Lying Low During Molt
The molting season, which begins after breeding, marks a significant shift in the appearance and behavior of birds. Molt is the systematic replacement of feathers. All birds do it—from hummingbirds to penguins. Because feathers deteriorate from physical abrasion and sun bleaching, they must molt in order to survive. Birds undergo a full molt once a year, during which they grow a whole new set of feathers (for temperate species, this occurs in the late summer).
Birds are especially vulnerable to predators while they are developing new flight feathers. Many of their flight feathers will be shorter than full length during wing molt, creating gaps in their wings that reduce their maneuverability and flying force. Many birds, including sparrows, warblers, and thrushes, lie low, calling infrequently, and hiding in vegetation to avoid drawing the attention of predators.
During molt, male ducks with bright colors have an additional tactic to prevent them from being noticeable to predators. All of a waterfowl’s primary and secondary feathers fall out at once, leaving them without wings for approximately a month, including grebes and loons. Male ducks develop eclipse plumage, a unique set of camouflaged feathers, to help them hide when they are unable to fly. If you visit a nearby park in July, you might notice that every Mallard appears disheveled and primarily brown, as if they were all female. Drakes’ vividly colored body feathers will grow back soon after their wing feathers have grown back and they can take flight once more.
Strangely, during the season when birds are most abundant, their quiet and reticent nature make them more difficult to locate, as adult populations are bolstered by the influx of young birds.
“Considerate these days as the ‘bird days’ of summer and make sure to go birding,” advises Jenna Curtis, the program coordinator for eBird. Although summer is a crucial season for bird populations, research during this time can be challenging. Answers to these and other significant questions, such as what happens to young birds after they fledge and where birds go when they stop nesting and defending their territories, can be obtained by birdwatchers. You might be the only one in your town or yard counting birds, so those checklists close a significant knowledge gap. ”.
Different tactics are used by groups of birds to accommodate molting into their yearly schedule. Soon after they fledge, the majority of songbirds in eastern North America, such as the Indigo Bunting, Baltimore Oriole, and Chestnut-sided Warbler, start to replace their body and flight feathers. They typically go through this full molt in or close to their breeding grounds, and once they have a fresh set of feathers, they migrate south.
However, some songbirds in western North America start their migration early and migrate a little further south before molting. Western summers can be extremely dry and desolate. Many species migrate in part to the Mexican Monsoon region (northeast Arizona, New Mexico, and northwest Mexico) to molt, including the Western Kingbird and Lazuli Bunting. There are lots of insects around to feed on thanks to the monsoon rains. These birds migrate even further south to their wintering grounds after molting their flight feathers.
Simply taking a moment to closely examine the feathers will allow you to identify molt in progress. Birds in heavy molt tend to be scruffy overall. Look for contrast between the new and old feathers, as well as spaces in their wings, resembling the gap-toothed smile of a jack-o’-lantern, where the old feathers have fallen out and the new ones have not yet grown in. For more on this, see Two Tips for Determining a Bird’s Age Based on Its Molt Patterns.
Understanding molting will help you realize that a bird’s appearance in the late summer is just another amazing stage of its life cycle. You’ll also understand how birds get ready for their arduous fall migration journeys.
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From the Summer 2021 issue of Living Bird magazine. Subscribe now.
Originally posted July 2013; updated May 2021.
The dawn chorus fades and an unusual quiet descends upon woodland areas during the sweltering summer months, as if the birds have moved on. Many of the birds appear disheveled, lacking their vibrant breeding plumage. Many ornithologists store their binoculars until the fall migration. (Usually, the two months with the fewest eBird checklist submissions are July and August.) ).
But there’s no reason to stop birding. The birds are still present; they’re just hiding since they’re growing new feathers. Gaining insight into the post-breeding lifestyle of birds can help you locate species well into the summer.
Birds sing primarily to defend their territory and to entice a mate. Many North American baby birds have flown by July, and even those that build several nests a year finish by early August.
Certain birds might keep singing for a while in order to teach their young the dialect of the local song. However, many birds—like Red-winged Blackbirds and American Robins—quit marking territories and begin to flock, and territorial singing is incompatible with flocking. Each species leaves the morning chorus one by one.
It’s evident that birds may be particularly harmed by heatwaves. After all, they are unable to perspire and are always covered in layers of feathers. Furthermore, did you know that the temperature of their bodies is higher than that of humans? For instance, the Northern Cardinal has a body temperature of approximately 106 degrees Fahrenheit, while the chickadee has a temperature of approximately 108 degrees.
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