Arctic Terns Research Articles

Resting and Peak Metabolic Rates of Arctic Tern Nestlings and Their Relations to Growth Rate

We measured resting and peak metabolism in relation to growth rate in arctic tern Sterna paradisaea chicks over the first 10 d after hatching. For chicks with varying growth rate, body mass seems to be a better predictor of resting metabolic rate than age. The effect of changes in growth rate on resting metabolism of arctic terns is smaller than that found interspecifically in hatchlings. It is possible that differences exist in the heat increment of feeding between fast and slow growers that would further reduce the effect of growth rate on resting metabolism. Chicks that had body masses lower than 75% of that expected for their age were metabolically inferior in withstanding a thermal challenge compared with chicks of the same age but of normal mass. In contrast to resting metabolic rate, the extent of peak metabolic rate is related to both body mass and age. Thus, in part, the maturation of the thermoregulatory system proceeds steadily with time even when body mass lags behind.

Radar observations of northbound migration of the Arctic tern, Sterna paradisaea, at the Antarctic Peninsula

An intensive migration of Arctic terns was observed from 7–9 March 1989 in Marguerite Bay (67°50'S 67°30'W). The movement pattern and speed of tern flocks were analysed from time-lapse films of a marine navigation radar. The terns migrated north at altitudes 30–60 m asl along the inner coast of Marguerite Bay. When approaching Pourquois Pas Island, the majority veered to the NNE flying into Bourgeois Fjord. Mean flock size was 11.6 (s.e. = 1.9). The estimated total during the three observation days was about 7600 migrating terns. Analysing flight speed in relation to wind showed that the terns increased their airspeed when flying into headwinds and decreased it with following winds. The terns' airspeeds, with an estimated mean of 11.3 ms-1 (s.e. = 1.3) with no wind effect, were significantly faster than the predicted maximum range speed. It is suggested that the terns were migrating on a connecting route between the pack ice of the Bellingshausen and Weddell Seas, involving a flight across the Antarctic Peninsula. Topographical conditions are favourable for such a passage close to the observation site in Marguerite Bay, where the distance across the 1500 m high ice cap of the Antarctic Peninsula is only 37 km. It remains to be clarified if the suggested migration route is of importance for regional tern populations only, or if it is part of a circumpolar Antarctic migration pattern.

Breeding Densities, Biogeography, and Nest Depredation of Birds on Igloolik Island, N.W.T.

The avifauna of Igloolik Island and immediate vicinity was studied during two breeding seasons in 1985-86. This is the first study to compile an intensive record of avifaunal migration patterns and nesting activity, density and success for Igloolik Island. Data for these years are supplemented by the observations of earlier explorers and researchers. During our two seasons of survey, we recorded 40 species of birds, of which 25 nested on the island. Combining our records with previously published data, a total of 48 species have been recorded, with 30 species nesting. Several interspecies matings of gulls and the first confirmed breeding record of purple sandpiper (Calidris maritima) for the Melville Peninsula area were recorded. The density of breeding birds on Igloolik Island (28.5 pairs/sq. m) is similar to other eastern high arctic sites at that latitude. Issues related to the biogeographic comparisons of arctic sites are discussed. In late August, the eastern end of the island acts as a significant staging area for gull species, oldsquaw (Clangula hyemalis) and arctic tern (Sterna paradisaea). A combined average of 58.3% of the nests of six species were depredated. As many as 73% of red-throated loon (Gavia stellata) and 93% of arctic tern nests suffered mainly human-related egg predation.Key words: Arctic, Igloolik Island, breeding avifauna, density, interspecies matings, biogeography

Seabirds and sandeels: the conflict between exploitation and conservation in the northern North Sea

Sandeels, especiallyAmmodytes marinus are a major component of the diet of many predatory fish, seabirds and seals. The industrial fishery for sandeels is now the largest of the North Sea fisheries. A sandeel fishery in the Shetland area began in 1974 but has recently declined. This change was accompanied by dramatic declines in the breeding success of certain seabirds, particularly Arctic terns and kittiwakes. Current information on seabirds and sandeels in the Shetland area is reviewed and areas where further research is needed, highlighted. The Shetland problem illustrates the difficulties of reconciling conservation and exploitation when fundamental ecological and behavioural knowledge is lacking, and also the need to obtain further information on the ecological impact of industrial fisheries.

Prefledging terns (Sterna paradisaea, Sterna hirundo) as bioindicators for organochlorine residues in the German Wadden Sea

Residues of organochlorine chemicals (OC) including polychlorinated biphenyls (PCB) were analyzed by gas chromatography in carcasses of young arctic terns (Sterna paradisaea) and common terns (Sterna hirundo). The birds found dead were collected in 1988 in a breeding colony of the German Wadden Sea. The birds were separated into two age-groups (2–14 days old and 15–27 days old). Most of the chemicals showed a higher concentration in younger birds. In contrast, the absolute amount of the chemicals was greater or at least equal in older birds. If food contamination is as high as shown in this study, the accumulation of chemical hazards in growing terns can only be recognized by measurement of the absolute content, because the concentration is diluted by growth effects. In comparison to food samples from the same breeding colony, one can recognize an accumulation from one trophic level to the next. This study proves that prefledging terns can be accepted as bioindicators. Presumably the residues of OC alone did not cause the death of the terns, yet they were definitely important stress factors.

A 16-year Record of Summer Birds on Truelove Lowland, Devon Island, Northwest Territories, Canada

An annual census of adult birds was conducted on the 43 sq km Truelove Lowland, Devon Island, N.W.T., Canada, in the summers of 1970-73 and 1978-89. Forty-three species were seen during 16 years. Of these, 18 species bred regularly on or immediately adjacent to the lowland and 10 were occasional breeders. In addition 15 species were visitors. The highest annual number for most breeding species was two to three times that of their lowest numbers, but some regular breeding species had far greater extremes. Extensions of the breeding range of Pacific Loon (Gavia pacifica), Purple Sandpiper (Calidris maritima), Wheatear (Oenanthe oenanthe), and Water Pipit (Anthus spinoletta) to Devon Island are reported. It is suspected that Hoary Redpolls (Carduelis hornemanni) and Red Knots (Calidris canutus) also nested there once each. A coefficient of detectability is presented for the 16 most frequently seen species. Synchronous fluctuations in Snow Bunting (Plectrophenax nivalis) and Lapland Longspur (Calcarius lapponicus) populations were observed. A possible replacement of Black-bellied Plovers (Pluvialis squatarola) by Lesser Golden-Plovers (P. dominica) was detected. An abrupt disappearance of all colonies of breeding Arctic Terns (Sterna paradisaea) from the lowland was seen in 1989.

The Relationship Between Food Supply, Reproductive Effort and Breeding Success in Arctic Terns Sterna paradisaea

The Relationship Between Food Supply, Reproductive Effort and Breeding Success in Arctic Terns Sterna paradisaea

The predation of Tern chicks by sheep

Between 1973 and 1980, sheep ate parts of at least 680 live Arctic Tern chicks and at least 10 Arctic Skua chicks on Foula. This predation was almost completely confined to the dry heath habitat in the southeast corner of Foula. Characteristically, the sheep bit off one or both legs or wings, or more rarely the head. Three different sheep were observed eating chicks, but the habit is probably widespread among sheep on that part of the island. It seems probable that sheep make up nutrient deficiencies by eating chicks. Although up to 8% of chicks were eaten by sheep, losses were low compared with egg desertion and chick starvation, but predation by sheep may have contributed to terns deserting this colony in favour of areas away from sheep.

Predation on ground‐nesting seabirds by island populations of red deer Cervus elaphus and sheep Ovis

On Foula, Shetland, sheep were observed biting off the legs, wings or head of unfledged young Arctic terns. Large numbers of tern chicks and a few Arctic skua chicks were found with amputations characteristic of these attacks by sheep. On Rhum, Inner Hebrides, red deer were watched biting the heads off manx shearwater chicks and occasionally also chewing the shearwaters' legs and wings to excise bone. Killing of birds and the selective ingestion of bone‐rich parts by ruminants has not previously been widely documented. It is presumably a response to mineral deficiencies in the vegetation, and it may only occur in rare situations where ruminants feed on mineral‐deficient vegetation on which there are dense colonies of ground‐nesting birds.

Comparison of total mercury levels in relation to diet and molt for nine species of marine birds

Total mercury (Hg) concentrations were analyzed for tissues of nine species of marine birds from the Quoddy region, New Brunswick, Canada, including cormorants (Phalacrocorax auritus), eiders (Somateria mollissima), guillemots (Cepphus grylle), phalaropes (Phalaropus lobatus), gulls (Larus argentatus, L. Philadelphia), terns (Sterna hirundo, S. paradisaea) and kittiwakes (Rissa tridactyla). There was a progressive decrease in Hg concentration from the innermost to the outermost primary feather in Bonaparte's gulls, herring gulls, black-legged kittiwakes and Arctic terns. Primaries of common terns and black guillemots showed no significant trend. Cormorants, guillemots and eiders, which feed on benthic organisms, and common terns, which feed predominantly on fish, had the highest tissue Hg levels, whereas birds such as kittiwakes and phalaropes, which consume mainly pelagic invertebrates, had the lowest Hg levels.

Ambivalence in the Structure of Display Vocalizations of Gulls and Terns: New Evidence in Favour of Tinbergen's Conflict Hypothesis?

This paper deals with the question whether and how motivational systems for attack and escape may find expression in social displays of gulls, with special reference to vocalizations. A comparison of sonagrams of the vocal display 'Long Call' of common tern, arctic tern and little gull with calls made by these species during overt attack and overt escape behaviour shows that attack and escape elements can be recognized in the structure of the Long Call (Figs 2 and 5). The alternation of notes of long and short duration in the Long Call of the little gull (Fig. 3) is regarded as an example of successive ambivalence; long and short notes representing attack and escape tendencies respectively. Whether nowadays occurrence of the Long Call is still under the influence of motivational systems for attack and escape has been studied by analysing the extent to which elements of attack recognized in the Long Call of the little gull alter with presumed motivational changes. It turned out that note duration increased with increase of the incidence of overt attack in three different situations. Similar changes were observed in form elements of the Oblique Posture which typically accompanies the Long Call by birds on the ground (Fig. 6). It is argued that it seems to be the rule rather than exception that the same gull display (visual as well as vocal) occurs in different contexts in which the probability that it is followed by attack or escape varies greatly. Evidence available from studies of a great number of gull species suggests that motivational state underlying a particular display may vary considerably and that different motivational states are reflected by the extent to which motivation specific components of the display manifest themselves. Thus, it is not the display itself (as proposed by TINBERGEN, 1959 and MOYNIHAN, 1955a), but certain elements of which it is composed, which are under the control of the attack and escape motivation. BEER (1975) has experimentally shown, that feature differences within Long Calls of laughing gulls determine different reactions. In case of the little gull, feature differences communicating about motivation might well explain the different reactions to Long Calls in different circumstances.

Spring migration of birds across the Greenland Inlandice

Radar observations from a long-range surveillance station in SE Greenland (65°31'N, 37°08'W) during the end of May and beginning of June 1980 and 1982, demonstrated regular bird migration across the Inlandice in both E/SE and W/NW directions. According to supplementary field observations from SE and W Greenland 1980, -82 and -84, and to available information from the literature, the most probable species to carry out a transglacial E/SE-migration in spring are Gavia immer, Clangula hyemalis, Mergus serrator, Anas platyrhynchos and, possibly, Alle ,alle and Larus hyperboreus. These birds probably depart from the ice-free coasts in W Greenland towards breeding sites along the E Greenland coast and, at least in Clangula hyemalis, Iceland and possibly even further to the east. Plectrophenax nivalis and Calcarius lapponicus probably also travel eastwards over the southern Inlandice to SE Greenland breeding sites.
 Species involved in the transglacial W/NW-migration comprise geese, Anser albifrons and Branta bernicla, and high arctic waders, Charadrius hiaticula, Arenaria interpres, Calidris canutus and Calidris alba. In addition, it is highly probable that also Oenanthe oenanthe, Sterna paradisaea and Phalaropus lobatus belong to this category.
 The geese and high arctic waders depart from staging areas in Iceland to undertake a long-distance flight to breeding grounds in W Greenland (Anser albifrons) or NW Greenland and N Canada. The flight route passes the Sermilik fjord region in SE Greenland, where the migrants shift from a W/WNW course over the Denmark Strait to a WNW/NW course across the Inlandice.
 The route from Iceland via Sermilik to NW Greenland and N Canada is about 10% longer than the great circle route across the central and northern Inlandice. However, wind conditions for a high altitude transglacial flight are much less favourable along the great circle route. The observed migration patterns involve the crossing of 450-700 km of inlandice, reaching 2500-2800 m asl, with temperatures about -10°C. The total flight distance from Iceland to NW Greenland and N Canada is 2300-3000 km.
 Staging areas for ducks and divers along the Greenland west coast, and for geese and waders in Iceland, are probably of crucial importance for the evolution of the observed transglacial migration patterns. The distance from Iceland to the northernmost part of the Nearctic is smaller than from corresponding spring staging sites in North America. Hence, Iceland serves as a spring-board to Nearctic breeding grounds for Old World winter populations of waders and geese. Staging sites probably have a dual effect as spring-boards and bottle-necks, respectively, for the evolution of migration patterns in arctic birds. Gaps in the circumpolar breeding distribution of arctic species, and a relatively low diversity of species breeding in the sector around Greenland, may be due to competition for limited staging resources in combination with the isolating effects in this sector of sea expanses and the Greenland Inlandice.

Observations on the breeding biology of Sabine's Gulls (Xema sabini)

The breeding biology of Sabine's Gulls (Xema sabini) nesting in a colony with Arctic Terns (Sternaparadisaea) was studied in 1980 at East Bay, Southampton Island, N.W.T. Sabine's Gull nests were initiated over a 1.5-week period, from 23 June to 3 July, and the mean clutch size was 2.77. The mean weight of freshly laid eggs was 22.3 g. Hatching was asynchronous and occurred from 14 to 22 July, following an incubation period of 21 days. Of 53 eggs laid, 44 hatched (83.0%). Chicks showed typical sigmoidal patterns of growth for weight, culmen, and tarsus, and a straight line pattern for ninth primary feather. Growth was rapid, and chicks attained nearly adult proportions by 13 to 15 days of age. The timing and duration of the breeding effort (just over 7 weeks) and the rapid rate of growth of Sabine's Gull chicks are seen as adaptations to the short Arctic summer. The mean internest distance between Sabine's Gulls on the colony was 92.5 m. Nesting was more dense on islands than on the mainland, reflecting the attractiveness of sites least accessible to mammalian predators. An apparent association between breeding Sabine's Gulls and Arctic Terns is reported and two explanations are offered: first, a reliance by Sabine's Gulls on the aggressive behaviour of Arctic Terns or second, coincidence.

Eggshells of Arctic Terns from Finland: Effects of Incubation and Geography

-Seventy-four eggs from seven colonies of Arctic Terns (Sterna paradisaea) in the Quark and the Bothnian Bay of Finland were collected in 1981 shortly after laying and immediately before hatching. Shell thickness, weight, thickness index, and egg weight index were determined and compared with the same characteristics of 200 eggs collected between 1874 and 1935. We found no significant differences in these measures of egg thickness between recent and museum shells from the same geographical areas. Shells of museum specimens from different geographical regions did show significant variations. The weight and the wing and tarsus length of the embryos correlated negatively and significantly with all measured characteristics of the shell except its thickness when the shell membranes were present. During the incubation period, the shell's thickness (without membranes) decreased 8%; thickness index and weight decreased 4%; and the shell's thickness with shell membranes present decreased 12%. In this paper, we discuss reasons for these changes. Pesticide-related reproductive failures have been reported in both American and European terns (Sterna spp.; Switzer and Lewin 1971, Koeman and van Genderen 1972, Switzer et al. 1973, Gochfield 1975, Fox 1976). For example, high levels of chlorinated hydrocarbons were found in the tissues of marine animals from the Baltic Sea (Jensen et al. 1969, Koivusaari et al. 1972, Anderson and Hickey 1974), an area where eggshell thinning of 1117% was reported in White-tailed Eagles (Haliaeetus albicilla) and Ospreys (Pandion haliaetus; Koivusaari et al. 1980, OdsjO 1982). In contrast, Lemmetyinen and Rantamiki (1980) reported low pesticide contamination in the eggs of Arctic Terns (S. paradisaea) from the archipelago of southwestern Finland. The thickness of eggshells from these terns has recently increased significantly (5.2%, P < 0.05) in Finland (Gulf of Bothnia; Pulliainen and Marjakangas 1980). Several studies concerning geographic variations in eggshells have been published (e.g., Anderson and Hickey 1970, 1972; Sutcliffe 1978; Olsen 1982), but there are almost no studies of this kind from Europe (e.g., Svensson 1978). Besides effects of pesticides and geography, the mobilization of eggshell calcium for the developing embryo is known to affect eggshell thickness (e.g., Kreitzer 1972). Our objectives, ther fore, were (1) to describe recent changes in the thickness and size of Arctic Tern eggshells in comparison to museum material; (2) to check the reliability of available museum material for use as a standard; and (3) to find a method for measuring shell variables that is independent of the shell thinning that occurs naturally during embryonic development. MATERIALS AND METHODS We collected Arctic Tern eggs in 1981 from three colonies in Quark (6 310'N, 2 12 5'E) and from four colonies in Bothnian Bay (65003'N, 25010'E) in the Gulf of Bothnia (Fig. 1). At ach nest, one egg was chosen randomly at an early stage of incubation (little or no embryonic development). Nine of these nests in the Quark colony were marked and two more eggs were taken from each shortly before hatching was expected. Where Arctic and Common terns (S. hirundo) bred in the same colonies, we confirmed identification of Arctic Tern nests by observation from a blind or by flushing a parent from its nest before taking an egg. Eggs were kept in a refrigerator until prepared. Their length and breadth were measured with a vernier caliper to the nearest 0.1 mm. A piece of shell, 16-18 mm in diameter, was cut out from the equator of each egg. The contents of the egg were then removed, the shells were rinsed with water, and the shell

Breeding Ecology of Common and Arctic Terns in the Mingan Archipelago, Quebec

Breeding Ecology of Common and Arctic Terns in the Mingan Archipelago, Quebec

Biometrics and colour forms of chicks of common terns and arctic terns

Methods of distinguishing the chicks of Common and Arctic Terns based on measurement of tarsus length and on the colours of the dorsal down and the belly down are described. The variation of tarsus length with age was investigated by relating it to bill length, to mid‐toe length, and to body weight. In all of these comparisons, length of tarsus provided a reliable method of distinguishing the species in the larger chicks, but there was some overlap in the ranges of tarsus length in the smaller chicks. Length of tibia was of little value in separating the species. Grey chicks and brown chicks were found in Arctic Terns in a ratio of about 1:1, but only brown chicks were found in Common Terns. The colour of the belly down was pure white in all Common Terns examined and white with a dark cast in all Arctic Terns examined. Criteria based on dorsal and belly down colour in smaller chicks and tarsus length in larger chicks thus allow the species to be distinguished for all chick ages from hatching to fledging. ...

Feeding methods and diving rates of migrating larids off Deer Island, New Brunswick

A study of three species of migrating larids was undertaken off Deer Island, New Brunswick, to compare feeding methods and diving rates of birds exploiting various prey types. Bonaparte's Gulls (Larus Philadelphia) fed mainly by diving (dipping and plunging) and surface seizing, whereas Common and Arctic Terns (Sterna hirundo and S. paradisaea) acquired food by diving only. Common and Arctic Terns foraged from greater heights than Bonaparte's Gulls, and both the gulls and the terns maintained a higher foraging height while feeding on small fish than while feeding on euphausiids or, in the case of the gulls, insects. Common and Arctic Terns had a steeper dive angle than Bonaparte's Gulls, and both the gulls and the terns dove more steeply when feeding on small fish than on euphausiids. The highest diving rate occurred when Bonaparte's Gulls were dipping for insects trapped in the water surface layer. There was no significant difference in mean dipping or plunging rates between the gulls and the terns feeding on euphausiids or small fish. Bonaparte's Gulls had a lower mean rate of incomplete dives than did terns, probably because of the gulls' lesser aerial manoeuverability reducing the likelihood of altering course after dive initiation. The mean dipping rate was higher than the mean plunging rate for both the gulls and the terns since most food was taken at the surface, and plunges were necessary only for deeper prey (usually small fish). Intervals between hovering and diving were similar for both the gulls and the terns.

Spring Distribution of Marine Birds in the Gulf of Alaska

Aerial surveys of marine birds were conducted in the Gulf of Alaska from March through June 1977. The surveys provide synoptic information on the relative seasonal abundance of seabirds and their use of the continental shelf and slope and deep oceanic areas. Northern Fulmars (Fulmarus glacialis), Sooty and Short-tailed shearwaters (Puffinus griseus and P. tenuirostris), Forktailed Storm-Petrels (Oceanodroma furcata), sea ducks, Black-legged Kittiwakes (Rissa tridactyla), murres (Uria spp.), and Tufted Puffins (Lunda cirrhata) were the most common of the 35 species observed in the Gulf. Most seabirds were found over the continental slope and oceanic waters in March. Densities, especially of shearwaters, increased as birds moved into waters over the continental shelf from April to June. Most species were associated with at least one other, and 11 statistically significant associations (P < 0.05) were found between the eight most common species. Tufted Puffins, Arctic Terns, and shearwaters were highly associated.

Feeding Ecology of Nonbreeding Populations of Larids off Deer Island, New Brunswick

Nonbreeding populations of three species of larids were studied off Deer Island, New Brunswick, Canada prior to migration to determine the extent of feeding interaction. The distribution of birds in the area followed prey distribution, with the Bonaparte's Gull frequenting areas with surface euphausiid concentrations and the Common and Arctic terns occupying areas harboring schools of small fish. Feeding distribution patterns were associated with the combined effects of tide phases and bottom topography on the availability of surface prey. The Bonaparte's Gull fed predominantly on euphausiids and insects. The Arctic Tern fed frequently on euphausiids and a variety of small fish, whereas the Common Tern took only small fish.

Levels of DDT and PCB's in different stages of life cycle of the Arctic tern Sterna paradisaea and the herring gull Larus argentatus

∑DDT and PCB levels were analysed in samples of arctic terns and herring gulls collected in the archipelago of southwestern Finland. Special attention was paid to the levels at various stages of the life cycle and in different sexes. The levels were nearly ten times higher in the herring gull. The highest loads were found in adult birds and in newly hatched chicks but the levels were much lower (only 7–12 % in the herring gull) in chicks just before fledgling. The levels in young gulls remained low until the end of August at least. Therefore it is plausible that the high levels found in adult gulls are a consequence of their wintering in the southern Baltic. The levels of ∑DDT and PCB residues were significantly lower in female arctic terns than in male terns. Differences between the sexes were small in the herring gull. Thus it is possible that the female of the arctic tern is able to release pollutants, especially PCB residues, more effectively into eggs than the female of the herring gull. The biochemical mechanisms involved are not clear but a possible explanation may be different lipoprotein structures in the eggs of the species.