I’m certain that thousands of folks have ventured to Brookside Cemetery in Tecumseh, MI this winter. There’s a lot to see and do in this quaint little town, but the burial ground has been the happening place as of late. Although a precious few may have been seeking solace there among the dead, most were actually out-of-towners in search of the living. As soon as a flock of White-winged Crossbills showed up on the rambling grounds, a flock of two-legged White-winged Crossbill watchers soon followed. I was part of that human flock.
These peculiar little finches are winter visitors from the high northern taiga forests. Their appearance in Lower Michigan created a mild stir among birders and photographers. Crossbills regularly extend their winter range down to this neck of the woods, but such “irruptions” (as they are called) are undependable and sporadic. A few years back they were even seen in cemeteries throughout NW Ohio and beyond. Why cemeteries? One might wonder if there is some creepy fascination with ancestor worship involved! The answer, however, lays not with what is below the ground at such places but what is growing above it – lots of evergreen trees. Crossbills are evergreen seed specialists and the mature stands of spruce and hemlock found at places like Brookside Cemetery offer a rich source of food.
When I went, there were about 12 individuals twittering about the Hemlock trees – two of them were human and the rest were avian. The birds were bunched into a tight flock (and the humans arranged in a loose flock around them). At first appearance the crossbills looked more like house sparrows because they were hopping around on the ground among the headstones.
Close examination revealed them to be a vari-colored bunch. Some -the male birds -were speckled with rose, orange, and off-yellow patches on their breast, back and rump. The female birds were yellowish olive and streaked with brown. All had the typical forked finch tail (say that three times) and all had two prominent wing bars. The wing marks, of course, are responsible for the common American name, although in Europe they are known as Two-barred Crossbills just to be contrary. Yes, the Euro-name is actually better than ours, but let’s not make a big deal out of it.
In spite of the Europeans, the Crossbill part of the name is universal across the northern globe. There really is nothing else to call these things. Their bills are definitely crossed. This feature is unique among the vast array of bill oddities found in the bird world. Only a half dozen bird species have it and they are all finches in the crossbill clan. In the case of the White-winged Crossbills, their lower mandibles project well out to the side and the tips do not meet – they are not even close. This asymmetric feature goes against most evolutionary trends but it is not at cross-purposes with evolution. This is a perfect adaptation for prying open cones. The smaller billed White-winged Crossbills are adapted to feeding on the smaller cones of black spruce, white spruce, tamarack, and hemlock.
When a crossbill approaches a cone (while hanging upside down or while on a loose cone on the ground) it inserts the open beak into the space between the scales and moves the lower (the crooked) mandible sideways. This widens the gap and frees the seeds which are scooped out with the tongue or with a sweeping action of the severely hooked upper bill. In the amount of time it takes to read those last few sentences a competent crossbill can pluck out two or three seeds. A slow crossbill could probably do 1. An un-crossed bill would be lucky to get .5 of a seed. In other words, these birds are really good at what they are designed to do. It has been estimated that they can extract over 3,000 seeds per day. Hemlock cones and seeds are very tiny (see below) , so it takes a lot to get a lot out of them.
There is one more amazing Crossbill fact that I’d like to fling at you before we leave these cemetery birds alone. The direction of the lower bill varies between individual birds. Some are right-handed (with the bill crossing to the right) and others are left-handed (with the bill crossing to the left). There are far more right-handed White-winged Crossbills than left handed ones. In fact, the ratio is 3:1. This is not the case with other crossbill species. It doesn’t seem to impart any advantage one way or the other, so it is probably a random matter of genes.
Dorsal view of left-handed and right-handed crossbills
Soon all the lefties and righties will depart for the northland. We’ll have to wait another year or two before we get a chance to see another one at our local cemetery. In the meantime, please Rest in Peace er…, wait a minute…perhaps that was not the best thing to say.