Here's what you should know about the blue jays in your backyard

Numerous recent reports of a local abundance of blue jays indicates a poorly understood behavior of the species: they migrate.

Well, some do; some don't. And those that migrate one year may not the next. Strangely, migrants seemingly have nothing in common: They're not the same age, sex, or heritage.

But they're not without good sense. As members of the Corvid family − including crows, ravens, magpies, and jays − they're acknowledged as the smartest creatures of the bird world.

We see them year-round, eating and even caching peanuts and other favored feeder seeds. One obvious clue to their sometimes-migratory habit, however, is their changing numbers at feeders.

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Surprisingly, a close look at individual jays will help birdwatchers recognize individuals, perhaps offering another clue about migration. While jays don't migrate out of North America, and mostly not out of the eastern half of the U.S., in winter the three geographic blue jay subspecies mingle with each other. Subspecies often wear slightly different shades of blue, so the irregular migratory habits add to the crossbreeding of some subspecies and account for color differences, especially in late winter.

Black facial markings also vary markedly, enough so that a keen eye will discern individual patterns. It's feasible, then, that backyard birders can pick out individual year-round residents and single them out from migratory visitors, distinguishing a northerner that may have joined the local flock that chose to stay the winter.

Such color variations and facial marking differences are unusual in the bird world, so identifying individuals adds another dimension to backyard birding.

Ornithologists nevertheless puzzle over jays' movements. True, thousands of jays migrate in flocks along the shores of both the Great Lakes and the Atlantic Ocean. Confounding the mystery is that in spite of known migration, according to BirdsoftheWorld.com, "individuals that depart an area in autumn may be replaced by those migrating from farther north."

So how can anyone fully identify which birds go where and which stay put? All in all, though, scientists believe that "the proportion of jays that migrate is probably less than 20 percent." The question remains: Why?

One expert suggested that "the propensity to migrate may be influenced by the fluctuations in mast abundance on a broad geographic scale." Perhaps last fall's drought reduced the acorns and other mast foods that jays crave and that such a shortage sent birds searching. Other scientists, however, find no consistent parallel to the mast supply-demand and migration.

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Migratory flight patterns are, however, observable and consistent. As strong, healthy-looking birds, jays almost always display apparent independence, even in flight. When they cross open areas, whether during migration or during more settled times, they fly singly, perhaps for safety. But even in migration, flying quietly in long strings, they usually move in small groups, no more than five to 15 together, seemingly independent even in migratory masses.

Unlike other songbirds, jays migrate during daylight hours. And those diurnal migratory flights are concentrated consistently in late April through late May − just as recent local reports indicate.

Several years ago, mosquito-borne West Nile virus hit the Corvid bird family hard, for they have no resistance to the disease. But their populations seem to have stabilized, and I celebrate the numerous bright, boisterous birds with us now, regardless of whether or not they're migrants.

For more information about birds and bird habitat, see Sharon Sorenson's books How Birds Behave, Birds in the Yard Month by Month, and Planting Native to Attract Birds to Your Yard. Follow daily bird activity on Facebook at SharonSorensonBirdLady, or email her at chshsoren@gmail.com.

This article originally appeared on Evansville Courier & Press: What do blue jays look like?