Stuff You Never Think About: How Do Crossbills Drink Water?


There’s things WC has never really wondered about until it’s right in front of him. Like, “How does a Crossbill drink water.”

Red Crossbill Female, Idaho City, Idaho

Red Crossbill Female, Idaho City, Idaho

Crossbills, for nonbirders, are a genus of birds with a specially adapted bill that allows them to quickly and efficiently pry open spruce and pine cones and extract the seeds. A Red or White-winged Crossbill can consume 3,000 seeds a day using that funky, offset bill.

Top: Crossbill feeding on spruce cone (drawing by J. Zickefoose). Bottom: Schematic of crossed bills and skull, showing how birds extract seeds from cones (D. Otte, redrawn from Benkman 1987b). Credit: Macaulay Library and the Cornell Lab of Ornithology

Top: Crossbill feeding on spruce cone (drawing by J. Zickefoose). Bottom: Schematic of crossed bills and skull, showing how birds extract seeds from cones (D. Otte, redrawn from Benkman 1987b). Credit: Macaulay Library and the Cornell Lab of Ornithology

The tongue is adapted as well, considerably longer, allowing it to probe further in than other members of the finch family. It’s a very cool set of adaptations to the species’ preferred food.

But it’s not a very useful tool for drinking water. Almost by definition, it’s a leaky bucket. So how does a Crossbill manage?

First, the Crossbill plunges it whole bill in to the water, much further than a bird with less specialized bills would. It’s a bit hard to see in this photo, but the bird’s entire bill, almost to the corner of its eye, is submerged. The mandible – the lower half of the bill – fills with water.

Red Crossbill Drinking, Step 1

Red Crossbill Drinking, Step 1

The bird lifts its head up, using its tongue – visible in this photo – as a kind of lid to hold the water in place.

Red Crossbill Drinking, Step 2

Red Crossbill Drinking, Step 2

And then the bird tilts its head back, drinking the water.

Red Crossbill Drinking, Step 3

Red Crossbill Drinking, Step 3

It’s not very efficient. WC counted and this bird took 14 sips; a Pine Siskin and a Cassin’s Finch took 4 and 5 sips, respectively. Yes, sample size equals one, But about three times as many sips.

There aren’t many settled issues about Red Crossbills. Depending on which ornithologist you are talking to, there are between one and eight species of Red Crossbills. But in WC’s mind, at least, the question WC had never wondered about before, how  Crossbill drinks water, is settled. Through clever use of its tongue, and every slowly.

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