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Natural selection may influence the arrangement of individuals into mated pairs through either inter-sexual (mate choice) or intra-sexual selection (competition). A study of the American kestrel, Falco sparverius, in northern Saskatchewan distinguished between these two processes using size as a measure of the bird's competitive ability, and condition (mass scaled to body size) as an index of quality. Both sexes arrive on the study area after spring migration in equal numbers and males establish territories. Males and females that moved among territories at the time of pair formation were not different in size or condition from those that did not move, suggesting that birds were not being displaced by superior competitors,...
Wolf, Canis lupus, recolonization of the Greater Yellowstone Ecosystem provides a rare opportunity to identify behaviours facilitating coexistence between sympatric canids. We investigated interactions between coyotes, Canis latrans, and recolonizing wolves at ungulate carcasses in Montana's Madison Range. We used a field-experimental study design consisting of a two-level carcass treatment (wolf presence, wolf absence) to assess factors influencing coyote risk assessment, carrion consumption and aggressive encounters with wolves. Socially dominant coyotes (alphas and betas) responded to wolf presence by increasing the proportion of time spent vigilant while scavenging. Vigilance behaviour was more pronounced when...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Animal Behaviour,
Canis latrans,
Canis lupus,
agonism,
resource partitioning,
Age-related differences in dominance ability and the effect of prior residence on age-related dominance were investigated in captive male dark-eyed juncos, Junco hyemalis. To determine if adults and first-winter birdsnext term differed in their intrinsic dominance ability, pairs of adult and first-winter previous termbirdsnext term of equal body size and winning experience were established. Because plumage influences status, young previous termbirdsnext term were experimentally darkened to match their older cage-mates. Adult and first-winter males became dominant with equal frequency. Because of this result and the fact that adults are usually dominant in the field, the effect of prior residence on age-related dominance...
We examined the relationship between mate fidelity and breeding site tenacity during a 5-year study of the black turnstone, Arenaria melanocephala, a socially monogamous sandpiper breeding in subarctic Alaska. We tested the predictions of several hypotheses regarding the incidence of divorce and the benefits of fidelity to mate and breeding site. Interannual return rates to the breeding grounds (88% for males, 79% for females) were among the highest yet recorded for any scolopacid sandpiper, and 88% of returning birds nested on their previous year's territory. The annual divorce rate was only 11%, and mate fidelity was significantly linked to fidelity to territory but independent of sex and year. Males arrived in...
Extrapair paternity varies from 0 to over 70% of young among various populations of birds. Comparative studies have suggested that this variation is related to nesting density, breeding synchrony and the proportion of extrapair copulations. We used minisatellite DNA fingerprinting to examine levels of extrapair paternity in Ross's geese, Chen rossi, and lesser snow geese, C. caerulescens c. (hereafter snow geese) nesting in the largest known goose colony in the world. These geese have one of the highest known percentages of extrapair copulation (46-56% of all attempted copulations), and all of these appeared to be forced. Among all successful copulations, 33 and 38% were extrapair in Ross's and snow geese, respectively....
We tested whether routes of raptors migrating over areas with homogeneous topography follow constant geomagnetic courses more or less closely than constant geographical courses. We analysed the routes taken over land of 45 individual raptors tracked by satellite-based radiotelemetry: 25 peregrine falcons, Falco peregrinus, on autumn migration between North and South America, and seven honey buzzards, Pernis apivorus, and 13 ospreys, Pandion haliaetus, on autumn migration between Europe and Africa. Overall, migration directions showed a better agreement with constant geographical than constant geomagnetic courses. Tracks deviated significantly from constant geomagnetic courses, but were not significantly different...
Pair bonds can provide social benefits to long-term monogamous species alongside their benefits for reproduction. However, little is known about when these bonds form, in particular how long they are present before breeding. Previous studies of pair formation in long-term monogamous birds have been rather data-limited, but for many migratory birds they report pair formation on the wintering grounds. We provide the first systematic investigation of prebreeding association patterns of long-term monogamous pairs by examining entire life histories based on tracking data of migratory whooping cranes, Grus americana. We found that a substantial portion (62%) of breeding pairs started associating at least 12 months before...
The hypothesis that a late spring arrival and a dull nuptial plumage can aid yearling male passerines in avoiding aggression from territorial adult males was tested. Adult male black-headed grosbeaks, Pheucticus melanocephalus, were presented with three types of conspecific models: (1) adult male, (2) yearling male with bright plumage, and (3) yearling male with dull plumage. Models were associated with a song playback and were presented at (1) the time of adult male arrival and territory establishment, and (2) 2 weeks later at the time of yearling arrival and settlement. Test males were more aggressive toward all model types during early presentations than during late presentations. In addition, adult models elicited...
Data were collected, for 20 consecutive days, on activity patterns in Merino wethers in an outdoor experiment conducted in early summer. A bimodal frequency distribution was found in respect to the activity pattern. Eating and drinking were the principal activities apart from walking between the food and water sources which were 3�2 km apart. Long periods of each day were devoted to idling. Onset of activity was found to be highly correlated with sunrise but cessation of activity showed no relationship with sunset. The relation of these observations to behaviour of free-ranging sheep is discussed. Published in Animal Behaviour, volume 19, issue 4, on pages 3 - 3, in 1971.
A female can usually obtain enough sperm to fertilize all her eggs from a single insemination, and copulation involves certain costs such as increased exposure to diseases and parasites. Why, then, do females of so many species routinely copulate with more than one male? A 7-year study of marked individuals provides an answer for 239 female Gunnison's prairie dogs (Sciuridae:Cynomys gunnisoni) living under natural conditions. The probability of pregnancy and parturition was 92% for females that copulated with only one or two males, but was 100% for females that copulated with at least three males. Further, litter size at weaning varied directly with the mother's number of sexual partners. Published in Animal Behaviour,...
The annual 29 000 km long migration of the bar-tailed godwit, Limosa lapponica baueri, around the Pacific Ocean traverses what is arguably the most complex and seasonally structured atmospheric setting on Earth. Faced with marked variation in wind regimes and storm conditions across oceanic migration corridors, individuals must make critical decisions about when and where to fly during nonstop flights of a week's duration or longer. At a minimum, their decisions will affect wind profitability and thus reduce energetic costs of migration; in the extreme, poor decisions or unpredictable weather events will risk survival. We used satellite telemetry to track the annual migration of 24 bar-tailed godwits and analysed...
Extra-pair paternity is common in many socially monogamous passerine birds with biparental care. Thus, males often invest in offspring to which they are not related. Models of optimal parental investment predict that, under certain assumptions, males should lower their investment in response to reduced certainty of paternity. We attempted to reduce certainty of paternity experimentally in two species, the eastern bluebird, Sialia sialis, and the tree swallow, Tachycineta bicolor, by temporarily removing fertile females on two mornings during egg laying. In both species, experimental males usually attempted to copulate with the female immediately after her reappearance, suggesting that they experienced the absence...
Animals assess many factors when choosing how aggressively to behave during interspecific competitive interactions. Aggressive behaviour can help win resources, but it can also be costly. Here we tested how context such as competitor familiarity, habitat type and resource value affect competitive behaviour using two ant species, Formica xerophila and F. integroides. We found that competitive encounters within an individual's territory yielded more aggressive interactions than encounters in a neutral arena, and aggression towards competitors increased with resource value. Using a recently developed design combining behaviour assays between live ant dyads and ants paired with glass beads chemically resembling competitors,...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Animal Behaviour,
Formica,
Tit-for-Tat strategy,
ant,
behavior assay,
Socially learned vocalizations, such as the songs of many songbirds, commonly show repertoires and geographical variation or dialects, but we have only a limited understanding of the cultural evolutionary processes that produce these patterns. In this paper we describe the singing behaviour of populations of black-capped chickadees in Fort Collins, Colorado that represents the apparent evolution of a repertoire of song types. In contrast to most black-capped chickadee singing behaviour, which consists of a single song type that is remarkably invariant across North America, chickadees throughout Fort Collins sing three acoustically distinct song types. Individual males have an average repertoire of 2.8 song types...
Many animals benefit from the presence of conspecifics by reducing their rate of scanning for predators while increasing their time spent foraging. This group size effect could arise from a decreased perception of individual risk (dilution hypothesis) and/or an increased ability to detect predators (detection hypothesis). We compared individual and group vigilance of Rocky Mountain elk, Cervus elaphus, in three regions of Yellowstone National Park, Wyoming, U.S.A. that varied in their encounter frequency with coyote, Canis latrans, grizzly bear, Ursus arctos, and grey wolf,Canis lupus , predators. Adult females without calves increased scanning and decreased foraging with high encounter risk and small herd size....
Research has shown that territories of animals are economical. Home ranges should be similarly efficient with respect to spatially distributed resources and this should structure their distribution on a landscape, although neither has been demonstrated empirically. To test these hypotheses, we used home range models that optimize resource use according to resource-maximizing and area-minimizing strategies to evaluate the home ranges of female black bears, Ursus americanus, living in the southern Appalachian Mountains. We tested general predictions of our models using 104 home ranges of adult female bears studied in the Pisgah Bear Sanctuary, North Carolina, U.S.A., from 1981 to 2001. We also used our models to estimate...
Animals have evolved an impressive array of behavioural traits to avoid depredation. Olfactory camouflage of conspicuous odours is a strategy to avoid depredation that has been implicated only in a few species of birds. Burrowing owls, Athene cunicularia, routinely collect dried manure from mammals and scatter it in their nest chamber, in the tunnel leading to their nest and at the entrance to their nesting burrow. This unusual behaviour was thought to reduce nest depredation by concealing the scent of adults and juveniles, but a recent study suggests that manure functions to attract arthropod prey. However, burrowing owls routinely scatter other materials in the same way that they scatter manure, and this fact...
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