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We have been studying cooperatively breeding superb starlings in Kenya since 2001. We conduct intensive behavioral, endocrine, immunological, and molecular studies using field observations, field manipulations, and captive experiments. We have shown that environmental variability drives much of the social behavior (breeding roles, reproductive conflict), physiology (stress hormones, immune function), and life history (offspring sex ratio). Using the entire group of African starlings (Sturnidae), one of the most socially diverse groups of birds in the world, we also studied how environmental variability influences the evolution of complex social systems. We have shown that cooperatively breeding species tend to be found in temporally variable environments where rainfall patterns are unpredictable.

For the past few years, we have been studying two additional species of co-occurring starlings from the same genus that have different social systems (simple cooperative and non-cooperative) and life history traits. Despite many similarities among these sister species, they have dramatic differences in their social behavior and reproductive life histories. We are examining the physiological mechanisms underlying reproductive timing in these co-occurring, closely related species, and we are also starting to look at seasonal trade-offs in immune function and other life history traits in this system.

Much of our work on African starlings suggests that environmental unpredictability plays an important role in the evolution of behavior, physiology, life history, and morphology in species living in the semi-arid tropics. One of the less publicized impacts of climate change is the increasing degree of environmental unpredictability and uncertainly that it will generate on a global scale. As environments everywhere become more unpredictable, it will be important to predict how species will respond to this increasing uncertainty. We are conducting a fine-scale analysis of avian physiology (stress physiology and immune function) over broad geographic scales (deserts to savannas to forests) to generate predictions about the future changes in avian physiological function as a result of global warming.

Our studies on the evolution of sociality in African starlings have led us to a similarly interesting, but complex system: social sponge-dwelling snapping shrimp. The genus Synalpheus is a species-rich group of sponge-dwelling snapping shrimp that exhibit a diversity of social systems that range along a continuum from a single pairs, to communally breeding colonies, to “eusocial” colonies with a single breeding queen and hundreds of non-breeders. We study a number of species, including Synalpheus brooksi, a species whose social structure is extremely complex and variable. S. brooksi lives in multigenerational colonies where the number of breeding females per sponge range from 1 to 15. Our molecular studies of kin structure suggest that S. brooksi live in extended family groups like many vertebrates. S. brooksi lends itself well to both experimentation and field studies; families can be housed in artificial sponges in self-contained aquaria, and the primary host sponge, the loggerhead sponge, is common across the Caribbean, including at our study site in the Florida Keys.

In superb starlings, we have been examining promiscuity and patterns of extrapair paternity. Although superb starlings exhibit one of the most complex social systems of any bird, they have relatively low rates of extrapair paternity.  However, we find that habitat quality influences variation in extrapair paternity among territories such that higher quality territories have lower rates of extrapair paternity and vice versa. We are testing these ideas further by looking at extrapair paternity rates in intact and degraded habitats, and we hope to begin large-scale ecosystem manipulation experiments to further test these hypotheses.

We are just beginning to comparatively study the mating systems of social snapping shrimp. We are looking at extrapair paternity rates in a number of species, but also patterns of sequential mating to determine how differences in mating systems might influence the evolution and maintenance of sociality.

Previous work involved using stable isotopes to better understand the population biology and life history of migratory warblers in North America. Although we know the breeding and wintering ranges for almost all species of neotropical migrant songbirds, we rarely know where individual populations of birds go. Using stable isotope mass spectrometry, we have gained new insights into the migratory patterns of these birds. We have helped develop new statistical techniques for analyzing isotopic data to improve the linkages between breeding and non-breeding populations, and we have helped synthesize the key issues and assumptions needed to design and interpret effective and insightful isotope movement studies

We have been developing a mathematical theory of sociality that explicitly considers the physiological and stress-related costs of group-living. This integrative and predictive theory synthesizes three disciplines (evolutionary biology, mathematics, biomedicine) and is grounded in evolutionary theory and physiological mechanisms. It has direct implications for social living in all vertebrates, and even links to human health. As we continue to develop these models, we will simultaneously test them in starlings using long-term data, newly collected samples, and captive experiments in the field using superb starlings. Ultimately, this research will help build a synthetic theory for understanding how tradeoffs in stress physiology and other physiological mediators influences the costs of sociality in vertebrates.

We previously examined how selective pressures (ecological forces and life history traits) influenced and/or constrained reproductive strategies, and ultimately governed lifetime reproductive success through tradeoffs among physiological condition, survival, and reproductive success in Galapagos marine iguanas. We were interested in how male reproductive success was influenced by physical condition, how environmental variation influenced reproductive timing, how steroid hormone levels varied seasonally and influenced male and female aggression in different reproductive contexts. We were also interested in how reproductive skew was affected by different male mating tactics and the costs of female choice, and how steroids vary in males that exhibit alternative mating tactics.

Kin selection plays an important role in the evolution of superb starling social systems. But how do bird recognize kin? We are studying the role of flight calls in kin recognition in this species. Although starlings sing complex songs, much like their European cousins, we believe that they use a series of flight calls to communicate with other group members. Using a long-term dataset of recorded calls and a series of playback experiments, we are examining how superb starlings communicate with and recognize kin.

The underlying physiological and genetic bases of sociality and its reproductive division of labor (castes) remain effectively unknown. Rather than focusing upon a single species to understand why some individuals forgo independent reproduction, we must study this question in a comparative context by simultaneously examining gene expression (transcriptome) in closely related species that show not only a range of social behaviors, but also a range of levels of physiological and morphological caste differentiation. Synalpheus snapping shrimp meet these criteria, and offer a model system in which to study the genetic and genomic bases of animal social behavior.

Using the African starlings as a model system, we have been examining how female-female conflict and competition influences the evolution of ornaments and other sexually-selected traits in social species where females often compete intensively for mates. We have shown that cooperatively breeding starling species are less sexually dimorphic in plumage and body size than non-cooperatively breeding species. These patterns are the result of increased selection on these traits in females, presumably because females in social species use these traits in competition for access to mates or other resources. We are now beginning a series of field studies to examine female-female aggression in social species including not only starlings, but also hummingbirds.

Although most of our research does not deal directly with conservation, much of it has important implications for the conservation of species and their habitats. Our work on neotropical migratory songbirds helped establish important seasonal linkages to help understand songbird declines throughout North America. Working and studying in Africa in particular has given us important insights into human-wildlife conflict and the plight of some of the world’s largest megafauna. For these reasons, we have been outspoken in our views on some of the more sensational conservation strategies, like Pleistocene Rewilding, a well-natured but misguided plan to return megafauna to North America. We advocate a cautious but optimistic approach to conserving species, ecosystems, and habitats.