The Sparrowhawk is arguably the most exciting of all the birds which visit our gardens, and is now a much more common sight having gone through a large population decline over many centuries – and especially during the 1950s and 60s – but has now bounced back. The female bird is larger than the male, and is brown on the back and wings, with brown bars on its pale underparts and breast. The adult male has a bluish slate-grey upperparts and wings, and more of an orange-brown colour to the bars on its underside and breast. Both male and female Sparrowhawks have yellow legs, which are long and with talons which are evolved to catch and hold small birds. Juvenile Sparrowhawks (up to the age of one year) have plumage which largely resembles female adults, though the breast markings are more streaked and with chevrons.
Female Sparrowhawks have a wingspan of up to 70cm, with the male’s being nearer to 55cm. Both male and female Sparrowhawks develop bright yellow eyes, though as the birds further mature the iris becomes more orange, and in some males even wine red.
Of the UK’s birds of prey, the Sparrowhawk is by far the most likely to visit gardens. Other than the larger Goshawk, which anyway is a much shyer and rarer bird of prey which doesn’t visit gardens, the Sparrowhawk cannot be confused with any other raptors – and is very different to the Kestrel which is a species of falcon rather than an accipitridae. It is also very different to Red Kites, the Peregrine Falcon and Buzzard.
Sparrowhawk nesting and breeding habits
The male Sparrowhawk does much of the nest building, which is located in the fork of a tree or on the base of a branch against the trunk, with a preference for conifers. The nest is usually fairly high in the canopy and hidden from view, and consists of a strong platform of twigs and sometimes also lined with flakes of bark. There is one brood of 3-6 eggs with the incubation carried out by the female alone, then also brooding the young birds after they hatch until they’re old enough to maintain their own body temperature. During all of this time, the male bird provides the food for both the female and young.
Sparrowhawk history and population trends
As a species which is dependent on woodland, deforestation in the British Isles over many millennia will have greatly reduced the population. However, persecution from gamekeepers from the 1840s (when guns became sufficiently efficient to make a negative difference) right up until 1961 when the species gained legal protection, further reduced the population. And a degree of illegal persecution still, sadly, takes place to this day and in particular on sporting estates.
In addition to this, the use of DDT pesticides in the 1950s and 60s lead to a further dramatic decrease in the Sparrowhawk population, with the effects of the poison in the food chain leading to infertility and a thinning of egg shells which then either a) meant the developing chick died of cold, or b) the egg was broken by the female when brooding. The good news is though that, with DDT banned and out of the food chain, the population has bounced back strongly from the mid-1970s onwards, though has levelled out somewhat since the mid-1990s.
Behaviour traits of Sparrowhawks
Sparrowhawks are a fantastic bird to observe, with their hunting behaviour often appearing to border on lunacy as they take huge risks when maneuvering between trees and other obstacles in order to catch prey. As part of this and in the early stage of the hunt, a Sparrowhawk will attempt to approach its target out-of-sight, and therefore will use the cover of buildings, hedgerows, undulations in the ground level etc. to get as close as possible before making a final lunge – and all of this at speeds of up to 50kph. Despite all of this effort, it’s likely that only about one in ten attacks are successful and result in a kill.
The alarm call and more general call of the Sparrowhawk is a single and slightly piecing note.
Sparrowhawk diet and food
The diet of the Sparrowhawk is almost exclusively small birds, though occasionally bats may also be taken. As female Sparrowhawks are larger than males, they’re able to prey on larger birds and can even kill something up to the size of a Wood Pigeon. The male bird’s limit is up to the size of a Mistle Thrush, though for both male and female birds they’re likely to take smaller birds than those two examples. Added to which, there is no preference for a particular species of prey, with whatever is available, most numerous and easy to catch being the first choice – hence why finches are often targeted on garden bird feeders. Thrushes including Blackbirds will also be taken in gardens. During the songbird fledgling season, around 40% of the Sparrowhawk’s diet is made of young birds such as Starlings, buntings and species of tit.
Occasionally Sparrowhawks will also catch and eat small mammals and including – and perhaps surprisingly – rats.
Do Sparrowhawks reduce songbird populations?
No, overall Sparrowhawks do not reduce songbird populations, and it’s an unfortunate misconception that they do. The reality is that there’s a positive correlation between good local populations of songbirds and that of Sparrowhawks. So with sufficient prey Sparrowhawks are able to successfully breed, but with less prey they’re less likely to be successful. For context, it’s worth remembering that song bird species typically have large broods and often multiple ones in each season, and this because the level of fatalities are very high. These fatalities can be for a host of reasons, with predation by Sparrowhawks representing a relatively low number.