Males arrive to the breeding area before the females, usually returning to the same general area year after year. Nesting pairs don't necessarily use the same actual site each year. In open country and grassland, nests are generally scrapes located in dense vegetation. In regions of sand dunes, dune grasses may be used to create a nest. Even in wooded areas, nests may be scrapes, but empty crow nests are preferred. During the nesting period, Falco_columbarius become highly aggressive towards other raptors and crows in the area. This aggressive behavior towards other predatory birds is beneficial to other woodland song and ground birds in the nesting range; since Falco_columbarius hunts only in open country, thereby leaving the woodland birds relatively free from predators during the mating season. Normally the nest contains four to six eggs measuring 1.5 x 1.22 inches. The eggs are laid at two-day intervals. The coloration of the round oval eggs are variations of light buff white almost obscured by a regular pattern of rich chestnut-brown, purple and chocolate blotchings.
The eggs are laid in early April to early May in the southern ranges and in late May through June in the North. The female is the main incubator, although the male does share in the duties. The incubation period lasts 25-32 days. At the end of the incubation period, the eggs hatch in intervals.
Quills appear on the young after fourteen days, and by eighteen days the down is almost completely covered with feathers, except in the head region. Flight is achieved at 25-30 days after hatching.
Upon leaving the nest, the young remain nearby for several weeks until they are mature enough to migrate southward. Within a week's time of leaving the nest, the young are capable of distance flights, and at two weeks' time, they begin to catch insects. By six weeks the young are skilled in catching small birds, and shortly afterwards, they migrate southward from the breeding area. The success rate among the the young is exceptionally high, often three birds per nest survive to continue breeding.
Falco_columbarius: Breeds throughout northern Europe, Asia and North America.
Falco_columbarius bendirei: Breeds in northwestern Alaska to northern Saskatchewan and into northern California.
Falco_columbarius columbarius: Breeds in eastern Canada to the eastern border of the Great Plains and southwards into Nova Scotia and northern Michigan.
Falco_columbarius richardsoni: Breeding range is located in the Great Plains from southern Alberta and Saskatchewan to northern Montana and North Dakota.
Falco_columbarius suckleyi: Breeding occurs only in western British Columbia and perhaps on Vancouver Island.
Breeding interval: Merlins breed once yearly.
Breeding season: Merlins breed from April to July, depending on the latitude.
Range eggs per season: 4 to 6.
Range time to hatching: 25 to 32 days.
Average time to independence: 6 weeks.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Average eggs per season: 5.