Crossbills on Canaan Street

A male (below) and female (above) Red Crossbill peer out from the salt-saturated ancient sugar maple trunk on Canaan Street.

The finches of the Galapagos islands helped Darwin develop his theory of evolution with their beaks. Darwin realized that these drab birds had managed to sort themselves into different species by varying nothing much other than their beaks. The drab little birds with the very chunky beaks are the only ones who can open certain very tough nuts and seeds. Now, they can only have babies with with the other drab little birds with very chunky beaks. The very drab little birds with the slender beaks, can gain access to some food source tucked deep inside something. That way, they can keep themselves fed without ever stepping on the toes of their big-beaked brethren who are busy over there cracking rocks.

In other words, bird beaks are more important and specialized than most of us usually think about. Enter the crossbill. The king of specialized equipment. That’s him at the top of this story. Notice that the tip of his beak does not meet in a nice, normal point. No, the points cross over one another in what appears to be a manufacturing error. But, of course, it’s not a bug, it’s a feature. Crossbills live almost exclusively on the seeds of pine trees. The shape of their bill allows them to pry open pine cones that have not  yet spread their scales and snatch the nutritious growing seed inside. That’s it. The whole beak evolved so they could be the first ones to eat pine seeds.

So when I saw a large flock of crossbills on Canaan Street fighting over access to the base of a very old sugar maple, I wondered why. There aren’t many pine seeds on a sugar maple.

There are eleven crossbills on this old tree trunk.

A little research turned up the fact that crossbills require minerals in their diet. I don’t know how they were originally supposed to fill this requirement, but they have come to fill it by utilizing our road salt. Journal articles document them licking tree stumps in road-side moose wallows because salts are concentrated in the wood.

This is probably what these crossbills were doing mobbing that tree on the Street for a week or so in March. On the photo below left, you can see the tiny pink tongue of the bird. You can see a tongue in the photo below it, also. More on tongues at the end.

But not all the crossbills were focusing on the salt-saturated base. Every now and then, one or two of them would try their luck higher on the tree, where there had to be less salt. Since I was basing my assumption on nothing more than observation, I had to ask myself whether the salt was really their objective or was there something else involved.

You can see this guy's tongue probing the disintegrating wood.

After looking at the photos I took, I realized that there was something else involved. This flock of crossbills contained many juveniles.

This is a juvenile Red Crossbill

The reason that juveniles might explain why some birds looked for salt in all the wrong places is that juvenile birds make mistakes. We don’t think about animals making mistakes. They don’t make a lot of them. A few mistakes in a row can cost an animal its life. But juvenile birds are a wonderful exception to that rule. They make mistakes routinely. It’s not their fault. They grow feathers long before they grow brains.

They do this because a baby bird is the world’s universal snack food. They are vulnerable to almost anything that’s hungry. Baby birds, at birth, do nothing but grow feathers until they can get out of the nest because in the nest, they are sitting ducks (or cardinals, blue jays, loons, etc.) Their parents continue to raise them on the wing. Which is why you will see a perfectly normal-looking bird helplessly flapping its wings at another perfectly normal-looking bird who, in response, feeds the flapper.

The point of this is that sometimes a perfectly normal-looking bird is an idiot who doesn’t have any experience of the world.

You can see this bird's tongue probing the wood. He has a combination of yellow and orange that is how the books describe juvenile male markings. But he's looking in just the right place for salt saturated wood.

But this raised another problem. What were juveniles doing on Canaan Street in March?Birds nest in the spring and raise their babies in the summer. I saw this flock in March. There were juveniles. Help.

A bit more research turned up the fact that crossbills, unlike most birds will, indeed have a brood in the winter if conditions are favorable. And they were favorable. That’s why they were here in the first place.

We had an epic white pine pinecone crop this year. It was such a feast, that the crossbills who do not usually visit places this far south, not only moved in for the winter, they had a bunch of kids. So, if you remember stirring up a bunch of nondescript birds at the base of that old sugar maple on Canaan Street a few months ago, you saw something pretty unusual. A bird that shouldn’t be here doing something you wouldn’t expect it to do!

A note about tongues

I have never photographed so many bird tongues in all my life. Part of the reason for all the tongue photos, I assume, is that the crossbills were licking the tree. As a person who has both observed and photographed birds for years, I can tell you, most birds don’t lick anything. They bite, they peck, they dig. They use their bills as scoops when they drink. Other than hummingbirds, I haven’t seen any licking.

This is pure speculation on my part, but I ran into a very complicated article that described how crossbills ate. It’s specificity was such that it noted that the foot used to stabilize the pine cone varied in line with whether the bill crossed to the right or left. I tried to imagine how this shape of beak and placement of foot facilitated the snatching of pine seeds from inside the cone. The beak is busy holding the scales apart and the foot is busy stabilizing the situation. What do they use to snatch the seed? I wonder if the crossbill’s very strong tongue doesn’t flick the seed into the mouth. Whatever the cause, they sure do like to show off those tongues.