|A Northern mockingbird in molt. Photo by J.J. Meyer|
That's because birds are starting to molt. The black phoebes and Bewick's wrens in my backyard seemed to start molting immediately after their last brood was chased off this year. Though I just heard the advertising call of a male mourning dove this morning, so not all species are done breeding.
Molting requires a lot of energy, so that's why it occurs after the breeding cycle is over. Birds tend to keep a low profile when molting because they're more vulnerable to predators during this time.
Every bird goes through a complete molt once a year. Most birds molt in late summer and early fall, but the way a bird molts differs among species. Some have a partial molt, then migrate. But they’re not normally in a full molt when flying long distances.
Birds in molt can look scruffy or unusual with stubby tails and patchy bald spots, which makes bird identification tricky this time of year.