Sparrowhawk (Accipiter nisus)
Over much of Europe this is one of the commonest birds of prey, but it can be difficult to see. It spends a great deal of time hidden in foliage, watching the comings and goings of potential prey. Only when displaying or soaring to scan the ground is this bird obvious, and then the sight of its familiar long tail and broad, blunt-ended wings will provoke calls of alarm from small birds as they dive for cover.
By Steve Ward – https://www.flickr.com/photos/steventimothyphotography/8649438128/, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=31706498
The Sparrowhawk is a small bird of prey, not much larger than a pigeon, but it is well adapted for rapid, manoeuvrable flight through trees and around obstacles. To hunt it sets off from an observation perch and accelerates very rapidly towards prey, with a few fast wing-beats interspersed with closed-wing glides; as it nears the target it usually keeps behind some kind of screen, such as a hedgerow or garden fence, to conceal its approach. If all goes well it will be spotted too late when it breaks cover, and the ambush is completed as the bird grips its prey in its talons. The claws administer the fatal wound, and the prey is taken to a special perch to be plucked and eaten.
In common with several bird hunting raptors, the sexes of the Sparrowhawk are of quite different size, the female being up to 25% larger and heavier. In the majority of bird species males tend to carry the greatest bulk, so this grandly titled “reverse sexual size dimorphism” in birds of prey is something of a puzzle. It is known that Sparrowhawks have gender-specific food preferences to prevent competition in the non-breeding season (males hunt tits and finches in woodland, females go for thrushes, Starlings and pigeons in more open country), but this doesn’t explain why it is the male that is the smaller. But it might be related to the division of labour in the breeding season. The male Sparrowhawk takes on the majority of hunting, bringing food to the female and nestlings up to 20 times a day. Perhaps having a small, highly mobile male to do the work, rather than a larger, slower hunter might be an advantage?
By gailhampshire from Cradley, Malvern, U.K – Sparrowhawk Accipiter nisus, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=63754710
Whatever the reason, the female’s size ensures that she is the dominant member of the pair, and it is in this role that she that initiates much of the courtship display. Soaring high above the territory, she fluffs out her under-tail covers, accentuating their white colour, and then either flies up and down in an undulating flight, or dives spectacularly from several hundred metres up, only to break the fall just above the treetops.
Sparrowhawk pair-bonds officially last only one season, although couples will reform if it is convenient to do so. The Sparrowhawk’s stick nest, placed at any height in a tree, is also remade each year.
From ‘Birds: A Complete Guide to All British and European Species’, by Dominic Couzens. Published by Collins and reproduced with permission.