Influxes Into Britain of Hen Harriers, Long-Eared Owls and Short-Eared Owls in Winter 1978/79

Influxes into Britain of Hen Harriers, Long-eared Owls and Short-eared Owls in winter 1978/79 D. L. Davenport Si.ATHstaeH. he winter of 1978/79 was the coldest in Britain since 1962/63, and Tproduced outstanding numbers of several species, particularly water- birds (Chandler 1981). The influx of Hen Harriers Circus cyaneus during the first quarter of 1979, however, was probably the most spectacular event of the winter. This paper documents this influx, together with those of Long- eared Asia otus and Short-eared Owls A. flarnmeus, which also occurred in outstanding numbers. (In order to hasten writing and publication, the regions listed in the paper are generally those covered by the individual annual county reports and, therefore, do not necessarily correspond to the areas of the new counties of England, Scotland and Wales.) Hen Harrier In England, the main autumn arrivals of Hen Harriers occur in the southeast from mid October and continue throughout November. By the end of 1978, there were six roosts each of seven or eight individuals in East Anglia and Kent; although these were record numbers, they were by no means unexpected, as a continuing increase has taken place since 1974/75 (see below). The onset of the hard weather, in particular the blizzard of 30th-31st December, and the continuing snowfalls throughout January, produced an unprecedented midwinter influx of Hen Harriers along the length of the east and south coasts of England, especially between North Yorkshire and West Sussex, where numerous roosts were discovered. A much smaller, but equally unusual, midwinter influx of Rough-legged Buzzards Buteo lagopus also occurred on the east coast at this time. The extent of this influx of Hen Harriers is shown in table 1, which gives wintering totals for the principal (mainly coastal) counties and a summarised total for the remaining counties of England. [Brit. Birds 75: 309-316,July 1982] 309 310 Hen Harriers, Long-eared Owls and Short-eared Owls in 1978/79 Table 1. Numbers and main roosts of Hen Harriers Circus cyaneus in England, January- March 1979 County areas are generally those covered by the annual county bird reports, and are listed in geographical order County area Total (main roosts) Northumberland 15 Durham 6 Yorkshire (incl. north Humberside) 55 (5,7) Lincolnshire (incl. south Humberside) 45 (4.5,7) Cambridge 26 (7,14) Huntingdon 13 Norfolk 90 (4,6,8,8,9,10.13) Suffolk 95 (5,5,6,9,10,14,18,19) Essex 50 (12) Kent 05 (4,4,4,10,13,20,27) East and West Sussex 60 (11) Hampshire 40 Wiltshire 11 Dorset 30 (8) Somerset 12 Devon 15 Cornwall 30 (5) Other county areas 55 GRAND TOTAL 753 Elsewhere in Britain, there were no reports of unusual numbers of Hen Harriers. In Scotland, for instance, five wintering on the Insh Marshes, Inverness-shire, were described as normal, while three (the same number as in the previous winter) at Loch of Strathbeg, Aberdeen, included one wing-tagged in Orkney. Many wintering in the north of England (including an unprecedented three at Washington, Co. Durham, and an exceptional three at Leighton Moss, Lancashire) probably involved moorland harriers driven to coastal feeding grounds by the severe weather: on the Derbyshire moors, which normally support a winter roost of four to six, there were no records between 31st December and 7th April; although numbers on the 107. Male Hen Harrier Circus cyaneus, Netherlands, February 1976 (Robin Williams) Hen Harriers, Long-eared Owls and Short-eared Owls in 1978/79 31 108. Female Hen Harrier Circus cyaneus, Hebrides, May 1976 (Dennis Green) Yorkshire moorlands were considered to be above average, as were those elsewhere in Yorkshire and North Humberside. The effects of the hard weather were immediate: by 4th January, there were already 14 roosting at Minsmere, Suffolk, and nearby at the Walberswick roost there was an early peak of 19 by 13th; a secondary roost between these two, at Dunwich, held a maximum often on 12th February. Elsewhere in East Anglia, the largest roosts were of 12 at Tollesbury, Essex, 13 at the main site (locality withheld) in Norfolk, 14 at Wicken Fen, Cambridgeshire, and 18 at Oulton Broad, Suffolk. In Kent, the roost at Stodmarsh increased to 25 by 24th January, with further high counts of 25 on 3rd February, and 27 on 11th comprising seven adult males, three second-winter males, and 17 'ringtails' (females/immatures). A roost on the Thames marshes, at Egypt Bay, Kent, not discovered until 20th February, was frequented by 15-20 harriers until 19th March; there was evidently a large turnover at this site, which was used by at least 28 different individuals (five adult males, three second-winter males, and 20 ringtails). A further roost, at Walland Marsh, Kent, reached a late peak of 13 on 7th March (this site is of particular interest because, before the recent increase, it was the only documented English roost, having been used by four to six harriers during 1953-55). A few other roosts also had their highest numbers in March, presumably owing to returning spring migrants. Information on age and sex was received for two-thirds of the national total of over 750 harriers. This showed that adult males, second-winter males and ringtails occurred in the ratio of 5:1:15, although it was apparent that many observers failed to distinguish second-winter males. Long-eared Owl As with the unprecedented influx of Long-eared Owls in 1975/76, the 1978/79 influx was heralded by an outstanding autumn passage, with 312 Hen Harriers, Long-eared Owls and Short-eared Owls in 1978/79 109. Long-eared Owl Asio otus, Netherlands, April 1978 (Frits Houtkamp) record numbers on Fair Isle, Shetland, in October. The main arrival was on 15th- 16th: six on the Isle of May, Fife, and ten on Fair Isle, where up to seven remained until 19th. Fair Isle had another peak of four on 16th November. Farther south there were numerous coastal records of singles in October-November; only one, however, was recorded at Spurn, North Humberside (on 31st October), although up to eight roosted there during 5th-9th December. By December, there were already 50 Long-eared Owls in Kent, half that county's eventual total. Information from other counties suggests that this gives a true indication of the comparative importance of the autumn migration and the subsequent hard weather: the combined effects of these two events produced a winter total second only to that of 1975/76. The 1978/79 influx was confined mainly to Shetland and Orkney, and the east coast from Northumberland to Kent. Table 2 shows the winter Hen Harriers, Long-eared Owls and Short-eared Owls in 1978/79 313 Table 2. Numbers and main roosts of Long-eared Owls Asia otus wintering in Shetland, Orkney and England, 1978/79 County areas are generally those covered by the annual county bird reports, and are listed in geographical order County area Total (main roosts) Shetland 45 (5,14,17) Orkney 61 (6,6,20,24) Northumberland 47 (10,21) Durham 23 (13) Yorkshire (incl. north Humberside) 40 (4,4,5,7,14) Lincolnshire (incl. south Humberside) 41 (4,13,16) Cambridge 15 (7) Huntingdon 15 Norfolk 20 (7) Suffolk 28 (4,5,9,10) Essex 51 (5,6,6,14) Kent .04 (4,5,5,5,7,8,18,32) London 27 (4,4,6) Lancashire 25 (5,6,12) Other English Counties 62 GRAND TOTAL 604 totals for the counties involved, with the largest roosts in brackets, and a summarised total for all other English counties. Short-eared Owl As with the Long-eared, the winter influx of Short-eared Owls in 1978/79 started with an outstanding passage in October. Fair Isle had an early count of 15 on 1st, while on 12th seven arrived on the Skerries, Shetland, 14 on Fair Isle and 25 at the Forties oilfield (176km ENE of Aberdeen). An even larger arrival followed on 15th October: 30 on Fair Isle, nine on the Isle of May, and 32 along the Aberdeen coast, including 17 between Peterhead and Rattray Head. Although these movements were noted all down the east coast, there was no indication that numbers south of Northumberland were unusual; Spurn, for instance, recorded only up to four between 13th and 22nd October. In the southwest, on the other hand, Cornwall also recorded an unprecedented passage of 50 Short-eared Owls during October-November. During November-December, it finally became evident that virtually all parts of England, both coastal and inland, were affected by an exceptionally large and widespread influx of this species. The effects of the subsequent hard weather served only to augment numbers. Table 3 shows the wintering totals for all English counties, with the largest concentrations in brackets. There was no indication of unusual numbers elsewhere (in Shetland, there were no records at all of Short-eared Owls in the first quarter of 1979). Discussion It is now evident, in retrospect, that numbers of Hen Harriers wintering in southeast England have increased steadily over the last 20 years. Recently, this increase has accelerated, and numbers have trebled between 1975 and 1980. In Kent, for instance, compared with a normal wintering population 314 Hen Harriers, Long-eared Owls and Short-eared Owls in 1978/ 79 110. Short-eared Owl Asioflammeus, Netherlands, February 1976 (Frits Houtkamp) of about 12 in the early 1970s, there were 18 in the winter of 1977/78 and 38 in 1979/80. An interesting aspect of this sudden increase has been the inevitable discovery of numerous winter roosts.

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