Why are these swallows overwintering at a Northeast Philly sewage plant?

 

Why are these swallows overwintering at a Northeast Philly sewage plant?.

The mystery of the attraction of Philly sewer sludge.

I saw a gnat flying in my garden yesterday. And it was pretty chilly (46 degrees F). So, it is possible there is a smorgasbord of  insects at the treatment plant. And the winter was rather mild this year.

 

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