A group of northern rough-winged swallows have been spending winters at the Northeast Wastewater Treatment Plant in Philadelphia. They appear to be feeding on midges.
The swallow usually migrate south for the winter; they are not found as far north anywhere else in the country, according an article in the Philadelphia Inquirer newspaper. This winer, as many as 142 of the swallows have been counted at the plant.
Read more at http://www.philly.com/philly/blogs/greenliving/139992543.html.
