There is a good push of Red Crossbills into the northeast right now and we want to encourage everyone to make an effort to record the flight calls of any birds observed. One spiffy way to visualize the recent increase is through eBird’s line graphs, plotting frequency (percentage of total checklists reporting Red Crossbills) over time – here is the graph for 2017 where you can see the irruption beginning in May: Red Crossbill line graph for Maine in 2017
By recording flight calls, we can identify which ‘types’ of Red Crossbills are involved in this movement. There had been 10 distinct call types that Red Crossbills give in North America – the “Type 9” birds, geographically restricted to the South Hills of Idaho, were recently elevated to species status, and now known as the Cassia Crossbill. For more information on these types and where they occur, Matt Young wrote a great article in 2012 called “North American Red Crossbill Types: Statues and Flight Call Identification” available here: http://ebird.org/content/ebird/news/recrtype/ Matt reports that four call types have been recorded in central New York recently: Types 1, 2, 3, and 10. He added that Type 10 are starting to nest and Type 3 typically aren’t seen in the east until November.
A recent example of recording crossbills can be read from the perspective of a Maine eBird reviewer, Doug Hitchcox: I spent last weekend around Baxter State Park and managed to record a couple Type 10 birds. What I really want to emphasize is that you don’t need fancy equipment to get a decent recording to identify these birds to type. Here is a list from the first leg of our hike up Katahdin (Abol Trail) where I recorded a Red Crossbill flying overhead with my cellphone: http://ebird.org/ebird/view/checklist/S37970680 Despite the car doors slamming and people talking in the background, the stock “Voice Memos” app on my iPhone was enough to get a few “whit” notes as the bird flew overhead.
There is also a nice push of White-winged Crossbills in Maine right now: White-winged Crossbill line graph for 2017 in Maine. So get out there, enjoy these bizarre-billed finches and try pointing an audio recording device at the red ones!
Here are a few additional links on this topic, like these range maps for the three Red Crossbill types that have been documented in Maine:
And if you haven’t seen the link to the Fifty-eighth supplement to the American Ornithological Society’s Checklist of North American Birds, where Cassia Crossbill was named a unique species, you can access it here: 55th Supplement to AOU Check-list