Effects of Breeding Experience and Familiarity on Site Fidelity in Female Red‐Winged Blackbirds

Abstract

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.

Dynamic versus static occupancy: How stable are habitat associations through a breeding season?

“…Past studies revealing patterns of nest abandonment and resettlement (e.g., Beletsky and Gordon 1991, Haas 1998, Hoover 2003 suggest that apparent moment at a population level may be driven by particular individuals that switch (''switchers'') to different cover-types as the breeding season progresses. However, within a population of breeding Song Sparrows (Melospiza melodia) in Pennsylvania, 25% of the population was firstyear males that began nesting late in the breeding season, whereas only 3.4% of the entire population nested in two separate territories within the same breeding season (Hughes and Hyman 2011).…”

“…For instance, birds often switch sites between nesting attempts in search of better habitat (Krebs 1971, Hoover 2003, Betts et al 2008). Even territorial species will move their territories after failed nesting attempts (Beletsky and Gordon 1991, Haas 1998, Hoover 2003. For instance, American Robins (Turdus migratorius) renest farther from previously unsuccessful nesting sites than successful sites within the same season (Haas 1998), and Black Kites (Milvus migrans) often abandon unsuccessful nest sites and attempt to renest in better habitat (Forero et al 1999).…”

Sequential mating patterns suggest extra–pair mating is not part of a mixed reproductive strategy by female red–winged blackbirds

“…Thus, their nest success, and hence mate ¢delity, was higher than when estimated for all nesting females. Although females appear to switch social mates for good reason, they did not appear to choose a new social mate that was superior to the mate they left, a result similar to that reported by Beletsky & Orians (1991). While this may re£ect the fact that females know their past success but must predict future success, selection should still only favour divorce when some bene¢t ensues.…”

“…Strong site ¢delity between years by both male and female red-winged blackbirds (Beletsky & Orians 1991;Weatherhead 1995) provides females ample opportunity either to be consistent in their choice of mates in successive years, or alternatively, to choose a better mate based on information gained the previous year. There was only equivocal evidence that females took advantage of these opportunities when choosing social mates, and no evidence that they did so when choosing extra-pair sires.…”

“…Weatherhead & Boak 1986;Beletsky & Orians 1991;Bensch & Hasselquist 1991). Thus, it is reasonable to expect that decisions a¡ecting EPF should be similarly £exible.…”