EFFECTS OF BREEDING EXPERIENCE AND FAMILIARITY ON SITE FIDELITY IN FEMALE RED-WINGED BLACKBIRDS

We used data from a 12-yr study of dispersal and breeding success to investigate how female Red-winged Blackbirds (Agelaius phoeniceus) make decisions about movements between nests, both within and between years. Females were studied on eight separate marshes that were sufficiently close to permit inter-marsh movement. Our analyses showed that (1) a female's previous success affects her subsequent nesting decision, especially between years; (2) females exhibit strong marsh fidelity; and (3) the presence of familiar male neighbors affects female movement decisions. Little support was found for the ideas that females move in response to different types of nest predators, familiarity with current mates, or nesting success of other females on their marshes. Our results suggest that (1) there is more social constraint on changing territories and marshes, especially within breeding years, than previously suspected, and (2) although mate fidelity is relatively weak and unimportant, male "neighborhoods" or "breeding groups" affect female nesting success and, hence, influence movements.