On The Trails: Steller’s jays

A Steller's Jay poses for the photographer. (Photo by Bob Armstrong)

By Mary F. Willson

Jays are perhaps the songbird most familiar to Juneau residents. They are known by their bright blue plumage, with black head and crest.

They barge their way among other birds at feeding stations, grabbing what they choose; they yell at us from trailside trees and deck railings; sometimes they harass a curious dog that they perceive as meddling with their plans. They are officially called Steller’s jays (Cyanocitta stelleri), although local folks sometimes call them “blue-jays.”

A blue jay in flight. (Barbara Schelkle / CC BY-SA 4.0)

They ARE blue, but they are not true blue jays — that name belongs officially to another member of the same genus. The true blue jays (Cyanocitta cristata) live in the eastern deciduous forest region of North America (and occasionally roam more widely); they share many behavioral traits with our jays.

Steller’s Jays range from southern Alaska southward through the western mountains into Central America.

They eat a lot of different things and have varied ecological roles. In some areas, they harvest the seeds of oaks and some kinds of pines, caching the seeds in small pits dug into the ground; not all caches are retrieved and the seeds can germinate — thus, the jays are seed dispersers. They eat berries in season and may well disperse those seeds too (no data).

They are predators of many kinds of insects, some (e.g. dragonflies) caught in mid-air, some gleaned from bark crevices or foliage, some found by scattering leaf litter — they can even raid wasp nests for the larvae. They prey on small vertebrates, including the eggs and nestlings of other birds; raiding the nests of other species may be especially important when jays have their own young to feed.

And they are thieves, raiding the caches of other jays or woodpeckers, and scavengers of human seed feeders and detritus. Of course, they are also prey: to hawks (especially goshawk, Cooper’s hawk) and humans in some areas; squirrels, raccoons, snakes, and weasels may prey on their eggs and nestlings.

Our jays are socially monogamous, often making long-term pair bonds. Like other socially monogamous birds, they sometimes engage in extra-pair copulations, leading to broods of mixed paternity. Both members of a pair participate in nest-building, although females do most of the work.

A bulky nest is commonly placed in shrub or tree, close to the trunk. Females may lay two to five eggs and incubate them (although there is one report of male participation); males typically bring food to the incubating female. Both parents feed the nestlings and fledglings. For some reason, there have been rather few detailed studies of nesting behavior, so this paragraph is, of necessity, a bare-bones version.

Our jays are noted for the huge variety of vocalizations — we most often hear loud, rather harsh calls in some form or another. These have been described in detail, although their specific functions are less well known. However, here I want to focus on two other kinds of calls.

Jays are good mimics; they can mimic the calls of hawks and other birds, squirrels, dogs, and cats, as well as mechanical noises such as telephones, squeaky gates, and so on. Sometimes a mimicked call may be used to startle other jays away from a coveted food source or to warn other family members nearby. But could they also be done just for fun?

Less well known to most of us are the soft, more melodic little songs they sing at various times, performed mostly (but not entirely) by males sometimes in a social context but also in solitary settings. The function of these delicate songs is unclear. Try to listen for them!

• Mary F. Willson is a retired professor of ecology. "On The Trails" appears periodically in the Juneau Independent. For a complete archive of Mary Willson’s “On the Trails” essays, go to https://onthetrailsjuneau.wordpress.com