Mechanisms of seasonal flocking in emberizid sparrows
Over the years, most of our work has focused on species differences in stable, year-round patterns of grouping behavior, ranging from large flocks to territorial pairs. Our work in sparrows is designed to determine whether seasonal switches between territoriality and flocking are associated with plastic modifications of the species-specific mechanisms identified in finches. Thus, we are working with four species, all of which are territorial during the breeding season. Two flock during winter (field sparrow and junco), one is territorial year-round (song sparrow) and the fourth species loosely distributes in winter and is neither territorial or flocking.
This collection of species not only allows us to identify possible mechanisms that underlie seasonal flocking, but also mechanisms that may serve to suppress winter aggression. For instance, if the two flocking species exhibit a winter upregulation in some aspect of neurochemistry that is not seen in the other two species, this suggests a relevance to flocking. Conversely, if the towhee shows winter neurochemistry that is similar to the flocking species, and all three differ from the territorial song sparrow, then this may be a mechanism for the suppression of winter territoriality. We have completed a large immunocytochemical dataset, focused on six different peptides and enzymes (Goodson et al., "To Flock or Fight: Neurochemical Signatures of Divergent Life Histories in Sparrows," PNAS, 2012), and are collecting a complementary dataset on receptor distributions. The receptor work is being led by graduate student Leah Wilson, who is also conducting a series of pharmacological experiments in which winter neurochemistry is altered in order to directly examine effects on flocking.
Goodson, J. L., Wilson, L.C., Schrock, S. E. (2012) To flock or fight: Neurochemical signatures of divergent life histories in sparrows. Proceedings of the National Academy of Sciences of the United States of America 109 (suppl. 1), 10685-10692. PDF