Woodland Hawks: Sparrowhawk and GosHawk
These two hawks – the supreme predators of our woodlands – are swift, silent and deadly in the hunt, specialising in the techniques of close encounter and surprise attack.
The sparrowhawk is well distributed throughout our more heavily wooded counties and is reasonably familiar to many people. But the goshawk is still a rare bird in the British Isles and its present status is poorly recorded and subject to much local secrecy.
What is surprising, making for great complications, is the considerable public confusion between the sparrowhawk and the familiar and conspicuous kestrel. People say that they have spotted a sparrowhawk hovering over a roadside verge, when this is the kestrel’s main hunting method, and something which sparrowhawks never do. Unlike the kestrel (which is a member of the falcon family), the sparrowhawk or broad winged hawk (an accipiter), is a shy, inconspicuous bird and the goshawk even more so. This is because both are predominantly woodland birds, and spend most of their time in the cover of trees.
Apart from a period in late winter and early spring when their high circling displays make them more visible, you are most likely to encounter a sparrowhawk as it sweeps low over gardens, along a country lane or hedgerow, or as it crosses at grass-top level from one wood to another. It sometimes makes a series of ‘kek-kek-kek’ calls, and also has a short cry ‘pew’.
Territory and display
The annual cycle of establishing a territory, advertising it to likely mates and courtship, begins much earlier than the usual breeding season of other birds. Sparrowhawks begin to soar and spiral above the nesting woods from late February onwards, especially on clear and breezy days. Females are usually more active than males, and the intensity of their high circling displays reaches its peak as nest building begins in the second half of March.
At this time of year the display also frequently includes a series of exciting, bounding undulations above the nesting wood. These are often so vigorous that the bird seems to ‘bounce’ upwards from the base of each steep descent. This is the one time of year when the birds are regularly in evidence, and you can expect to look for them with some degree of success.
Goshawks stake out their territories even earlier in the year than sparrowhawks. The female can become vocal soon after the new year. She is notably noisy early in the morning – when you may hear a harsh chattering cry ringing through the breeding woodlands even before dawn.
Females call the tune
Part of the reason for the louder, more noticeable female display is due to the dominant role that the much larger, more robust females play in each season’s pairing. The females also tend to stay in or near their nesting territories throughout the year; this makes them sitting tenants when the new year comes. The females make the first moves in attracting a mate into the territory that they have kept exclusively as their own for the past three or four months.
The hawks probably seek new mates each year, since they go their separate ways at the end of the breeding season. Both the male and female usually remain solitary throughout the autumn and winter, each with its own hunting territory. The female stays in her nest and the male drifts away, or even sometimes migrates south.
The goshawk lays her eggs from early April onwards, and the sparrowhawk some three weeks later. Clutch sizes are surprisingly large; five to six is normal for the sparrow-hawk, and three to four for the goshawk. The female is almost exclusively responsible for incubating the eggs while the male does all the hunting-calling the female off the nest to feed her once or twice each day.
Before the sixteenth century, when the British Isles were still heavily wooded, sparrowhawks and goshawks were abundant. Nowadays their presence and distribution are strongly influenced by the number of suitable woodlands still remaining.
The sparrowhawk survives just as well in a pattern of small woods and open fields as it does in extensive woods. The goshawk. However, requires a considerably larger territory. Often in excess of 8000 acres. About a quarter of this area must be relatively undisturbed woodland. Although both birds once prospered in the former extensive deciduous cover. They are now equally at home in conifers or mixed woodland, provided the cover is not too close. The goshawk favours spruce or pine, while the sparrowhawk prefers larch plantations for nesting, as well as mixed deciduous woodland for hunting.
By the 16th century 90%, of the former woodland cover in the British Isles had disappeared. The clearance of this native woodland was a major factor in reducing the numbers of goshawks and sparrow-hawks.
By 1900 the ravages of game preservation had removed the last breeding goshawk from this country, and had taken a heavy toll of sparrowhawks throughout the game-rearing areas. In the 1960s goshawks began to re-establish themselves, helped by the release of falconers’ birds. By this time, however. Sparrowhawks were suffering from the serious effects of DDT and other organochlorine pesticides. They were virtually exterminated from south and east England, and their numbers were much reduced elsewhere in the country.
The sparrowhawk accumulates DDT through what it eats. Insects and earthworms are the first to take in DDT sprayed on crops. Lawns or flowers; they are eaten by birds like thrushes which then fall prey to such predators as the .sparrowhawk. DDT interferes with the breeding biology of the sparrow-hawk. For example causing the female to lay thin-shelled eggs which break easily, and it also affects their general behaviour. Most of the DDT is laid down in the bird’s fat. When it starts to use up the energy stored in the fat-for example, to keep warm on a cold day, or to power itself for a long flight—the DDT is liberated and poisons the bird.
The use of DDT has been restricted or banned for many years, and the sparrowhawk has recovered some of its former numbers, with the current population estimated to be about 25,000 breeding pairs.
Given protection from pesticides and gamekeepers, the prospects for both the sparrow-hawk and the goshawk are good. The maturing of many forestry plantations will eventually help to provide the ideal habitat for returning goshawks.
The hunting methods of the sparrowhawk and goshawk rely mainly on silent observation. Stealth and final explosive acceleration. Both hawks exploit rich food sites within a territory, and return to them repeatedly as long as they remain productive.
The hawk sits silently on a perch, hidden in the cover of woodland, waiting for likely prey. It glides low to the ground, only as far as the next perch if necessary, until it singles out its victim. Then it approaches fast and low, using the cover of hedgerow or trees, flicks over the final hedge or bush at full speed and takes the unsuspecting prey with outstretched talons, either while the victim is still perched, or after a short and frantic pursuit.
The hawk’s tenacity sometimes leads it to pursue its prey into buildings (even occasion-ally to fly through glass windows). Sometimes too it chases its victim on foot into bushes. Individuals have been known to take house martins from under eaves, and young moorhens off the surface of a pond, and sometimes a hawk prospects for prey by soaring high into the air. Occasionally stooping (falcon-like) on prey on the wing.
After catching prey (with both feet if it is as large as a jay or wood pigeon), the hawk usually takes its victim into cover and perches on a tree stump, ant-hill or old nest platform to pluck the feathers off with its beak. You can easily identify such plucking posts by the scatter of feathers around them. The bird’s sharp talons then make short work of tearing the meat to pieces.
The hawks’ food includes game birds, wood pigeons and other woodland species. The goshawk, unlike the sparrowhawk, readily takes prey on the ground- attacking medium-sized mammals such as hares and rabbits.
Neither bird appears to be the specialised villain it is made out to be by gamekeepers, and game birds seldom form a substantial part of their diet. Some farmers and foresters today reckon that the increase in goshawk numbers will provide them with an ally against the destructive wood pigeon.