Merlin (Falco columbarius)
Merlins are small, fierce falcons that use surprise attacks to bring down small songbirds and shorebirds. They are powerful fliers, but you can tell them from larger falcons by their rapid wingbeats and overall dark tones. Medieval falconers called them “lady hawks,” and noblewomen used them to hunt Sky Larks. Merlin populations have largely recovered from twentieth-century declines, thanks to a ban on the pesticide DDT and their ability to adapt to life around towns and cities.
The Merlin is 24–33 cm (9.4–13 in) long with a 50–73 cm (20–29 in) wingspan. Compared to most other small falcon, it is more robust and heavily built. Males average at about 165 g (5.8 oz) and females are typically about 230 g (8.1 oz).
Merlins are generally dark and streaky, though their coloration varies geographically and by gender. Adult male Merlins are slaty gray to dark gray; females and immatures are browner. The chest is usually heavily streaked and the underwings are dark. The dark tail has narrow white bands, and the face often lacks a prominent malar or “mustache” stripe.
Merlins inhabit fairly open country, such as willow or birch scrub, shrubland, but also taiga forest, parks, grassland such as steppe and prairie, or moorland. They are not very habitat-specific and can be found from sea-level to the treeland. In general, they prefer a mix of low and medium-height vegetation with some trees, and avoid dense forests as well as treeless arid regions. During migration however, they will utilize almost any habitat.
Merlins rely on speed and agility to hunt their prey. They often hunt by flying fast and low, typically less than 1 m (3.3 ft) above the ground, using trees and large shrubs to take prey by surprise. But they actually capture most prey in the air, and will “tail-chase” startled birds. Merlins eat mostly birds, typically catching them in midair during high-speed attacks. They often specialize on hunting a couple of the most abundant species around; prey are generally small to medium-sized birds in the 1–2 ounce range. Common prey include Horned Lark, House Sparrow, Bohemian Waxwing, Dickcissel, Least Sandpiper, Dunlin, and other shorebirds
Merlins do not build their own nests; they reuse old crow, raven, magpie, or hawk nests, making few, if any, modifications to the original nest. They only rarely reuse a nest in subsequent years. The dimensions of the nest can vary greatly depending on which species’ nest they reuse.
References: Wikipedia, Cornell Lab of Ornithology