Host use and fecundity of individual female brown-headed cowbirds

摘要: Abstract Descriptions of the laying behaviours obligate brood parasites such as brown-headed cowbird, Molothrus ater , typically fall into one two categories. These categories are ‘shotgun behaviour’, where females predicted to distribute their eggs apparently at random between available host nests, or ‘host selection lay discriminately, placing them most suitable nests. To test these hypotheses, data on individual female fecundity and use patterns required, but until recently, information has been largely unavailable. We used field observations genetic parentage analysis describe cowbirds over six breeding seasons Delta Marsh, Manitoba, Canada. Although some more than species both within seasons, other parasitized specific regardless availability. This nonrandom suggests degree in this population. also found that realized was low ( X ±SD=2.3±0.6 per female) compared with previously published estimates. Our results suggest behaviour lies a gradient extreme pure ‘shotgun’ selection’ behaviours, may optimize reproductive effort by varying environmental conditions dictate. When high-quality hosts not for parasitism, switch parasitizing lower-quality hosts. Flexibility cowbird be an adaptation enables individuals successfully exploit local temporal variation availability different Copyright 2003 Published Elsevier Science Ltd behalf The Association Study Animal Behaviour.