The role of behavioral dominance in structuring patterns of habitat occupancy in a migrant bird during the nonbreeding season

Several species of territorial migratory birds exhibit sexualhabitat segregation on their wintering grounds, with some habitatscontaining mostly males and others mostly females. The objectiveof this study was to determine if in the American redstart(Setophaga ruticilla) in Jamaica habitat segregation is dueto social mechanisms or due to sex-specific habitat specialization.I used habitat-specific patterns of arrival by young males and females, observations of territorial displacements, removalexperiments, and simulations of territorial intrusions to differentiatebetween these two mechanisms. Redstarts were studied in twohabitat types, a male-biased mangrove forest and a female-biasedscrub habitat. In autumn, male and female hatch-year redstartsinitially settled in equal numbers in each habitat, and segregationof the sexes occurred gradually and mostly later in the arrival period. This shift corresponded with an increase in densityof older birds and an increase in territorial displacements.Removal experiments showed that vacancies in male-biased habitatwere filled more rapidly and with greater frequency than thosein female-biased habitat and that vacated male territoriesin mangrove were replaced more often by females than by males. Simulations of territorial intrusions and analyses of body sizeindicated that levels of aggression and body size of both malesand females were greater in mangrove habitat, suggesting thatthese factors may be important in determining the outcomesof dominance interactions. I conclude that patterns of sexualhabitat segregation in redstarts are structured by the dominance behavior of older and more dominant individuals, and these aremostly males.     

Effects of vegetation type on habitat use by crop-raiding Japanese macaques during a food-scarce season

Habitat use by crop-raiding Japanese macaques (Macaca fuscata) was studied in western Japan from December 2005 to February 2006, a food-scarce season. To examine how different vegetation types affect habitat use by monkeys, two crop-raiding troops were compared: the first troop inhabited a habitat involving more wild food resources; the second troop inhabited a habitat providing fewer wild food resources. It was hypothesized that monkeys living in the habitat with fewer wild food resources are more likely to utilize human settlements and areas around them (i.e. adjacent zones), with a dependence on crop foods. Comparisons of observed and expected habitat use frequencies showed that the first troop selected evergreen broad-leaved forests and conifer plantations, and avoided adjacent zones, rice fields, and golf courses. The second troop selected adjacent zones and avoided conifer plantations, pine forests, and deciduous broad-leaved forests. Both troops moved rapidly in avoided habitat types. These results suggest that monkeys living in the habitat with fewer wild food resources are more likely to utilize areas around human settlements during a food-scarce season.     

Inter-specific association and habitat use in a farmland passerine assemblage

We studied the pattern of inter-specific association of breeding territories in a passerine assemblage of dry cereal farmland in central Spain and evaluated the role of the presence of heterospecifics in the habitat use patterns exhibited by different species. Bird territories showed a non-random inter-specific spatial aggregation pattern. We studied territory abundance variation in the three more abundant species: the corn bunting, the crested lark, and the fan-tailed warbler. Crested lark and fan-tailed warbler territories were more abundant in plots where corn bunting territories were present and vice versa, while their respective abundances did not vary with the breeding presence of the other species. We used landscape and agricultural management variables to analyze the relationships between habitat and each species?? breeding territories by means of classification trees. While the corn bunting showed a marked pattern of nesting habitat use, the crested lark and the fan-tailed warbler exhibited a much more generalist one. Corn Bunting presence was affected negatively by intensification-related variables, such as field size and percent cover of cereal crops. Similarly, the presence of crested larks was negatively related to high yielding areas. However, when the presence of hetero-specific territories was considered, the presence of corn bunting territories was the most important variable explaining the occurrence of breeding fan-tailed warblers, and the second most important in the case of the crested lark. These results suggest that inter-specific attraction could play a role in the formation of farmland bird assemblages, while adding further evidence for the detrimental effect of agricultural intensification at the community level.     

Fertility of fresh and frozen-thawed goat semen during the nonbreeding season

A total of 4109 does of a local Greek breed (Capra prisca) were synchronized with intravaginal MPA-sponges and PMSG, and 24 bucks of Alpine (n = 8), Saanen (n = 8) and Damascus (n = 8) breeds were used for studying the fertility of nonfrozen and frozen-thawed semen during the nonbreeding season (June to August). Artificial insemination (AI) was performed once (50 to 55 h after sponge withdrawal) or twice (36 and 60 h after sponge withdrawals with fresh semen (collected during the nonbreeding season, stored at 16 degrees C and inseminated within 6 h) or frozen semen (prepared from the same bucks during the preceding breeding season). The induction of estrus was successful, varying between 91.0 and 95.0%. The form of semen (fresh or frozen-thawed used for inseminating the synchronized does affected their fertility: the overall kidding rate with fresh semen (65.5%) was higher (P < 0.05) than that with frozen-thawed semen (53.4%). The fertility level was also affected by the number of inseminations performed: the overall kidding rate was significantly higher (P < 0.001) in the does inseminated twice with fresh or frozen-thawed semen (70.4 and 59. 1%, respectively) than in those inseminated only once (48.9 and 44.9%, respectively). Finally, the breed of the buck used for preparing the fresh or the frozen-thawed semen affected the fertility level of the does. The kidding rate was higher in does inseminated with fresh semen prepared from bucks of the Damascus breed than from bucks of Saanen or Alpine breed. However, when frozen-thawed semen was used the kidding rate was lower in does inseminated with semen prepared from bucks of the Damascus breed than from bucks of the Alpine or Saanen breed. It is concluded that the fresh semen of Alpine, Saanen and Damascus breed bucks, born and raised under the climate conditions prevailing in Greece (34 degrees to 41 degrees N), can be used successfully during the nonbreeding season (June to August) for inseminating does.     

Induction of sexual activity in female camels during the nonbreeding season

Sixteen anestrous adult female camels (Camelus dromedarius ) in good health and with inactive ovaries were selected from the herd during the month of June (non-breeding season). The camels were randomly divided into 4 equal groups. To induce ovarian activity, camels in Groups I,II and III were given an intramuscular injection of 250 mg hydroxyprogesterone hexanoate followed by 1000 IU eCG on days 2 and 3 of treatment. The camels were mated on Day 5 after the last eCG injection. Ovulation in Groups II and III was induced by intravenous administration of 3000 IU hCG and 40 mcg GnRH, respectively. Group IV was administered saline and served as the control. Periodic examinations per rectum were performed to explore the status of the ovaries. Blood samples were collected at 8 different stages and sera were analyzed for estradiol 17-B and progesterone using specific RIA kits. All camels in the control and treated groups were mated successfully. Levels of estradiol 17-B did not exhibit any particular trend. Blood progesterone levels suggested ovulation in 2 camels (50%) in Group I and in 3 camels (75%) in each of Groups of II and III. This was confirmed by presence of CL in the ovary during per rectum examination. No camel ovulated in the control group. One camel conceived in each of Groups I and III.     

黄河三角洲东方白鹳繁殖期觅食栖息地的利用

2008和2009年3—6月,在黄河三角洲自然保护区采用定点观察、GPS定位、样方调查和逐步判别分析等方法对东方白鹳(Ciconia boyciana)繁殖期觅食地的利用进行了研究。共测定了75个觅食利用样方和74个对照样方的14个生态因子。结果表明,东方白鹳繁殖期倾向于在明水面、芦苇沼泽和滩地中觅食,对草地和农田利用极少。偏向于食物丰富度较高的觅食点;对隐蔽级高低没有明显的偏好。对利用样方和对照样方进行比较,发现利用样方具有植被高度和植被盖度较低,觅食地水深相对较浅,距明水面、芦苇沼泽、树林等距离较近,距重度干扰源较远等特征。逐步判别分析表明,距芦苇沼泽距离、样方内水深、距重度干扰源距离、食物丰富度和明水面距离具有重要作用,由这5个变量构成的方程在对繁殖季节东方白鹳觅食地利用样方和对照样方进行区分时,正确判别率可以达到95.5%。东方白鹳繁殖期觅食地的利用主要与水源、人为干扰和食物条件有关。     

Medroxyprogesterone priming and response to the ram effect in Corriedale ewes during the nonbreeding season

The "ram effect" (RE) is an inexpensive technique that allows farmers to obtain out-of-season lambs. Five hundred and ninety-six Corriedale ewes were used in three experiments to determine the effectiveness of different medroxyprogesterone (MAP) treatments associated with the ram effect during the nonbreeding season. The aim of the first experiment was to evaluate the effectiveness of short-term (6-day) MAP priming. We obtained similar results in estrus incidence and fertility after using MAP sponges for 6, 9, and 13 days. In the second experiment, we compared the effect of sponges containing 20, 40, or 60 mg of MAP used in 6-day priming. Estrous behavior and fertility were not affected by dosage. In the third experiment, 2.5mg of MAP was administered in single treatments 0, 1, 3, or 5 days before the introduction of the rams. Medroxyprogesterone administration 1, 3, or 5 days before the introduction of the rams concentrated estrus in ewes 17 to 20 days later.     

Stimulation of testicular function during the nonbreeding season in the woodchuck (Marmota monax)

Treatment of male woodchucks with a series of s.c. injections of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) induced testicular growth, sperm production and marked increase in serum testosterone levels in the fall, approximately 4 mo before the expected spontaneous onset of testicular activity. These results suggest that it may be possible to induce and/or maintain reproductive competence in this species outside of its normally brief breeding season.     

Migration patterns and habitat use by passerine and near-passerine migrant birds in eastern Africa

Palaearctic migrant passerines and near-passerines which visit eastern Africa can be divided into six groups based on the latitude of their final wintering area. Species wintering further north in Africa tend (a) to breed in more southern parts of the Palaearctic, (b) to prefer drier habitats and (c) to feed more from the ground than those wintering further south. Many species use quite narrow passage routes through eastern Africa and, for some species, passage is centred further east in spring than in autumn. Southward migration can take more than 4 months from the Palaearctic breeding grounds and many birds stopover in the northern tropics from September to November. By contrast, the return migration takes only about 6 weeks. The timing and strategy of migration within Africa can be broadly related to seasonal patterns of rainfall and vegetation.     

Within‐year movements and site fidelity of Purple Sandpipers during the nonbreeding season

ABSTRACT Although within‐year site fidelity to specific wintering sites allows shorebirds to use prior knowledge of resources and microhabitats, such fidelity may also make populations more vulnerable to extirpation in the event of increased predation pressure, habitat loss, or disturbance. In the eastern Atlantic, Purple Sandpipers (Calidris maritima) have been found to be highly faithful to specific sites in wintering areas. However, little is known about the use of wintering areas by these sandpipers along the coast of Maine. We quantified movements of 60 radio‐marked Purple Sandpipers in a bay near the mainland and on an offshore cluster of islands along the mid‐coast of Maine during two winters (2005–2006 and 2006–2007). Birds marked in early‐ and mid‐December remained until spring migration, with no evidence of onward migration. Mean maximum distances moved did not differ significantly between either males (8.6 ± 1.0 [SE] km; N= 30) and females (7.4 ± 0.8 km; N= 30) or juveniles (9.9 ± 1.6 km; N= 9) and adults (7.8 ± 1.1 km; N= 26). We also detected no monthly (January–May) differences in maximum distances moved. Sixty percent of marked individuals moved ≤5 km between the two most distant relocations and no birds moved >25 km during the 2‐ to 4‐month tracking period. We attribute the high site fidelity primarily to the plentiful prey base in the study area. During a 2‐d period with severe cold, feeding areas at locations protected from wave action became encased in ice and birds at these locations moved up to 10 km offshore to sites with less ice. Species with strong site fidelity, like wintering Purple Sandpipers, may be at higher risk in the event of large‐scale changes in their food base, increased predation pressure, habitat loss, or disturbance. However, the short‐distance movements made when intertidal feeding areas became encased in ice suggest that Purple Sandpipers could potentially move greater distances in response to changing conditions in their wintering areas.     

Effects of food value, predation risk, and pilferage on the caching decisions of Dipodomys merriami

Animals that scatter cache their food face a trade-off betweenthe benefits of protecting caches from pilferers and the costsassociated with caching. Placing food into a large number ofwidely spaced caches helps to protect it from pilferage butalso involves costs such as greater exposure to predators. Ipredicted that animals would disperse food into a larger numberof more widely spaced caches when caching (1) a preferred foodversus a less preferred food and (2) under conditions of lowpredation risk versus high predation risk. To test these predictions,I examined the scatter-caching decisions of Merriam's kangaroorats (Dipodomys merriami). D. merriami distributed caches inclumped patterns, regardless of food preference, but they showeda tendency to invest more in a preferred food by distributingcaches more widely. Under the relative safety of the new moon,they did not disperse caches more widely, rather they partitionedthe same amount of food into a larger number of caches thanthey did under the full moon, when predation risk is higher.To examine whether their cache spacing decisions had a significantimpact on the success of cache pilferers, I measured discoveryby pilferers of artificial caches of two food types at differentcaching distances. Results indicate that the cache spacing behaviorof D. merriami functions to protect caches from pilferers, becauseincreased spacing of artificial caches decreased the probabilityof pilferage for both types of food.     

Age and season determine European rabbit habitat use in Mediterranean ecosystems

Knowledge about the factors determining habitat use is especially interesting for herbivores living under seasonal climates as they have to deal with food shortage during the drought season. In this context, different-aged individuals are expected to respond differently to seasonal variations because nutritional requirements and predation risk can vary with age. We investigated adult and juvenile European rabbit (Oryctolagus cuniculus) habitat use in a Mediterranean ecosystem of central Spain, during spring, summer and winter. Relationships between adult and juvenile rabbit pellet abundances and 11 environmental variables related to food availability and refuge density were analysed by means of multiple regression, and evaluated using information theory to identify the set of models best supported by the data. Density of warren entrances was the more constant predictor of habitat use for juvenile rabbits in all the seasons. Herbaceous vegetation volume had a negative influence and was the strongest predictor for adult rabbit habitat use in spring and winter. In summer, green vegetation cover became the strongest positive habitat use predictor. These results suggest that adults prefer to forage in low volume swards ensuring a wide sensory range for the detection of approaching predators. However, the arrival of summer and its associated food depletion forces them to shift toward more open productive areas where green vegetation persists, but at the expense of higher predation risk. Seasonal variation induces minor changes in juvenile habitat use due to their strong dependence on warrens. Thus, our results show that rabbit habitat use is influenced by animal age and seasonal variations in resources.     

Optimizing stream bioassessment: habitat, season, and the impacts of land use on benthic macroinvertebrates

Bioassessment of running waters should ideally be optimized to include sampling of the biota when and where they are most sensitive to anthropogenic disturbances, but direct comparisons of the responses of biota across habitats and seasons are lacking. We sampled benthic macroinvertebrates from nine boreal streams situated along an agricultural land use gradient in two seasons (spring and autumn) and two habitats (pools and riffles). Univariate (e.g., diversity) and multivariate (ordination scores) metrics, as well as biological traits, were used to assess changes in assemblage composition associated with agricultural land use. Abundances were generally higher in agricultural compared to forested streams, and in riffles compared to pools. Spring samples had lower mean abundances of several insect taxa (e.g., chironomid midges) compared to autumn samples, while abundances of non-insects (e.g., oligochaetes and Pisidium spp.) remained unchanged. Community turnover (correspondence analysis) had higher precision and sensitivity compared to diversity metrics, and samples from the spring and from riffles responded more to the land use gradient than those from autumn and pool habitats, respectively. The finding that catchment land use resulted in macrohabitat differences and, ultimately, differences in taxonomic composition between agricultural and forested streams and between pool and riffle habitats can be used to optimize future bioassessment based on macroinvertebrates.     

Hazel grouse (Bonasa bonasia) pairs during the nonbreeding season: mutual benefits of a cooperative alliance

During the nonbreeding season (autumn and winter), hazel grouse(Bonasa bonasia) males and females associate as loosely boundpairs, not as strongly bound pairs as previously thought. Thesepairs could be considered cooperative alliances, with each membergaining both direct and indirect benefits. The most importantdirect benefit appeared to be mutual vigilance against predators.This benefit was found at two levels: at the level of arborealfeeding sites, two birds could forage faster and farther fromcover than single birds, and at the territory scale, the pairwas together more in dangerous habitats. By foraging fartherfrom cover, two birds could use about 23% more of the preferredfood trees and 9%–10% more of the food available withina territory than a single bird, partially mitigating the costof having two birds feeding on limited winter food in the samespace. Defending a common territory appeared to be a less importantdirect benefit of the alliance because the members of a pairdid not defend the same territory and often associated withneighboring birds of the opposite sex. A future benefit of thealliance was having breeding partners in the spring; this wasmost beneficial for males, as the sex ratio was male biased.Members of the pair were often apart. At arboreal feeding sites,this separation was perhaps because the most preferred trees,black alders (Alnns glutinosa) with the most staminate catkins,were located in areas with the most cover, where one bird maybe safer from predators than two. Members of pairs in more securehabitats were more often with extrapair birds of the oppositesex. This suggested a trade-off; birds in safe habitats mayhave visited potential breeding partners, but birds in dangeroushabitats may have had to remain together, foregoing this option,to increase their survival probability. This social organizationappeared to be an adaptation to surviving in a heterogeneoushabitat, with some of the winter food located in dense coverand some located in more open and dangerous situations.     

Stable isotopes reveal individual variation in migration strategies and habitat preferences in a suite of seabirds during the nonbreeding period

Information on predator and prey distributions is integral to our understanding of migratory connectivity, food web dynamics and ecosystem structure. In marine systems, although large animals that return to land can be fitted with tracking devices, minimum instrument sizes preclude deployments on small seabirds that may nevertheless be highly abundant and hence major consumers. An increasingly popular approach is to use N and C stable isotope analysis of feathers sampled at colonies to provide information on distribution and trophic level for the preceding, and generally little-known, nonbreeding period. Despite the burgeoning of this research, there have been few attempts to verify such relationships. In this study, we demonstrate a clear correspondence between isotope ratios of feathers and nonbreeding distributions of seven species from South Georgia tracked using loggers. This generated a rudimentary isoscape that was used to infer the habitat preferences of eight other species ranging in size from storm petrels to albatrosses, and which could be applied, with caveats, in other studies. Differences in inferred distribution within and between species had major implications for relative exposure to anthropogenic threats, including climate change and fisheries. Although there were no differences in isotope values between sexes in any of the smaller petrels, mean stable C (δ¹³C), but not stable N isotope ratios (δ¹⁵N), tended to be greater in females than males of the larger, and more sexually size-dimorphic species. This indicates a difference in C source (distribution), rather than trophic level, and a correspondence between the degree of sexual size dimorphism in Procellariiformes and the level of between-sex niche segregation.     

Spatio-temporal patterns of habitat use in voles and shrews modified by density, season and predators

1.?Although the intrinsic habitat preferences of a species can be considered to be fixed, the realized habitat use depends on the prevailing abiotic and biotic conditions. Often the core habitats are occupied by dense and stable populations, while marginal habitats become occupied only at times of high density. In a community of interacting species, habitat uses of different species become inter-related, for example an increased density of a strong competitor forcing a weaker competitor to use more marginal habitats. 2.?We studied the spatio-temporal distribution patterns of three common small mammal species, the bank vole Myodes glareolus; the field vole Microtus agrestis; and the common shrew Sorex araneus, in a 4-year trapping study carried out on six large islands, each containing a mixture of three main habitat types (forest, field and clear-cut). We experimentally released least weasels (Mustela n. nivalis) to some of the islands to see how the focal species respond to increased predation pressure. 3.?Both vole species were largely restricted to their core habitats (bank voles to forests and field voles to fields) at times of low population density. With increasing density, the relative habitat use of both species increased in the clear-cut areas. The common shrew was a generalist in its habitat use at all population densities. 4.?The release of the weasels changed the habitat use of all study species. 5.?The vole species showed a stronger aggregated pattern than the common shrew, especially at low population density. The vole aggregations remained in the same localities between seasons, except in the case of bank voles after the weasels were released. 6.?Bank voles and field voles avoided each other at high density. 7.?We conclude that intrinsically differential habitat requirements and flexibility to modify habitat use facilitate the coexistence of the two competing vole species in mosaic landscapes consisting of boreal forests and open habitats.