The Merlin is 24-33 cm (9.4-13.0 in) long with a 50-73 cm (20-29 in) wingspan. Compared to most other small falcons, it is more robust and heavily built. Males average at about 165 g and females are typically about 230 g. Thus, adult males may weigh 125-210 g, and females 190-300 g. The male Merlin has a blue-grey back, ranging from almost black to silver-grey in different subspecies. Its underparts are buff- to orange-tinted and more or less heavily streaked with black to reddish brown. The female and immature are brownish-grey to dark brown above, and whitish buff spotted with brown below.
Habitat and Distribution
The Merlin breeds in the northern Holarctic; some migrate to subtropical and northern tropical regions in winter. Merlins inhabit fairly open country, such as willow or birch scrub, shrubland, but also taiga forest, parks, grassland such as steppe and prairies, or moorland. They are not very habitat-specific and can be found from sea level to the treeline. They avoid dense forests as well as treeless arid regions, but will utilise any form of habitat during migration.
Merlins rely on speed and agility to hunt their prey. They often hunt by flying fast and low, using trees and large shrubs to take prey by surprise. But they actually capture most prey in the air.
Breeding occurs typically in May/June. Most nest sites have dense vegetative or rocky cover. The Merlin does not build a proper nest of its own. Most will use abandoned corvid or hawk nests which are in conifer or mixed tree stands. The female will usually make a shallow scrape in dense heather to use as a nest. Others nest in crevices on cliff-faces. Three to six rusty brown eggs are laid. The incubation period is 28 to 32 days.