![]() ![]() We discuss possible explanations why sparrow populations may not differ in competitiveness despite the smaller body mass of urban birds. Thus our results did not support the hypothesis that urbanization shifts population structure towards an over-abundance of weak competitors in house sparrows. Moreover, the variance in competitive abilities also did not differ between birds from more and less urbanized habitats. We found that sparrows exhibited consistent individual differences in competitiveness, but these differences were not related either to the degree of urbanization of their original habitats or to their body mass. Here we compared several aspects of their competitiveness (fighting, scrambling and searching for food) in captive mixed flocks of urban and rural birds. We previously showed that wild urban sparrows are smaller and leaner than rural conspecifics, and this difference persists for months under identical captive conditions. To evaluate this hypothesis, we tested whether competitive performance differs between differently urbanized populations of house sparrows Passer domesticus. Existing theory of this topic suggests that the cities' more constant food supplies and lower predation pressure lead to a high proportion of weak competitors in urban populations. How urbanization affects animal populations is in the focus of current ecological research. Our findings indicate that the significance of kin selection may be restricted in some social systems such as winter aggregations of birds. due to competition among relatives as predicted by a recent refinement of kin-selection theory. These results suggest that the pay-offs of reduced aggression towards kin may be low in non-breeding flocks of sparrows, e.g. Fighting success was also unrelated to kinship and the presence of relatives in the flock did not influence the birds’ dominance rank. We found that sparrows did not reduce their aggression towards kin, as neither the frequency nor the intensity of fights differed between close kin and unrelated flock-mates. To test this hypothesis, we investigated whether relatedness affects aggressive behavior during social activities in captive house sparrow (Passer domesticus) flocks. Sign up here to receive the RCC E-News and other RCC newsletters, information and alerts.Kin-selection theory predicts that relatedness may reduce the level of aggression among competing group members, leading to indirect fitness benefits for kin-favoring individuals. The Rachel Carson Council depends on tax-deductible gifts from concerned individuals like you. He is also the owner/art director of New Age Graphics, a full-service graphic design firm in Wheaton, MD. Ross also serves as a guide at the Patuxent National Wildlife Refuge, a frequent birding spot for Rachel Carson who first learned about the health effects of DDT at the laboratory there. ![]() ![]() Ross is a life-long birder and photographer who is the editor of the Friends of Patuxent National Wildlife Refuge newsletter. Ross Feldner is the lead, with Bob Musil, of the RCC Bird Watch and Wonder Program. Wrens: herd, chime The next time you’re at the beach impress your friends and say “will you look at that squabble of gulls!” Swans: wedge, ballet, lamentation, whiteness, regatta Watch this amazing murmuration of starlings in the United Kingdom! Other birds, such as dunlins, may synchronize a subtle tilt to their bodies while in a flight flock as a way to camouflage their plumage to confuse predators. This flock behavior is meant to quickly deter their predator, the fast and furious falcon. Birds drafting off of each other’s flapping wings can make the journey easier and less exhausting.Ĭertain birds, such as starlings, for example, form acrobatic flocks that can turn on a dime to create shapes and undulating feats in the air. Flocks of birds that fly in “V” formations may be doing so to conserve energy. Flocking can increase the possibility of finding food and protecting each other from trouble and predators. Most experts believe flocks increase the odds of survival and safety. Many make perfect sense, but some are real head scratchers.īirds form clusters of organized groups, called flight flocks, for a reason. Ever wonder what a group of turkeys is called, or maybe a flock of gulls? Most of us have heard the term a gaggle of geese but what about a group of cardinals? Here’s a fun listing of names for various groups of birds. ![]()
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