Merlin (Falco columbarius)

Also known as: pigeon hawk
  
French: Faucon émerillon
KingdomAnimalia
PhylumChordata
ClassAves
OrderFalconiformes
FamilyFalconidae
GenusFalco (1)
SizeLength: 28 cm (2)
Wingspan: 56 cm (2)
Male weight: 180 g (2)
Female weight: 230 g (2)

The merlin is classified as Least Concern on the IUCN Red List (1) and listed on Appendix II of CITES (3).

An extremely fast, agile hunter (4), the merlin (Falco columbarius) is a small, distinctive species of falcon from the northern hemisphere (5). The adult male and female’s plumage differs greatly in appearance, and the female merlin is markedly larger than the male. Both sexes have a yellowish-green eye-ring and cere, dark brown eyes and pale orange to yellow legs (6).

The male merlin’s crown, back, uppertail and upperwings are light greyish-blue and it has contrasting black upper flight feathers. There is a black streak running through the centre of the feathers on the upperparts, and its light reddish-brown chest has large, dark brown speckles (6) (7). Light grey shading surrounds the pale cheeks of the male, and it has very faint moustache markings under each eye. The throat is white (6). The merlin’s underwings appear dark with uniform markings, and it has a long, square-cut tail with broad, black banding and a narrow, blue-grey stripe near the tip (4) (5) (6).

With predominantly greyish-brown plumage, the female merlin also has a pale red chest, which, like the male, is covered in speckles (6) (7). It has a white throat, and the orange-brown cheeks are surrounded by darker brown areas, with faint moustache markings below each eye. Narrow black streaks run across the female merlin’s dark brown upperwing coverts, and the undersides of the wing are lighter, with uniform markings (6). The female’s tail is the same shape as the male’s and has broad, black banding, but the uppertail is brown (4) (5) (6). The juvenile merlin is similar in appearance to the female (4).

Occurring throughout much of the northern hemisphere, the merlin has an extremely large range. It is found across Europe and North America (1) (8), occurring south to Afghanistan, Panama, Mexico and Haiti, and north as far as Iceland, Russia and Canada (1).

Some merlin populations may migrate to avoid the cold winter months; for example, many of the Icelandic breeding birds move to the UK to overwinter (5).

The merlin can be found in a variety of habitats, including woodland, open pasture, marsh, heathland and moorland (4) (9). In Canada, the merlin frequently inhabits coniferous plantations, but it can also occupy cities, where there is an abundance of house sparrow (Passer domesticus) prey (8). The merlin has also been recorded in rice paddies in Portugal (10).

Small birds make up the biggest part of the Merlin’s diet, with a variety of bird species targeted depending on regional availability (4) (8). Species including sandpipers and blackbirds are frequently taken, while in Britain, the meadow pipit (Anthus pratensis) forms the majority of the merlin’s diet. During the breeding season in Shetland, the merlin is also particularly known to prey upon the northern wheatear (Oenanthe oenanthe) and skylark (Alauda arvensis) (11).

The merlin often catches pigeons in urban areas, and in Canada it feeds mainly on house sparrows (Passer domesticus) (8). Dragonflies are also captured, and the merlin feeds on these during flight (4). In Alaska, it has been known to scavenge food, such as road-killed snowshoe hares (Lepus americanus) (12).

In Europe and Canada, the merlin prefers nesting in abandoned corvid nests (8) (13) (14), but if these are unavailable it may nest on cliff ledges or even on the ground (14). A clutch of 4 to 5 eggs is normally laid during May, and incubation lasts for 30 days (2) (14). The female performs the majority of the incubation, only briefly leaving the nest to feed (8) (14).

Like many other raptors, the male merlin invests more energy in the offspring than the female (8). The nestling period lasts from 28 to 31 days (2), and during this stage, most of the nestling’s food is provided by the male (8) (14). After fledging, merlin chicks remain dependent on the adults for a few more weeks (14). The high energy cost of reproduction for male merlin’s is thought to explain why the male breeds from two years of age, whereas the female breeds from one year of age (8).

In the 1950’s the merlin population fell almost to extinction in the UK, with low populations also recorded in other parts of Europe (13). The drastic population decline was likely to be the result of a number of threats, including loss of suitable habitat through overgrazing, insensitive management, and increased tourism disturbing nest sites, which all negatively influence the merlin’s breeding success (11).

Pesticide contamination also weakens the merlin’s egg shell and results in breakages and lower egg production (15).

In Shetland, the otter, hedgehog, stoat and ferret can predate eggs and offspring, although this risk is generally low. Predation by the hooded crow poses more of a threat (11).

As well as being listed on Appendix II of CITES (3), which makes it illegal to trade the merlin without a license, it is also protected in the UK by The Wildlife and Countryside Act 1981. This makes it an offence to disturb, take, kill or injure a merlin, its eggs, offspring, or nest (16).

Recommendations to protect the merlin include increasing suitable breeding habitat, sensitive grazing of heathland in the UK, confining people to footpaths away from breeding grounds to avoid nest disturbance, and the close monitoring of pesticide use (9) (15).

For more information on the merlin:

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  1. IUCN Red List (August, 2011)
    http://www.iucnredlist.org/
  2. British Trust for Ornithology - Merlin (August, 2011)
    http://blx1.bto.org/birdfacts/results/bob3090.htm
  3. CITES (August, 2011)
    http://www.cites.org/
  4. Latimer, J.P. and Stray Nolting, K. (1999) Birds of Prey. Houghton Mifflin Company, New York.
  5. RSPB A-Z of Birds - Merlin (August, 2011)
    http://www.rspb.org.uk/wildlife/birdguide/name/m/merlin/index.aspx
  6. Clark, W.S. (1999) A Field Guide to the Raptors of Europe, the Middle East, and North Africa. Oxford University Press, Oxford.
  7. Audubon, J.J. (1972) A Synopsis of the Birds of North America. Johnson Reprint Corporation, New York.
  8. Espie, R.H.M., Oliphant J.L.W., Warkentin, I.G. and Lieske, D.J. (2004) Influence of nest-site and individual quality on breeding performance in merlins Falco columbarius. Ibis, 146: 623-631.
  9. Haworth, P.F. and Fielding, A. (1988) Conservation and management implications of habitat selection in the merlin Falco columabrius L. in the South Pennines, UK. Biological Conservation, 46(4): 247-260.
  10. Lourenco, P.M. (2009) Rice field use by raptors in two Portuguese wetlands. Airo, 19: 13-18.
  11. Ellis, P.M. and Okill, J.D. (1990) Breeding ecology of the merlin Falco columbarius in Shetland. Bird Study, 37(2): 101-110.
  12. Warkentin, I.G. (2009) Merlins (Falco columbarius) scavenge road-killed show shoe hares (Lepus americanus) in interior Alaska. Journal of Raptor Research, 43(3): 254.
  13. Parr, S.J. (1994) Changes in the population size and nest sites of merlins Falco columbarius inWales between 1970 and 1991. Bird Study, 41(1): 42-47.
  14. Snyder, N.F.R. and Snyder, H. (2006) Raptors of North America: Natural History and Conservation. MBI Publishing Company, USA.
  15. Walker, L.A., Shore, R.F., Turk, A., Pereira, G. and Best, J. (2008) The predatory bird monitoring scheme: Identifying chemical risks to top predators in Britain. Journal of the Human Environment, 37(6): 466-471.
  16. JNCC Conservation Designations for UK Taxa (August, 2011)
    http://jncc.defra.gov.uk/default.aspx?page=3408