Weekly Bird Report
9:38 pm
Wed September 11, 2013

Clouds of Tree Swallows Descend on the Cape and Islands

Tree Swallows
Tree Swallows
Credit Carol Foil / flickr

Even the most hardened nature cynic has a hard time shrugging off the wonder of a seething mass of graceful swallows. The Cape and Islands is a great place to observe this fall phenomenon. Counting the number of individual birds is problematic as the moving flock resembles a smoky cloud, not birds, as it twists and turns. However, with practice, and after analyzing photos, the art of estimating numbers of birds in enormous flocks, can be remarkably accurate. In our area these massive flocks of birds can range from two to three hundred thousand individuals.

Tree swallows, like most birds, have extremely efficient digestive systems for processing food. As flying animals, weight is critical and they must be able to get sustenance for energy but not carry the added weight. They eat the berries and shortly after excrete the seed. Swallow flocks leave a virtual blanket of bayberry seeds upon large parts of dune areas thereby assuring a new crop of plants into the future.