Birds on Stamps

Loxia curvirostra 

Loxia curvirostra

In English fi

The Red Crossbill, or the Common Crossbill (Loxia curvirosta) is one of the four crossbill species in the world. Of all the species in the family Loxia, the Red Crossbill has the widest distribution, extending to all the coniferous forests of Europe. The Red Crossbill’s nesting area covers the entirety of Finland, excluding the northernmost Lapland. The amount of the birds in our country is directly proportional to the seed production of our spruces, and because of this the stock can fluctuate heavily, causing the estimates of the bird’s numbers in Finland to vary quite a lot. During a bad year, the stock will decline down to 50.000 couples, while in the top years it might be close to 400.000.

By its appearance, the Red Crossbill is clearly larger than the Chaffinch, around the size of the Bullfinch. The male has a mostly crimson red coloration, excluding the dark wings. The female, however, has a grayish-green plumage with dark wings, and no lines on the belly. The young bird is of grayish color and clearly lined from below. The lines usually persist for far into the following winter.

The Red Crossbill can be confused for the Parrot Crossbill, as they are about equal in size – however, a keen-eyed observer can distinguish the Parrot Crossbill from its stockier and sterner overall impression, which might be due to its shorter neck, slightly larger head and stouter beak. The beak, upon closer inspection, can be used to distinguish the two species: the Parrot Crossbill’s beak is noticeably larger and shaped differently. Its upper and lower beak are about the same size, and the length of the beak corresponds with its width.  The peak of the lower beak is usually not visible from behind the upper beak. On the Red Crossbill however, the lower beak is visible, the beak is more slender, with the lower beak being narrower and  the entire beak being longer than its width. The differences is beaks can be explained with the food of the stronger-beaked Parrot Crossbill, the seeds inside of a hard pine cone. The Red Crossbill’s main choice of food can be found from within a much squishier source - a spruce’s cone.

The living habits of the Red Crossbill include some functions that cannot be found in any other bird species in our country, excluding other crossbills. With their crossed upper- and lower beak, the crossbills cleanly split in half the shells covering the seeds in pine- and spruce cones, thus gaining access to the seeds. The leftover cones from crossbills are easily distinguishable from other food waste, and so it’s easy to identify the crossbill as the culprit. A squirrel only leaves behind the core of the cone, and the cones picked apart by the Great Spotted Woodpecker are nothing but messy broken mush.

What are the reasons for the fact that during the ages, the Red Crossbill has evolved to nest during the cold of winter? The spruce’s seeds are likely to be most plentiful at that time, more easily accessible and probably at their peak in terms of nutritional value. What, then, are the reasons for the bird to have specialized in spruce cones? Well, there isn’t much of anything else to eat in a northern coniferous forest in such amounts throughout the year, so that’s probably where the Red Crossbill has found its own ecological niche.

Another specialty of the crossbills is the exceptionally early nesting. The Red Crossbill already begins nesting at February in the earliest, but most commonly during March. The female usually builds the nest high into a pine located at the edge of a spruce forest, while the male follows from nearby.  The nest is multi-layered, and thus quite warm. The female lays three to four light blue-green, dark-spotted eggs, and begins to brood right after having laid the first one. The male doesn’t participate in the brooding at all, but keeps the female fed, as well as the young birds that have hatched while the female is still brooding the rest of the eggs. Once all the eggs have hatched, the parents feed them together, with a diet consisting almost entirely of spruce seeds, which they regurgitate from their stomachs as a porridge-like mixture. The young birds leave the nest when approximately three weeks old, and the parents take care of them for yet another three weeks, until they have learned to feed on spruce seeds by themselves.

More birds

Tyrvään Lintu