A merlin devours a junco in Groton on Jan. 2, 2022. (Photo: Tom Murray)

Henry David Thoreau once said that the hawk is the “aerial brother of the wave which he sails over and surveys.” Although a merlin is a falcon, not a hawk, this description fits it perfectly, for the merlin (Falco columbarius) is a small, extremely fast falcon that skims low over the ground like a wave. Once called a pigeon hawk, it is about a foot long with a 2-foot wingspan. In the Middle Ages, falconers called this bird the “Lady’s hawk.” Mary Queen of Scots and Russia’s Catherine the Great used these feisty birds to hunt for larks. Other royalty prized its maneuverability and speed when hunting small birds from the size of a sparrow to the size of a pigeon.

Although about the same size as an American kestrel, merlins weigh three times as much and are much more powerful. Renowned ornithologists Pete Dunne, David Sibley and Clay Sutton once wrote, “The merlin is to an American kestrel what a Harley-Davidson motorcycle is to a bicycle.”

A merlin in Salisbury fans its tail, displaying alternating light and dark bands, on Feb. 18, 2018. (Photo: Tom Murray)

Unlike some other falcons, a merlin does not dive bomb prey to catch it. Rather, it darts with rapid wingbeats low over the ground into flocks of starlings, sandpipers or pigeons at speeds up to 30 mph, catching the prey in flight. It makes a quick turn, smacking the prey with its feet to kill or stun it. Merlins sometimes prey on bats leaving their roosts or large insects such as dragonflies. A merlin feeds mostly on smaller birds, such as sparrows. Occasionally it will attack a pigeon. Birds make up about 80 percent of a merlin’s diet. Insects make up about 15 percent, and mammals 5 percent.

A merlin eats a house finch in May. (Photo: Tom Murray)

According to W.B.O. Peabody in 1839, the pigeon hawk, as the merlin was then known,

is migratory in its habits, and, when in pursuit of its prey, cares not whither it goes. It seizes the robin, the wild pigeon, and even the gold-winged woodpecker, on the land; and on the water, it pursues much larger birds, which can escape from it only by diving. It has been known to attack birds in cages, in the very heart of cities; and so indifferent is it to danger, that it does not even shun the presence of man …When wounded, it throws itself on its back as the hunter approaches, and with angry screams, prepares to defend itself to the last.

Merlin populations declined after World War II when the miracle pesticide DDT was introduced. Meant to control mosquitoes and other insects, it washed into waterways and worked its way up the food chain, interfering with a bird’s ability to absorb calcium – which is why merlin eggshells were so thin they broke while being incubated. In 1972, the Environmental Protection Agency banned the use of DDT in the United States. Merlin populations rebounded.

A merlin perches in a tree on Broadway in Somerville on Nov. 12, 2021. (Photo: Kate Estrop)

Merlins breed in Alaska, Canada and parts of the northern and western United States. Today, their breeding range is creeping south into New England. A few pairs have recently begun nesting and breeding in Massachusetts. Since 2016, observers have spotted nesting merlins in Barre, Northampton and Nantucket. These little falcons are still rare in the summer, but you might spot one during the rest of the year, especially near the coast.

Adult male merlins are bluish-gray; females and young merlins are brown. Like most raptors, females are larger and heavier than males. These are noisy birds that give a shrill, chattering kikikikikiki call that can last four seconds. They use this call during courtship or when challenged, or hunting. Merlins make a chip note to contact a partner, especially during courtship.

A merlin in Cambridge on Dec. 18, 2020. (Photo: Richard George)

Merlins are monogamous. The couple chooses a nest site, often the abandoned stick nest of a crow or hawk. They do not much modify this nest, but may add a bit of moss or feathers. The female lays four or five rust-colored eggs at two-day intervals in April or May. She incubates them for a month, sitting on the eggs in all weather conditions. The male hunts for her and will incubate the eggs briefly while the female perches nearby to feed. The male caches any extra food nearby. The female retrieves it if the male is late returning. Once the eggs hatch (also in intervals), the female keeps the chicks warm for another week. After this time, she keeps them warm only during cold, windy or rainy weather.

The male chases off intruders that want to feast on the small hatchlings. The male also brings food, calling to the female as he approaches, and she flies to him to retrieve the prey for the nestlings. After about a month, the chicks leave the nest but stay close by. The parents defend them against predators and feed them until they are successful at capturing prey by themselves. In two weeks, they are catching insects on their own. After about five weeks, they can catch small birds. Soon thereafter, the young merlins leave their parents’ territory. The survival rate for merlin chicks is very high, with about three chicks per nest reaching adulthood.

A merlin scans for prey in Hadley in February 2021. (Photo: Tom Murray)

After the breeding season ends, the parents go their separate ways for the winter. In the spring, they reestablish their pair-bond after returning to their previous nesting territory. Males arrive at the territory about a month before the female. He performs aerial acrobatics to attract the female and to discourage males that may intrude upon the territory.

This daring and courageous little bird is a marvel to witness. If you are lucky enough to spot one, consider yourself fortunate (and please share your photos with us).

Seen nearby

Abigail Stone spotted this orange-crowned warbler in Magoun Square, Somerville, on Jan. 24, 2022.

Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name, date and the general location where the photo was taken as well as any other relevant information.

Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.