Of a Feather: Waiting for crossbills with crossed fingers

By BILL CHAISSON
Of a Feather
Last week, in a column about birds that we see only in winter, I mentioned the rough-legged hawk and that it deserved its own column. In fact, I wrote that column last November, so I will not repeat myself. Instead, I will dwell upon a couple of species that I have never seen, but very much hope to, now that I have decided to stay in a northern place. The red and the white-winged crossbills are finches, and they are known to breed in the coniferous forests of northern New England and Adirondacks.

But I have somehow avoided encountering them.

As their name implies, the mandibles of their bills actually cross at the ends. My ancient “Birds of America” volume, originally published in 1917 and republished without alteration in 1936, includes a charming description of this unique adaptation. Writing a full 68 years after the publication of Charles Darwin’s “The Origin of Species,” contributor L. Nelson Nichols notes that “all-wise man” would lament the “deformed” appendage of the crossbill, when in fact it is a marvel of evolution.

“An important part of the crossbill’s diet consists of pine-cone seeds, and these it readily obtains by means of its ‘deformed’ bill,” Nichols wrote. “The process consists of inserting the closed bill into the side of the cone, and then opening the mandibles with a movement which tears out the scales and thus leaves exposed the seeds at their bases. These seeds are then seized by the peculiarly shaped, scoop-like tongue.”

“Birds of America” calls the red crossbill Loxia curvirostra minor, while David Sibley presents it — in the first edition of his guide published in October 2000 — without the “minor” subspecies tag and allows that there may be nine different species of red crossbill in North America. They are distinguished by their different flight calls and diets, and, related to diet, their bill size and shape.

The genus Loxia ranges throughout the Northern Hemisphere and six species worldwide are generally accepted, including one of the nine ecotypes described by Sibley, the cassia crossbill (Loxia sinesciuris). The latter is regarded as a true species based on molecular genetic data and the specificity of its diet; it specializes in lodgepole-pine cones.

In the Northeast we have both red and white-winged crossbills, but they are not common as breeders. Some sources declare that they don’t breed outside of Maine, but the “Field Guide to Birds of New York” by Corey Finger states categorically that they breed in the Adirondacks and even in the central New York uplands. His information is apparently based on “The Second Atlas of Breeding Birds in New York State,” which documents 18 confirmed nests in the 1980-85 survey (for the first atlas) and 14 in the 2000-05 survey, with many more in the “possible” and “probable” categories.

The “Atlas of Breeding Birds of Vermont,” published in 1985, does not record the red crossbill as breeding in the state. The white-winged crossbill wasn’t observed during the observation period for the atlas but has been observed historically in the Northeast Kingdom in particular.

I do not yet own a copy of the “Atlas of Breeding Birds of New Hampshire,” although it does exist and was most recently updated in 1995. But many range maps indicate that the red crossbill breeds from the Adirondacks across northern Vermont and New Hampshire and into most of Maine. It is acknowledged to be scarce in this region, but the confusion, not to say contradiction, between generalized range maps and the specificity of atlas surveys is in part due to the irruptive habits of the bird.

During irruptive events crossbills can show up almost anywhere in the United States and, like other irruptive finches, they sometimes settle down to breed wherever they are instead of returning to their “usual” breeding grounds. Unlike most birds, they have two distinct breeding seasons, one in July-September when cones are ripe, and another January-April wherever cones are plentiful.

The Winter 2018 issue of Living Bird magazine reported that following the drought of 2016 and the wet spring of 2017 many coniferous trees in the Midwest and Northeast produced a bumper crop of cones. At the same time western cone crops were failing. The magazine predicted the largest irruption since the winter of 2011-12.

I spent the winter of 2017-18 outside of Saranac Lake in the Adirondacks and saw nary a crossbill of either species. Searching online, I didn’t find any evidence that it was an event for the ages, although there was a write-up in the 2017-18 winter issue of New Hampshire Bird. Irruption events, it turns out, are exciting to some extent because they are so hard to predict.

So, what are you looking out for? The red crossbill lives up to its name; the males have a red blush over much of their bodies with the wings and tails being charcoal colored. The females and first-year males are a greenish-yellow where the males are red. If you are lucky enough to live where they breed, the juveniles are streaked with brown on the breast and belly and have two narrow white wing bars. The size and shape of the bill varies widely. At least three, and in irruption years four, of the ecotypes can be found in the northeastern United States.

The white-winged crossbill, at 6.5 inches long, is slightly larger than the red and has a smaller bill. This smaller bill is due to the species’ association with smaller-coned conifers, like firs and larches. In addition to the broad white wing bars on its dark wings, the red of the white-winged males is tinged with gray along its sides. But the females are likewise greenish-yellow, and the juveniles streaked, but both with the distinctive wide wing bars.

The red crossbill ecotypes are distinguished by slight variations in the tone of their foraging calls, the sound is generally described as “kiip” (Type 1), “kewp” (Type 2),” or “kyip” (Type 3), but the flight call of all ecotypes is a hard “gyp.” In contrast, the white-winged crossbill call is a weaker and thinner “tyik-tyik,” according to Sibley.