Unlike the American Kestrel, the Merlin does not hover. Its flight is direct, the rapid wingbeats shallow and fluttery at times, creating a diagnostic flight pattern often linked with the bird's characteristic "ki-ki-ki-ki-ki" call. It occasionally soars with wings flat and tail fanned. Wing beats during hunting flight are deep and powerful but more rapid than a Peregrine or a Prairie falcon. The average flight speed has been estimated at about 30 miles per hour (48 kilometers per hour). During migration Merlins appear to migrate much of the day, including in pre-dawn darkness and late in the day. It will migrate on days of light rain when other hawks do not. It will also migrate across stretches of open water, including the ocean, flying low over the waves. Young Merlins are often fairly tame during the first month or two of life, sometimes flying close to people.
The Merlin hunts mostly in early morning and late afternoon. Most prey is captured in mid-air after the Merlin has spied it from a prominent perch overlooking an expanse. It will also coarse over the landscape using hills, dikes, and trees for concealment. Dives or "stoops" from a height are uncommon. The Merlin will engage in a series of short stoops after escaping prey. It will also engage in aerial chases when its prey attempts to out-fly it. The famous "ringing flight" occurs when the prey (classically a European Skylark in Europe) seeks to escape by rising higher and higher in circles with the Merlin close behind. Co-operative hunting between two Merlins has been seen. The species is an opportunistic feeder taking flying insects on the wing, hunting bats at the cave mouth and using other birds (such as a Northern Harrier), people, hunting dogs, or vehicles as "beaters", flushing prey for the falcon to pursue. At a plucking post the Merlin stands on its prey, kills it by biting the neck, and typically discards the head, feathers, legs and wings. After feeding it wipes its beak and cleans its feet with its beak and may rotate in place, kneading its feet. Like the American Kestrel, the Merlin will cache prey for later consumption.
Home range sizes vary in nesting season from 8.9 square miles (23 square kilometers) in Montana to 3.1 square miles (8 square kilometers) in Saskatchewan. Resident and immigrant males in Saskatoon differ in breeding season home range size - 2.3 square miles (6 square kilometers) for residents and 12.7 square miles (33 square kilometers) for immigrants. Home range sizes are much smaller where prey is abundant. Males appear to have a stronger fidelity to the same territory year after year than females. Fidelity to the territory is a well known and long-lived phenomenon in Europe. Differences in site fidelity may be a function of the availability of nest sites. The Merlin is fairly social for a falcon. Pairs wintering together have been reported, as have migrations in loose groups and occasional communal roosts..
In early fall, young Merlins may occasionally hunt and migrate with young Sharp-shinned Hawks without much animosity, which is odd since Merlins are well known harassers of other migrating hawks. In migration, Peregrine Falcons sometimes rob Merlins. Once a Merlin struck and killed a Red-tailed Hawk. In defense of a nest, a Merlin has killed a crow, and in Alaska the species has chased Golden Eagles, Common Ravens, Gyrfalcons, Black-billed Magpies, and Willow Ptarmigan from its territory. In Europe, Fieldfares (large thrushes) often nest within the same grove with a pair of nesting Merlins.
Courtship behavior is complex. The male engages in "power flying" with deep wingbeats, showing alternate views of his ventral and dorsal surfaces while giving tics. Power flying is often done at territorial boundaries by neighbouring males. The male may also "power dive", like the above display, but terminating in a u-shaped climb. This display is advertisement and territorial defense. Sometimes both sexes dive together. Both male and female show the "rocking glide", a less intense version of power flying with no flapping. Males use it to attract females. Females use it as a threat against other females. Males also "flutter fly" near their perched mates, typically around the nest site. "Ki-ki-ki-" vocalizations are given which the female may answer. Both sexes "high soar" near the nest, a territorial display. The male may "slow land" with stiff legs and a bowed head as a terminal component of other displays. It may also be given before or after copulation. The "ki-ki-ki" vocalization may accompany it. A female may "food beg" with whining. Males may transfer food to females in the air, to a perch, or from perch to perch, giving "tics" or "ki-ki-ki" calls. At the nest, both sexes may give "tic" calls and the male may settle with arched back, drooped and trembling wings and a fanned tail. Before mating the male may bow, fan its tail and stare at the female while chuttering. The female solicits copulation by bowing and fanning her tail.
The Merlin seldom lives longer than eight years. First year birds may have a mortality rate as high as 60 to 70 percent. The maximum mortality rate for breeding birds in Saskatoon was 29 percent. In one study, collisions with vehicles and windows (43 percent), shooting (7 percent), poisoning (2 percent), predation by cats (2 percent) and weather (1 percent) were the known agents of mortality.
ADAPTATIONS
Merlins breeding along the extreme northern edge of their range in Canada may nest on the ground in areas where trees are scarce. Further investigations are needed of this possible adaptation, but ground nesting does occur in some European parts of this species' range.
Merlins have adapted well to the human settlement of the Northern Great Plains. During the last twenty years small but growing breeding and wintering populations have become established in prairie cities like Saskatoon (an increase from one pair in 1971 to 27 pairs in 1987) where the Merlins take mainly House Sparrows. They breed in old crow nests in large shade and coniferous trees. Similar urban populations exist in Regina, Moose Jaw, Calgary and Edmonton and may be spreading across Canada. Urban birds tend to accept the near presence of human beings more calmly than birds in the country. Urban birds roost in tall conifers with large, thick crowns. Such trees have only recently reached such a size in the northern Great Plains. This may explain why Merlins now winter in the area.
