A Fascinating Finch | CAI

A Fascinating Finch

Nov 18, 2020

2020 has been a year to forget in so many ways. But many of us have been given a glimmer of hope in recent weeks, a beacon of light in a dark year. Many voices were heard, and their message was resounding and clear. “We are the winter finches”, they said “and we are here in big numbers."

Last month I covered the unprecedented irruption of Pine Siskins and hinted that this may be the best Evening Grosbeak irruption in decades. As of this week, there’s a new finch in town. It’s a species, or rather a vaguely defined group of biological entities, that laughs in the face of the biological species concept. It’s the Red Crossbill, a bird that, with every cheerful chirp, exposes the dirty little secret of biology:  that we really have no idea how to define what species are. Currently, ornithologists are not sure if Red Crossbills represent one or upwards of 12 species, each differing in call notes and bill structure.


Red Crossbills are like a bull-headed House Finch with a funny bill. Males are a dull brick red and females are vaguely yellow. Evolution has double-crossed these birds, or at least their bills – the mandible tips cross each other, allowing them to efficiently extract seeds from cones of various evergreens. That’s pretty much all they eat, even feeding cone seeds to their nestlings. The different subspecies often have different bill shapes to specialize on certain conifers, like Western Hemlock, Sitka Spruce, and so on. But their different call types have received the most attention from researchers, who can differentiate the types by looking at sonograms of the calls.

There’s a scene in The Matrix, where Joe Pantoliano’s character, Cypher, is watching the underlying computer code for the Matrix stream across a screen, and says to the Keanu Reeves character, Neo, that he doesn’t even see the code anymore, he just sees “blonde, brunette, redhead”. Replace Redhead with “Red Crossbill” and you’ve got “finch guys” Tim Spahr and Matt Young, the ornithological versions of Cypher. Birders send these guys their recordings, they convert them into sonograms. We see inscrutable squiggles, but all they see is distinct crossbill types. You can see these squiggles in the eBird reports of local birders, who have been including their field recordings in their checklists.

Tim Spahr is actually a local birder, a part time Cape Codder and finder of many rare birds at Fort Hill in Eastham. When he’s not deciphering crossbill call types, he’s busy with his day job as an internationally famous astronomer, one with both a comet and an asteroid named after him. And he’s manager of the International Asteroid Warning Network, meaning he’s in charge of letting us know if we are all about to be pulverized to dust by an apocalyptic asteroid. Maybe searching these twittering flocks of enigmatic songbirds for cryptic new species hiding within is not so different from discovering new comets and asteroids in the vastness of space.

Because several of the dozen or so Red Crossbill types wander the continent in search of good cone crops, we see multiple types on the Cape in an irruption year. Sure enough, Tim picked out four types from recordings of hundreds of Red Crossbills at High Head in Truro last week. Unlike other, feeder friendly finches, these guys probably won’t come to your yard unless you’re serving pine nuts, which at $30/lb seems unlikely. But you can learn their calls to pick out overhead flocks, and even contribute to the research by sending your phone or camera recordings to Tim at the crossbill project. Just don’t send him too many, because he’s got an important day job, and if a huge asteroid slams into the earth, ending life as we know it, that’s on you….