British Birds
Vol. 57 No. 6
JUNE 1964
Observations in Hampshire and Dorset during the 1963 cold spell By J. S. Ash
INTRODUCTION VERY MANY BIRDS died during the cold spell of early 1963 and, sad and unfortunate though this was, a large supply of potentially interest ing biological material was made available. An examination of such material provides information on minimum survival weights, differen tial mortality and resistance to cold of the two sexes, the incidence of disease and parasites, and whether there are factors influencing survival under adverse conditions. This paper summarises observations made at that time in a relatively small part of central southern England on the borders of Hampshire and Dorset; it concerns the area between Fordingbridge and Cran- borne, extending to the coastal zone around Poole Harbour and Studland. A few notes from other localities are included. Much of it is based on the examination of a total of 332 dead birds of 46 species, many of which were aged, sexed by dissection, weighed and measured. They were also examined for disease and endoparasites and some were submitted for toxic chemical analysis, but these results will be published elsewhere (Ash and Sharpe in press). There have been few similar surveys: I have discussed relatively small samples in the cold spells of 1954 and 1956 (Ash 1957); Harris (1962) examined a large number of corpses on Skomer Island, Pembrokeshire, in January 1962; Jones
Since Dr. Ash's paper is primarily concerned with weights and racial determinations, we believe it merits separate publication from the main analysis of the 1963 cold spell which is being prepared by H. M. Dobinson and A. J. Richards, for the latter will deal chiefly with the general effects of that period over the country as a whole rather than with these specialised aspects (see Brit. Birds, 56: 228-229; and 57: 42)- This main analysis is now in draft and awaits only the completion of certain regional summaries which are due to appear in county reports. We hope to publish it in an enlarged issue in the late autumn (probably October).—EDS. 221 BRITISH BIRDS (1962) confined himself to a study of one species, the Fieldfare,* of which many died in Anglesey in January 1962. The sections which follow include a general summary of the effects of the cold spell in the area concerned (though for many species there is little or no information), racial determinations in a few particular Table 1. Maximum day and minimum night temperatures (° C) at Fordingbridge (January only) and Hum, Hampshire, 21st December 1962 - 6th March 1963 The Fordingbridge site is sheltered from easterly winds; Hurn is in a frost hollow, but it is nearer the coast than Fordingbridge and this no doubt accounts for the higher day and lower night temperatures. The mean figures for December and March at the foot of the table are limited to the duration of the extreme cold; in other words, the December mean is taken from the 22nd and the March mean to the 5 th. The total duration of the cold spell was 74 days and during this period the maximum and minimum means at Hurn were 1.10 C and — 3.90 C December January February March HURN HURN FORDINGBRIDGE HURN HURN Q Max Min Max Min Max Min Max Min Max Min
1st — 0.3 —0.8 —0.5 —1.5 —0.1 —2.8 5.0 -5.2 2nd —0.2 —2.1 — 0.5 — 0.5 —0.8 —7.2 7.6 -4.5 3rd 0.5 —1.2 —0.5 —1.0 -0.1 -5.5 8.9 -4.5 4th —0.2 —2.1 0 —2-7 0.8 —4.8 7.1 -4-3 . 5th 0.5 —4.8 0.5 0 1.2 —0.8 7.8 1.5 6th 2.3 —1.3 0.5 —1.0 3.6 —2.0 11.5 5.9 7th 0.2 —2.6 —0.5 —3.2 2.8 1.6 8th 1.1 -5.2 0.5 -4.4 3-4 -2-7 9th 0.8 —4.3 —0.5 —3-2 2.4 0.9 10th 0.5 —2.4 —1.0 —6.5 1.6 —0.2 nth — 2.2 —6.8 —3-2 —10.4 1.1 0 12th —4.6 —10.4 —6.0 —10.4 2.8 —0.9 13th — 3.6 —12.5 —3-8 —8.3 5.0 —1.8 14th 1.9 —7.6 1.8 —8.7 3.1 1.0 15th 1.2 —10.2 —o-5 —8.3 2.5 1.2 16th 1.7 —4.2 1.2 —2.7 0.9 0.2 17th —0.8 —6.3 —1.0 —6.0 2.0 —2.7 18th -1.2 -7.2 -3.8 -4.4 3-4 -5-7 19th -2.1 -5.8 -4.4 -5.5 0.2 —1.5 20th —0.4 —6.3 —i-5 —6.0 1.7 —2.1 2ISt 8.7 4.5 -1.1 -5.4 -1.0 -9.3 3.0 —2.6 22nd 2.7 —2.6 —1.6 —10.7 —2.7 —11.0 3.9 -1.3 23rd 0 —3.1 1.1 —13.4 —2.2 —10.4 3.6 -5.3 24th 0.2 —6.2 —0.5 —11.3 —i-5 —9.8 1.3 -4.6 25th o-5 -5-4 -3-5 -II-2 —1.0 -8.7 4.5 -7-8 26th 0.7 —8.6 4.4 —11.7 2.8 —3-8 5.0 —6.2 27th 1.4 0.1 3.7 -2.4 3.4 1.2 6.3 —2.0 28th 0.2 —0.2 3.1 —4.3 2.8 1.8 6.4 —0.8 29th —0.1 —1.6 2.7 1.2 2.3 0.5 30th 0.3 —2.1 2.0 —0.4 1.8 —2.2 3ISt 2.0 0.3 1.0 —3.2 0.5 —2.2
Mean 0.8 —2.9 0.2 —5.7 —0.6 —4.8 2.6 -2.8 7-3 -3-4 •Scientific names are given in appendix 2 on page 241.
222 1963 COLD SPELL IN HAMPSHIRE AND DORSET cases, and a discussion of weight losses; the weights of the birds found dead are analysed in detail in table 4 on pages 234-236, which also gives normal weights wherever possible, while their wing- lengths are summarised in appendix 1 on page 240. Some birds, particularly waders, had been partly or wholly eviscerated by scaven gers, so that sexing was then impossible; these corpses and any others which were incomplete were, of course, not weighed. Dates refer to when bodies were found and do not necessarily bear any relation to when birds died. It was fortunate for many species that there was a great abundance of certain natural foods in this winter of 1962-63. If the cold had occurred without the heavy snowfalls which made a lot of this food unavailable (particularly seeds, beechmast, acorns and fallen apples), survival would undoubtedly have been much greater. Even so, various thrush species certainly benefited from the profuse crops of wild berries, although these soon disappeared. There was little evidence of spectacular mass-movements, such as were observed in the cold weather of December 1961. In 1962-63 the migration was more protracted and probably most of it occurred in the anticyclonic weather ahead of the first heavy snowfalls; this would largely pass unnoticed high against the blue sky or at night. As the hard weather affected most of western Europe, except the southern tip of Iberia, it is doubtful whether many of the migrants fared much better than those which stayed behind. However, in this connection, K. D. Smith (in lift.) observed large arrivals of such birds as Lapwings, Golden Plovers and gulls in Morocco at the beginning of the cold spell; being on the south side of the depressions which brought the snow to Europe, north-west Africa received one of the wettest periods on record and thus provided ideal conditions for many species. In southern England the cold set in on 22nd December 1962 for a period of several days and nights of intense frost until the night of the 29th/3oth when there was heavy snow and drifting in a south-east gale. Unusually cold conditions with occasional further snowfalls persisted until the thaw set in on jth/6th March 1963. Temperatures seldom rose above freezing for long, although there were several periods when the cold was rather less intense. Much of the snow persisted throughout the period. In all, the cold spell lasted for 74 days (table 1).
NOTES ON SPECIES One Great Crested Grebe was found dead in the middle of a snow- covered field on Salisbury Plain, Wiltshire; others died on the coast. Herons virtually disappeared, either through death or emigration, early in the period; several bodies were reported, but none was received for examination.
223 BRITISH BIRDS The surface-feeding ducks which remained inland were in remark ably good condition, and this was commented on by several people who shot them. Those in Poole Harbour suffered more, and most of them left when the area froze over. Genuine wildfowlers responded extremely well to the appeal to refrain from shooting them, but 'pot hunters' took a heavy toll of these and other wildfowl. A very thin Shoveler was found dead on 27th January. Diving ducks also did not appear to be greatly affected and unusual numbers occurred on local streams and rivers and in Poole Harbour. Exceptionally large num bers of some species were reported, including, for example, 600 Goldeneye and 400 Scaup in Poole Harbour, and a flock of 100 Goosan ders (as well as other smaller groups) on the River Avon at Fording- bridge where there had been only one record in the previous eleven years. Two dead Common Scoters in Poole Harbour on 27th January and 3rd February were both in poor condition and two thin dead Velvet Scoters were reported in the same locality by other observers. Scoters may have suffered because of the heavy mortality of shore crabs Carcinus. At least 2,500 Shelducks congregated in Poole Harbour and many died there; many of the dead were trapped in the ice and carried out to sea with the tide after the thaw. Flocks of grey geese, mostly White-fronts, were seen almost daily; they resorted to unusual places to feed, such as a field of rape and a roadside cress-bed, and 'pot-hunters' stated that birds they shot were in poor condition. No unusual numbers of black geese occurred. Single Whooper Swans on a small inland pool and in Poole Harbour appeared to be ailing. Most shoot-owners distributed food for wild game-birds and un doubtedly this greatly helped both them and other species. Even so, their ability to burrow down through snow to underlying food suggests that they are not particularly adversely affected by either cold or snow cover. It is significant that the only ones picked up were sick. Apparently healthy Partridges were paired by 13th February. Figures from the National Game Census (Middleton 1964) show that, on average, there was a 20% decrease in the breeding population of partridges in Britain in March 1963 compared with March 1962, but, except in the area of the Cotswolds, where many deaths were reported during the cold spell, this reduction is considered to have been due to the poor survival rate of young birds in the summer of 1962. Numbers of Coots increased greatly both inland and in Poole Harbour. Individuals trapped inland seemed to be in a good physical state, but severe conditions on the coast caused the death of some there; a few of the latter were surprisingly heavy. The large wintering flocks of Lapwings in the Avon valley water- meadows and on the chalk downlands moved on before the end of the
224 I963 COLD SPELL IN HAMPSHIRE AND DORSET year. A very few lived out the cold spell on cress-beds. Large cold-weather movements and local concentrations occurred at Port land Bill, where many weak individuals were shot by irresponsible gunners; the only dead ones came from there. Small numbers were returning to thawed out places inland as early as 18th February. Ringed Plover numbers in Poole Harbour were very low, presumably as the result of an efflux, and large flocks of Golden Plovers moved out with Lapwings before the end of the year, this being noted particularly at Portland Bill. Both Snipe and Jack Snipe moved on in the early days of the cold spell. Local concentrations occurred in unfrozen areas, such as cress-beds, where many were shot. No dead ones were found. Woodcock, however, were probably affected as badly as any species. Many sportsmen reported very large bags and the National Game Census (unpublished) shows that, as in 1961-62, there were clearly exceptional numbers of winter visitors before the cold spell. Weak and starving Woodcock were reported from many unusual sites in towns and villages. Large numbers congregated in coastal areas such as Poole Harbour and Portland Bill where probably few survived. Most coastal flocks of Curlews moved on, but many weak Black- tailed Godwits were seen in Poole Harbour in January and, when only four or five of the wintering flocks of 400+ remained there after the ice broke up in early February, it was assumed that the majority had died. The remains of several others besides those examined were found. Only one or two Black-tailed Godwits were reported in March, when they are normally very evident. An estimated 90-95% of the hundreds of Redshanks wintering in Poole Harbour had gone by early February and it could be assumed that all were dead. The remains of many were found besides those examined. A few survived inland, where they occur in winter on cress-beds and similar places during hard weather only. The sample of corpses examined included 64 immatures and 24 adults, a ratio of 2.7:1. Many of these could be sexed and among the immatures were 26 males and 18 females, while the adults included 9 males and 7 females, ratios of 1.4:1 and 1.3:1 respectively. Most of the Spotted Redshanks wintering in Poole Harbour moved on early in the cold spell, but a few remained and survived. Knots there increased to 100+, but only three deaths were reported. Three Avocets were present in the same area before the cold spell and one stayed throughout, at least until the thaw. Gulls generally fared well, though there was a vast reduction in the numbers coming inland to feed. A large concentration of up to 20,000 fed on the enormous quantity of dead sub-littoral organisms (such as Carcinus, Crepidula, Ensis, Nereis and Cardium) in Poole Harbour
225 BRITISH BIRDS and Studland Bay; on 4th February freshly dead Ensis were lying a foot deep in places on the shore and it was estimated that there were literally millions of them. However, Common Gulls were reported to be very weak at a Poole tip, where they were being knocked down by refuse lorries. Tens of thousands of hungry Woodpigeons were shot or died of starvation; for example, about 3,000 were shot in a 20-acre crop of kale near Fordingbridge. On Salisbury Plain, Wiltshire, 70 were found dying in if hours' searching on nth January and literally thousands were dead or dying by the 17th (reminiscent of toxic seed- dressing mortality at its worst). Large numbers were also killed by cars when they sought exposed road surfaces in an apparent quest for grit; for instance, 47 were found freshly dead in a quarter-mile stretch of the A.338 near Fordingbridge on 25th January. Many died at night whilst at roost; at Cranborne about 30 were found frozen to the branches of one oak tree, as if they were still sleeping. After the initial mortality, which may have amounted to about 90% of the popu lation in this area, the survivors appeared to thrive; periods of slow thaw apparently exposed sufficient acorns and other food for these birds in conditions of reduced competition. Stock Doves were probably not affected to the same extent. Some were shot with the large numbers of Woodpigeons, but apparently in a smaller proportion to their relative numbers (see Ash, Ridley and Ridley 1956). Over 50 survived in one area by utilising Pheasant feed-rides. A pair were in display-flight at Fordingbridge on 18 th February. Barn Owls appeared to be greatly reduced but only one was found dead. Green Woodpeckers also seemed to be much scarcer after the thaw. The large wintering flocks of Skylarks on the chalk downs moved on early in the cold spell. Big concentrations occurred at some coastal localities (for example, 2,000+ at Portland Bill), but only a very few survived inland. Rooks were little affected and Long-tailed Tits were reduced to a small extent only. However, Wrens virtually disappeared inland early in the cold spell and none was seen alive after mid- January, though survival was much better closer to the sea; there was a strong suggestion that some died directly as a result of low tempera tures, and not necessarily through shortage of food. Mistle Thrushes suffered badly and early on in the cold spell. They died even when there was a plentiful supply of fallen apples, which they ate readily (though some local birds, identified by rings, were too weak to feed). Low temperature in itself appeared to be the vital factor. Inland only three live birds were seen after the end of January, but one of these was singing on 17th February. It was noticeable that Song Thrushes were much more adversely affected early in the cold 226 I963 COLD SPELL IN HAMPSHIRE AND DORSET spell than Blackbirds, but they apparently moved out on a large scale and most of the bodies came from the coast. Those that remained inland survived better than Mistle Thrushes and one was heard singing well on 13 th February and subsequently. Although a very large number of Blackbirds died, the heaviest mortality appeared to be amongst adult males in open country (perhaps territory-holding residents). Most survivors were close to human habitations, and it was again apparent that Blackbirds were able to fend for themselves better than Song Thrushes {cf. Ash 1957). At one time, in a small orchard at Fordingbridge, up to 200 were feeding on apples dug out from overlying snow; even so, some of these died. Fieldfares fed on wild berries and fallen apples, but all moved on before the end of December; no bodies were found. The Redwing picture was similar, except that a very few remained inland and a few bodies were found; none was seen alive inland after about 10th January, until one feeding on fallen holly berries on 19th February. Not one of the wintering Stonechats on heathland, on downland (few only) and in coastal areas could be located after early January; no bodies were found. Dartford Warbler numbers on local heaths had been considerably reduced in the much less severe weather of January 1962 {cf. Tubbs 1963). Soon after the first heavy fall of snow in the present cold spell it became evident that most of the remainder had gone. During March only four or five could be found in the whole of Hampshire and Dorset, and all these were near the coast. In each winter it seemed that a heavy fall of snow at night was responsible for their disappearance, this presumably smothering them as they roosted. At first Goldcrests appeared to survive .well inland, but after a day of freezing rain in mid-January when every twig was coated with ice, none was seen alive in woodland areas. As with Robins, however, some of the country population appeared to move in close to human habitations, and these garden birds were frequently heard singing from 2nd February. The small population of Meadow Pipits wintering inland on farm land, on cress-beds and in wet valleys dwindled during the cold spell and, although no corpses were found, only one live one could be located on 16th February. Although obviously pressed for food, the few Pied Wagtails seen during the hard weather appeared to be thriving close to human habitations and farm buildings; their aggressive habits at the bird-table ensure that they obtain more than their fair share. Of five Great Grey Shrikes known to be wintering in the area before the cold spell, three inland could not be found after the snow had cleared but two near the coast were present throughout the period. Although locally there were large concentrations of Greenfinches round stacks, and a few in gardens and poultry farms, it seemed that "7 BRITISH BIRDS many had moved on; only two were found dead. Goldfinches are always few in number in this area during winter and these left at the beginning of the hard weather; only odd ones were seen in the first three weeks of January and then none. The wintering population of Linnets was probably lower than normal in any case—there were not the usual large flocks in the kale fields—and most moved on early in the cold spell. The very few remaining seemed to weaken rapidly and none was seen alive inland after the middle of January; no corpses were found. Before the hard weather began, up to about 40 Crossbills were wintering in the area of my garden near Fordingbridge and some were still singing regularly when the first snow fell, but they then dis appeared (though odd ones were seen until the end of the first week in January). However, observers elsewhere reported the species throughout the cold spell. There had been large numbers of Chaffinches feeding on the abun dant beechmast, but many of these apparently moved on. Those remaining settled in areas such as gardens, stacks and Pheasant feed- rides, where there was an available food supply, and appeared to thrive successfully; they returned to the beechmast as soon as it was un covered. Although song normally begins in early January, it was surprising to hear Chaffinches singing from 4th February when many birds of other species were still dying. Bramblings wintering with Chaffinches and feeding on beechmast mostly moved on, but small numbers remained throughout the cold spell in the same way as Chaffinches; others returned to inland areas on 17th and 18th Feb ruary. Reed Buntings feeding round the shores of Poole Harbour early in the cold spell had dwindled considerably by the time the big freeze-up was over. The following species were apparently unaffected by the cold (those in italics have additional comments in the succeeding paragraph): Red-throated Diver, Little Grebe, Cormorant, Shag, Teal, Mute Swan, Sparrowhawk, Kestrel, Hen Harrier, Pheasant, Water Kail, Moorhen, Oystercatcher, Grey Plover, Turnstone, Bar-tailed Godwit, Green Sandpiper, Dunlin, Sanderling, Tawny Owl, Short-eared Owl, Kingfisher, Carrion Crow, Jackdaw, Magpie, Jay, Great Tit, Blue Tit, Coal Tit, Marsh Tit, Willow Tit, Nuthatch, Treecreeper, Robin, Rock Pipit, Starling, Bull finch, Yellowhammer, Cirl Bunting, Corn Bunting, House Sparrow and Tree Sparrow. Red-throated Divers were present in exceptionally large numbers on some parts of the coast. Even where there was no artificial feeding, Pheasants fared well on the abundant supply of natural foods beneath the snow. Water Rails and Moorhens thrived along the banks of swifter-flowing rivers and on cress-beds. In Poole Harbour Oyster- catchers wintered in several hundreds, Grey Plovers remained in
228 1963 COLD SPELL IN HAMPSHIRE AND DORSET normal numbers, Turnstones increased and fed on dead sub-littoral organisms, about 200 Bar-tailed Godwits survived successfully, and there was an increase of thousands of Dunlins and many Sanderlings. At least five Green Sandpipers overwintered successfully inland. Tawny Owls were frequently heard calling at night during the very worst weather. Jays apparently had an ample supply of accessible acorns. In mid-February Marsh Tits and Treecreepers were the birds most often seen in deciduous woodlands; many Great Tits were singing from 6th February onwards and Marsh Tits from 18th February. Near the end of the cold spell I examined twenty nest-boxes in my garden near Fordingbridge: most had been used as roosting sites and there were no corpses in them. The majority of the countryside Robins appeared to move in close to human habitations where they seemed to thrive, but even those left in exposed sites also apparently survived; song was first resumed on 9th February. Starlings were singing throughout and even bathing frequently during the very coldest weather; the very large wintering population moved on, but the numbers frequenting built-up areas apparently increased and were mostly dependent on man for food. Many Yellowhammers (including a flock of 60 on 12th February) and Cirl Buntings fed round stacks and particularly on seeds put out for stock. Corn Buntings frequently occurred in areas where they are not normally seen. The wintering population of Tree Sparrows was very small in 1962-63.
ICELANDIC BLACK-TAILED GODWITS AND REDSHANKS There was sufficient useful material among the dead Black-tailed Godwits and Redshanks collected in Poole Harbour and adjoining Shell Bay, Dorset, to make a special study of the races involved. The Icelandic forms of both species were recognised and are discussed below. On the other hand, the five Redwings examined during the cold spell were all of the nominate Continental race T. i. iliacus.
Black-tailed Godwit Salomonsen (1935) showed that the Icelandic form of the Black-tailed Godwit islandica is separable from the nominate Continental form limosa by its shorter bill (sex for sex) and he gave the following figures: islandica, JQ* 76-85 and 22 85-100; limosa, $$ 83-99 an^ 9? 101-121. Witherby et al. (1938-41) quoted the same figures for islandica, but extended the range for limosa: $$ 82-107 and 22 104-126. Information on the wing length of islandica is sparse. William son (1958) stated, 'The wing-length range appears to be much the same in the two races, except that 29 islandica are perhaps a trifle bigger than Continental.' The wing lengths of 2? islandica were given by Hachisuka (1927) as 217-230 and by Salomon-
229 BRITISH BIRDS sen as 210-228, but Witherby et al. put a considerably higher upper limit on $$ limosa with 215-240 (although it should be added that they did not apparently recognise islandica as a valid race). This suggests that $$ limosa may have longer wings than $$ islandica. There is even less information on male wing-lengths, beyond Williamson's statement quoted above.
Table 2. Measurements of Black-tailed Godwits Limosa limosa from Poole Harbour and Shell Bay, Dorset, January and February 1963, showing which could be assigned to the Icelandic race islandica on bill length Measurements are in mm. and weights in gm. Salomonsen (1955) gave the bill length of this race as 76-85 for males and 85-100 for females (as against 83-99 and 101-121 for the corresponding sexes of nominate limosa) Sex Bill Wing Weight Locality Date
Definite islandica ? 100 221 ? Poole Harbour 27.1.63
Probable islandica
Indeterminate 6* 82 209 ? Shell Bay 28.1.63 Damaged by scavengers 3 ? 208 ? Poole Harbour 27.1.63 ? 96 225 ? Shell Bay 28.1.63 During the 1963 cold spell 19 Black-tailed Godwits were found dead in Poole Harbour and Shell Bay between 27th January and 3rd February, and a summary of their measurements is given in table 2. These figures show that the 19 birds included twelve definite and two probable islandica; two more were indeterminate, while the last three could not be adequately examined because they had been partly eaten by scavengers and were either eviscerated or decapitated. 230 1963 COLD SPELL IN HAMPSHIRE AND DORSET During the last few decades Black-tailed Godwits have wintered in large numbers in Ireland and parts of England. Morley and Price (1956) did not know from where these populations were drawn, but the findings of Williamson and Ruttledge (1957) showed that some of those in Ireland, and probably the great majority there, have been islandha. More recently, Vernon (1963) examined a number of speci mens in various museums and demonstrated that 34 of these could be assigned to islandica; of these 34, 29 were from various parts of Britain and Ireland and, though most were passage birds obtained in April, May, August, September or October (among them one from Dorset), they included winter records from Carmarthen and Hampshire. The data in table 2 now confirm that the wintering range of islandica extends to Dorset and further research will no doubt show that other wintering areas in England are also occupied by this race. The measurements of the bills and wings of the nine males in the first three sections of table 2 have been plotted graphically in fig. 1. From this and the table it will be seen that the wings of £$ islandica can be as short as 202 and probably as little as 198 (this latter measurement was doubly checked). None of the $$ wings in table 2 falls outside the known range of 210-230. FIG. 1. Bill and wing lengths of nine male Black-tailed Godwits Limosa limosa from Poole Harbour and Shell Bay, Dorset, January and February 1963, plotted against the normal ranges of the Icelandic race islandica and the Continental race limosa. Measurements are in mm. and the normal ranges are based on Salomonsen (1935) and Witherby et al. (1938-41) 23I Table 3. Wing lengths of Redshank Tringa totanus from Poole Harbour and Shell Bay, Dorset, January and February 1963, showing which could be assigned to the British race britannicus and which to the Icelandic race robusta Measurements are in mm. The ranges of the wing lengths of the two races are based on Witherby et al. (1938-41), who gave 145-166 for $$ britannicus, 153-165 for ?$ britannicus, 157-171 for (J(J robusta and 158-170 for $$ robusta; Harrison (1944) gave 165-172 for c?6" robusta and 164-177 for $$ robusta. Continental birds of the nominate race totanus fall in the range 147-163, but are unlikely to be involved here (see text). In this table the mean wing length of the 36 males is 160.4, that of the 27 females is 163.2 and that of the whole 93 is 161.5 BRITANNICUS RANGE OF OVERLAP ROBUSTA Wing lengths I50 151 152 153 I54 I55 I56 157 158 159 160 161 162 163 164 165 166 167 168 169 I70 17I I72 Males (36) - - - 2 4 I - 3251 26-3-4 I 2 — — — Females (27) - - I - - - 2 36331- 1 5 1 1 - 1 Unsexed (30) I - - I - I 2 I I 4 3 2 4 I I I 2 1 1 1 - 1 1 Totals (93) I - I 3 4 2 4 4 3 9 5 7 16 4 7 2 6 2 5 4 1 1 2 I963 COLD SPELL IN HAMPSHIRE AND DORSET Redshank Three races of Redshank occur in Britain. These are the British britannicus, the Icelandic robusta and the nominate Continental totanus. Ogilvie (1963) was able to list only two winter recoveries (both February) of Continental-ringed Redshanks in England and he con cluded that very few Continental Redshanks visit Britain. There is thus no evidence that nominate totanus winters here on any large scale and Salomonsen (1954) found from ringing recoveries that this race moves to the Mediterranean region and north Africa. Some britan nicus stay here throughout the year (Witherby et al. 1938-41), though much of the British-bred stock emigrates south as far as Portugal (Ogilvie 1963); and the wintering range of robusta includes Britain (Williamson 1958). It thus seems safe to conclude that Redshanks found dead in the 1963 cold spell were probably either britannicus or robusta and that there was little likelihood of any totanus occurring in the series. A total of 96 Redshanks were found dead in Poole Harbour and Shell Bay between 27th January and 3rd February. Of these, 93 were measured and 63 could be sexed on dissection. According to Witherby et al. (1938) Redshanks with wings longer than 166 'may certainly be accepted as Iceland'. On wing length, therefore, 15 of the 93 (16.1%) were referred to robusta and another 15 to britannicus; the remaining 63 (67.8%) were in the area of overlap and subspecies could not be deter mined. The wing lengths of the whole series are summarised in table 3. The Icelandic race has not previously been recognised in Dorset and only rarely elsewhere in southern England. Of the 15 birds referred to this race, one was an adult male, one was an adult female, one was a full-grown female and twelve were first-winter birds which included two males and five females. The adult female and one of the first- winter birds were preserved. WEIGHT LOSSES Weight losses are analysed species by species in table 4. The ranges and the means of the present cold spell weights are given there in comparison with 'normal' weights; and the percentage decreases of the mean cold spell weights below the minimum, maximum and mean normal weights are also shown. It has been difficult to obtain an adequate range of normal weights for some species, and many of those quoted are from birds weighed at observatories; as these will mainly have been migrants, such weights are certain to be on the low side. Harris (1962) indicated that loss of weight seems to be more serious in small birds, and the present study shows that 'end-weights' of large species tend to be proportionately lower than those of small ones. However, end-weights for any species are very variable and the minima obtained are presumably the thresholds beyond which recovery is 233 Table 4. Comparison of weights of birds found dead in Hampshire and Dorset during the cold spell of 1963 with 'normal' weights Normal weights have been obtained from the following sources: Ash (1957) for Partridge; Ash (unpublished) for Pheasant, Woodpigeon, Skylark, Starling and Chaffinch; Browne and Browne (1956) for Dunlin and Redwing; F. R. Clafton {in litt.) for Dunlin and Brambling; Dementiev and Gladkov (1951-54) for % DECREASE OF MEAN COLD SPELL WEIGHTS NORMAL WEIGHTS COLD WEIGHTS BELOW MEAN NORMAL Age/Sex Range Mean No. Range Mean No. Min .Max Mean Red-throated Diver f.g. c? - 1454.7 1 1400--2460 1889.5 4 + 3-9 40.9 23.0 Great Crested Grebe f.g- 555.5-853.2 717-3 3 1050—1200 II25 6 3'-7 40.2 36.2 2 Little Grebe f.g. 207.1-231.8 215.6 3 125 -200 ? ? +72-5 + 7-8 (+3 -7) Mallard f.g. 6" - 887.0 1 > II50 ? ? ? 22.9 Teal f.g. 6" 281.5-310.0 295.8 2 250--450 ? 3 + 18.3 34-3 (15.5) Shoveler f.g. S - 349.0 1 337--505 ? > + 3-6 30.9 (17-2) Pochard istW. Oystercatcher f.g-ct _ 470.8 1 495"-51 0 ? 3 4-9 7-7 6.5 Lapwing f.g. c? 132.8-146.5 139.0^8.5 4 191--226.5 205.3 8 27.2 38.7 32.3 f.g.? 116.0-130.0 123.0 2 180--210 196.7 6 3r-7 41.4 37-5 Total 116.0-146.3 i33-7±i°-3 6 180--226.5 201.6 14 25-7 41.0 33-7 Golden Plover f.g. 3 - 128.1 1 200--2IO 203 5 35-9 39.0 36.9 Total 108.2-128.1 114.9^9.0 4 200--210 203 5 42.5 45-3 43-4 Woodcock f.g-? - 175.8 1 275--3OO ? 3 36.1 41.4 (38.9) Total 170.6-241.0 195.8 3 270--305 ? 5 27-5 35.8 (31.9) Curlew f.g. 419.1-469.4 444-3 2 i? ? ? 5 ? ? Black-tailed Godwit f-g. 6* 150.4-201.5 I7I-5 4 235--367 252.3 11 27.O 53-3 32.0 f.g-? 224.2-233.2 229.5 3 297--362 329.7 11 22.7 36.6 30.4 Redshank f.g- ? - ? ? ? f.g.? 71.6-92.9 83.1^4.6 8 :? ? - ? ? ? Total 70.4-96.2 85.0^7.0 28 102--I48 127.0 ? 16.7 42.6 33.1 Iceland Redshank f.g- 79.1-92.9 87.4 3 127--I48 T33-3±9-9 J 31.2 40.9 34-4 Dunlin f.g-6* - 32.9 1 33-7--52.8 43-5 8 2-4 37-7 24.4 Herring Gull zndW. 9 - 818.6 1 945"-I38 5 1069.4 18 13.4 40.9 23-5 Common Gull ad. 6" - 334-3 1 377"-55 2 46.33 15 11.3 39-4 27.8 Black-headed Gull ad. 201.1-254.5 233.6^28.2 3 257-"343 ? 183 9.1 31.9 (22.1) Woodpigeon f.g. f.g.? _ 6.3 1 ? ? - ? ? 30.8 Total 6.3-8.6 7-4±i-4 7 7.4-11.4 9.1 + 1.3 50 0 35.1 18.7 Mistle Thrush f.g. 6" 71.9-76.7 74.1 3 95.0-107.5 102.9 5 22.0 31.1 27.0 f.g. 9 66.7-75-4 70.0 3 108-130 ? 3 35.2 46.2 (41.2) Total 66.7-76.7 72.o±3.8 6 95-130 ? 8 24.2 44.6 (33-o) Song Thrush f.g. 6" - 49.1 1 ? ? - ? ? ? f.g.? 41.3-55.9 46.5 ±4-7 7 ? ? - ? ? ? Total 41.3-58.6 47-9±5-3 11 61.8-111.6 73.9±io.2 5° 22.5 57-i 35.2 Redwing f.g. a" - 36.6 1 ? ? - ? ? ? f.g. 9 36.3-40.5 38.3 + 1.8 4 ? ? - ? ? ? Total 36.3-40.5 37-9±°-7 5 75.5-88.2 81.8 2 49.8 57.0 53-7 2 Blackbird ad. (J 53.1-76.0 63.5±7.T 12 78.6-103.0 9 -7±6.5 12 19.2 38.3 31-5 istW. 237 BRITISH BIRDS January. A Rook with an injured foot on 28th January weighed 282.3 gm., the same as one in poor condition mentioned by Mac- donald (1962). Wrens showed a loss in weight of 0-35%, with an average loss of 19% which is much smaller than that found by Harris (1962) in a sample of similar size; the present figure may mean that in 1963 they were killed by the extreme cold rather than by starvation. Mistle Thrushes, which seem to be one of the earliest sufferers in any cold spell, lost 24-45% of their normal weight, with an average of about 33%; females appeared to lose much more (41%) than males (27%) in the small sample of three of each sex. It is of interest that some Song Thrushes, although smaller than Mistle Thrushes and similar in size to Redwings, lost relatively less weight; it would thus appear that they were more vulnerable to the cold itself. Eleven Song Thrushes were 22-57% below normal, with an average of 35%; there were insufficient males to compare with the weights of the females. This indicates less weight loss amongst some individuals than in the similar sample weighed by Harris, again possibly a reflection of the low temperatures in 1963. A male killed by a car on 16th February weighed 88 gm., and a female during very cold weather on 16th January weighed 79 gm.; these are not included in table 4. Redwings, like Mistle Thrushes, appear to be able to withstand greater weight losses: the average was 54% over a rather narrow range of 50-57% and, though the sample of only five is very small, these figures are close to those given earlier by both Harris and Ash. By contrast, Blackbirds were rather more like Song Thrushes with weight losses of 34% among 15 males (range 19-49%) and 31% among 12 females (range 14-42%), rather less loss than the 40% in the small samples weighed by Harris and Ash in earlier cold spells. As adult female Blackbirds cannot be separated with certainty from first-winter females, no comparisons there are possible, but twelve adult males averaged 32% below normal, while three first-winter males had lost 40%. A sample of Blackbirds killed by other means during the cold spell, and so omitted from table 4, showed that some individuals were maintaining high weights: adult <$, 30th January, 92.1 gm. (?shot); $, 31st January, 106.i gm. (rat trap); $, 30th January, 106.3 gm- (?car); 9, 16th January, 110.9 gm. (shot); $, 7th February, 116.6 gm. (?shot); and first-winter 238 I963 COLD SPELL IN HAMPSHIRE AND DORSET A male Greenfinch at 20.0 gm. and a female at 16.2 gm. were respect ively 29% and 42% below normal, and the lighter of two Goldfinches had lost 32%. Three Chaffinches were within a rather smaller range and averaged 23% below, but a male Brambling had lost about 34%. Losses in small samples of other species for which normal weights are available included Partridge (38%), Dunlin (24%), Herring Gull (24%), Common Gull (28%), Black-headed Gull (22%), Dunnock (22%) and Starling (8%). ACKNOWLEDGEMENTS I am extremely grateful to the following who provided 199 of the 332 bodies examined: J. Ambrose (1), T. H. Blank (2), A. Bromby (18), Miss H. A. J. Brotherton and Mrs. A. Hughes (56), F. R. Clafton (30), J. C. Follett (1), R. F. Hemsley (20), C. Horsey (1), G. Howells (1), P. Mays (5), H. Moore (17) and Dr. K. B. Rooke (47). My best thanks are also due to G. Newman of the Hum Meteorological Office and D. Jackson for the temperature records from Hum and Fordingbridge respectively; to D. D. Harber for going to much trouble to abstract weights of certain species from the Russian literature; to Miss H. A. J. Brotherton for some additional comments on the effects of the cold spell in the Poole Harbour area; to Mrs. J. M. Finney for typing the final draft; to Dr. G. I. Sharpe for the statistical analyses; and to I. J. Ferguson-Lees. SUMMARY A total of 532 birds of 46 species found dead in Hampshire and Dorset during the prolonged cold spell of 1963 were examined. Mortality was very heavy, but an abundance of some natural foods and a relative absence of the icing-up of vegetation helped some species. The local effects of the cold spell are summarised; among birds which suffered particularly badly were Black-tailed Godwits Limosa limosa and Redshanks Tringa totanus on the coast, and Wrens Troglodytes troglodytes, Wood- pigeons Columba palumbus and some thrushes Tardus spp. inland. The races of the Redwings Tardus iliacus, Black-tailed Godwits and Redshanks involved are discus sed; the Icelandic forms of the two waders, previously only rarely recorded in England, were identified. Decreases of the minimum, maximum and mean cold spell weights below the mean normal weights are given for a wide range of species in table 4; 'minimum threshold weights' were very variable, but were mainly in the order of 35-45%. Wing-lengths are summarised in appendix 1. REFERENCES ASH, J. S. (1957): 'Postmortem examinations of birds found dead during the cold spells of 1954 and 1956'. Bird Study, 4: 159-166. , RIDLEY, M. W., and RIDLEY, N. (1956): 'On the movements and survival of Woodpigeons and Stock Doves'. Brit. Birds, 49: 298-305. and SHARPE, G. I. (in press): 'Postmortem and pesticide examinations of birds in the cold spell of 1963'. Bird Study. BROWNE, K. and E. (1956): 'An analysis of the weights of birds trapped on Skok- holm'. Brit. Birds, 49: 241-257. DEMENTIEV, G. P., and GLADKOV, N. A. (1951-54): The Birds of the Soviet Union. Moscow. 6 vols. 239 BRITISH BIRDS HACHISUKA, M. U. (1927): A Handbook of the 'Birds of Iceland. London. HARRIS, M. P. (1962): "Weights from five hundred birds found dead on Skomer Island in January 1962'. Brit. Birds, 55: 97-103. HARRISON, J. M. (1944): 'Some remarks upon the Western Palaearctic races of Tringa totanus (Linnaeus)'. Ibis, 86: 493-503. JONES, P. H. (1962): 'Mortality and weights of Fieldfares in Anglesey in January 1962'. Brit. Birds, 55: 178-181. MACDONALD, J. W. (1962): 'Mortality in wild birds with some observations on weights'. Bird Study, 9: 147-167. MIDDLETON, A. D. (1964): 'The National Game Census'. )rd Ann. Rep. of tie Game Research Assoc.: 48-60. MORLEY, A., and PRICE, K. L. H. (1956): 'The Black-tailed Godwit in Great Britain and Ireland, 1938-1952'. Brit. Birds, 49: 258-267. OGILVIE, M. A. (1963): 'The migrations of European Redshank and Dunlin'. Wildfowl Trust 14th Ann. Rep.: 141-149. SALOMONSEN, F. (1935): 'Aves' Part LXIV, Zoology of the Faeroes. Copenhagen. (1954): 'The migration of the European Redshanks (Tringa totanus (L))'. Dansk Orn. Foren. Tidsskr., 48: 94-122. TUBBS, C. R. (1963): 'The significance of the New Forest to the status of the Dartford Warbler in England'. Brit. Birds, 56: 41-48. VERNON, J. D. R. (1963): 'Icelandic Black-tailed Godwits in the British Isles'. Brit. Birds, 56: 233-237. WILLIAMSON, K. (1958): 'Bergmann's Rule and obligatory overseas migration'. Brit. Birds, 51: 209-232. and RUTTLEDGE, R. F. (1957): 'Icelandic Black-tailed Godwits wintering in Ireland'. Brit. Birds, 50: 524-528. WITHERBY, H. F., JOURDAIN, F. C. R., TICEHURST, N. F., and TUCKER, B. W. (193 8-1941): The Handbook of British Birds. London. Appendix 1. Wing-lengths (mm.) of birds found dead in Hampshire and Dorset during the cold spell of 1963 Red-throated Diver: 240 1963 COLD SPELL IN HAMPSHIRE AND DORSET $83. Goldfinch:^ 76; unsexed 77. Chaffinch: (J(J 89, 90(2);$ 84. Brambling: (J 93. House Sparrow: