Around this time of year, Common Mergansers cross the US-Canadian border on their way to wintering grounds in the Lower 48. But how do they know when to go? Ducks are well insulated against frigid winter temperatures, but mergansers can find their fishy prey only by diving below the…

The Common Merganser is one of our biggest ducks, about the size of some loons. Although it’s not closely related to loons, it has evolved a similar overall structure and predatory behavior. But a merganser has a unique feature: tooth-like serrations along the edge of the bill that help…

The drumming of the male Ruffed Grouse is one of the most evocative sounds of the North American forest. Familiar as these accelerating burps are to hunters and hikers, the origin of this bizarre sound was long a mystery. It took the advent of wildlife cinematography to solve the riddle…

Many woodpeckers chisel out deep cavities in tree trunks in order to lay their eggs and raise their brood. The cavities hollowed out by the birds vary in size, depending on the species of woodpecker. The chamber of a tiny Downy Woodpecker descends about a foot from the opening, while the…

Eared Grebes eat brine shrimp and aquatic insects for sustenance, but rigid exoskeletons make them hard to digest. So these grebes -- along with their other grebe cousins -- evolved to use their feathers as a way to slow down digestion. The feathers form dense balls in the digestive tract…

The bill and legs of Arctic Terns are shorter than those of Common Terns. Because Arctic Terns breed in the Arctic and winter in the Antarctic, they are subject to much colder weather than are Common Terns. Birds' bills and legs lose heat, because they're not covered by feathers. Birds in…

The Eurasian Collared-Dove is rapidly increasing across the US and southern Canada. This sandy pink bird with the neat black neckband was released in the Bahamas in the 1960s. Brought in as pets, some doves escaped. They made it to Florida a few years later and have been spreading in a…

The late Yogi Berra, renowned New York Yankees catcher, is sometimes remembered less for his exceptional play and more for his turns of phrase. One of which was reported as, “You can observe a lot by just watching.” When it comes to observing birds such as this Golden-crowned Kinglet…

Greater Yellowlegs — not surprisingly — have bright yellow legs and feet. And why? While foraging through shallow water, a yellowlegs (like this one) can keep track of its legs by the color, which contrasts with the sometimes dark and irregular bottom. A Sanderling, on the other hand, has…

Have you ever seen a Peregrine Falcon attack a flock of shorebirds, igniting a breathtaking aerial display? The late falcon researcher Steve Herman called this pattern of evasion "instantaneous synchronicity." The shorebird flock will often form a cone, with the sharpest point shifting…