By performing DNA analysis on the feathers left behind at nesting sites, the researchers were able to identify individual Eastern imperial eagles in a nature reserve in Kazakhstan. Their analysis showed that not one adult strayed from its mate - a degree of fidelity highly unusual among birds, the vast majority of which mate with and raise offspring from multiple partners.
Not only is this study the first to confirm monogamy in eagles, more importantly, it also is the first to rely on feathers collected "noninvasively," or without trapping and handling, to provide a source of DNA to determine relationships among individuals and determine various population parameters.
"That we were able to use feathers we collected noninvasively as a source of DNA is the number one thing scientists will be interested in," said Andrew DeWoody, associate professor of genetics and senior author of the study, which was published online Friday (July 1) in the journal Molecular Ecology.
"People have been doing studies like this for several years with mammals, but this is a first for birds."
By developing a protocol for extracting DNA from feathers, the researchers also have added another tool to help conservation biologists study rare and elusive birds of prey.
The researchers used a technique called DNA fingerprinting to help them genetically "tag" individuals in the population without capture, said Jamie Rudnick, the paper's first author and a graduate student who conducted the study as part of her doctoral thesis.
"Collecting feathers at the nest site helped us determine population parameters we wouldn't have been able to otherwise," she said.
Those parameters, such as yearly survival rates and ratios of males to females, help conservation biologists monitor populations of ra