“Understanding how and why birds
respond to changing climate patterns and food availability is
central to conservation and environmental management strategies.”
photo Paul Vuocolo
Survival of the fittest. Red crossbills migrate following bumper conifer cone crops. Red crossbills vary in their plumage color from yellow to red, depending largely on their diet. Shown here is an adult male.
Red crossbills live
in northern regions of North America, including Michigan. They feed on seeds within conifer pinecones, and migrate annually as far north as Alaska, following bumper conifer cone crops. “Conifers produce
cones in cycles, so seeds can be present in one region for several years and absent in other years,” Cornelius says. “The variable location of seeding conifers makes red crossbill migration risky.” Depending on the level of environmental stress, birds are in
photo Paul Vuocolo
Watchful eyes. EMU biology students closely monitor the migratory behavior of goldfinches.
years when they have a lot of food and other years when the food supply is low. We want to know what their baseline need is for reproducing under certain conditions.” Cornelius and other
research collaborators traveled in 2011 to Grand Teton National Park in Wyoming to study red crossbills that breed in all seasons. “The transmitters
emit a continuous tone,” she says. “I stood under a tree with a handheld
either a reproduction or a survival mode. Cornelius is studying red crossbill stress levels by implanting the birds with small heart rate transmitters. These devices measure heart and metabolic rates when the birds are engaged in activities like reproducing, migrating and molting (shedding and producing new feathers). “This study is the first to look at seasonal changes for this species,” Cornelius says. “We can compare the difference between
device that recorded their output. We followed 75 percent of the implanted birds for 24 hours, which was a pretty good success rate.” Cornelius also made some interesting observations about
implanted birds in her lab. “We limited their food supply or made the supply
unpredictable to study their response,” she says. “We noted the crossbills somehow use ‘public information’ to modify their perception of their environmental condition. A bird with limited
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