Complexity of Winter Flocks

This Turkey Tuesday is about emerging data showing that the composition of winter flocks may be more complex and variable than we’ve believed. Our understanding of how winter flocks are structured comes largely from observational work done back in the 1960s. That work suggested that brood flocks (groups of poults with hens) in the summer ended up becoming the winter flocks we see each fall, composed of adult hens, juvenile hens, and often jakes. The juvenile hens and jakes were assumed to be full genetic offspring of the hens that raised them, so they were referred to as siblings – a human term if you will. Well, ongoing research being conducted by Sara Watkins is showing that the composition of winter flocks isn’t that simple. First, how flocks are structured appears to vary dramatically across the landscape. Members of winter flocks on some sites are closely related (true siblings, cousins), whereas on other sites they’re entirely unrelated or are only distantly related (have a common ancestor). Second, it appears that the most likely flocks to have related members are indeed those that have adult and juvenile hens, along with those jakes. But, on some sites, even those flocks are comprised of mostly unrelated birds, suggesting that blending of summer brood flocks into winter flocks may be more pronounced on some sites than others. Why does this matter? Well, having flocks of unrelated birds suggests that dispersal and genetic exchange are common, whereas having flocks of mostly related birds suggests a lack of gene flow. A lack of gene flow and dispersal at the flock level could matter, as research on other species has noted impacts such as reduced reproduction and fitness. The take home is, the winter flocks we see across the landscape appear to be more complex and dynamic than we’ve believed.

Photo © Tes Randle Jolly

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