by Denny Olson
I have to admit that a good part of my attraction to tree-line in Northwest Montana — aside from pikas in the talus, whitebark pines, nutcrackers and rosy finches — is the 50-50 chance of a conversation with Boreal Chickadees. They are relatively tame and curious after the breeding season when they flock together in small groups. And to my aesthetic sense, they are cute as heck with that little milk-chocolate cap of theirs.
Boreal Chickadees (BOCH) aren’t particularly rare, but they demand some work to get to where they live. Lots of birders have never seen one. BOCH are as “boreal” as a critter can get, barely dipping into the far northern reaches of the contiguous U.S., and the highest treed elevations in the Northern Montana Rockies. They are most common where the spruce-fir forests are densest
, and are strongly associated with Engelmann spruce in the western mountains and black spruce in the east. They eat a variety of insects and spruce seeds, feeding acrobatically (like nuthatches) high in the trees. Like Tennessee and Nashville Warblers, population spikes are associated with fresh outbreaks of spruce budworms. In late summer they can be seen going back and forth from the treetops to the lower parts of trees to cache food for their winter supplies. They stuff the “pantry” (between spruce needles, and in bark furrows) and often use combinations of spider web and saliva to hold the food in place, with a bark-chip covering to hide the morsels. They even make aphid-balls by gluing a number of the tiny insects together.
The food-caching is particularly critical for them, even compared to other chickadees, because the true boreal forest often has temperatures dipping below minus 50 Fahrenheit! Black-capped Chickadees simply die of exposure when it gets that cold, but BOCH seem to “weather” it well. Like other Chickadees, BOCH nest in cavities and roost in them as well during those frigid nights. They can lower their body temperatures as much as 16 degrees to save energy overnight. In the morning they have to shiver for almost a half hour to get back to their 104-degree daytime operating temperature.
Because of their choice of environs, BOCH are obviously not well studied. But perhaps we can safely extrapolate from the adaptations of their closest relatives. Mountain Chickadees have this marvelous ability to grow the size of their brains annually by 30%, to more efficiently forage in winter, and perhaps just to ensure their larger brain will be warmer. I think it is reasonable to suspect that BOCH do something similar. This is a half-ounce bird after all, living in a very hostile winter environment, so thermodynamics are certainly paramount.
BOCH are very active, but also secretive, during the nesting season. They take from 2 – 10 days to excavate a nest cavity, depending on the softness of the tree heartwood. When a female is done with lining it to her satisfaction, she does her “come-hither” wing quiver to attract a male. He then gathers insects and seeds to feed her, demonstrating his provider ability, before she is willing to pair-bond. She lays from 4 to 9 eggs, and the fledglings from the hatch eventually will form their family flock — which is not exclusive
, and can even include Black-capped and Mountain Chickadees.
When predators like red squirrels or Sharp-shinned Hawks show up nearby, BOCH freeze instantly, holding the motionless pose for a good minute after the predator leaves. When a predatory squirrel appears around nests or fledglings, the adults sometimes go “cataleptic” as a decoy, quivering or even playing dead on the ground.
BOCH have declined (where they can be counted) 73% in the last 50 years according to National Audubon
, and are likely to be forced northward or higher with projected climate changes. Needless to say, get to where they live and watch some “terminal cuteness” (pun intended) while you can. And for their sake, shrink your carbon footprint!