During the final segment in the ascent of a high peak, before coming to the tree line, or on a trip through a lowland forest of spruce and fir, a very hoarse-sounding chickadee may be heard. While a novice birder or an inexperienced naturalist may assume that the individual responsible for this raspy chickadee song is the common black-capped variety with a bad head cold or a case of throat congestion, the more knowledgeable outdoorsman would recognize the voice as that of a cold-hardy resident of the far north–the boreal chickadee.
Aside from its similar call, the boreal chickadee is nearly the same size and has a color pattern that resembles its friendly, perky relative that is familiar to anyone with a feeder in his/her yard. When getting only a quick glimpse of one, seeing one in a dimly lit spot, or when its body is partially obscured by evergreen boughs, it is a challenge to distinguish between these two birds.
The boreal chickadee is known to some as the brown-capped chickadee because of the brown patch that covers the top of its head. This area of brown plumage occasionally extends down the back of its neck and a short distance over its back. Like the black-capped chickadee, the boreal chickadee has a black bib under its mouth; this colored marking however does not extent as far down its throat as the black bib on the body of its close relative.
Despite the intense cold that periodically becomes entrenched in those Adirondack lowlands covered with spruce and fir, or over high elevation slopes, the boreal chickadee remains a permanent resident of these conifer thickets. The limited variety of food in a spruce and fir forest causes the diet of this bird to be composed of only a handful of different items. The tiny kernel of matter attached to the papery-wing of the spruce seed is believed to be the main item of plant material in this chickadee’s diet.
A more important component of the diet of this omnivore is the invertebrate matter that it gleans from the twigs and foliage in this area. Insects in all stages of their life cycle, spiders, millipedes and various other bugs are all nabbed by a foraging boreal chickadee. Throughout the autumn, this bird collects as many invertebrates as it encounters and consumes as many as needed to appease its appetite. Those dormant larvae, pupa and inactive adults that are found after this bird has filled its stomach are placed in storage by the chickadee for consumption during winter. It has been discovered by researchers that a boreal chickadee is capable of remembering the location of thousands of individual items it has cached for use when additional food is required. The high fat content contained in the bodies of overwintering bugs helps this small bird achieve the high caloric level of nutrition needed to sustain its internal temperature during prolonged periods of intense cold. A crack behind a loose piece of bark, a crevice in a chunk of rotted wood, a small hole in a dead limb, and the pocket formed by a crotch of a split tree trunk are all places utilized by this bird to hold small stores of food.
The boreal chickadee is also able to survive the bitter cold of this region by lowering its body temperature shortly after reaching its roost at dusk. By entering into a nightly state of torpor, this bird can channel most of its energy into generating heat, rather than maintaining a metabolism that would also require a significant amount of energy.
The size of a winter flock of boreal chickadees tends to be smaller than that of its black topped relative. While the occasional red-breasted nuthatch or golden-crowned kinglet will temporarily travel with a flock of boreal chickadees, these birds are more inclined to associate with a flock of black-capped chickadees because of the more favorable weather conditions that prevail in settings that supports this familiar, backyard bird. With fewer boreal chickadees roaming a section of woods, there are fewer voices to be heard as they slowly meander through a stand of spruce and fir during the day. The less vocal foraging habits of the boreal chickadee and the limited visibility of the places that support this bird make detecting one a challenge.
On a hike through an upper elevation forest, it may seem that there is no life stirring, especially during winter. A patient person, listening carefully, may be able to hear a raspy sounding chickadee, which is a unique species well adapted for a life in the boreal zone here in the Adirondacks.
Photo courtesy Wikimedia user David Mitchell.