Last year we had the snowy owl irruption, and this year it is looking like crossbills are the irruption species of choice. Thanks to Harry Potter and Hedwig almost everyone knows what a snowy owl looks like, but no one has written a book (and made subsequent movies) about a wizard boy and his mail carrier crossbill, so a little bit of an explanation may be in order.
Crossbills are aptly named for the interesting biology of their beak. The tips of the beaks are (yup you guessed it) crossed. This makes it all the better to crack cones with (ok sorry slight off topic diversion to the world of Little Red Riding Hood).
There are two species of crossbills that are making a presence in PA at the moment: Red Crossbills and White Winged Crossbills. It is predicted that the Red Crossbills will make more of a splash than the White Winged Crossbills, but it is important to look for (and listen) both. If you come across a Red Crossbill vocalizing and have the capacity make sure to record the sound. There are different "Types" of Red Crossbills and the Cornell Lab for Ornithology wants to hear the vocalizations for data on the "Types" that are being seen. As you may imagine, the identification for the various types is in the sound that they make, and birders are at the ready with their recording devices as they hunt the Red Crossbill.
These birds are stocky finch-like birds that will be found in coniferous forests. They have nomadic habits and heavily rely upon the cone crops for survival. These birds will breed at any time of the year as long as the cone crop is sufficient for survival of their young. Spend time scanning the tops of the evergreen trees--especially spruce and fir to find your own crossbill sighting this fall!
To hear vocalization of the Red Crossbills go HERE
. White winged Crossbills can be seen and heard HERE