins Sotalia guianensis and sea birds, Larus dominicanus, Sula leucogaster, Sterna sp. and Fregata magnificens have been frequently observed during the feeding behavior of the dol- phins in the North Bay of Santa Catarina, (26°00'-28°25'S, 48°30'-48°49'W), Southern Brazil. Boat and land surveys were performed, using focal group sampling method, in blocks of five minutes. In 81 surveys, between 1993 to 1997, as- sociations with birds were observed in 67% of the days (n= 54 days). The most representative years were 1993 (63.16%) and 1994 (73.68%), with a total frequency of 62.72%. In 1995, less associations were registered, only 8.5% of the total. In the following years associations were registered more frequently (16.13% in 1996 and 12.64% in 1997), but with lower intensity and numbers than the early years. The frequency of occurrence of the bird species also varied each year. Sterna sp. showed the highest time of occurrence in observed association (1587 minutes, 33.32% of the total time observed) and the highest frequency days in associations (n = 46, 85.18% of the total (= 54)). The second most representative bird spe- cies was F. magnificens with 1218 minutes of associations, almost 26% of the total, and observed in 40 days (74.07%of the total). S. leucogaster appeared with 951 minutes in association (19.97%) and it was observed in 29 (53.70%) of the 54 total days of associations registered. L. dominicanus showed the smaller time of occurrence, 925 minutes (19.42%) and it was registered in 29 days (53.7%) of associations, mainly in the austral winter. These associations occurs principally when the dolphins are executing coordinated feeding strategies, railing the fishes in big groups, making easy the obtain- ment of food to the birds, that is characterize this relation like commensalism.

We investigate mitochondrial DNA and craniometric variation in southern African and Malagasy populations of the small and morphologically variable, house-roosting molossid bat, Chaerephon pumilus in relation to Malagasy populations of the related, smaller-sized species, C. leucogaster. Both cytochrome b and D-loop sequences show C. leucogaster to be nested within C. pumilus sensu lato, with Malagasy C. pumilus forming a sister group to African C. pumilus and Malagasy C. leucogaster. Four distinct D-loop clades are found in southern African populations, all of which occur sympatrically in the greater Durban area of KwaZulu-Natal Province, whilst two of the Durban clades also characterize 1) northern KwaZulu-Natal and low-lying ( 600 m) areas of Swaziland. Clades from low-lying areas show evidence of historical demographic expansion around 3300–13 000 years ago (KwaZulu-Natal coastal clade, Clade A1...

The present paper reviews the published information on the mating systems and reproductive biology of Neotropical waterbirds. Thirty-four scientific articles were included, which were divided into two main themes: “mating systems” (10 articles) and “reproductive biology” (24 articles). Extra-pair copulation and/or fertilization were reported to occur in 60% of the Neotropical species investigated, while monogamy was reported in 22%, bigamy in 11% and nest parasitism in 11%. General aspects of reproductive biology of 30 species were more extensively reviewed, of which 20 were seabirds and 10 were lacustrine species. Aspects most frequently described were reproductive chronology (73% of species), clutch size (80%) and reproductive success defined by the number of hatched eggs (73%). Only one species in Sulidae (Sula leucogaster) and one in Threskiornithidae (Eudocimus rubber) were studied for both, mating system and reproduction. A global analysis of the available data revealed that seabirds and Ciconiiformes birds were most intensively studied in terms of reproductive biology, while their mating systems remain largely uninvestigated.

SUMMARY Bird bones and feathers found in phosphate deposits and fumaroles on Ascension during the B.O.U. Centenary Expedition were used to supplement the historical records in building up a picture of the original avifauna of the island. The remains which can be definitely identified provide strong circumstantial evidence that the sea-bird colonies on the main island included at least the following species: Oceanodroma castro, Phaethon aethereus, Sula sula, S. dactylatra, Fregata aquila and Sterna fuscata: a skull apparently of Gygis alba was also obtained. No remains definitely referable to Phaethon lepturus, Sula leucogaster or Anous stolidus have yet been found, but it seems very likely that these species also nested in numbers on the main island of Ascension, while Anous tenuirostris, which still nests on the cliffs of the main island, doubtless also did so in the past. In addition to sea-birds, a skull and a tarso-metatarsus of a small rail, found in separate localities, probably represent the extinct flightless species described by Peter Mundy. The rail whose bones were obtained is provisionally considered as a new member of the genus Rallus. The only surviving species that is endangered locally is the Red-footed Booby Sula sula: the history of this species on Ascension is discussed.

One hundred and thirty-eight echolocation calls of 63 free-flying individuals of five bat species (Rhinolophus ferrumequinum, Myotis formosus, Myotis ikonnikovi, Myotis daubentoni and Murina leucogaster) were recorded (by ultrasonic bat detector (D980)) in Zhi’an village of Jilin Province, China. According to the frequency-time spectra, these calls were categorized into two types: FM/CF (constant frequency) / FM (R. ferrumequinum) and FM (frequency modulated) (M. formosus, M. ikonnikovi, M. daubentoni and M. leucogaster). Sonograms of the calls of R. ferrumequinum could easily be distinguished from those of the other four species. For the calls of the remaining four species, six echolocation call parameters, including starting frequency, ending frequency, peak frequency duration, longest inter-pulse interval and shortest inter-pulse interval, were examined by stepwise discriminant analysis. The results show that 84.1% of calls were correctly classified, which indicates that these parameters of echolocation calls play an important role in identifying bat species. These parameters can be used to test the accuracy of general predictions based on bats’ morphology in the same forest and can provide essential information for assessing patterns of bat habitat use.

Summary The Dahlac Archipelago, in the southern Red Sea, is described. Eighteen of its islands were visited by an expedition in August and September 1962, and 33 species, excluding migrants, were recorded. The distribution of these species between islands is summarized (Table 2), and observations are made on their habits, habitats, food, and liability to predation. Evidence of breeding is given for Sula leucogaster, Falco concolor, Larus hemprichi, L. leucopthalmus, Sterna bengalensis and Sauropatis Moris; breeding is also suggested for five further species. Particular attention is paid to Falco concolor, and existing knowledge of this species is summarized. Information is given about breeding biology, food, hunting methods, call and other habits, and the species is compared with F. eleonorae, from which it differs chiefly in the absence of colonial breeding. The breeding biology of Sula leucogaster is briefly discussed, and attention is paid to the differences between Larus leucopthalmus and L. hemprichi.

Toxoplasma gondii is a coccidian parasite that infects almost all warm-blooded animals, including birds. Abrolhos is an archipelago of five islands, located in the Atlantic Ocean, 56 nautical kilometers from the south coast of the state of Bahia, northeastern Brazil. Part of this archipelago is a National Marine Park, which is a conservation area protected by the Brazilian government. The objective of this study was to determine the occurrence of T. gondii antibodies in sera of seabird’s species Sula spp. and Phaeton spp. from breeding colonies located in the Islands of Santa Barbara and Redonda, Abrolhos’s archipelago. Sera were tested by modified agglutination test, first screened at 1:5 dilution (cut-off point) and the positive samples were titrated at a two-fold serial dilution. Serum samples were obtained from 69 birds of four species: Sula dactylatra (23 birds), Sula leucogaster (19 birds), Phaeton aethereus (25 birds) and Phaeton lepturus (2 birds). Antibodies to T. gondii were found in 24 (34.8%) of 69 seabirds with titers that ranged from 5 to 640. Occurrence value in S. dactylatra was 34.8% (8/23), in S. leucogaster was 47.4% (9/19), in P. aethereus was 28% (7/25) and the 2 P. lepturus were negative. This is the first description of T. gondii antibodies in free ranging seabirds of the orders Suliformes and Phaethontiformes.

The Bonin Islands provide breeding habitat for many species of seabird, but detailed information on breeding sites is unavailable. Here, we describe the recent species composition of breeding seabirds on 66 islands. A total of 15 species (Diomedea immutabilis, D. nigripes, Pterodroma hypoleuca, Bulweria bulwerii, Puffinus pacificus, Oceanodroma tristrami, O. matsudairae, Phaethon rubricauda, Sula leucogaster, S. dactylatra, S. sula, Thalasseus bergii, Sterna fuscata, Anous stolidus and A. minutus) was recorded breeding in the Bonin Islands based on field and literature surveys. The sole nesting record of S. sula was on a small island near Haha-jima, where it has failed to breed since a typhoon struck the island. We did not detect Puffinus lherminieri bannermani, although it bred on Kitaiwo-jima before World War II. S. leucogaster was the most widespread species and bred on 39 islands. The second most widespread species was P. pacificus, which bred on 35 islands. There was a positive relationship between species richness and island area. The distribution of breeding sites may be affected by human settlement and introduced species such as feral goats Capra aegagrus. Introduced animals should be controlled to protect the seabird fauna on the islands.

The Fregetta storm-petrels generally are regarded to comprise two species: black-bellied storm-petrels F. tropica (monotypic) breed at Antarctic and sub-Antarctic islands (46-63°S), and white-bellied storm-petrels F. grallaria breed at south temperate islands (28-37°S), with four recognized subspecies. Confusion surrounds the status of birds at Gough Island (40°S), central South Atlantic, which have been attributed usually to a white-bellied form of black-bellied storm-petrel F. t. melanoleuca. We use cytochrome b and nuclear β-fibrinogen gene sequences to show that F. t. melanoleuca are present during the breeding season at Gough and islands in the nearby Tristan da Cunha archipelago (37°S), exhibiting limited divergence from F. t. tropica. We also show that there is greater diversity among F. grallaria populations, with eastern South Pacific F. g. segethi and F. g. titan differing by c. 0.011, and both differing from western South Pacific nominate F. g. grallaria by c. 0.059. The Tristan archipelago supports a population of F. grallaria closely allied to the nominate form, as well as a distinct form identified as F. g. leucogaster. Further research is needed to assess how F. grallaria and F. tropica segregate in sympatry at Tristan and Gough, and why this is the only location where both species have white-bellies.

The south-western subspecies of the Crested Shrike-tit (Falcunculus frontatus leucogaster) is uncommon and declining in abundance. Moreover, populations fail to persist in even large remnants of native vegetation within agricultural areas. Reasons for the scarcity of Shrike-tits in south-western Australia, their decline, and their failure to survive in fragmented habitats are unclear, but are possibly related to the scarcity of persistent decorticating bark on south-western Australian eucalypts relative to eucalypts in habitats where the species is abundant in eastern Australia. At two widely separated areas of eucalypt forest and woodland in eastern Australia, where Shrike-tits have been studied and appear relatively abundant, they take most of their prey from bark, particularly loose and decorticating bark. By contrast, in woodlands of south-western Australia, most prey appears to be obtained by foliage gleaning. I suggest that bark substrates provide a richer food resource for Shrike-tits than foliage, and that Shrike-tits in south-western Australia must forage over much larger areas to obtain adequate food than those that have been studied in the east. Other studies have shown that canopy arthropods are less abundant on eucalypts in south-western than in eastern Australia. Thus, as a result of both differences in foraging substrate availability and lower arthropod abundances, Shrike-tit population densities are lower in south-western Australia than much of eastern Australia. Low population densities and the need for large home-ranges typify organisms sensitive to habitat fragmentation. It is therefore hypothesised that both low numbers and a failure to persist in habitat fragments by Shrike-tits in south-western Australia are a consequence of the limited abundance of suitable bark substrates for foraging, a reliance on foliage gleaning, and lower arthropod abundances. Conservation of this species in south-western Australia therefore requires protection of large contiguous areas of eucalypt woodlands and forests.

We examined host usage and seasonal activity patterns of the nymphal stage of the ticks Ixodes kingi and I. sculptus within a prairie rodent community in north-central Colorado. Ixodes kingi was commonly encountered on both northern grasshopper mice (Onychomys leucogaster) and thirteen-lined ground squirrels (Spermophilus tridecemlineatus), whereas I. sculptus frequently infested S. tridecemlineatus but was absent from O. leucogaster. Low numbers of ticks of both species were collected from deer mice (Peromyscus maniculatus) and Ord's kangaroo rats (Dipodomys ordii). Nymphal loads of I. kingi and I. sculptus increased dramatically on commonly infested rodent species from spring (May-June) to summer (July-August). Further, rodents trapped on prairie-dog towns tended to experience increased nymphal loads of I. kingi (O. leucogaster, S. tridecemlineatus) but decreased loads of I. sculptus (S. tridecemlineatus) following plague epizootics among prairie dog populations. A summary of published North American host records revealed that I. kingi has been recorded from humans, domestic animals (cat, dog), 17 species of carnivores, 40 species of rodents, and four species of lagomorphs, and that I. sculptus has been recorded from humans, domestic animals (cat, dog, goat), 13 species of carnivores, 34 species of rodents, and three species of lagomorphs. In accordance with our observations from Colorado, I. kingi commonly has been found to infest heteromyid and murid rodents (such as grasshopper mice), whereas I. sculptus most frequently has been collected from ground-dwelling sciurid rodents, especially Spermophilus ground squirrels. The potential roles of I. kingi and I. sculptus as enzootic vectors of human pathogens, particularly the agents of tularemia (Francisella tularensis), Q fever (Coxiella burnetii), and Colorado tick fever (CTF virus), are discussed.

The aim of this research was to know waterbirds diversity in the Peniti mangrove forest, Pontianak Regency. This research was found 19 species (9 families) of waterbirds that living in the Peniti mangrove forest, Pontianak Regency, West Kalimantan. This identification showed that four species were member of Sternitidae Family, three species were member of Ardeidae Family, other three species were member of Anatidae Family, two species were member of Laridae Family, two species from Accipritidae Family, and Alcedinidae Family. One species from Ciconidae Family, Scolopacidae Family, and Ploceidae Family. Thirteen species of them were protected in Indonesia; there were Egretta garzetta, E. sacra, Ardea cinerea, Ciconia episcopus, Larus ridibundus, L. brunnicephalus, Sterna sumatrana, S. dougallii, Anous minutus, Gygis alba, Halcyon pileata, Todirhamphus chloris, and Lonchura fuscans. Lochura fuscans was belonging to Indonesian endemic birds, because we only found this bird species in Kalimantan Islands. Two species, Haliaetus leucogaster and Haliastur indus were the International protected species according to Appendix II Convention on International Trade in Endangered Species (CITES). © 2006 Jurusan Biologi FMIPA UNS SurakartaKey words: waterbirds, protected, endemic, species.

Sex differences in the foraging behaviour of adults have been observed in a number of sexually size-dimorphic birds, and the usual inference has been that these sex-specific differences are driven primarily by differences in body size. An alternative explanation is that foraging differences result from sex differences unrelated to size, such as sex-specific nutritional requirements. To examine these alternative hypotheses, the foraging behaviour of parents was compared between two sympatric and congeneric species of seabird, the Brown Booby Sula leucogaster , which is highly sexually size-dimorphic (females 38% larger) and the Red-footed Booby S. sula , in which sex differences in body size are less marked (females 15% larger). Using temperature and depth loggers, we found that there were highly significant differences in the foraging trip durations and diving behaviour of male and female Brown Boobies. These sex differences were less marked in Red-footed Boobies. Thus, our interspecies comparison revealed that the magnitude of the difference between the sexes matched the sexual size dimorphism of the species, providing support for the size hypothesis.

We report the predation by a coyote (Canis latrans jamesi) on a foraging, adult blue-footed booby (Sula nebouxii) during the early afternoon on 2 December 2009 on the west coast of Isla Tiburon in the Gulf of California, Mexico. The observed event took place while a flock of blue-footed and brown boobies (Sula leucogaster) was plunge-diving close to shore. The food habits of coyotes on Isla Tiburon are not known, and capture of live adult boobies by coyotes has not previously been documented in the literature.

Although much is known about truffle abundance and rodent mycophagy in mesic Douglas-fir forests in the Pacific Northwest, few data are available for dry interior montane forests dominated by ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), and grand fir (Abies grandis). Our objective was to quantify the relationship between the abundance and diversity of ectomycorrhizal fungal sporocarps in the soil and in the diets of northern flying squirrels (Glaucomys sabrinus) in low-elevation forests of the eastern Washington Cascades. We randomly sampled four stands each of three cover types: dry open ponderosa pine, mesic young mixed-conifer forest, and mesic mature mixed-conifer forest. We sampled the soil for hypogeous sporocarps during the spring of 1999 and 2000. We collected fecal pellets from 318 flying squirrels live-trapped during the fall of 1997–2000. We sampled 2400 m2 of soil surface and found truffles in 40% of 600 plots. Total biomass collected was 609 g. Spring truffle biomass on a kg/ha basis averaged 1.72 in open pine, 3.56 in young, and 4.11 in mature forest. Twenty-two species were collected across all cover types, with all but three species belonging to the Basidiomycotina. Eleven dominant species accounted for 91–94% of truffle biomass in each cover type. Four dominant species accounted for 60–70% of spring truffle biomass: Gautieria monticola, Hysterangium coriaceum, Rhizopogon parksii, and R. vinicolor. Truffle assemblages, richness and total biomass differed among cover types: richness and biomass were highest in young and mature mixed-conifer forest, and lowest in open ponderosa pine forest. Fall squirrel diets were composed of 23 genera or groups of fungi, plus about 22% plant material. Rhizopogon was the most abundant genus in the diet, followed by plant material, then Gautieria, Leucogaster, Alpova, and Hysterangium. Diets in different cover types were similar in the composition, richness, evenness, and the ratio of fungus to plant material. Diet richness varied over the study period. Nineteen truffle genera were detected in fall fecal samples versus 12 in spring soil samples. Management of low-elevation dry forest to maintain or restore stable fire regimes might reduce truffle diversity at stand scales by simplifying stand composition and structure; but, such management might increase long-term beta and landscape truffle diversity and persistence by reducing the occurrence of high-intensity fires and stabilizing inherent fire disturbance regimes.

We examined mitochondrial cytochrome b sequence variation in masked Sula dactylatra, red-footed S. sula, and brown S. leucogaster boobies sampled from islands in the central and eastern Pacific Ocean and in the Caribbean Sea. Each species showed a different phylogeographic pattern. Whereas haplotypes in masked and red-footed boobies were shared across the central and eastern Pacific (i.e., across the Eastern Pacific Basin), brown booby haplotypes were not shared across the Eastern Pacific Basin. Although most masked booby haplotypes from the Pacific were distinct from those in the Caribbean, one haplotype was shared across the Isthmus of Panama. Red-footed and brown boobies, however, did not share haplotypes across the Isthmus of Panama. We estimate that divergence of these regional populations occurred within the last 560,000 years. Thus, the Isthmus of Panama and the Eastern Pacific Basin (albeit to a lesser degree) appear to have played a role in the diversification of these species.

Even though not yet considered as endangered, White-bellied Sea Eagle’s global population is decreasing due to illegal hunting, bird trading, and deforestation. So far, there hasn’t been any report regarding the phylogenetic study of the White-bellied Sea Eagle inhabiting the coastal regions of Java. Moreover, there hasn’t been any report on the genetic data, especially COI gene, of the White-bellied Sea Eagle living in coastal area of Java. Thus, in this research, two individuals of Heliaeetus leucogaster (Gmelin, 1788); are compared based on its COI gene sequence to the member of genus Haliaeetus to determine their position in the phylogenetic tree of genus Haliaeetus. COI gene amplification is performed using Forward primer BirdF1 5’- TTC TCC AAC CAC AAA GAC ATT GGC AC-3’ and Reverse primer BirdR2 5’ ACT ACA TGT GAG ATG ATT CCG AAT-3’. The phylogenetic analysis using MEGA6 with Maximum Likelihood method shows that Haliaeetus leucogaster in this study is related to Haliaeetus leucocephalus (Linnaeus, 1766), Haliaeetus pelagicus (Pallas, 1811), and Haliaeetus albicilla (Linnaeus, 1758). Keywords: phylogenetic study; Heliaeetus leucogaster (Gmelin, 1788); DNA barcoding, Cytochrome-c Oxidase Subunit I (COI).

Many seabirds are impacted by marine debris through its presence in foraging and nesting areas. To determine the extent of this problem, marine debris use in nest material of the brown booby (Sula leucogaster) in the Great Barrier Reef, Australia, was investigated. Nine cays were examined using beach and nest surveys. On average, four marine debris items were found per nest (n = 96) with 58.3% of surveyed nests containing marine debris. The source of marine debris in nests and transects were primarily oceanic. Hard plastic items dominated both nest (56.8%) and surveyed beaches (72.8%), however only two item types were significantly correlated between these surveys. Nest surveys indicated higher levels of black and green items compared to beach transects. This selectivity for colours and items suggest these nests are not good indicators of environmental loads. This is the first study to examine S. leucogaster nests for marine debris in this location.

In Iowa, the northern grasshopper mouse (Onychomys leucogaster) previously was known only from the northwestern part of the state. Herein, we report records of O. leucogaster from the 1970s and 1980s that extend its dis- tribution into west-central and southwestern Iowa. These records may represent dispersal movements into these parts of Iowa by southward movements from populations in northwestern Iowa or they may represent eastward movements of individuals from Nebraska prior to channelization of the Missouri River.

SummaryThree archaeological sites on or near Mussau Island (Bismarck Archipelago, Papua New Guinea) have yielded 58 bird bones that represent 17 species (six seabirds, eight resident landbirds, two migrant shorebirds and one introduced species). Four of these (the petrel Pterodroma sp., Brown Booby Sula leucogaster, cockatoo cf. Cacatua sp. and owl Tyto sp.) have not been recorded previously from Mussau. The archaeological samples of birds from Mussau are too small to represent thoroughly the island's prehistoric avifauna. Nevertheless, they are important among avian bone assemblages from the Lapita Cultural Complex (c. 3500–2000 yr BP) for being the westernmost, among the best dated and associated with extensive cultural and environmental information. The Mussau samples also demonstrate that prehistoric losses of birds, such as those well documented in Polynesia, occurred as well in the Papuan region. Compared to avifaunas from Lapita sites in Western Polynesia (Tonga), the lower percentage of extinct/ex...

Local assemblages of rodents in northern shortgrass prairie may reflect either predatory or competitive effects of northern grasshopper mice (Onychomys leucogaster) on other species such as deer mice (Peromyscus maniculatus). In an effort to distinguish these two types of effects, during the summer of 1994 I compared abundances, patterns of microhabitat use, and diets of P. maniculatus on four areas of shrub-dominated prairie in north-central Colorado to these characteristics on four similar sites where 0. leucogaster was removed. The abundance of P. maniculatus decreased during the study on both control and removal sites, but the decline was greater on controls, where numbers of 0. leucogaster increased. Declines in the abundance of P. maniculatus on individual study plots were correlated with abundances and recolonization rates of 0. leucogaster. Only 6% of P. maniculatus present on controls during pre-removal trapping were captured 7 wk later, compared to 32% of those initially present on removal sites. Furthermore, changes in the number of P. maniculatus were inversely related to the amount of shrub cover on sites, suggesting that shrubs may have provided refuge from 0. leucogaster, which rarely uses these microhabitats. Analyses of microhabitat use support this assertion; individual P. maniculatus increased their use of shrubs on control sites when 0. leucogaster was abundant, but there were no shifts in microhabitat use on removal sites. The proportions of arthropods in the diets of the two species were similar prior to Onychomys removals, and although P. maniculatus consumed fewer arthropods as the experiment progressed, diets did not differ between control and removal sites. In addition, Ord's kangaroo rats (Dipodomys ordii) increased slightly in number following removals, and western harvest mice (Reithrodon- tomys megalotis) colonized two removal sites. These results suggest that predatory or aggressive interference by 0. leucogaster, rather than exploitative competition, was re- sponsible for the observed changes in abundance and microhabitat use. Risk of aggression or predatory interference therefore may influence the local abundance and distribution of P. maniculatus and other small rodents on areas of shortgrass prairie where habitat char- acteristics permit coexistence.