New Project on Montane Birds in Vermont

Great Hollow’s research fellow Dr. Sarah Deckel and executive director Dr. Chad Seewagen recently headed to Vermont to kick off a new study of the physiological ecology of Bicknell’s thrush, a rare migratory songbird that nests only on the highest mountain peaks of New York, New England, and eastern Canada. Bicknell’s thrush is uniquely adapted to the cold and wet climate of high-elevation zones, where few other bird species can also successfully breed and competition for resources is relatively low. However, climate change is altering these conditions and threatening to disrupt the current balance among species, making it important to understand what makes high-elevation specialists like Bicknell’s thrush better suited to their environment than the generalists that climate change may favor. One possibility is that the energy metabolism of Bicknell’s thrush is more efficient than that of other birds, allowing it to better thrive in the harsh conditions of mountaintops. Another possibility is that the plumage of Bicknell’s thrush is more insulative and water-repellant than that of other species, which would save energy in the face of cold temperatures and frequent precipitation. To test these hypotheses, Great Hollow is comparing the energetics and plumage water repellency of Bicknell’s thrush to the closely related Swainson’s thrush, which also nests at high elevation but in much lower abundance than downslope. In collaboration with scientists from the Vermont Center for EcoStudies (VCE), UMass-Amherst, and Old Dominion University, we are collecting feather and blood samples from Bicknell’s and Swainson’s thrushes at VCE’s long-term monitoring station on Mount Mansfield — Vermont’s tallest mountain. We are measuring an oxygen isotope, Δ’¹⁷O, in the blood samples to compare energy use between species and analyzing the “hydrophobicity” of the feather samples to compare water repellency. We are also examining energy use in relation to temperature and precipitation to investigate whether Bicknell’s thrush incurs lower energy costs than Swainson’s thrush during particularly cold and wet days and nights. The findings of the study will help us understand the threat posed to Bicknell’s thrush from Swainson’s thrush and other competitors that may further expand into high-elevation areas as a result of climate change.