A new study, headed by Ph.D. student Ryan Norris and his advisor, Professor Laurene Ratcliffe, shows for the first time that declining winter habitats of migratory songbirds significantly affect their ability to reproduce when they return north in the spring and the evidence is found in tiny drops of their blood.
The study, highlighted recently in the journal Science, and co-authored by Dr. Peter Marra of the Smithsonian Institute, appears on-line in the current Proceedings of the Royal Society: Biological Sciences, and will be published in an upcoming print edition of Proceedings.
"Our findings help explain why many species of long-distance migratory songbirds have declined over the last few decades," says Mr. Norris, noting that a relatively small geographic band across the Caribbean, Greater Antilles, and central America is the annual destination of an estimated five billion migratory birds flying south each year from Canada. The species in this study is a small, migratory warbler called the American redstart.
Until now, understanding how and why these migratory populations are declining has been a problem, since it is difficult to track individuals throughout their yearly travels. A new technique for detecting "biological signatures" provides the solution.
Using equipment and expertise of the Queen's Facility for Isotope Research (QFIR) headed by geology professor Kurt Kyser, the team measures stable carbon isotopes found in the warblers' blood. These samples are taken immediately after the birds arrive at the university's biological field station north of Kingston, Ontario in the spring.