On the watch for snaggle-billed birds
Tis the season for many things, including the annual Christmas Bird Count. I’ll be going forth with Team Dublin as usual this Saturday for the Dublin segment of the local count. On Sunday teams will survey the Keene area.
This particular year we’ll all be watching conifer treetops and gritty roadsides with special interest.
That’s where two crossbill species are likely to be found — red crossbills and white-winged crossbills.
Unlike many bird species, crossbills are well named. It’s hard to see red on the belly of a red-bellied woodpecker; a ring-necked duck has a white ring on its bill and no discernible ring on its neck; a palm warbler should be called a northern-bog warbler. . . I could go on at length.
But crossbills do have seriously crossed, elongated bills, well engineered to extract seeds from closed conifer cones. They grab a cone with one foot and pry between the cone scales to extract a seed at each scale base with its tongue. Reportedly they move their way through branches like a parrot, using bill as well as feet to hold on. Their feet also are larger than those of most songbirds — all the better to grasp a conifer cone.
Crossbills move in flocks from small to very large in number and feed one tree at a time, consuming two to three thousand seeds each day. Their vocalizations communicate whether a tree has high-quality seeds, and when it’s time to move on to the next tree their chatter rises in volume.
When they set to work feeding, they’re quiet. If you’re walking in the forest and notice cone scales wafting down from above, you’re in the company of crossbills.
If you’re under a hemlock or a white pine tree, you’re in the company of red crossbills, while white-winged crossbills favor spruce and tamarack.
Their bills aren’t the only unusual feature of crossbills. They’re nomadic while other birds move north to south on predictable timetables and routes each spring and fall.
Like other nomads, crossbills follow the food resource. When they find a region with a boom crop of their preferred conifer cones, they’ll nest — even in the depths of winter.
As for watching gritty roadsides for these exotic visitors, crossbills ingest grit and salt most likely for mineral dietary supplements and to assist grinding up and digesting food in the crop and gizzard.
For some birds, salt is a fatal attraction. Tom Warren, ace and knowledgeable birder from Dublin, directed me to some studies that suggest salt toxicity impairs the birds’ reactions, making them more vulnerable to vehicle strikes. One study reports that winter finches are killed frequently enough in one region of Canada to be called “grill birds” by the locals, referencing the grills on the fronts of cars.
All vertebrates, humans included, require salt in their diet; and all vertebrates suffer salt toxicity when too much is consumed. Mammalian kidneys remove sodium more efficiently than avian kidneys do. Also, consuming too much salt leads to thirst, and drinking water in response to thirst helps the elimination of excess salt.
Both crossbills drink a lot of water — up to 20 percent of their body weight daily —perhaps as one way to help them handle their apparent over-attraction to salt.
The studies of road salt and avian toxicity are fairly recent and ongoing.
It’s a general cone crop failure in the Canadian boreal forest that has launched both crossbill species south of their usual winter range. More typically there’s a cyclical cone failure in one or two conifer species and just one of the two crossbills irrupt south.
Along with volunteers on the two Christmas Bird Counts coming up this weekend, keep an eye out for birds working conifer cones or roadsides. These winter finches are slightly larger than our state bird, the purple finch, and the males are rosier in color. Two white wingbars show up well on white-winged crossbills.
Irruption years are rare, and crossbills may not linger long in the region as our cone crop isn’t very robust either. We may experience them more as passersby or flyovers.
Stay tuned. We’ll know a lot more after this weekend.
The traditional post-count potluck is here at our house this year. Since the count began over 100 years ago, people have gathered at day’s end to exchange tales of the day’s adventures. We’ll probably go out to the backyard and hoot with hopes of an owl response. The count period is 24 hours, beginning and ending in the dark.
I hope to have a tale of crossbills. After researching this article, I now know to watch for parrot-like behavior as crossbills move about in a tree; and I know to watch for lethargic behavior as a sign of salt toxicity if Team Dublin comes upon crossbills feeding alongside the road.
Backyard Birder by Francie Von Mertens appears every other week in the Monadnock Ledger-Transcript.