August 29, 2008

Warmer Nests Mean Healthier Mothers and Chicks, Finds Amherst College Research Team

AMHERST, Mass. – Heating the nests of tree swallows enables them to spend more time incubating their eggs and maintain higher egg temperatures as a result, according to Amherst College biology professor Ethan Clotfelter and his team of collaborators, who conducted a series of experiments investigating the energetics of reproduction in tree swallows in 2006 and 2007. Through the studies, Clotfelter and his research group also discovered that swallows whose nests had been experimentally warmed had higher body mass and fed their babies at higher rates, leading to healthier nestlings overall.

Biology professor Ethan Clotfelter examines one of his research subjects. Hear him discuss his studies in this multimedia presentation.

Their findings, which have been published in Biology Letters and the Journal of Animal Ecology, provide a better understanding of the evolution of reproductive strategies in temperate zone birds.

“It’s clear from these studies that changes in the thermal environment of the nest have profound implications for all aspects of avian reproductive biology,” said Clotfelter. He studied the birds with two former Amherst students, Elise K. Chad ’07E and Jonathan H. Pérez ’07; Pérez was the lead author on the Biology Letters paper. Also crucial to the research were colleagues Daniel R. Ardia, former visiting scholar at Amherst and now an assistant professor of biology at Franklin & Marshall College, and Margaret A. Voss, an assistant professor of biology at Penn State Erie.

In their experiments, Clotfelter and his team reduced the energetic constraints on tree swallows by heating their nests in specially designed boxes installed in the Amherst College Wildlife Sanctuary. Compared to a control group of unwarmed swallows, the heated birds spent more time incubating their eggs, maintained higher egg temperatures and then fed their hatched babies at higher rates. Females in warmed nests also lost less body mass than unwarmed females. Nestlings incubated in warmed nests had higher body condition and body mass, regardless of whether their mothers had been heated. The evidence indicates that warmed nests produce superior mothers and chicks, said Clotfelter.

“I think the most interesting finding is that heating some nests decreased the energetic costs of incubation for those mothers, which gave them an energy surplus they were able to draw upon once the eggs hatched out and the babies needed food every five minutes. This is an energetic demand that every parent, humans included, can appreciate.”

See Clotfelter and his current research students in action.

Founded in 1821, Amherst is a highly selective, coeducational liberal arts college with approximately 1,600 students from most of the 50 states and more than 30 other countries. Considered one of the nation’s best educational institutions, Amherst awards the B.A. degree in 34 fields of study.