My Interests

I am an ornithologist with strong interests in physiological, evolutionary and behavioral ecology. In my present work, I explore the causes of temporal and spatial variation in the life histories of birds, focusing mostly on breeding biology and movements. Though I have an abiding fondness for birds in the Charadriiformes, since the mid 1980’s I have been focusing on Tree Swallows (Tachycineta bicolor) in my studies of life history variation. Swallows are obligate aerial insectivores during the breeding season, and because air temperatures in spring often are too cold for aerial insects to fly, food availability for swallows can go from feast to famine over a few hours swallowswith the passage of a cold front, leading to our current focus on the effects of weather and climate change on swallow reproduction. We are developing, through a Long Term Research in Environmental (LTREB) grant from the National Science Foundation (NSF), a sensor network of 25 instrumented boxes in Ithaca, each of which contains a web-cam, egg and nest-chamber thermocouples, a Radio Frequency Identification reader and a Peltier device to cool or heat the box contents. All these nodes are networked to a common server to allow us to observe and control temperature, etc. remotely. With these boxes, we are gathering detailed information on the effects of nest temperature on patterns of parental care and offspring development, and we have coupled this work with experimental work on the effects of temperature on flight performance in insects to allow us to better predict and understand organismal responses to climate change.

One of the key aspects of biology underlying avian life histories is how the activities of birds affect their chances of survival and how the increasing age of individuals affects their abilities to be good parents. This biology thus mediates the costs of reproduction and connects individual-level biology with life history theory. It is for this reason that I have been happily engaged with Carol and David Vleck and their students in a study of aging biology and age-effects in Tree Swallows. Using our large population of known-aged Tree Swallows, we have been conducting detailed studies of telomere dynamics and the effects of various biochemical processes on telomeres in known-aged individuals in the wild. A four-year NSF-IOS grant experimentally testing the effects of oxidative stress on telomere shortening and other aspects of intermediate mechanisms recently concluded, and we are continuing with other comparative work exploring the role of telomere variation on life-history variation and flexiblity.

Another key aspect of the life histories of swallows that has fascinated me for years is where the swallows go and what they do when they are not tending to reproduction in their nest-boxes. Recently, many years after the excellent start by Curt Burney on the large swallow roost near Ithaca, we have two new collaborations on roosting and migration. First, Daniel Sheldon recently completed an NSF Bioinformatics Post-doc (co-sponsored with Thomas Dietterich at Oregon State) to systematize and make available in real time the changing distribution (and if possible, the size) of roosts all around the country as revealed in Doppler weather radar. This work will complement a new collaboration with Caz Taylor (Tulane University) and Ryan Norris (Guelph University) on the connectivity of Tree Swallow breeding populations with their wintering areas in the U.S. and Mexico. This project will give us a species-wide look at how the migrations of swallows fit into their overall annual cycles. We are using new solar-geolocation loggers  developed in Britain and Canada together with those developed with Cornell engineers Rich Gabrielson and Rob MacCurdy in collaboration with Eli Bridge at the University of Oklahoma, and we are keen to learn more about the role of annual movements in the lives of these birds.

We did a good deal of work on both natal and breeding dispersal in Tree Swallows in the 1990’s with a team of about 100 volunteers around New York and surrounding states. We were never able to fund this work as well as we think it deserved, and I feel that the way forward in studying dispersal in swallows is to develop methods to radically increase our chances of recapturing a given bird. This would allow us to better understand the process of dispersal by allowing us to relate differences in, e.g., individual experiences as a chick, to the resulting pattern of dispersal that the individual displays. For some years, we have been working on a “dispersal tag” that would allow us to use modern solid-state technology to dramatically increase the chances of finding a bird once it has dispersed and begun breeding at a site far away from the nest from which it fledged. Working with MacCurdy, Gabrielson and Cornell engineer Steve Powell, we have recently created a family of entirely solar-powered tags that seem finally, and very simply, to fit this bill.

This work on migration and dispersal gets us thinking about spatial ecology, and this focus takes me back to a very long-standing theme in my research: the basis of geographic variation in life histories. Tree Swallows, with their congeners in the genus Tachycineta, comprise an excellent system in which to explore these questions through the full range of latitudes in the Americas, from Alaska to Tierra del Fuego. Starting in the late 1990’s, I began thinking of a network of collaborating scientists studying the nest-box populations of Tachycineta throughout the Americas. And now, almost a decade later, the Golondrinas de las America network is finally starting to take off. Recently supported by a five-year Partnership in International Research and Education (PIRE) grant, we deployed approximately 15 students per year to sites from Ushuaia to northern Alberta in a collaborative study of the causes of geographic variation in the clutch sizes of these very accommodating birds. Even though the PIRE grant is finished, we remain dedicated to continuing the Golondrinas network with collaboratively funded research in comparative ecology and breeding biology. All our teams use standardized methods to gather information on all aspects of the breeding biology and ecology of these birds.