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For birders, every season holds its own delights, from the glory of spring migration to winter’s panoply of ducks. Nesting and baby birds may be the warmer months’ best-known thrills, but by late summer many species experience another life event that is just as critical—though admittedly less cute. As we reach the dog days, watch for birds looking faded, patchy, and—well, a little ugly. Those shabby-seeming creatures are due for, or in the midst of, something amazing. Right before you, birds are molting.

Most species need to fly to survive, but their feathers are constantly worn down by the elements. Before they’re left grounded, birds replace their plumes—a strategy researchers believe evolved from skin-shedding reptile ancestors. All avians need to refresh their feathers at least once a year, and many species molt more often, especially long-distance migrants. Some take the opportunity to change their looks for a seasonal wardrobe, like the flashy courting colors of male Scarlet Tanagers and Indigo Buntings. When and where molts take place vary widely between and even within species, but pay attention: This is your chance to appreciate an ancient solution to a life-or-death problem.

The best months to look for active molting are July and August, a window for many species between breeding and migration. Sometimes it will be obvious: You might spot a ragged robin or a grackle with a scraggly tail; uneven or missing feathers are telltale signs in any bird. 

Here are some more specific tips to get started: 

• Waterfowl have “simultaneous” molts, replacing many feathers at once, which leaves them temporarily flightless. Resident Mallards and Canada Geese often undertake these dramatic renewals on full display in city parks—you might even see “pins:” keratin sheaths around the growing feathers, which resemble drinking straws.
• The easiest way to see molt in action is to study large birds like gulls, herons, and raptors. Look for gaps in wing and tail feathers, most noticeable when birds are in flight.
• Turkey Vultures are especially visible molt models. In fact, if you see one in late summer with pristine wings, it’s likely a freshly fledged juvenile. Look for a dark (instead of red) head for confirmation.

Although molting is vital to all birds and fascinating to observe, scientists are still learning about it, especially at the species level. You can help: While a bedraggled-looking finch at your feeder might not strike you as the most photogenic, consider picking up the camera. Images of molting birds shared on community science platforms like eBird are helping researchers discover more. And you might come to appreciate those pictures—proof that you witnessed the essential, still-mysterious, process that keeps birds on the wing.