Except for the monotonous droning of cicadas and katydids, August is a quiet month. Most birds have wrapped up their nesting season. Sex hormone levels have plummeted, and males no longer have a powerful urge to sing to attract mates and defend territories.
Instead, most birds’ energy this time of year is devoted to another critical life event — molting, or the replacement of old feathers with new ones. Feathers are amazingly strong, light and resilient, but, like our clothes, they eventually wear out and must be replaced. Thus, the annual molt.
The process requires a lot of energy, so birds time their molts to avoid other periods of high energy demands, such as nesting or migration.
By keeping feathers healthy, molting keeps birds in top flying condition and helps them stay warm and dry. In males, a healthy plumage also is important for attracting females.
All birds molt (most songbirds do it from July to September), but the process varies according to the species. Robins, cardinals and chickadees, for instance, undergo a complete molt only once a year. Long-distance migrants, such as tanagers and warblers, may molt twice a year — a complete molt in late summer and a partial molt before the breeding season in spring. A few species, such as the American goldfinch, may completely change colors during their twice-a-year molts.
In most songbirds, molting may take as long as eight weeks. Most songbirds shed their flight feathers symmetrically, a few from each side at a time, so as not to affect flying. For ducks and geese, though, a complete molt occurs in about a month, during which time they are flightless. For raptors, such as hawks, molt takes place over an extended period and often overlaps with breeding.
In the sky: From David Dundee, Tellus Science Museum astronomer: The year’s showiest meteor shower, the Perseid, reaches a peak of more than 50 meteors per hour this weekend (Aug. 13-14) and will be visible through Thursday. Look to the northeast from 2 a.m. until dawn.
The moon will be full on Thursday — the “Fruit Moon,” as the Cherokee people called August’s full moon. Mercury and Venus are low in the west, Mars and Jupiter are in the southwest and Saturn is high in the west around nightfall.
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