Immature birds feature distinctive qualities
November 24, 2008 · Updated 6:40 PM
By Frances Wood
A couple weeks ago a loud noise startled me as I stepped outside into a dark September evening. Halfway between a snarl and a bark, the piercing ``neeyah'' came from a large maple tree beside the house. Right away I recognized the sound: an immature owl saying ``feed me'' in ``owlese.'' I ran inside to get a flashlight, but its beam didn't reach high enough into the tree to let me see the young owl.
I waited and listened and soon heard the parents' deep, muffled hooting from another tree. It was the familiar sound of great horned owls.
It seemed strange to have a young bird calling for food at this time of year. Most of last spring's hatchlings -- particularly small and mid-sized birds -- are independent from their parents by fall. These smaller birds become mature and ready to breed by the following spring.
However the young of many large birds, including hawks, eagles, owls and gulls take two to five years to reach maturity. The owl I heard begging to be fed will remain near the parents until they begin nesting again. Then the adults will force it from their breeding territory and the immature owl will wander looking for its own territory. It will spend a relatively solitary life until it is old enough to breed in two to three years.
If I could have seen a silhouette of the immature owl, it would have been hard to distinguish it from the adult owl. All immature birds, even those that can't breed for another five years, attain adult size and shape by the fall of their first year although their plumage may be different.
We often see immature birds on Mercer Island. The large mottled birds that look like bald eagles, but without the distinctive white head and tail, are immature bald eagles. They take four years to reach maturity. The red-tailed hawk-like birds that don't sport a rusty red tail are immature hawks. Perhaps you've noticed cormorants sitting on pilings at Luther Burbank Park. The solid black ones are mature, but the ones with buffy or mottled breasts are immature. Red-tailed hawks and cormorants may begin breeding as early as the end of their second year.
The plumage of immature birds, often mottled and subdued, serves to camouflage and protect them from predators. Also, without the distinctive adult plumage the immature birds are left alone and not considered a threat or competition to breeding adults of their own species.
If you've spent time looking at gulls, you've noticed brownish ones the color of coffee and cream with dark bills. Those are immature gulls, different from the distinctive white- and gray-colored adults. Because gulls are common, fairly large and sit still, they make good study subjects if you want to observe the plumage changes as they mature.
For example, let's follow the changes in plumage for a young glaucous-winged gull, the most common gull around Puget Sound. The coffee and cream gulls were born last spring. Their plumage will fade somewhat during their first year, but the birds keep that general coloration until the summer of their second year, when they molt. The new feathers on their backs change to gray and the wings become a mixture of brown and gray. Their beaks remain dark.
During their third summer, immature gulls molt again and the brown feathers on the birds' bellies and tails drop away and grow in white. However, their heads continue to be mottled brown and white. The bills turn cream-colored with a black band.
Finally, at four years, the gulls lose any brownish camouflage and become brilliant white and gray. Their bill turns lemon-yellow with a red spot and the gulls are ready to breed.
So, while the fall weather is still inviting, visit a park or other natural area and watch the birds. Mixed in with the familiar adults, you may see immature birds. And if you hear an eerie crying in the night, don't assume it's an October ghost; it could be an immature owl, still begging for food.
Frances Wood is the author of ``Brushed by Feathers: A Year of Birdwatching in the West,'' which is available in local bookstores. She can be reached at firstname.lastname@example.org.