LITMIR.BIZ

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of a mile or more; speeds in excess of sixty m.p.h. were only attained for a much shorter time. The speed of the vertical stoop is undoubtedly well over a hundred miles an hour, but it is impossible to be more precise. The excitement of seeing a peregrine stoop cannot be defined by the use of statistics.

      Peregrines arrive on the east coast from mid-August to November; the majority reach here in late September and the first half of October. They may come in from the sea in any weather conditions, but are most likely to do so on a clear sunny day with a fresh north-west wind blowing. Passage birds may stay in one area for two to three weeks before going south. Return passage lasts from late February to May. Winter residents usually depart in late March or early April. Juvenile falcons are the first peregrines to arrive in the autumn, followed by juvenile tiercels, and later by a few adult birds. Most adults do not come so far south, but remain as close as they can to their breeding territory. This order of migration, which prevails along the European coastline from the North Cape to Brittany, is similar to that observed on the eastern coast of North America. Ringing recoveries suggest that immigrants to the east coast of England have come from Scandinavia. No British-ringed peregrines have been recovering in south-east England. Generally speaking, all the juveniles that wintered in the river valley, and along the estuaries, were paler in colour than juveniles from British nests; they had a distinctive wing pattern of light reddish-brown wing coverts and secondaries contrasting with black primaries, similar to that of a kestrel.

      The territory in which my observations were made measures roughly twenty miles from east to west and ten miles from north to south. It was hunted over by at least two peregrines each winter, sometimes by three or four. The river valley and the estuary to the east of it are both ten miles in length. Together they formed a long narrow centre to the territory, where at least one peregrine could always be found. Why these particular places were chosen it is difficult to be sure. Most parts of England, including towns and cities, could provide a winter’s keep for a resident peregrine, yet certain areas have always been regularly visited, while others have been ignored. Peregrines that have a definite liking for duck or shore birds will obviously be found on the coast, at reservoirs and sewage farms, or in fenland. But the birds that wintered in the valley took a wide range of prey, in which woodpigeons and black-headed gulls predominated. I think they came here for two reasons: because this was a wintering place that had been used for many years, and because the gravelly streams of the valley provided ideal conditions for bathing. The peregrine is devoted to tradition. The same nesting cliffs are occupied for hundreds of years. It is probable that the same wintering territories are similarly occupied by each generation of juvenile birds. They may in fact be returning to places where their ancestors nested. Peregrines that now nest in the tundra conditions of Lapland and the Norwegian mountains may be the descendants of those birds that once nested in the tundra regions of the lower Thames. Peregrines have always lived as near the permafrost limit as possible.

      Peregrines bathe every day. They prefer running water, six to nine inches deep; nothing less than two inches or more than twelve inches is acceptable to them. The bed of the stream must be stony or firm, with a shallow incline sloping gradually down from the bank. They favour those places where the colour of the stream-bed resembles the colour of their own plumage. They like to be concealed by steep banks or overhanging bushes. Shallow streams, brooks, or deep ditches, are preferred to rivers. Salt water is seldom used. Dykes lined with concrete are sometimes chosen, but only if the concrete has been discoloured. Shallow fords, where brown-mottled country lanes are crossed by a fast-running brook, are favourite places. For warning of human approach they rely on their remarkably keen hearing and on the alarm calls of other birds. The search for a suitable bathing place is one of the peregrine’s main daily activities, and their hunting and roosting places are located in relation to this search. They bathe frequently to rid themselves of their own feather lice and of the lice that may transfer to them from the prey they have killed. These new lice are unlikely to live long once they have left their natural host species, but they are an additional irritation to which the hawk is most sensitive. Unless the number of lice infesting the hawk’s feathers is controlled by regular bathing, there can be a rapid deterioration in health, which is dangerous for a juvenile bird still learning to hunt and kill its prey.

      Though there can be many variations, a peregrine’s day usually begins with a slow, leisurely flight from the roosting place to the nearest suitable bathing stream. This may be as much as ten to fifteen miles away. After bathing, another hour or two is spent in drying the feathers, preening, and sleeping. The hawk rouses only gradually from his post-bathing lethargy. His first flights are short and unhurried. He moves from perch to perch, watching other birds and occasionally catching an insect or a mouse on the ground. He re-enacts the whole process of learning to kill that he went through when he first left the eyrie: the first, short, tentative flights; the longer, more confident ones; the playful, mock attacks at inanimate objects, such as falling leaves or drifting feathers; the games with other birds, changing to a pretence or attack, and then to the first serious attempt to kill. True hunting may be a comparatively brief process at the end of this long re-enactment of the hawk’s adolescence.

      Hunting is always preceded by some form of play. The hawk may feint at partridges, harass jackdaws or lapwings, skirmish with crows. Sometimes, without warning, he will suddenly kill. Afterwards he seems baffled by what he has done, and he may leave the kill where it fell and return to it later when he is genuinely hunting. Even when he is hungry, and has killed in anger, he may sit beside his prey for ten to fifteen minutes before starting to feed. In these cases the dead bird is usually unmarked, and the hawk seems to be puzzled by it. He nudges it idly with his bill. When blood flows, he feeds at once.

      Regular hunting over the same area will produce an increasingly effective defensive reaction from possible prey. It is always noticeable that the reaction of birds to a peregrine flying above them is comparatively slight in September and October, but that it steadily increases throughout the winter, till in March it is violent and spectacular. The peregrine has to avoid frightening the same birds too often, or they may leave the area altogether. For this reason he may be seen hunting in the same place for several days in succession, and then not be seen there again for a week or more. He may move only a short distance, or he may go twenty miles away. Individuals vary greatly in their hunting habits. Some hunt across their territory in straight lines five to fifteen miles long. They may suddenly turn about and fly back on the same course to attack birds already made uneasy. These hunting lines may run from estuary to reservoir to valley, and from valley to estuary; or they may follow the lines of flight from roosting places to bathing places. The territory is also effectively quartered by long up-wind flights, followed by diagonal down and cross wind gliding that finishes a mile or two away from the original starting point. Hunting on sunny days is done chiefly by soaring and circling down wind, and is based on a similar diagonal quartering of the ground. When an attack is made, it is usually a single vicious stoop. If it misses, the hawk may fly on at once to look for other prey.

      In early autumn, and in spring, when days are longer and the air warmer, the peregrine soars higher and hunts over a wider area. In March, when conditions are often ideal for soaring, his range increases, and by long stoops from a great height he is able to kill larger and heavier prey. Cloudy weather means shorter flights at lower levels. Rain curtails the hunting range still further. Fog reduces it to a single field. The shorter the day the more active the hawk, for there is less time available for hunting. All its activities contract or expand with the shortening or lengthening of days on either side of the winter solstice.

      Juvenile peregrines hover whenever the wind is too strong to allow them to circle sufficiently slowly above the area they are surveying. Such hovering usually lasts for ten to twenty seconds, but some birds are more addicted to the habit than others and will hover persistently for long periods. The hunting hawk uses every advantage he can. Height is the obvious one. He may stoop (stoop is another word for swoop) at prey from any height between three feet and three thousand. Ideally, prey is taken by surprise: by a hawk hidden by height and diving unseen to his victim, or by a hawk that rushes suddenly out from concealment in a tree or a dyke. Like a sparrowhawk, the peregrine will wait in ambush. The more spectacular methods of killing are used less often by juveniles than they are by adults. Some soaring peregrines deliberately stoop with the sun behind them. They do it too frequently for it to be merely a matter of chance.

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