Lech Iliszko

The effects of loggers on the foraging effort and chick-rearing ability of parent little auks

We studied the effects of loggers attached to chick-rearing little auks (Alle alle) on their daily time budget (proportion of time spent in the colony and at sea), foraging activity (duration and proportion of long and short foraging flights), chick provisioning rate and their growth and development on Spitsbergen. We found that experimental parent birds performed shorter but more frequent long foraging flights and reduced the frequency of short foraging flights. They spent more time at the colony and reduced chick provisioning rate compared to control birds. Nestlings reared by experimental parents weighed significantly less at their middle, peak and fledging age and departed colony later than chicks of control parents. Little auks depend on energy-rich copepods associated with cold Arctic waters and are expected to face the climate-induced worsening of the foraging conditions, which may have negative impact on their time/energy budget and survival. The study may help to determine the level of extra effort little auks need to invest to breed successfully.

Unusual hunting and feeding behaviour of polar bears on Spitsbergen

Prolonged chasing of an adult reindeer ( Rangifer tarandus ) by a polar bear ( Ursus maritimus ) was observed both on land and in the sea, in Magdalenefjorden, northwest Spitsbergen. Polar bears were also observed catching black guillemot ( Cepphus grylle ) in the sea in northwest Spitsbergen and feeding on chicks in the arctic tern ( Sterna paradisea ) colony in Hornsund, southwest Spitsbergen. While feeding on seabird species is unsurprising, the prolonged chasing of adult reindeer is unusual for polar bear hunting behaviour. The few documented cases of polar bear hunting reindeer consist of either surprising and killing resting/sleeping prey or stalking and a short rapid chase of the reindeer. Our observations describe new feeding habits of polar bears that may be in response to decreasing seal availability due to shrinking sea-ice cover in the Arctic.

Subglacial discharges create fluctuating foraging hotspots for sea birds in tidewater glacier bays

Although the processes occurring at the front of an ice face in tidewater glacier bays still await thorough investigation, their importance to the rapidly changing polar environment is spurring a considerable research effort. Glacier melting, sediment delivery and the formation of seabird foraging hotspots are governed by subglacial discharges of meltwater. We have combined the results of tracking black-legged kittiwakes Rissa tridactyla equipped with GPS loggers, analyses of satellite images and in situ measurements of water temperature, salinity and turbidity in order to examine the magnitude and variability of such hotspots in the context of glacier bay hydrology. Small though these hotspots are in size, foraging in them appears to be highly intensive. They come into existence only if the subglacial discharge reaches the surface, if the entrainment velocity at a conduit is high and if there is sufficient macroplankton in the entrainment layer. The position and type of subglacial discharges may fluctuate in time and space, thereby influencing glacier bay hydrology and the occurrence of foraging hotspots.

Post-breeding prospecting trips of adult Sandwich Terns Thalasseus sandvicensis

Capsule Multiple tracking methods (colour-rings, plumage-markings and GPS-loggers) revealed that adult Sandwich Terns Thalasseus sandvicensis from the Netherlands showed prospecting behaviour in other colonies within Northwest Europe. Birds were recorded from a few kilometres to over 850 km away and in different countries around the Southern North Sea. Our data suggest large-scale connectivity between Northwest European Sandwich Tern colonies. Such connectivity is potentially of great importance when modelling the population structure of this species.

Body Size and Timing of Fledging of Atlantic Puffins in the Faeroes and Northwest Norway

Abstract We studied the way, timing and diurnal rhythm of young Atlantic Puffins (Fratercula arctica) leaving colonies in NW Norway and Faeroes. The colonies differed in nesting habitat and predatory pressure. Both adult and young Puffins from Bleiksøy were significantly larger and heavier than those from Nólsoy. Young birds left the Bleiksøy colony about ten days later in the season, but considerably earlier during the night (22.00-04.00 h; peak: 00.00-01.00 h) than those on Nólsoy (24.00-0600 h; peak: 02.00-03.00 h). The fledging period was more synchronized on Bleiksøy, both within the season and on particular nights. Body mass and size of young puffins leaving the colony tended to decrease through the fledging period. Well-developed young birds from sloping parts of the Bleik colony flew down to the sea, while those from the lower-lying, flatter parts of the colony and those in poor condition walked to the sea. Fledglings which left on the wing reached the sea about one hour earlier and could fly beyond the inshore waters before daybreak, thus avoiding the risk of gull predation. They were more numerous during the first six days of the 10-day fledging period and were larger than those, which left on foot. The latter lost much time and energy overcoming dense vegetation, boulders and the tidal zone on their way to the open sea. As a result, they were still near the shore at dawn, in the zone intensively penetrated by predators. We suggest that predatory pressure of the big gulls, which are numerous on Bleiksøy but almost absent from Nólsoy, could have a significant impact on timing of fledging of their prey.

Flexibility of foraging strategies of the great skua Stercorarius skua breeding in the largest colony in the Barents Sea region

BackgroundForaging strategies of seabird species often vary considerably between and within individuals. This variability is influenced by a multitude of factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions.ResultsUsing GPS-loggers, we investigated factors affecting foraging flight characteristics (total duration, maximal range, total distance covered) of great skuas Stercorarius skua of known sex breeding on Bjørnøya, Svalbard, the largest colony in the Barents Sea region. We examined influence of sex (females are larger than males), phase of breeding (incubation, chick-rearing), reproductive status (breeders, failed breeders) and bird ID (they are known for individual foraging specialization). Our analyses revealed that only bird ID affected foraging flight characteristics significantly, indicating a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized three main groups of individuals: 1) those preying mainly on other seabirds in the breeding colonies (6%), 2) those foraging at sea (76%) and kleptoparasiting other seabirds and/or foraging on fish and/or offal discarded by fishing vessels, and 3) those alternating between preying on other seabirds in breeding colonies and foraging at sea (18%). Despite marked size sexual dimorphism, we found no apparent sex differences in flight characteristics. Birds after egg- or chick-loss and thus not constrained as central foragers did not modify their foraging flights.ConclusionsGreat skuas breeding on Bjørnøya displayed a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized groups of individuals regularly preying in the seabird colonies, foraging at sea, and alternating between both strategies. This suggests foraging specialization of some individuals.

Habitat foraging niche of a High Arctic zooplanktivorous seabird in a changing environment

Here, we model current and future distribution of a foraging Arctic endemic species, the little auk (Alle alle), a small zooplanktivorous Arctic seabird. We characterized environmental conditions [sea depth, sea surface temperature (SST), marginal sea ice zone (MIZ)] at foraging positions of GPS-tracked individuals from three breeding colonies in Svalbard: one located at the southern rim of the Arctic zone (hereafter ‘boreo-Arctic’) and two in the high-Arctic zone on Spitsbergen (‘high-Arctic’). The birds from one ‘high-Arctic’ colony, influenced by cold Arctic water, foraged in the shallow shelf zone near the colony. The birds from remaining colonies foraged in a wider range of depths, in a higher SST zone (‘boreo-Arctic’) or in the productive but distant MIZ (second ‘high-Arctic’ colony). Given this flexible foraging behaviour, little auks may be temporarily resilient to moderate climate changes. However, our fuzzy logic models of future distribution under scenarios of 1 °C and 2 °C SST increase predict losses of suitable foraging habitat for the majority of little auk colonies studied. Over longer time scales negative consequences of global warming are inevitable. The actual response of little auks to future environmental conditions will depend on the range of their plasticity and pace of ecosystem changes.