The Hen Harrier Page 9
The results of my own studies and enquiries, including reference to the provisional map for the Atlas of Breeding Birds, show that in the first half of the 1970s, there has been continued increase and spread in some areas, but in others there has been no definite change and there have even been some local decreases. In Orkney, Balfour considered that the population was still increasing in 1974, with 63 nests found (many polygynous matings) and an estimated minimum of 75 nests on Mainland, six to eight on Rousay and three on Hoy. In Sutherland, Nethersole-Thompson reported a good many pairs in 1975 and an evident increase, but Pam Collett told me that nesting was still rather sparse in Caithness in 1974 and 1975. In the Outer Hebrides, Peter Hopkins doubts if the breeding population is increasing, with a minimum of 13 pairs divided between North and South Uist in 1975. The results of my own enquiries and observations, in 1974, suggested about 15 pairs in the Outer Hebrides including one nest on a third island. There was still no confirmed breeding in Lewis or Harris during the Atlas years (1968–72), but there were records for Skye, Mull and Islay. Extensive plantations of young conifers are at present favourable to an increase on Mull, but on the moors of Islay, Graham Booth (1975) said that Hen Harriers are still only attempting to re-establish themselves in the face of persecution.
There are large areas in the West Highlands where breeding has not been reported and the main strength on the mainland continues to be in parts of Deeside, East Sutherland, Perthshire and Argyll.
On 18,000 hectares (70 square miles) of Deeside, where Nick Picozzi has studied moorland nesting, displaying harriers were seen in 17 moorland localities in spring 1974, but young fledged from only six nests. Here, and on the Perthshire moors, persecution is heavy and although a moor owner in southern Perthshire assured me that harriers were common and increasing in 1974, he made it clear that keepers are generally encouraged to destroy nests and birds, and it is unlikely that many young survive there. Geoffrey Shaw, however, found birds present in the breeding season in nine scattered localities in the Southern Highlands, between 1972 and 1975, and confirmed breeding in four of these. In 1973, he found five pairs in Dunbartonshire, where recent nests have mostly been on moorland in close proximity to forest; and single pairs, near the Perthshire/Kinross border (1972) and in Stirlingshire (1973), were in new localities. On the other hand, the maturing forest plantations of Loch Ard, west of Aberfoyle, which were an important breeding area in earlier years, had almost ceased to provide the conditions for nesting, and over the Southern Highlands in general there is a changing situation as some forests become too old for nesting and new ones are colonised.
A small number of pairs continue to breed in Arran where I found them in afforested localities in 1975, but I was also told of nesting on open moorland (Hogg, 1976). Across the water in Kintyre there has been some recent decrease from about 20 pairs in 1973 (Turner) to nearer ten in 1975. In the old counties of Ayr, Wigtown, Kirkcudbright and Dumfries not less than 12 pairs were present in 1974 but the number of nests was probably fewer than this, both in 1974 and 1975. In south-west Scotland as a whole, there is no sign of a recent increase in spite of a massive extension of afforestation on hill land. In this region there is evidence of persecution on moorland. The decline in Kielder Forest, Northumberland, which began in the late 1960s, was not halted and no evidence of breeding was obtained there in 1974 or 1975.
Graham Williams estimated some 20 pairs nesting in Wales in 1975 and reports that they had ‘a good year again’. He also noted colonisation of new areas in mid Wales, but he considers that the rate of increase in Wales generally has slowed down in recent years. Apart from one site in a forest plantation, which was occupied for six years in the 1960s, all the Welsh nests have continued to be found on the moors, although in 1975 the behaviour of one male was indicative of another forest nest. Nearly all the sites are on keepered ground and Graham Williams has known four instances of nest destruction by man. Nevertheless, compared with most Scottish grouse moors, persecution seems less intense in Wales and a good proportion of pairs rear young.
There has been some recent extension of breeding in England by a small number of pairs as far south as the West Midlands, which suggests that Hen Harriers might become re-established in haunts where they were lost as breeding birds more than a century ago.* In Ireland there had been a spread of nesting into 13 counties by 1971 when, for the first time this century, successful nesting (two broods) was recorded in the north, in Co. Antrim.
In 1973, Parslow estimated the breeding population of Britain and Ireland as over 100 pairs, perhaps much more. It is doubtful if there has been a substantial increase since then, but in any of the last two or three years the total has certainly been much more than 100 pairs. Particular caution is needed in any attempt to give a figure for the number of pairs owing to the occurrence of polygyny in some places. David Scott’s estimate for Ireland is an average of 250–300 pairs in 1973–75 and I think that the average annual total for Britain in this period may be at least 500 pairs, so that a total population of 750–800 pairs might not be very wide of the mark. In some regions it is very likely that further colonisation is being prevented by persecution, but it is difficult to account for the lack of increase, and even some decrease, in the extensive tracts of young forest in southern Scotland and northern England. Disappearance of birds in spring, after they have settled and displayed on forest breeding grounds, has been noted in Kintyre and Galloway and it is likely that in Galloway, at least, the great reduction of open moorland at fairly low elevations, which may be important for hunting, is have a limiting effect. In the absence of intensive grouse moor management, Hen Harriers in Ireland are evidently less dependent on the new forests for nesting cover and comparative freedom from human persecution than in many parts of the mainland of Scotland. It is interesting that such a successful colonisation of the open moorland has been made in North Wales in spite of some persecution. Breeding failure by Hen Harriers in France and Scandinavia has been attributed to the effects of agricultural pesticides. Many of our own Hen Harriers must at times be at risk from these, especially those which winter at long distances from their breeding grounds, but there has been no clear evidence of increased hatching failures or egg breakage to suggest that pesticides have reduced breeding success.
Postscript. Since I completed this chapter Edward A. Blake’s paper ‘The Return of the Hen Harrier’ has appeared in The Forth Naturalist and Historian, Vol. I, 1976. This paper includes interesting data on the colony at Carradale, Kintyre, where over 300 young were fledged, 1957–64. Food, habits and habitats are also discussed.
On the post-1939 recovery of the Hen Harrier on the Scottish mainland Blake repeats his earlier statement (see here) that it was already common in the Highlands by 1945 but apart from a shepherd’s evidence of several nests near Callander in the late 1940s, he cites no sources to add significantly to J. W. Campbell’s summary (see here–here). Blake found his first nest in Glen Artney, Perthshire, in 1951. He emphasises the decline on the Perthshire grouse moors, in the 1950s, caused by persecution. Campbell also commented on this (see here). Today (1977), persecution on moors appears to be continuing to prevent consolidation in Britain and David Scott tells me that in Ireland it has probably been severe in some localities and may have cut back some gains.
* Possibly the Goshawk, but the reference to size is more suggestive of Sparrowhawk.
* British Birds Vol 65, No 8, p. 358.
* Michael Seago considers that the evidence for a recent nest in a coastal part of Norfolk is not entirely satisfactory.
CHAPTER FOUR
What Kind of Predator?
Hunting methods
In its most usual type of hunting flight, the Hen Harrier flies low, flapping and gliding at an average of less than three metres above the ground. C. A. B. Campbell found that a female hunting rough pasture flew at 50 km/h alongside his car. Many of those who have described the manner of hunting have been shooting men and, not surprisingly, have likened it to a w
ell-trained setter or pointer ‘working every inch of the ground’. Yet, to my mind, the most evocative description was by the Frenchman, Lafond (Geroudet, 1965), who said it hunted ‘comme s’il cherchait un objet perdu’. Like any expert searcher, it examines the ground selectively, often doubling back to course a promising patch of cover a second or third time. Its progress over a moor or marsh may seem slow and wayward until the observer realises how skilfully it uses variations in contour and height of vegetation to achieve the best chance of surprising prey. It flaps and tacks laboriously to reach the summit of a little hill crest, then angles downward into a hollow beyond with a sudden surge of speed. Eric Ennion (1943) described how Montagu’s Harriers, in a comparable way, surprised ground-feeding Turtle Doves by a lightning drop after an approach screened by clumps of tall reeds. The technique of low-level flight, varied pace and use of ground enables a harrier to exploit its long legs to maximum effect in striking at prey on, or close to, the ground.
To a human observer the hunting flight of a Hen Harrier often seems to involve a prodigious amount of travelling for infrequent reward, but in most kinds of terrain it is extremely difficult to keep the bird continually in view for a long time. I have watched a male hunting five year old conifers and forest rides for two hours without making a capture. On the other hand, I have seen one, in autumn, catch three voles on upland pasture in little over 20 minutes. It may have been killing more than it could eat, for the third vole was dropped and the harrier flew on without retrieving it. A very characteristic way of making a kill, on the ground, begins with a swift pirouette or half-turn, with tail fanned, as the low flying harrier suddenly stalls and drops into tall vegetation. The outcome of these pounces may not be apparent for a few minutes, or longer, when the bird may rise with prey in a foot.
One June evening in South Uist, with the low sun flooding a vast amphitheatre of moor and mountain with rich colour, I watched a male hunting during the hour before sunset. In the brilliant light I could follow his movements with my binoculars as he worked a gully below Beinn Mhor, two kilometres away. He began to come nearer, following the course of a burn and was then lost among the heathery mounds of the low moor. For two minutes I had no idea where he was and had little hope of finding him again. Then he re-appeared, in the foreground of this great landscape, still following the burn, just below me. Even so, he kept so low between the steep banks of the burn that when he pirouetted and pounced I could not be certain whether the prey, a Meadow Pipit, had been taken on the ground or just above it. I glimpsed a second pipit escaping by flying to one side and believe that the other had been caught as it began to rise. The prey was taken a short distance to a prominent perch above some old peat cuttings and, after feeding, the harrier remained perched there, quite still and upright, like a tiny grey statue until, long past sunset, I gave up hope of discovering whether it would seek a more sheltered spot for the night.
From his extensive studies of Marsh, Montagu’s and Hen Harriers, Schipper concluded that the last was the most agile hunter. His evidence was from observation of hunting behaviour and from a comparison of prey brought to nests. Hen Harriers caught more passerine birds, able to fly, than either of the other harriers. I can cite several instances of Hen Harriers capturing flying birds. I have seen a male take a small bird, by a sudden jink, as it flew just above a moor, while Louis Urquhart has recorded how a male, in Arran, put out a foot and caught a small flying bird, ‘like a cricketer in the slips making a brilliant one-handed catch’, less than three metres above the ground. Dick Orton observed another male, in Wales, taking ‘the tail-end Charlie’ from a flock of Starlings, in a sudden burst of acceleration. D. H. Macgillivray, of Machrie, Arran, has seen a low-flying Snipe caught after it had been flushed by a dog. The harrier showed remarkable acceleration. I have seen several captures among 2–6 metre conifers when the prey was almost certainly in flight. Schipper considers that the Hen Harrier is even more manoeuvrable in flight than the lighter-bodied Montagu’s Harrier, due to its longer tail in relation to wing-length from wrist to tip.
Long flight pursuits of prey are not often observed, but H. M. S. Blair (Bannerman, 1953) saw a male in Norway chase and capture a Meadow Pipit, ‘stretching out one long talon to grip it’, while Geroudet wrote that the Hen Harrier could chase and capture passerine birds with as much speed as a Sparrowhawk. The examples I have cited, of Hen Harriers taking flying prey, mostly refer to males, which are generally more agile than the heavier females. The habit of capturing flying prey is certainly commoner in the Hen Harrier than many writers suppose. A species which so often preys on full-grown passerine birds is, I believe, as likely to catch them in the air as on the ground. In this respect Jacques Delamain’s suggestion that Crested Larks flew up as a harrier’s shadow passed over them is intriguing.
In view of the fact that Red Grouse are an important prey of Hen Harriers in some districts (see here), it is surprising how little has been recorded about the way in which they are caught. Packs of grouse usually fly when they see the approach of any broad-winged predator, such as eagle or harrier, unless it is high in the sky, but single birds or pairs may try to escape attack by crouching. Watson and Jenkins described how a cock Red Grouse, when stooped at by a male Hen Harrier, stood up and struck towards the attacker with its bill, repeating this behaviour when the harrier stooped a second time. The harrier then flew on. On another occasion a hen Red Grouse flattened herself into long heather beneath a stooping harrier. She then jumped up with wings spread and avoided the harrier’s strike by ‘a quick bouncing movement’ back to the ground. I have observed rather similar incidents; once I saw a single grouse and, another time, a pair, rise almost vertically into the air immediately under a hunting Hen Harrier. On each occasion the harrier jinked but failed to make contact with the grouse which ‘bounced’ back to the ground while the harrier proceeded on its way. I have never been near enough to a Hen Harrier killing a grouse to see whether it was caught on the ground or just above it. A 19th century observer, Mr McCalla in Connemara (Thompson, 1849), who had often seen harriers attack grouse, wrote that a struggle took place, the grouse rising into the air contrary to its usual mode of flight. His account suggests similar behaviour by the grouse to that already described. Graham Williams has seen a male diving continually on to a patch of heather where there was a brood of Red Grouse; the adult Red Grouse ‘jumped’ out of the heather each time the harrier swooped past but in spite of this the latter was seen to pick up a young grouse and fly off with it.
William Macgillivray’s son, while searching for insects on the Pentland Hills in 1835, saw a pair of Hen Harriers ‘start a Red Grouse which one of them captured after a short chase’. I have often seen both Red and Black Grouse flushed by Hen Harriers on ground where all three species roosted in proximity; the grouse did not then rise unless a harrier passed very near to them. A harrier coursing low over marsh or field will flush duck, and even geese, but they do not rise until the hunter is close upon them. I have seen this happen many times in Galloway but not once has the harrier struck at or pursued the wildfowl. It has always seemed intent on watching the ground for smaller prey in its immediate path. Harriers spend much more time in coursing flight than other predators of comparable size, and they appear to husband their energies by waiting for the chance of captures easily within their manoeuvrability and grasp.
Breckenridge’s verdict that it is a predator of comparatively weak grasp needs some qualification, at least in respect of females*, which are certainly able to kill prey as large as adult Red Grouse and half-grown rabbits. Nevertheless, Hen Harriers do sometimes appear to have difficulty in retaining their grasp, even of comparatively small prey. I have seen a small bird escape after being carried a short distance in the foot—in this instance the prey was retrieved and secured—but a better example of a harrier’s ‘weak grasp’ is given by R. C. Dickson; he observed a ringtail drop into rough grass and rise with prey, possibly a rat, which it dropped. Twice more the harrier clutched
and released the prey which jumped up at it and finally escaped. During this episode a male Hen Harrier, which had been hunting near by, came close to the ringtail and itself dived into rushes, possibly after the same prey, without success. Dugald Macintyre (1936) saw a Hen Harrier turn on its back to capture a mobbing Lapwing which was then carried a short distance before it escaped, apparently unharmed. In this incident the harrier evidently took the Lapwing in reaction to its mobbing, but its release was perhaps another example of the difficulty of maintaining a firm grasp. Prey which has been secured is not always crushed to death, as I have found a fledgling Skylark still alive after being dropped to a brood of young Hen Harriers and Nick Picozzi has found a fledgling Meadow Pipit, alive but dazed, at a Hen Harrier’s nest. Schipper, however, noted living prey only at nests of Marsh and Montagu’s Harriers, not at those of Hen Harriers.
An unusual attempt by a Hen Harrier to lift a full grown duck, probably a Wigeon, from the sea is quoted by Bannerman (1953). The harrier (the sex was not stated) made two unsuccessful attempts to secure its prey, once carrying it for about ten metres before dropping it. In Kintyre I was told the story of a male Hen Harrier striking down a Greylag Goose. It was vouched for by five witnesses familiar with harriers, and there was no doubt about the goose, which fell injured and ended up in the pot. It seems a pity to have to add a note of scepticism, but perhaps the possibility of confusion between a grey harrier and some other light-coloured predator such as a Greenland Falcon or a grey Goshawk cannot be discounted. Nick Picozzi considers that it would be impossible for even a female Hen Harrier ever to strike down a bird as large as a goose.