Chronicles

Tips For Beginner Birders With Mike Lushington by: Mike Lushington   5.      Birds of a Feather                                                                                                                                                                  As soon as a bird hatches, it begins to acquire its first set of feathers. This Juvenile Plumage, as it is called, lasts until into the fall when the young bird moults and replaces those feathers with its first Winter, or Basic,  Plumage. That, in turn, is replaced in the late winter or early spring with its first Breeding, or Alternate, Plumage. From then on the bird will undergo a partial or complete moult twice a year for as long as it lives.              That pattern - from Juvenile to Basic to Alternate Plumage - is the standard one for all birds, but there are many variations. Many birds add an additional stage after their first Basic plumage, a sort of "teenager" set of feathers for their first full summer. This pattern will resemble that of adult birds, but not completely; it might be nature's way of saying that the young bird is not completely ready yet to assume adult responsibilities. Other species, often larger birds, will undergo several sub-adult" plumages before achieving that full adult appearance. Several of the large gulls - our Herring gull and Great black-backed gull are two examples - will exhibit eight different patterns before finally reaching full adult plumages, these in their fourth year of life.              There doesn't seem to be any guideline to follow in determining which birds will have more or less complex patterning. Often, smaller species will have the simpler strategies, although many of them will have the "teenager" plumage that I mentioned above.Others, including the largest bird that we encounter in our area - the Canada goose - have very simple variations - from Juvenile to Adult, while eagles will have four or five stages. And then there are those gulls!              All of this begs the question: why so much variation? I have no idea, but I have learned one thing: whatever happens in nature does so because it affords some advantage to the creatures that exhibit it. There is a reason why large gulls will display nine plumage variations from Juvenile to Adult; we may not know that reason, but we can be certain that it occurs invariably, given only that the individual bird lives long enough.              However, there are some factors that we do understand. One of the more interesting ones has to do with the sometimes brilliant plumage exhibited by male birds during breeding season. It seems that those gorgeous feathers not only attract females (they do), but also predators. Thus that brightly coloured little bird singing so conspicuously from a tree top is proclaiming that he is a survivor - brave enough to show off, but cagey enough to be able to avoid a hungry hawk. In so doing, too, he is distracting attention from the female that may be sitting on a nest nearby, secure in her soft browns and dull whites. Once breeding is done, it must be noted, males shed their bright feathers for the drabber - and safer - colours of their Basic plumage, which they will wear for the bulk of the year.              It is interesting to note, too, that those male birds that share most actively in the brooding and raising of their young are often more conservatively clad than are those who share little such responsibility; brilliant colours around an active nest may well advertise helpless prey to any opportunistic predator.Thus many male ducks abandon the female soon after she begins to brood, while geese (where both adults are similiarly feathered) share in the raising of their young.      One thing is definite in all of this: why birds appear as they do is a very complex and intriguing question.

Links

Irene's Nature Page  Margaret's Gallery  Restigouche Naturalists' Club