Arctic Breeding Research Articles

Rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird.

The adaptive value of size changes in different organ and muscle groups was studied in red knots (Calidris canutus islandica) in relation to their migration. Birds were sampled on five occasions: at arrival in Iceland in May 1994, two times during subsequent refueling, at departure toward, and on return from, the high arctic breeding grounds. During their 24-d stopover in May, body mass increased from 144.3 to 214.5 g. Mass gains were lowest over the first week (0.85 g/d, only fat-free tissue deposited). Over the subsequent 10 d, average mass increased by 5.0 g/d (fat contributing 78%), and over the last week before takeoff, it increased by 2.0 g/d (fat contributing over 100% because of loss of lean components). There were no sex differences in body and fat mass gains. Over the first interval, lean masses of heart, stomach, and liver increased. During the middle 10 d, sizes of leg muscle, intestine, liver, and kidneys increased. Stomach mass decreased over the same interval. In the last interval before takeoff, the stomach atrophied further and the intestine, leg muscles, and liver became smaller too, but pectoral muscles and heart increased in size. Sizes of "exercise organs" such as pectoral muscle and heart were best correlated with body mass, whereas sizes of organs used during foraging (leg muscles) and nutrient extraction (intestine, liver) were best correlated with rate of mass gain. Kidneys changed little before takeoff, which suggests that they are needed as much during flight as during refueling.

Frequency and timing of extrapair fertilisation in the polyandrous red phalarope ( Phalaropus fulicarius )

In sequentially polyandrous bird species, where females mate with different males in succession during a single breeding season, sperm stored by females can occasionally lead to extrapair fertilisations (EPFs) in clutches cared for by the second and subsequent males. Thus, we predicted that in red phalaropes (Phalaropus fulicarius) – a sex-role-reversed, sequentially polyandrous, arctic breeding shorebird – EPFs would occur more frequently in clutches laid later in the breeding season. We used multilocus DNA profiling to examine the frequency and timing of EPFs in a population of red phalaropes breeding in the Canadian high arctic. Using a technique to determine parentage without maternal DNA, we inferred that 6 of 70 chicks in 18 broods resulted from EPFs – one extrapair chick in each of 6 broods. These results were supported by a further analysis using microsatellite DNA. As predicted, broods containing EPFs hatched from clutches laid significantly later in the season than did broods containing no EPFs. The difference in median hatch dates between broods with and without EPFs was 9.0 days, or 38% of the entire egg-laying period in that season. For the whole breeding season, we estimated that 6.5% of chicks were sired by extrapair males, which is similar to extrapair paternity estimates for other sex-role-reversed birds, but relatively low compared to the majority of socially monogamous species studied so far.

Male traits, mating tactics and reproductive success in the buff-breasted sandpiper,Tryngites subruficollis

Buff-breasted sandpipers use a variety of mating tactics to acquire mates, including remaining at a single lek for most of the breeding season, attending multiple leks during the season, displaying solitarily or displaying both on leks and solitarily. We found that differences in body size, body condition, fluctuating asymmetry scores, wing coloration, territory location and behaviour (attraction, solicitation and agonistic) did not explain the observed variation in mating tactics used by males. Which males abandoned versus returned to leks was also not related to morphology or behaviour, and there was no tendency for males to join leks that were larger or smaller than the lek they abandoned. These results suggest that male desertion of leks was not dependent on a male's characteristics nor on the size of the lek he was presently attending. Males did join leks with larger males than their previous lek, perhaps to mate with females attracted to these larger ‘hotshot’ males. Males at both leks and solitary sites successfully mated. Lek tenure did not affect mating success, although lekking males appeared to mate more frequently than solitary males. Courtship disruption and to a lesser extent, female mimicry, were effective at preventing females from mating at leks, and may offer a partial explanation for female mating off leks. Our analysis that combined all males together within a year (regardless of mating tactic) indicated that males that attended leks for longer periods of time and that had fewer wing spots were significantly more likely to mate. Given some evidence that wing spotting declines with age, and that females inspect male underwings during courtship, the latter result suggests that female choice may play some role in determining male success. We suggest that male buff-breasted sandpipers may use alternative mating tactics more readily than males in other ‘classic’ lek-breeding species because: (1) unpredictable breeding conditions in this species' high arctic breeding range leads to low lek stability, which in turn hinders mate selection mechanisms mediated by male dominance and female choice; and (2) males are not constrained by morphological markings that indicate status or sex. Both characteristics may reduce the reproductive benefits associated with males adopting one mating tactic and result in a sort of scramble competition in which males switch between tactics as local conditions change.

The detection of vegetational change by multitemporal analysis of LANDSAT data: the effects of goose foraging

1 The North American mid‐continent population of lesser snow geese now exceeds 3 million birds and the population is increasing in the order of 7% per annum. The foraging activities of the birds on Arctic breeding grounds are leading to loss of vegetation and habitat destruction, particularly in coastal areas bordering the Hudson and James Bays. 2 Multitemporal analysis of LANDSAT data has been carried out to detect vegetational change from 1973 to 1993 at La Pérouse Bay and its vicinity, the site of a breeding colony of snow geese. 3 Difference vegetation images (DVI) (difference between infra‐red and red images) were prepared from images obtained in late summer in 1973, 1984 and 1993, in order to enhance vegetation density. Pair‐wise differences were calculated between these DVI images, which resulted in three, secondary, classified images. Classification of the three secondary images (1973–84, 1984–93, 1973–93) yielded three well‐defined classes: water, vegetation decline and no change in vegetation. 4 Histogram counts gave the following values for areas of vegetation decline: 1973–84, 1026 ha; 1984–93, 1428 ha; 1973–93, 2454 ha. 5 The loss of vegetation and the destruction of habitat are discussed in relation to the foraging activities of the expanding goose population.

Genetic Differentiation between Wintering Populations of Lesser Snow Geese Nesting on Wrangel Island

Arctic breeding populations of Lesser Snow Geese (Chen c. caerulescens) range from Baffin Island in eastern Canada to Wrangel Island, Russia, which is located 650 km west of Alaska (Bellrose 1980). Although hundreds of thousands of Lesser Snow Geese may have occupied the Russian arctic in the mid1800s (see Takekawa et al. 1994), the Wrangel Island birds constitute the only remnant colony on the Asian continent (Syroechkovsky and Litvin 1986) and may represent a matriarchal population for the species (Quinn 1992). In the past 30 years, the Wrangel Island colony has declined from more than 200,000 to less than 75,000 breeding adults (Pacific Flyway Technical Subcommittee 1992, V. Baranyuk unpubl. data), which has resulted in increasing concern about its conservation and management. The Wrangel Island colony consists of two wintering populations that migrate to different regions and are faithful to their wintering areas (McKelvey et al. 1989). The larger northern population (about 60% of the total from Wrangel) migrates to the Fraser River delta of British Columbia and the Skagit River delta of northern Washington, whereas the southern population flies 600 km farther south to the Central Valley of California (Rienecker 1965, Teplov and Shevaryova 1965, Jeffrey and Kaiser 1979, Priklonsky and Sapetin 1979). The northern population is isolated from other Lesser Snow Geese during the winter, but the southern population mixes with geese from Banks Island, Canada and from the smaller Anderson and Sagavirniktok River deltas (Dzubin 1974, Johnson 1995, Syroechkovsky et al. 1994). Although Lesser Snow Geese are colonially nesting birds that typically show little genetic structuring (Ely and Scribner 1994), there are potential differences in genetic exchange at Wrangel Island because the birds pair during the winter (Cooke et al. 1975). However, a recent study (Syroechkovsky et al. 1994) suggests that gene flow between wintering

Effects of Oiling on Feeding Behavior of Sanderlings and Semipalmated Plovers in New Jersey

I examined the foraging behavior of Sanderlings (Calidris alba) and Semipalmated Plovers (Charadrius semipalmatus) during their spring stopover period along the Atlantic coast of southern New Jersey following an oil spill. I used focal animal sampling to test the null hypothesis that there are no differences in foraging behavior as a function of the degree of oiling of birds. Nearly 50% of the foraging time of shorebirds was interrupted during the main period of beach oiling, primarily by clean-up personnel and vehicles that moved up and down the oiled beach, compared to less than 5% of the foraging time disruption at a control beach where birds were interrupted only by walkers and joggers. For both species, the time devoted to feeding decreased significantly, whereas the time devoted to standing about and preening increased significantly as percent of oiled plumage increased. For shorebirds that are already time-stressed in their refueling efforts before their long journey to arctic breeding grounds, these interruptions may prove fatal or might lower reproductive success once they reach the breeding grounds.

Effects of murre nest site characteristics and wind conditions on predation by glaucous gulls

Glaucous gulls, Larus hyperboreus, are the primary predator of thick-billed murre, Uria lomvia, eggs at arctic breeding colonies. This study used eggs placed experimentally on murre nesting ledges to test the effects on glaucous gull foraging success of (i) murre nesting density; (ii) murre group defence; (iii) nesting ledge width; (iv) timing of murre laying; and (v) wind speed. Defensive responses by murres increased egg survival times, and gull foraging success was reduced by high murre nesting density. The timing of murre egg laying and ledge width also influenced the effectiveness of murre defence within the colony. Eggs placed following the peak of murre egg laying survived longer than eggs placed on the same nest sites prior to the peak. Murres without eggs early in the season often abandoned the group when attacked, leaving experimental eggs and brooding murres vulnerable to gulls. Gulls had difficulty reaching exposed eggs on narrow ledges when foraging on foot. At wind speeds greater than 15 km/h, however, egg survival was independent of ledge width because wind increased the maneuverability of gulls in flight and enabled them to reach narrow ledges. Murre defence at high nesting densities was also less effective on narrow ledges. Apparently, murres had difficulty rotating on their nest sites to face attacking gulls without dislodging their eggs. We conclude that moderate wind speeds enhanced the ability of gulls to reach narrow ledges and avoid contact with defending murres while stealing eggs. Consequently, the vulnerability of murre nest sites depended on wind conditions at the colony.

Breeding-site infidelity in greater snow geese: a consequence of constraints on laying date?

We studied annual variation in the distribution of greater snow goose (Chen caerulescens atlantica) nests and colonies at a High Arctic breeding site (Bylot Island, Northwest Territories, Canada) from 1988 to 1994. Annual distribution and size of colonies within the study area were highly variable. The distance between colony centres in successive years ranged from 2.9 to 6.9 km [Formula: see text], with no overlap of the areas occupied. Timing of snowmelt and nest-site availability were also very variable. In some years, the area was snow-free at the time the geese arrived, whereas in others, snow persisted for up to 3 weeks after their arrival. However, even in the 3 years of earliest snowmelt (1988, 1993, and 1994), geese used markedly different nesting areas, in both lowland and upland areas. Geese nested in association with snowy owls (Nyctea scandiaca) in the 2 years that owls nested and their nesting success was markedly improved, probably because of the deterrent effect of owls on arctic foxes (Alopex lagopus), the main nest predator. This suggests that protection from nest predators is an important determinant of nest-site selection. The lack of fidelity to a specific nesting location is unusual in geese. We suggest that large annual variability in timing of snowmelt, predation pressure, and availability of feeding areas during the prenesting period, combined with the need to lay at an optimal date because of the short arctic nesting season, probably explain the low nest-site fidelity in this population.

The dispersion of Arctic breeding birds according to snow-free patch dimensions during the spring thaw in the north-eastern Taimyr Peninsula, Russia

The dispersion of Arctic breeding birds according to snow-free patch dimensions during the spring thaw in the north-eastern Taimyr Peninsula, Russia

The dispersion of arctic breeding birds according to snow-free patch dimensions during the spring thaw in the north-eastern Taimyr Peninsula, Russia

The dispersion of passerines, ptarmiganLagopus mutus and waders in relation to available snowfree patches is described after spring arrival but prior to the main thaw at Pronchishcheva Lake, north-eastern Taimyr, in June 1991. The numbers of ptarmigan and passerines were proportional to patch perimeter but disproportionately more birds occurred on smaller patches. In contrast, wader numbers were proportional to patch area but disproportionately more occurred along the perimeters of large patches. These patterns are discussed in relation to risk of predation and food availability. We speculate that the predation risk is higher in small patches for uniformly coloured birds but may be lower for white and pied species. The availability of overwintering plants, fresh plant growth and insects is thought to be highest at the perimeters of snow-free patches.

The morphological development of the locomotor and cardiac muscles of the migratory barnacle goose (Branta Leucopsis)

The masses of the locomotor and acardiac muscles of wild barncale goose gollings, from migratory population, were examined systematically during development and their values compared to those of pre‐migratory geese. Pre‐flight development was typified by approximately linear increases of body, leg, and heart ventricular mass with respect to age. Flight muscle showed an exponential increase in mass. Pectoralis muscle mass was 14.2 ± 0.3% of body mass (1297 ± 73g, n=7) in early flying goslings compared to 16.6 ± 0.3% of body mass (2318 ± 109g, n=8) in pre‐migratory geese. Post‐flight development was typified by stasis of leg muscle mass but hypertrophy of Ventricular and pectoralis muscle mass in proportion to body mass. Ventricular mass relative to body mass showed the lowest values at 5 weeks of age (0.62 ± 0.01%) with peak values at 1 week of age (10.4 ± 0.04%). The latter may be associated with both requirements of thermoregualation in these precocial, arctic breeding geese and the need to forage approximately 24 hours post‐hatch. Peak values for leg muscle mass, relative to body mass, were found at 3 weeks of age (12.7 ± 0.36%), with lowest values in the pre‐migratory geese (6.7 ± 0.21%), while peak values for pectoralis muscle mass were expressed in the premigratory geese with lowest values at 1 week of age (0.94 ± 0.07%). Ventricular mass was proportional to leg muscle mass up to 5 weeks of age (Mv= 0.38Mt0.68, r2=0.95), but subsequent increase in ventricular mass was proportional to pectoralis muscle mass (Mv= 0.25Mp0.73, r2= 0.81).

Endocrine Bases of Spatial and Temporal Opportunism in Arctic-Breeding Birds

Synopsis. The primary objectives of this paper are to define, explore the environmental factors favoring, and discuss hypotheses concerning the endocrine bases of two important arctic breeding strategies that we call spatial and temporal opportunism. We identify several species that display spatial opportunism in the Arctic, and one that displays temporal opportunism. In spatial opportunism, breeding may be highly seasonal but the locality where individuals breed may change from year to year as a result of unpredictable spatial distribution of food, nest site availability, or other factors such as predator abundance. We suggest that flexibility ofthe transition from migration to settlement distinguishes spatial opportunists from site-faithful migrants. Thus far, data are available for only two hypotheses regarding the endocrine basis of this flexibility. Circulating patterns of testosterone (associated with territory establishment) and cor? ticosterone (associated with migratory activity) appear not to be involved in the regulation of spatial opportunism in white-crowned sparrows (Zonotrichia leucophrys gambelii), but more detailed study is necessary. In temporal opportunism (that may occur simultaneously with spatial opportunism), temporally variable food availability apparently selects for the capacity to initiate reproduction across a wide portion of the year. Tonic activity ofthe hypothalamo-pituitary-gonad (HPG) axis could pro? vide a mechanism to minimize the delay between discovery of abundant food and onset of nesting in any season. However, the evidence for one arctic temporal opportunist, the white-winged crossbill (Loxia leucoptera), indicates that the HPG axis is not tonically active, but probably switches off (i.e., becomes photorefractory) in autumn, as for other birds breeding at these latitudes. Opportunistic breeding very early in the year (e.g., March near Fairbanks, Alaska) is associated with increased luteinizing hormone secretion, probably in response to a combination of abundant food and social stimuli, after refractoriness dissipates. We have taken the first step of identifying spatial and temporal opportunism as important phenomena in the Arctic, and discussing hypotheses related to endocrine mechanisms. Future research should identify specific environmental cues involved, and elucidate the neuroendocrine and endocrine mechanisms underlying these two reproductive strategies.

Seasonality in basal metabolic rate and thermal conductance in a long-distance migrant shorebird, the knot (Calidris canutus)

Knots Calidris canutus live highly seasonal lives, breeding solitarily on high arctic tundra and spending the non-breeding season in large social flocks in temperate to tropical estuaries. Their reproductive activities and physiological preparations for long flights are reflected in pronounced plumage and body mass changes, even in long-term captives of the islandica subspecies (breeding in north Greenland and northeast Canada and wintering in western Europe) studied in outdoor aviaries. The three to four fattening episodes in April-July in connection with the flights to and from the high arctic breeding grounds by free-living birds, are represented by a single period of high body mass, peaking between late May and early July in a sample of ten captive islandica knots studied over four years. There are consistent and synchronized annual variations in basal metabolic rate and thermal conductance in three islandica knots. Basal metabolic rate was highest during the summer body mass peak. Within the examined individuals, basal metabolic rate scales on body mass with an exponent of about 1.4, probably reflecting a general hypertrophy of metabolically expensive muscles and organs. Any potential effect of moult on basal metabolic rate was obscured by the large seasonal mass-associated variations. In breeding plumage, insulation (the inverse of thermal conductance) was a factor of 1.35 lower than in winter plumage. This was paralleled by the dry mass of contour feathers being a factor of 1.17 lower. In this subspecies the breeding season is indeed the period during which the costs of thermoregulation are lowest. In captive knots seasonal changes in basal metabolic rate and thermal conductance likely reflect an anticipatory programme adaptive to the variable demands made by the environment at different times of the year.

Spring-Staging Ecology of Midcontinent Greater White-Fronted Geese

A major part of the midcontinent greater white-fronted goose (Anser albifrons) population stages for several weeks in spring in the Rainwater Basin Area (RBA) of south-central Nebraska where substantial mortality from disease occurs periodically. Effective management of this population requires better data on use of habitat, vulnerability to disease, and the role of staging areas in migration and reproduction. We studied use of habitat, foods, nutrient dynamics, and effect of changes in agriculture on food availability and habitat needs in spring 1979-80. During daylight, geese were observed primarily in harvested cornfields (76%) and growing winter wheat (23% ). Corn grain and winter wheat shoots composed 90 and 9%, respectively, of foods consumed by collected geese (n = 42). Feeding activity did not vary among post-harvest cornfield treatments except that little feeding occurred (P 0.05) of temporal variation in calcium content. Adult geese storing 14.2 g of fat per day deposited approximately 582 g of fat between 22 February and 3 April. Energy requirements for thermal regulation were small compared with requirements for fat synthesis and probably had little effect on nutrient deposition. The 34,000 white-fronted geese present on the Harvard Marsh and Prairie Dog Marsh study areas in March 1980 probably used <20% of the corn available within a 5-km radius. We believe that midcontinent white-fronted geese arrive on Arctic breeding grounds with larger and less variable fat reserves than prior to modern agricultural development. We attribute this response to increased food availability on staging areas where the net effect of agricultural changes has been an increase in corn availability. Waterfowl managers can increase dispersion of geese and provide favorable foraging conditions by maintaining well-distributed wetland roosting habitat and by working with private landowners to ensure access to grain in the vicinity of wetlands.

Resources for Long-Distance Migration of Knots Calidris canutus islandica and C. c. canutus: How Broad Is the Temporal Exploitation Window of Benthic Prey in the Western and Eastern Wadden Sea?

In the course of each spring, two subspecies of knots Calidris canutus (islandica wintering in Europe and breeding in the Nearctic, and canutus wintering in west Africa and breeding in Siberia), stage in the international Wadden Sea before their northward flights to the arctic breeding grounds. In March-April islandica-knots predominantly use the intertidal flats in the western part of the Wadden Sea in The Netherlands (canutus is still in west Africa). In May both subspecies use the eastern part of the Wadden Sea in Schleswig-Holstein, Germany only. We studied these knots in core areas at both ends of the Wadden Sea in 1990, to examine whether the absence of knots in the western Wadden Sea in May is related to food resources or to other factors connected with the energy budget of these long-distance migrants. Islandica-knots in March-April in The Netherlands and canutus-knots in May in Germany had similar diets and showed similar size selection of their major bivalve prey Macoma balthica, giving the possibility for indirect competitive interactions. Knots spent more time feeding per day in Germany. The harvestable biomass of Macoma was of comparable magnitude in both parts of the Wadden Sea in May. That knots always leave the western Wadden Sea in late April is, therefore, not a direct response to prey depletion. If Macoma always subsides earlier in the year in the western part of the Wadden Sea than in the east as in 1990, the knots' absence in the west may represent the riding of an eastward wave of good feeding conditions resulting from longitudinal variation in bivalve-prey biology. At least for canutus, the reliance in May on the eastern Wadden Sea may (additionally?) represent early movements - at relatively low body masses - towards the breeding areas to gain the benefits of a small saving on the cost and time of travel, and of being closer to the weather systems that may help their flight into the breeding areas.

SITE FIDELITY IN HIGH ARCTIC BREEDING WADERS

Summary Tomkovich, P.S. & Soloviev, M.Yu. 1994. Site fidelity in High Arctic breeding waders. Ostrich 65:174-180. The return rate and fluctuations in density between years were determined for colour-marked populations of Grey Plover Pluvialis squatarola. Little Stint Calidris minuta, Curlew Sandpiper C. ferruginea, Sanderling C. alba and Knot C. canutus in a study in the Knipovich Bay area, northern Taimyr, Central Siberia (76°05'N. 98°32'E) during three breeding seasons, June 1990 to August 1992. No birds marked as chick were recorded as returning to the study area. Females of all species exhibited low site fidelity. The return rate of males varied between species. No marked male Curlew Sandpiper or Little Stint were recorded in the season following the marking, which is compatible with the nomadic behaviour of these two species. In contrast, males of Grey Plover and Knot were site faithful and had return rates of 78% and 8% respectively (though the latter value may have been underestimated). Site fideli...

Resources for Long Distance Migration: Intertidal Exploitation of Littorina and Mytilus by Knots Calidris Canutus in Iceland

We investigated the resource basis and energy budget of migrating knots Calidris canutus on spring stopover in NW Iceland, where large concentrations of birds deposit extensive fuel reserves for long distance flights to high arctic breeding grounds. Prey composition was determined on the basis of crushed shell and other fragments in faecal droppings. The daily foraging time, and dropping frequency, in two main intertidal habitats - seaweed beds on rocky shores and mudflats - was monitored in relation to the tidal cycle. Main food sources were 4-15 mm periwinkles Littorina spp. (providing 147 kJ of daily gross energy intake) taken from seaweed, and 8-23 mm common mussels Mytilus edulis (134 kJ), taken from both seaweed and mud. Additional contributions obtained from mud include chironomid larvae (9 kJ), small gastropods (3 kJ) and probably also unidentified softbodied prey (about 73 kJ). Food resources at the stopover site are probably not limiting for the population of migrating knots. Estimated seasonal prey depletion rates were low, only 1-4% for Littorina, 0.5-1.7% for Mytilus and 11% for chironomid larvae. The knots' estimated daily energy intake was below the predicted limit for maximum metabolisable energy intake. Although this indicates that the knots' rate of fuel deposition probably was constrained by food availability and foraging time rather than the metabolic capacity, it could not be ruled out that the knots at least on some days reach their metabolic ceiling for energy accumulation. A combination of factors may explain why the study region offers highly favourable stopover conditions for transient knots, and why the surplus of resources are not exploited instead for breeding or winter survival by resident shorebirds: (a) macrotidal variation; (b) pronounced seasonality; (c) combined exploitation of different intertidal habitats (seaweed and mud) during different tidal phases; (d) exuberant food availability. The shore crab and limpet are absent from the study region, which may explain the unusually high Littorina densities as a result of significant release from predation and competition, respectively.

Digestion by Barnacle Geese in the Annual Cycle: The Interplay Between Retention Time and Food Quality

Structural carbohydrates in plants are hard to digest by the animals that eat them, and they hamper digestion of the content of the plant cells. The efficiency of digestion by herbivores is, therefore, closely related to both the retention time of the food in the digestive tract and the proportion of cell walls in the food. This study examined food digestion by free-living barnacle geese Branta leucopsis in relation to food quality and retention time. Over the range of short winter days (8 h light) to continuous light in the arctic breeding area the geese increased the food retention time two- to four-fold. Low throughput rates in summer resulted in enhanced digestion of the food. The organic matter digestibility of graminoids, corrected for differences in protein content, was 37% in winter, and 56% in summer. Enhanced digestion allowed the geese to extend their food spectrum by exploiting mosses (bryophytes), which are, at least temporarily, the only plants available in the summer range. The disadvantage of prolonged food retention time is the concurrent decrease of the amount of food that can be processed per time unit. The digestion pattern in the successive periods of the year can be regarded as an adaptation to differences in energy needs, and to differences in the selective force acting on the geese to minimize feeding time.

Arctic Sounds on Temperate Shores: The Occurrence of Song and Ground Display in Knots Calidris canutus at Spring Staging Sites

In May 1990, more than 4500 km away from, and up to three weeks before arriving on their high Arctic breeding grounds, individuals of two subspecies of Knots, Calidris canutus islandica and canutus, showed ground display and song whilst foraging in flocks on the tidal flats in the Wadden Sea of Schleswig-Holstein, FRG. Similar displays and songs were recorded in May 1987 and 1988 on the staging areas of C.c. islandica in northwest Iceland. The display behaviour, identified as the 'tail-up display', is probably performed only by males towards females, and occurs commonly just after arrival at the tundra breeding sites. Tail-up displays may result in copulations both on the staging and on the breeding sites. On the staging sites, tail-up displays were most frequent in the days prior to the departure of flocks to a subsequent stopover area (Iceland) or for presumed direct flights to the Canadian and the Siberian Arctic. Our observations suggest that the behavioural condition required for reproduction may, at least in males, develop some weeks before the actual arrival in the breeding areas.

Patterns of Nutrient and Energy Expenditure in Female Common Eiders Nesting in the High Arctic

Patterns of Nutrient and Energy Expenditure in Female Common Eiders Nesting in the High Arctic