Its reputation as a nest-robber (mostly-undeserved) and its feistiness at the feeder make it unwelcome in some backyards, but its antics endear it to many feeder-watchers (including the BugLady), who secretly confess, “I know it’s a troublemaker, but I love watching it.” Its role as the neighborhood watchdog benefits other songbirds. And, it plants trees.

Ravens, crows, and Blue Jays (Cyanocitta cristata) are members of the Crow family and are considered to be very intelligent birds. As proof, scientists point to the richness of their vocabulary and the tightness of their family bonds. Blue Jay vocalizations are complex, and along with their loud “Jay, Jay” and “pump handle” sounds, they have a number of softer, more “conversational” call notes.

They can imitate the calls of several species of hawks, though scientists aren’t sure whether the jay is checking to see if hawks are around, is psyching out other songbirds, is scaring everyone else away from the feeder, or is just having fun. If it encounters a bird of prey, a Blue Jay’s excited “mobbing calls” attract other birds to harass the predator. A glance at its expressive crest can tell you if a bird is scared (a bristling crest), aggressive (an erect crest), or peaceful (a flat crest).

Males and females collaborate to build a cup-shaped nest, preferably in an evergreen, in which the female lays an average of four or five eggs. Totally helpless when they hatch, young Blue Jays continue to be incubated for a week or two, and they stay with their parents for two months. Both parents care for them.

Blue Jays are never totally absent in winter from the territory they inhabit in summer, but their migratory habits are quirky. Studies are contradictory, suggesting that from fewer than 20% to almost 50% of Blue Jays migrate in a given year, and huge flocks can be seen along the Great Lakes and Atlantic coasts (this fall, a hawk counter on the shores of Lake Michigan tallied more than 2,600 jays in four hours!).  While both old and young birds may migrate, some birds travel one year and not the next, and one banded Blue Jay become a first-time migrant at the age of five.

They migrate by day, coming down for a rest around midday and then resuming their flight. Blue Jay migration is probably food-driven, and the increasing popularity of bird feeders may encourage them to stay home. These are not long-distance migrants – many travel only a few hundred miles – but migration is still a dangerous undertaking, and birds that stay home tend to live longer.

Blue Jays measure nine to twelve inches – a little bigger than a robin – and males and females look alike. Their feathers are actually a dull brown, the blue color caused by physics, not by pigments (life is physics). It’s called a “structural color,” and it’s the result of the light bouncing off of feather barbs and being scattered by tiny air pockets in the feather’s “skeleton.”

They are omnivores, but only about one-quarter of their diet consists of animals like insects, spiders, snails, small frogs, mice or salamanders. Fruit, seeds, and nuts make up the rest (they are frequent flyers at the BugLady’s peanut feeder), and most of what they eat is wild, not cultivated. They may cache food, hiding it for later use, although in 1895, an observer noted that jays do not cache food unless they are permanent (rather than summer) residents of an area. According to the Cornell University Lab of Ornithology’s All About Birds site, “Their fondness for acorns is credited with helping spread oak trees after the last glacial period.”

Blue Jays are preyed on by hawks, and their eggs and nestlings are eaten by squirrels, cats, hawks, owls, crows and raccoons. Although the record for a wild bird is seventeen years, a seven-year-old Blue Jay is an old Blue Jay. Both jays and crows have been hit hard by West Nile Virus.

So, the Blue Jays that spend the winter at your feeder might be the same crew that you fed all summer, or they could be birds that migrated south to get there and replaced the summer residents, or they could be a little of each.

[Credit where credit is due: A version of this article (written by the BugLady, wearing a different hat) first appeared in The BogHaunter, the newsletter of the Friends of the Cedarburg Bog.]

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/