Hello and welcome. This is the Science of Birds.

I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners.

This is episode 111, and it's all about crossbills.

This is a special group of finches.

Crossbills are all the birds belonging to the genus Loxia,

and most ornithologists agree that there are six species in that genus.

Finches in general, members of the avian family fringility,

are specialized seed eaters.

They're granivores.

The typical bill of a finch is stout and cone-shaped.

It's an excellent tool for cracking open small seeds. Crossbills are among the most specialized members of the Finch family. They eat seeds, yes, but their focus is on the seeds hidden inside

the cones of coniferous trees. We're talking pine cones, spruce cones, and so on. From a distance,

you might mistake a crossbill for something like a house finch, but if you get a closer look,

you'll see that there's something really weird about its

beak, like it's deformed or something. The top and bottom halves of the bill are indeed crossed.

In this episode, we'll talk about why crossbills are so unusual, what's going on with that

strange beak, and why scientists have been fascinated by these

birds for a long time.

First, let's get familiar with the basic traits of crossbills, what they look and sound like.

If we ignore the bill for just a moment, if we just look at the body, we see that the body and wing shape of a crossbill are pretty typical for a small songbird.

Nothing unusual there. But I suppose the head might be on the large-ish side proportionally.

In terms of overall size, the six species are roughly similar, somewhere between 5.5 to 7.5

...