Abstract
Open-ended learning of flight calls has been found consistently in the subfamily Carduelinae. Understanding call learning is especially important in Red Crossbills (Loxia curvirostra complex) because calls appear to play an instrumental role in assortative mating, perhaps by acting as a marker trait that signals ecological adaptation for foraging on a particular species of conifer. We analyzed flight call recordings from a banded population of the South Hills (call type 9) crossbill to examine whether young birds imitate the calls of their parents and whether, as adults, individuals modify their calls to match those of their mates. The calls of offspring were more similar to the calls of their parents than to the average adult in the population. This indicates that calls are, at least initially, culturally inherited from parents and thereby could act as marker traits. Adults did later modify their calls to match the calls of their mates, which presumably aids in individual and pair recognition. Comparisons within individuals over time also showed that call structure decreased in similarity to the calls of crossbills with another type of call (type 2) that regularly occur in the South Hills of Idaho. This should make it easier for individuals to distinguish between individuals of different call types. However, one of 91 crossbills recorded over more than one year changed the type of its call. This type 2 female bred successfully with a type 9 male for two years and by the second year changed her call to match that of her type 9 mate.
Highlights
Vocalizations are critical for communication in birds, influencing social interactions, mate choice and reproductive isolation (Mundinger 1970, Kroodsma and Byers 1991, Slabbekoorn and Smith 2002)
Understanding call learning is especially important in crossbills because calls appear to play an instrumental role in assortative mating, perhaps by acting as a marker trait that signals ecological adaptation for foraging on a particular species of conifer (Smith et al 1999, Snowberg and Benkman 2007)
Three important findings arise from this investigation of crossbill flight calls
Summary
Vocalizations are critical for communication in birds, influencing social interactions, mate choice and reproductive isolation (Mundinger 1970, Kroodsma and Byers 1991, Slabbekoorn and Smith 2002). One species of cardueline finch, the Pine Siskin (Carduelis pinus), imitates the calls of flock mates This suggests that call learning in carduelines may relate to pair bonding but may play a role in the recognition of flock mates and group identity (Mundinger 1979). Understanding call learning is especially important in crossbills because calls appear to play an instrumental role in assortative mating, perhaps by acting as a marker trait that signals ecological adaptation for foraging on a particular species of conifer (Smith et al 1999, Snowberg and Benkman 2007). Such shifts in call structure would cause us to overestimate the extent of assortative mating by call type
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