Space use and social interactions

I am interested in how animals with multiple, discrete phenotypes exhibit different behavioral strategies during non-breeding periods. Along with colleagues from Cornell University, we investigated differences in home range size and sociality among phenotypes of red-backed fairywrens near Brisbane, Australia. Red-backed fairywrens are an excellent study organism to investigate this question because they exhibit variation in social behaviors and ornamentation between the non-breeding and breeding seasons. Male phenotype varies within and between seasons, such that some males have ornamented red/black plumage whereas others have unornamented brown plumage. Importantly, in other fairywren species, displaying ornamented plumage for longer periods is a robust proxy for male mating success: males that complete the prenuptial molt into ornamented plumage earlier have higher extra-pair mating success. It is not clear if females select early molt as a sexually selected signal per se, or if early molt covaries with other male qualities that influence reproductive success.  By comparing home range size and social metrics among ornamented and unornamented birds, we found that phenotypic variation was related to in space use and social interactions in the non-breeding season. An interaction between plumage phenotype and habitat greenness in predicting home range size indicated that ornamented and unornamented individuals may have different drivers of space use. Unornamented males had smaller home ranges when they occupied greener habitat, indicating that space use by unornamented birds may be driven by food availability. However, in contrast to unornamented males, ornamented males ranged over large areas whether or not their habitat was green. This suggests that the driver of space use in ornamented males is social interactions rather than food availability. Measuring how phenotype affects non-breeding season behaviors, including space use and sociality, is an important first step in understanding how these behaviors in the non-breeding season may carryover to influence reproductive success in the breeding season. This can also indicate the degree to which female mate choice decisions may be taking place months prior to breeding. We are currently investigating this potential by analyzing paternity data to compare to non-breeding season social networks and breeding season reproductive success.

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