Mechanisms of grouping and territoriality in estrildid finches
Large-scale species differences in grouping behavior are surprising difficult to study in most vertebrate taxa, either due to lack of sufficient variation, or because species that differ in grouping also differ in other ways that confound the comparison. For instance, the species may also differ in mating system or the provision of parental care, and neural mechanisms that influence grouping may also evolve in relation to these other aspects of behavior. Because 1) all members of the finch family Estrildidae exhibit long-term (typically life-long) pair bonds and biparental care, 2) that territoriality and massive flocks are uncommon in this family, allowing us to examine independent evolutionary events at both ends of the spectrum, and 3) we can identify study species that occupy similar habitats and exhibit similar patterns of breeding, estrildid finches offer a virtually unique opportunity to study the neural mechanisms that drive large-scale species differences in grouping.
Over the years we have identified numerous aspects of neurochemistry and receptor distributions that evolve in relation to species-typical group size (see our Research Overview page), and have shown how some groups of cells respond to social stimuli differently across territorial and flocking species (e.g., Goodson et al., "Valence-sensitive neurons exhibit divergent functional profiles in gregarious and asocial species," PNAS, 2006). More recently we have been conducting experimental manipulations of those neurochemical systems to demonstrate direct relevance to the birds' decisions about group size. These include experimental manipulations of mesotocin and its cognate receptor (Goodson et al., "Mesotocin and nonapeptide receptors promote estrildid flocking behavior," Science, 2009) and both antisense and antagonist manipulations of vasotocin circuitry (Kelly et al., Vasotocin neurons and septal V1a-like receptors potently modulate songbird flocking and responses to novelty, Horm. Behav., 2011). Graduate student Aubrey Kelly is greatly expanding our work in this area through a series of antisense experiments in which nonapeptide production is knocked down in specific brain loci. Finally, co-PI Marcy Kingsbury is leading a new line of work that is focused on the grouping-related functions of vasoactive intestinal polypeptide, a widespread but little studied modulator of behavior.
Grouping represents only a subset of the work that we conduct in estrildids. These birds are also excellent for experiments focused on nesting and pair bonding (as in the work being conducted by graduate student James Klatt), and for studies of aggression. We have discovered that the neurochemical regulation of aggression varies dramatically across social contexts, such as competition for mates versus defense of nesting space or a territory, and most recently have identified the first cell type in the brain that functions solely to promote aggression (Goodson et al., "An aggression-specific cell type in the anterior hypothalamus of finches", PNAS, in press). For a full list of relevant papers, see our Publications page.
(1) Goodson, J. L., Wang, Y. (2006) Valence-sensitive neurons exhibit divergent functional profiles in gregarious and asocial species. Proceedings of the National Academy of Sciences of the United States of America 103, 17013-17017. PDF
(2) Goodson, J. L., Schrock, S. E., Klatt, J. D., Kabelik, D., Kingsbury, M. A. (2009) Mesotocin and nonapeptide receptors promote songbird flocking behavior. Science 325, 862-866. Abstract Full Text
(3) Kelly, A. M., Kingsbury, M. A., Hoffbuhr, K., Schrock, S. E., Waxman, B., Kabelik, D., Thompson, R. R., Goodson, J. L. (2011) Vasotocin neurons and septal V1a-like receptors potently modulate songbird flocking and responses to novelty. Hormones and Behavior 60, 12-21. PDF
(4) Goodson, J. L., Kelly, A. M., Kingsbury, M. A., Thompson, R. R. (2012) An aggression-specific cell type in the anterior hypothalamus of finches. Proceedings of the National Academy of Sciences of the United States of America. PDF