Nature: Genetics play role in blue jay's lack of blue

NATURE
Jim McCormac

In my last column, I wrote about an unusual melanistic fox squirrel. Although the average fox squirrel is dashing in tones of rufous and brown, this one is black. Dark forms of the eastern gray squirrel are well-known in Ohio, including Columbus, but melanin-enriched fox squirrels are far scarcer.

The dark fox squirrel turned up in my Worthington backyard on Jan. 9. Three days later, I glanced out the back windows and did a double-take. A blue jay with a white head was wolfing down seeds at the feeder.

I’m writing this column on Jan. 26, and both of these odd critters are still frequenting the yard. Sometimes at the same time, which makes for interesting wildlife-watching.

The squirrel looks as he/she does because of an excess of melanin, or dark pigment. It’s the opposite with the jay. He or she — it’s tough to impossible to determine sex in the field — lacks dark pigments only in the head and neck area.

Animals with localized patches of white often are referred to as piebald. Commonly seen examples include white-tailed deer and American robins. These animals can be splotched throughout with white, have pale heads or other localized concentrations, or occasionally are nearly all white. The latter examples differ from true albinos in lacking pink eyes, and normally aren’t as bright white.

The genetic condition that typically causes piebaldness is leucism, and splotchy animals are said to be partially leucistic (loo-sis-tic). When I first saw the unusual blue jay, that’s what I thought it to be — a partially leucistic specimen.

Leucism is a genetic condition that inhibits normal melanin deposition, causing dark areas to become washed out. But genetics that cause color anomalies are complex and imperfectly understood. One can get bogged down in complicated and perhaps unverifiable explanations for various pigment anomalies. Other factors might be at work with this jay.

Suffice it to say, this blue jay is an extraordinary avian no matter the explanation for its unusual coloration.

Odd color genetics is largely a numbers game. The more common the species, the more likely that leucism will manifest itself. That’s why deer, robins and other common animals are the most commonly seen species expressing color mutations.

There are an estimated 15 million blue jays in the U.S., so it’s not surprising that leucism would rear its head in this species on occasion. A quick internet search will reveal numerous examples, but few of them possess the showiness of “my” jay (in my biased opinion).

Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature at www.jimmccormac.blogspot.com.