We've been monitoring a dozen Wood Thrush nests this summer and about half have failed. We didn't have cameras on them until recently so we weren't sure why they failed. Yesterday, I finally checked out an SD card from a camera that was on a nest in Schnecksville, PA - an area of farmland.
One photo shows a red squirrel pulling a young fledgling out of the nest. What's remarkable is that red squirrels are largely restricted to pines. So what's this guy doing?
This nest was doubly damned. It also had a cowbird egg. So even if the squirrel didn't consume the nestlings the cowbird would likely kick out all the nestlings.