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Archived Postings

July 10, 2006 – July 16, 2006

July 10 to July 16, 2006 We may try to deny it, but it has arrived….fall migration. The migration station has reopened with the binoculars now facing north to await birds to begin to pass over. Fall migration monitoring officially began on July 12. Most days throughout the opening week were greeted with strong winds. At times the winds were strong enough to keep the two most productive shoreline netlanes closed, which kept the banding total for the week to 123 birds. The wind blowing through the trees and the crashing waves made observations difficult. Although it was difficult to see or hear the songbirds in the trees, it was not very hard to notice the thousands of Franklin’s gulls that were flying overhead. Aging birds is one of the most important and, of course, one of the most difficult areas of banding. The key to aging birds is to understand moult strategies. Moult strategies are basically the patterns in which birds replace old with new feathers. The extent of the moult is dependant on the species, the age of the bird, and the time of the year. Both adult and young go through a moult on the breeding grounds before they begin migrating south. Young birds replace their wing coverts and body feathers; they lose their juvenile plumage. Adult birds completely moult all flight and body feathers; they resemble little footballs when they fly around with no tails. The adults primary flight feathers are replaced a few at a time (otherwise they couldn’t fly) and it is easy to see the contrast between the new fresh feathers and the old worn feathers. It is one of the easiest times of years to age birds now that all the different age classes are in the middle of their respective moults. Although it may be the easiest time of year to age birds, it may be one of the most difficult times of year to identify some species. Juvenile plumages often have only a few features associated with adult plumages. Sparrows are the best example of this. Sparrows are brown birds with streaks. The streaking on adult sparrows is distinct to each species. The streaking on juvenile sparrows seems to be universal among all sparrow species. It can be tough to figure them out, even in hand. Look hard at the size of the bird and any other distinct features (such as wing bars or tail spots) and you can start to narrow down some of the possibilities. Here’s one encouraging thought: young birds are in their juvenile plumages for a very short time, they will begin to look somewhat like adults very soon.

2010