Studies of less familiar birds 123. Glaucous Gull Photographs by W, PuchalsM (Plates J 9-42) AN EDITORIAL COMMENT with the photographs and paper by Kay (1947) on the characters of the Glaucous Gull (Larus hyperboreus) in winter expressed the hope that pictures of adults on the breeding grounds would soon be available. In fact, however, those now published sixteen years later are the first to have been sent to us and even they do not include any of the bird at the nest. Nevertheless, they illustrate rather strikingly the strength and power of this Arctic predator (especially plate 42a) and its varied feeding habits (plates 39 and 42b). The distant shot of a group by a tundra pool (plate 41) also shows how conspicuous, even at long range, are the white wingtips which this species shares with the Iceland Gull (L. ghucoides). The white tips to the pale grey primaries are also seen to advantage in the flight study on plate 40. Plate 42b brings out the features of the immatures which are much paler than the corresponding plumages of all gulls except the Iceland and become progressively whiter until adult in the fourth or fifth year. The Handbook emphasised the proportions of wings to tail as a means of separating Glaucous and Iceland Gulls. It was considered that Continued... 263
BRITISH BIRDS the wings of the Glaucous Gull scarcely reached the tip of the tail while those of the Iceland Gull extended well beyond. In fact, however, Kay (1947) pointed out that this largely depended upon the time of year. The Iceland Gull is relatively longer-winged, but Kay observed that only in winter do Glaucous Gulls' wings fall short of the tail because the primaries are moulted in autumn and are not fully grown before the end of the following February. He pointed out that first-winter Glaucous Gulls (which do not moult their primaries in autumn) have tips reaching well beyond the tail and he presumed this to be the case with adults in summer. Unfortunately none of these photographs is a side-on close-up, but a careful examination of plate 41 certainly shows the wings projecting and a similar impression is given by plate 42a. The most puzzling feature, however, is the timing of the moult, for while The Handbook states that there is a complete moult from July to November or December, and that only the body feathers are changed in March or April, Johnston (1961) found that Glaucous Gulls in arctic Alaska moulted their primaries from May onwards. For example, adults collected there in July (the month in which these photographs were taken in Spitsbergen) had six new inner primaries. Johnston also calculated that each primary did not take more than 14 days to replace. The only possible solution to this apparent contradiction seems to be that the outermost three or four primaries are not moulted until September or October and that they take much longer than the others to reach their full length. Anyway, it is clear that wing length alone is not to be relied upon as a field character, and nor is size. Glaucous Gulls are usually considerably larger near the size of Great Black-backed (JL, marinus) but Kay showed that a small female Glaucous Gull may be little larger than a Herring Gull (JL. argentatus) and so very near to a large male Iceland Gull. The best distinctions, in fact, lie in the form of the head and bill. The Iceland Gull is markedly smaller even than the Herring Gull about the head and its bill is very much shorter and less heavy than the massive hooked dagger of the Glaucous Gull which shows well in these pictures. The immature Glaucous Gull has the added distinction that its bill is creamy-flesh for three-quarters of its length, with only the tip dark brown (plate 42b), while in the young Iceland Gull this dark colour extends back for at least half the length. Mention of Alaska and Spitsbergen will already have shown that the Glaucous Gull has a wide range and its distribution is actually circumpolar. The southern limits of its breeding range roughly coincide with the Arctic Circle, except that it does not quite reach this latitude in Scandinavia and parts of Siberia, while it extends south of the Arctic Circle in Iceland, Greenland, Canada (including Newfoundland) and Alaska. In winter the species wanders as far south as the British 264
GLAUCOUS GULL STUDIES Isles (especially north Scotland to East Anglia, chiefly from mid- October to early April) and other coasts of the North Sea and southern Baltic, also to the north-eastern United States, California and Japan; beyond these limits (roughly latitude 4o N to 5o N) stragglers occur very much more irregularly. At all times they are found mainly on the coast or in offshore waters and seldom inland but, for example, one or two (usually immatures) are recorded at the London reservoirs most winters and in parts of Scotland they frequent rubbish dumps some miles from the coast. Sometimes individuals return year after year to the same places in Britain and occasionally one will stay throughout the summer. The Glaucous Gull's traditional victim is the Little Auk {Platttus die) and two years ago we published a photograph, also by Mr. Puchalski, of one with a dead Little Auk in its bill (Brit. Birds, 54: plate 47a). Indeed, nearly every colony of Little Auks in the Arctic has a dependent community of these gulls nesting near-by. Glaucous Gulls are able to catch Little Auks on the wing with comparative ease (Bateson 1961). They will also hover over the surface when one dives into the sea and swims under water, waiting to attack it as soon as it comes up (Bent 1919). They take their greatest toll, however, from recendy fledged young birds (Lovenskiold 1954). They also destroy many eggs and young of other auks especially Briinnich's Guillemot (Uria lomvidy ^na of terns, ducks and geese. Plate 39 shows one in the act of swallowing the egg of an Eider (Somateria mollissimd). Pennie and Andrew (1956) found them a considerable menace in the colonies of Pink-footed Geese {Anser brachyrhyncbus) and Barnacle Geese (Branta hucopsis) in Spitsbergen. They also saw a Glaucous Gull attempt to take an egg of a Red-throated Diver (Gavia stellata) which, however, drove it off. Barnacle Geese nest mainly on rocky buttresses and ledges where they are safe from such predators as Arctic Foxes (A/opex lagopus), indeed from everything except Glaucous Gulls. On the other hand, Larson (i960) found the nest of a Pink-footed Goose only eight to ten metres from the nearest Glaucous Gull nest at the edge of a colony of the latter. He concluded that, since Glaucous Gulls are capable of defending themselves against Arctic Foxes (Lovenskiold 1954) and since they begin breeding first, the goose must have built its nest deliberately there. Incidentally, while many authors state this species to be less fierce and rapacious, more sluggish and cowardly than the Great Blackbacked Gull, Duffey and Sergeant (1950) recorded adults diving at intruders and striking them with their feet, and others (e.g. Paget Wilkes 1922) have observed them 'stooping' like terns, skuas and Great Black-backed Gulls. Perhaps the Glaucous Gull does not always have things its own way, however. Burton et al. (i960) recorded that 265
BRITISH BIRDS Glaucous Gulls were sometimes struck by Arctic Terns {Sterna macrurd) and that one dead one at Kapp Linne., Spitsbergen, had apparently been killed by them. The Handbook gives as the food of this species such varied items as carrion, blubber, excrement, birds and their young or eggs, fish, crabs, molluscs, starfish, worms, insects, seaweed, moss and berries. It is also a pirate, robbing Eiders and other birds of food. Duffey and Sergeant (1950) examined the contents of the stomachs of five Glaucous Gulls and these included remains of eggs, young birds and cephalopods. They added, 'Pellets showed that the food near the southern auk colonies was largely eggs and young birds, but in the north and west, where there were few auks, it was almost exclusively the crab Hjas araneusj Burton et al. (i960) found that Hjas crabs made up 25% of the volume of the contents of twelve stomachs they examined; these otherwise contained 40% remains of young Arctic Terns, 15% echinoid plates and spines, 15% garbage and 5% fish. Plate 42b shows an immature Glaucous Gull eating the corpse of an adult. This form of cannibalism must be accidental and probably rather unusual, since the number of dead Glaucous Gulls cannot be all that large in any one area, but (as happens with many other gulls) adults will regularly eat wandering chicks of their own kind. They are also said to encourage their young in the art of sucking eggs at a very early stage, sometimes when still in the nest (Fisher 1954); the adult breaks a hole in the egg and the chick leisurely helps itself. At a later stage, when they are deserted by their parents, the fledged young feed on crowberries (Empetrum nigrum). I. J. FERGUSON-LEES REFERENCES BATESON, P. P. G. (1961): 'Studies of less familiar birds: 112 Little Auk'. Brit. Birds, 54: 272-277. BENT, A. C, (1919)". L/f<? Histories of North American Gulls and Terns. United States National Museum Bulletin 115. Washington. BURTON, P. j. K., BWIRTON-JONES, N. G., and PSNNYCUICK, C. J. (1960): 'Bird notes from Vest-Spitsbetgen in the summer of 1957*. Sterna, 4: 113-151. DUFFEY, E., and SERGEANT, D. E. (1950): 'Field notes on the birds of Bear Island'. Ibis, 92: 554-565. FISHER, },, and LOCKXEY, R. M. (1954): Sea-Birds. London. JOHNSTON, D. W. (1961): 'Timing of annual molt in the Glaucous Gulls of northern Alaska'. Condor, 63: 474-478. KAY, G. T. (1947): 'The Glaucous Gull in -winter'. Brit. Birds, 40: 369-573. LARSON, S. (i960): 'Ornitologiska iakttagelset ftin Vast-Spetsbergen sommaren 1958*. Vir FdgehSrld, 19: 193-207. L0VENSKIOLD, H. L. (1954): Studies on the Avifauna of Spitsbergen. Skr. Norsk Polarinst. 103. Oslo. PAGET WILKES, A. H. (1922): 'On the breeding-habits of the Glaucous Gull as observed on Bear Island and in the Spitsbergen Archipelago'. Brit. Birds, 16:2-8. PENNIE, I. D., and ANDREW, D. G. (1956): 'Bird notes from Spitsbergen, summer 1955'. Sterna, 2: 49-63. 266
PLATE 39. Adult Glaucous Gull (Icarus byperboreus) swallowing an Eider's egg, Spitsbergen, July 1957. Besides carrion and crabs, the species takes many chicks and eggs of auks, terns, ducks and geese, and even grown birds, especially Little Auks which it can easily catch on the wing (pages 263-266) {photo: W. Pucbalski)
PLATE 40 (below.) Adult Glaucous Gull (Larus hyperboreus) in flight. This bird is variable in size, from Herring Gull to Great Black-backed. The plumage of the adult is entirely white and pale grey, and the total lack of black on the whitetipped grey primaries is well shown here, as are the heavy yellow bill and pale eye
PLATE 41 {above). Glaucous Gulls (Larus hyperboreus), mostly adults, by a tundra pool on Spitsbergen. These birds breed mainly on coasts, sometimes on low-lying shores but more often on sloping cliffs and stacks. Note that when the primaries are full-grown the wings reach well beyond the tail (page 264) {photos: W. Puchalski)
PLATE 42. Adult Glaucous Gull {hams hyperboreus) calling by a broken Eider's egg; this species is rather silent except when it is feeding. Below, first-summer bird eating the corpse of an adult; note the paleness of its markings, the lack of black on wings and tail, and its dark-ended bill (page 264) (photos: W. Puchalski)