What Do Birds of the Year tell us?
This reminder from Randy Babb, AGF:
"During bad years it is not uncommon to see chicks in late June or even July or August. Some mistake these late broods for second clutches...particularly when there is good or moderate nesting success earlier in the year. Late chicks are not a sign of a good year. A very convincing bit of evidence that "second broods" do not regularly occur is the fact that the percent of young birds in the fall bag never exceeds 80% or 8 young per pair."
It follows that finding 60-80% Birds of the Year indicates a great hatch. Conversely, if Birds of the Year percentages are very low, say 5 to 15%, that indicates either a poor hatch or low chick survival rates. Checking your early percentages can give you a predictor of the season.
This reminder from Randy Babb, AGF:
"During bad years it is not uncommon to see chicks in late June or even July or August. Some mistake these late broods for second clutches...particularly when there is good or moderate nesting success earlier in the year. Late chicks are not a sign of a good year. A very convincing bit of evidence that "second broods" do not regularly occur is the fact that the percent of young birds in the fall bag never exceeds 80% or 8 young per pair."
It follows that finding 60-80% Birds of the Year indicates a great hatch. Conversely, if Birds of the Year percentages are very low, say 5 to 15%, that indicates either a poor hatch or low chick survival rates. Checking your early percentages can give you a predictor of the season.
Birds of the Year Reminder: So how do you identify juvenile birds of the year? With Scalies and Gambel's, check the primary covert feathers. See the center of photo (and click to enlarge.) David E. Brown, "Arizona Game Birds, c.1989, pgs, 6, 163-164, is a great resource for that. The small primary covert feathers just behind the front edge of the wing are mottled white with white margins on birds of the year. Adult carry-over birds have primary coverts that are completely gray, no white.
In center of photo see small primary covert feathers mottled white with white margins of a juvenile Gambel's bird of the year. Adult covert feathers are completely gray. Scaled and Gambel's are identified this same way. Mearn's young, however, have irregular barring on the covert feathers, so somewhat different means of identification. Click on photo to enlarge.
I've always had a tough time identifiying Mearn's birds of the year with their irregular barring of covert wing feather. BUT check the mature plummage and distinct fully developed head feathers of a mature male on the right vs. the juvenile, not yet distinct plummage of the bird of the year on the left.
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