The merlin (Falco columbarius) is a small species of falcon from the Northern Hemisphere, with numerous subspecies throughout North America and Eurasia. A bird of prey, the merlin breeds in the northern Holarctic; some migrate to subtropical and northern tropical regions in winter. Males typically have wingspans of , with females being slightly larger. They are swift fliers and skilled hunters which specialize in preying on small birds in the size range of sparrows to doves and medium-sized shorebirds. In recent decades merlin populations in North America have been significantly increasing, with some merlins becoming so well adapted to city life that they forgo migration; in Europe, populations increased up to about 2000 but have been steady subsequently. The merlin has for centuries been well regarded as a falconry bird.

Nomenclature

The merlin was described and illustrated by the English naturalist Mark Catesby (as the "pigeon hawk") in his Natural history of Carolina, Florida and the Bahama Islands published in 1729–1732. Based on this description, in 1758 Carl Linnaeus included the species in the tenth edition of his Systema Naturae and introduced the present binomial name Falco columbarius with the type locality as "America". The genus name is Late Latin; falco derives from falx, falcis, a sickle, referring to the claws of the bird. The species name columbarius is Latin for "of doves" from "columba", "dove". Thirteen years after Linnaeus's description Marmaduke Tunstall recognized the Eurasian birds as a distinct taxon Falco aesalon in his Ornithologica Britannica. If two species of merlins are recognized, the Old World birds would thus bear the scientific name F. aesalon. Wycliffe's Bible, around 1382, mentions An Egle, & agriffyn, & a merlyon. The wizard's name is an English cognate of the Welsh name "Myrddin" and is unrelated to the name of the bird.

Systematics

left|thumb|[[European subspecies F. c. aesalon, Dumfries & Galloway, Scotland]]

The relationships of the merlin are not resolved to satisfaction. In size, shape and coloration, it is fairly distinct among living falcons. The red-necked falcon is sometimes considered more closely related to the merlin than other falcons, but this seems to be a coincidence due to similar hunting habits; it could not be confirmed in more recent studies. Indeed, the merlin seems to represent a lineage distinct from other living falcons since at least the Early Pliocene, some 5 Ma (million years ago). As suggested by biogeography and DNA sequence data, it might be part of an ancient non-monophyletic radiation of Falco species from Europe to North America, alongside the ancestors of forms such as the American kestrel (F. sparvierus), and the aplomado falcon (F. femoralis) and its relatives. A relationship with the red-necked falcon (F. chicquera) was once proposed based on their phenetic similarity, but this is not considered likely today.

In that regard, a fossil falcon from the Early Blancan (4.3–4.8 Ma)

By and large, color variation in either group independently follows Gloger's Rule. The Pacific temperate rain forest subspecies F. c. suckleyi males are almost uniformly black on the upperside and have heavy black blotches on the belly, whereas those of the lightest subspecies, F. c. pallidus, have little non-dilute melanin altogether, with gray upperside and reddish underside pattern. house sparrows (Passer domesticus), other Old World sparrows (Passeridae), northern wheatears (Oenanthe oenanthe), thrushes (Turdus), kinglets (Regulidae) or buntings (Emberiza) ptarmigan, other grouse, and even rock doves), small mammals, (especially bats, shrews, rabbits, and other small rodents) reptiles (such as lizards and snakes)—complement its diet. These are more important outside the breeding season, when they can make up a considerable part of the merlin's diet. But for example in Norway, while small birds are certainly the breeding merlin's staple food, exceptional breeding success seems to require an abundance of Microtus voles. They also offer an exciting style of flight, generally at closer range than large falcons where it may be more clearly witnessed and enjoyed by the falconer. In addition to horizontal tail-chases in the manner of American kestrels, they will also "ring up" in pursuit of prey that seeks to escape by out-climbing them, and perform high speed diving stoops on prey beneath them in the manner of larger falcons. Quoting from one popular falconry book on the eagerness of merlins to chase a swung lure, "Every stoop, outrun, dodge, and aerial maneuver of a hard flight to real quarry can be duplicated with no risk of loss of the falcon. Merlins regularly flown to the lure take most field quarries with such ease and such assurance as to make the field flight the less interesting and exciting of the two." Concerning suitable game for these two species, he states "To snipe, dove, quail and open-country sparrows, merlins are best suited. For most blackbirds (Icteridea), either falcon can prove effective. Starlings in close are extremely vulnerable to kestrels; but in the open are best prey for merlins."

Status and conservation

thumb|upright|Hunter with trained merlin, Jandari Lake, [[Georgia SSR, November 1979]]

Altogether, the merlin is not particularly rare, and due to this and its wide range it is considered a species of least concern by the IUCN.

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  • Merlin Species Account – Cornell Lab of Ornithology
  • Merlin - Falco columbarius - USGS Patuxent Bird Identification InfoCenter
  • Picture of Black Merlin (Falco columbarius suckleyi subspecies)
  • Merlin photos at Oiseaux.net
  • Ageing and sexing (PDF; 5.3) by Javier Blasco-Zumeta & Gerd-Michael Heinze
  • Merlin, Canadian Peregrine Foundation
  • [https://web.archive.org/web/20181228033438/http://merlinfalconfoundation.org/] Merlin Falcon Foundation

Historical material

  • "The Merlin, called in Latine Æsalon." Page 85 in The Ornithology of Francis Willughby, translated by John Ray (1678). Engraving of a perched merlin, tableaux III.
  • "Falco columbarius, Pigeon Hawk"; from American Ornithology 2nd edition, volume 1 (1828) by Alexander Wilson and George Ord. Color plate from 1st edition by A. Wilson.
  • "The Pigeon Hawk" and "Le Petit Caporal", John James Audubon, Ornithological Biography volume 1 (1831). At Pigeon Hawk; Petit Caporal, in the appendix to Ornithological Biography volume 5 (1839), Audubon notes that his Falco temerarius of volume 1 was a small male merlin, and that this was brought to his attention by Charles Bonaparte, nephew of "the little corporal". Illustration from Birds of America octavo edition, 1840.