Red for a reason
March 13, 2013 —
In my last column about webcams, readers were pointed to opportunities to intimately observe birds with the aid of modern technology. Those who prefer a more active role can consider participating in the Cornell Lab of Ornithology’s NestWatch project, in which “citizen scientists” are helping to provide answers to questions about bird nesting behavior by monitoring nests and reporting their observations utilizing online data entry tools.
NestWatch is a nationwide program designed to track trends in the reproductive biology of birds, including when nesting occurs, the number of eggs laid, how many eggs hatch and how many hatchlings survive. The database will be used to study breeding bird populations and how they may be changing over time as a result of climate change, habitat degradation and loss, expansion of urban areas and the introduction of non-native plants and animals.
Based on details of nesting behavior reported to the program so far, project leader Jason Martin recently reflected on the question of how a bird such as the Northern cardinal, which frequently nests close to the ground and is so visually conspicuous, can still be so abundant.
Despite its low rate of nesting success, with typically fewer than 40% of nests fledging at least one young, cardinals still thrive. Martin believes the answer can be found partly in the long breeding season, which may begin in late February and continue into September, allowing for more than one brood of young per year. As habitat generalists, cardinals successfully nest in a variety of habitats, building nests in the lower reaches of trees, shrubs or brush.
Their high survival rates may also be attributed to avoiding the stress of migration. One Pennsylvania cardinal was recorded to be at least 15 and a half years old.
The intense red color and vigorous song of the male serve as advertisements for mates. According to the Birds of North America Online, the intensity of a cardinal’s redness is related to the quality of his food source and indicates that he holds a good territory. Females respond to redness as a sign of a healthy mate, thereby encouraging the evolution of bright coloring in males.