Lesser Black-backed Gull Larus Fuscus Research Articles

‘Flying barnacles’: implications for the spread of non-indigenous species

The presence of adult barnacles of Fistulobalanus pallidus (Darwin) and Fistulobalanus albicostatus (Pilsbry) attached to field-readable plastic leg rings on the Lesser Black-backed Gull Larus fuscus in Northern Europe is reported. L. fuscus is a long-distance palaearctic migrant, breeding in temperate areas spreading widely over inland and marine habitats outside the breeding season. The species is known to perform long-distance migration to Africa and the Middle East. Combining present knowledge on the birds' migratory pattern and the home range of the barnacle species, it is concluded that the cypris larvae of F. pallidus must have settled in African waters, whereas the area where F. albicostatus settled on the bird leg rings is less certain. The barnacles were of adult size and must thus have been attached for a period of no less than 2 months. More than 30 individual barnacles could occur together on a single field-readable plastic leg ring. The barnacles could therefore, if ported alive to a new area, reproduce successfully and thus either introduce the species or genetically affect other native populations. This may pose a new and wholly unexpected transportation pathway for barnacles as invasive species.

Spring arrival of adult Lesser Black-backed Gulls Larus fuscus nesting in Guernsey, Sark and Herm, Channel Islands

Lesser Black-backed Gulls Larus fuscus nest in all the Channel Islands, with strongholds in Alderney and Sark. Breeding numbers in the islands (c. 1,730 pairs) appear presently stable, and the whole population is believed to leave the islands in winter. A colour-ringing programme began in 2008 and the timing and pattern of arrival for 125 colour-ringed adults, believed to be local breeders, was recorded at a landfill site on Guernsey from 1 January to 8 May 2010. Birds arrived back from 15 January to 1 May. Arrivals were slow initially, with only 6% back by mid February and 22% by the end of February. Peak arrival was from 27 February to 10 March, when 34% of birds were first recorded, and by the end of March 82% of birds had returned. Males did not arrive earlier than females. Five birds left the Channel Islands again soon after arriving, although all returned within a few days or weeks. Winter 2009/10 was unusually long and cold in the Channel Islands, and most of Western Europe, and further study should ascertain whether the arrival pattern of Lesser Black-backed Gulls in spring 2010 was affected by the harsher than average winter weather.

Seasonal differences in at-sea activity of seabirds underline high energetic demands during the breeding period

We assessed seasonal differences in at-sea activity of Lesser Black-backed Gulls Larus fuscus, Black-legged Kittiwakes Rissa tridactyla and Common Guillemots Uria aalge in the south-eastern North Sea. The three species correspond to different ecological groups, with Lesser Black-backed Gulls representing omnivorous generalists, Kittiwakes representing surface-feeding pelagic seabirds, and Guillemots representing pursuit-diving pelagic seabirds. Using data from aerial surveys, we differentiated between active (flying or scavenging at fishing vessels) and inactive behaviour (swimming). We estimated the activity budgets of all three species for the different seasons and tested for differences in activity between different seasons. All species exhibited significant seasonal differences in activity, with the highest levels of activity observed during the breeding season. Numbers of flying auks were, however, exceptionally low in autumn due to moult and guarding of not-yet fledged chicks at sea. Our results underline the high energetic demands of the breeding season that lead to increased foraging and travelling activity.

Migration Patterns of Adult and Juvenile Lesser Black-Backed GullsLarus fuscusfrom Northern Norway

To explore migration patterns of Lesser Black-backed Gulls Larus fuscus breeding in northern Norway, this study presents resightings of 16 adult and 83 juvenile birds marked in this region. Adults of the endangered nominate sub-species L. f. fuscus had a low probability of being observed (only 3.5% of marked birds were observed), probably because the adults winter in areas with few observers, such as eastern and central Africa. In contrast, birds of the greyish-mantled subspecies L. f. intermedius or L. f. graellsii had a high probability of being observed (45.5%). Adults of intermedius/graellsii had a western migration route and wintered mainly in western Europe and northwest Africa, Adults exhibited a high site fidelity to wintering areas. Birds marked as juveniles had two different migration routes. (1) 30% of the observed birds crossed the Scandinavian Peninsula to Finland and the Baltic countries, and then migrated to the eastern Mediterranean (Israel and Egypt) down to eastern and central Africa (Kenya and Cameroon). (2) The other 70% followed the European coast and overwintered in UK, the Iberian Peninsula, Morocco, Mauritania and Senegal. There were no indications that juvenile migration patterns differed among subspecies as juveniles from mixed and pure fuscus colonies exhibited similar patterns. The apparent differences in migration patterns between adult and juvenile fuscus may be a result of juvenile exploratory migration.

Formation of a bird community on a new island, Surtsey, Iceland

The present paper summarizes bird observations from Surtsey, iceland since the formation of the island in 1963 until 2008. Continuous observations were maintained in the early years of the island; in spring and autumn 1967–1971 and summers 1970–1973. Since then much of the bird observations are incidental by various scientists and bird watchers visiting the island for a limited period. Different aspects of the bird fauna are examined, the at-sea bird community, vagrants, migrant species, and winter birds, while emphasis is placed on the formation of the breeding bird community. With increasing numbers of breeding species and size of breeding populations as the years passed more structured census of the breeders was needed. Hence whole island censuses were organized in 1990 and 2003. Ringing has been carried out on five occasions. in total 91 bird species have been recorded on or offshore from the island. The first birds started breeding in 1970, Black Guillemot Cepphus grylle and Fulmar Fulmarus glacialis. A total of fourteen species have since bred on the island. Four species of large gulls breed (mostly in one colony); Great Black-backed Gull Larus marinus (bred first in 1974), Herring Gull Larus argentatus (1981), Lesser Black-backed Gull Larus fuscus (~1985), and Glaucous Gull Larus hyperboreus (1993). The colony, starting to form in 1984, has been particularly important for furthering the development of plant and invertebrate communities. Through the fertilizing agency complete vegetation cover is now found in the oldest part of the gull colony. This development has paved the way for terrestrial birds to start breeding; Snow Bunting Plectrophenax nivalis (1996), Greylag Goose Anser anser (~2001) and Meadow Pipit Anthus pratensis (~2003). other breeding species are kittiwake Rissa tridactyla (1975) and White Wagtail Motacilla alba (~2003), but Arctic Tern Sterna paradisaea (1975) has not bred since 1978. in 1990 the island had 316 breeding pairs of six species. in 2003 eleven species bred on the island with a total of about 850 breeding pairs. After 2003 two more species have started breeding, Common Puffin Fratercula arctica (2004) and Raven Corvus corax (2008). Surtsey island was entered on the UNESCo World Heritage list in 2008, not the least for the long history of research and monitoring of various aspects of the island’s natural history. As the breeding bird fauna develops a structured bird monitoring program becomes the more important. Recommendations on how this should be carried out are presented in the paper.

Lesser Black-backed Gulls Larus fuscus nesting in an inland urban colony: the importance of earthworms (Lumbricidae) in their diet

Capsule Earthworms can be an important food of birds breeding inland and on the coast. Aims To identify food and feeding sites of Lesser Black-backed Gulls Larus fuscus breeding on buildings in Dumfries, Scotland. Methods Direct observations were made of feeding behaviour, and 181 regurgitated pellets, obtained from flat roofs where only Lesser Black-backed Gulls nested, were analysed. Food items were identified using standard techniques with microscopic examination used to identify the presence of earthworm chaetae. Results Lesser Black-backed Gulls breeding in Dumfries fed extensively on earthworms and insects obtained from agricultural land (55% of pellets). They also fed on landfill (23% of pellets) and marine sites (12% of pellets), but they did not take fish or fish offal. Conclusions Previous studies on the food of large gulls have often overlooked the importance of earthworms because of the lack of macro-remains in stomachs and pellets. New studies are required to establish the general extent of earthworm consumption in these large gulls.

First records of lesser black-backed gullsLarus fuscuscrossing the Sahara non-stop

Lesser black-backed gulls Larus fuscus migrate regularly along coastlines or the Nile to their wintering grounds in sub-Saharan Africa. They usually avoid the interior of the Sahara, but occur occasionally far inland when moving upstream along rivers. We discovered several flocks of lesser black-backed gulls crossing the western Sahara about 500 km east of the Atlantic coast. Their concentrated flight directions along a northeast-southwest axis indicate that the gulls were on an intended migratory flight and not incidentally drifted inland. Ground speed of 8 flocks of gulls averaged 20 m/s and was considerably larger than the mean air speed (12 m/s) demonstrating that the gulls were strongly assisted by tailwinds. Highest ground speed was 26 m/s. Warmest temperature encountered when crossing the study site was 13° C due to relative high flight altitudes of 3,500 m above sea level. Thus, lesser black-backed gulls migrated under favourable conditions with respect to energy and water consumption. Our observations strongly suggest that the gulls performed long non-stop flights between the eastern Atlantic coast of sub-Saharan Africa and the Mediterranean Sea.

Taxonomic recommendations for British birds: Fourth report

Taxonomic recommendations for British birds: Fourth report

Current status and population dynamics of nominate subspecies of Lesser Black-backed Gull Larus fuscus fuscus in the White Sea

The size of the colonies of the nominate subspecies of Lesser Black-backed Gull Larus fuscus fuscus was monitored annually in Onega Bay of the White Sea in 1989—2006. The total current population in the studied area is about 2,100 pairs or 10% of the world population of this subspecies. During the time of monitoring the population increased more than three times, and since the 1960s it has increased more than six times. The main increase was observed in the seven biggest colonies (more than 100 pairs) where more than 60% of the White Sea population was breeding. Average long-term clutch size was 2.44, and breeding success was 1.0 fledgelings per pair. The increase in number probably results from the decrease of disturbance in the breeding area and improvement of feeding resources. The increase of the White Sea population contrasts with a strong decline of the Baltic population.

Diurnal attendance of nominate Lesser Black-backed Gulls Larus f. fuscus at a Ugandan lake: implications for the conservation of a globally threatened subspecies

The nominate Lesser Black-backed Gull Larus fuscus fuscus has experienced dramatic population declines on its northern breeding grounds. The global population is assessed at 18,000–119,000 pairs (BirdLife Finland), compared with 175,000 pairs of the British form graellsii (Wetlands International 2002). Although the species as a whole is not regarded as threatened, nominate fuscus is listed in the Red Data Books of Finland, Sweden, Norway, Estonia and Russian Karelia, i.e. it is classified as Threatened over its entire current range, falling into the Endangered and Vulnerable categories in the IUCN Red List categories.

Energetic influence on gull flight strategy selection

During non-migratory flight, gulls (Larids) use a wide variety of flight strategies. We investigate the extent to which the energy balance of a bird explains flight strategy selection. We develop a model based on optimal foraging and aerodynamic theories, to calculate the ground speeds and airspeeds at which a gull is expected to flap or soar during foraging flight. The model results are compared with observed flight speeds, directions, and flight strategies of two species of gulls, the black-headed gull Larus ridibundus and the lesser black-backed gull Larus fuscus. The observations were made using a tracking radar over land in The Netherlands. The model suggests that, especially at combinations of low ground speed (approximately 5-10 m s(-1)), high air speed (approximately 20-25 m s(-1)) and low ground and air speed, gulls should favor soaring flight. At intermediate ground and air speeds the predicted net energy gain is similar for soaring and flapping. Hence the ratio of flapping to soaring may be higher than for other air and ground speed combinations. This range of speeds is broadest for black-headed gulls. The model results are supported by the observations. For example, flapping is more prevalent at speeds where the predicted net energy gain is similar for both strategies. Interestingly, combinations of air speed and flight speed that, according to the model, would result in a loss of net energy gain, were not observed. Additional factors that may influence flight strategy selection are also briefly discussed.

Long-term population trends in the Lesser Black-backed Gull Larus f. fuscus at Stora Karlsö and Lilla Karlsö, and initial results on breeding success

Censuses of the breeding population of the nominate race of Lesser Black-backed Gull Larus fuscus fuscus were performed on the islands Lilla Karlsö and Stora Karlsö in the Baltic Sea in 2003 and 2004. At Lilla Karlsö, 126 and 136 nests were found, whereas the figures for Stora Karlsö were 532 and 477. These figures were evaluated together with previous censuses and the conclusion is that the population of both islands has recovered from the decrease that took place during the eighties and early nineties. The breeding success was found to be very low in 2003 and 2004 – about 0.11 respectively 0.02 fledglings/nest at Stora Karlsö and 0.16 respectively 0.07 at Lilla Karlsö. The reasons for the reproductive failure are not clear.

Effects of vegetation on nest microclimate and breeding performance of lesser black-backed gulls (Larus fuscus)

For birds that breed in large colonies, the overall area occupied by the colony generally comprises several sub-areas that differ in physical and social features such as vegetation and breeding density. Birds arriving at a breeding colony select their nesting sites through a hierarchical process of selecting a sub-area, then a particular nest site with appropriate biotic and physical attributes. Optimal vegetation cover is one such important attribute. Many ground nesting gulls preferentially select nest sites that provide shelter during reproduction, but this presumably has to be balanced against any costs such as reduced visibility of potential predators. The effects of vegetation height in the sub-areas within a colony, and of the amount of vegetation in the immediate vicinity of the nest on nest microclimate were investigated in lesser black-backed gulls Larus fuscus in a colony in which overall vegetation height differed in different sub-areas and was patchily distributed within these areas. Tall vegetation did have a sheltering effect, and this was positively related with chick growth. However, this vegetation area was associated with lower breeding densities, relatively late laying birds and lower chick survival rate, suggesting that sub-areas with tall vegetation held more lower-quality or young breeders. Within the sub-areas, the birds preferentially selected nest sites with more surrounding vegetation, and this was positively correlated with their hatching success.

At-sea distribution and behaviour of a surface-feeding seabird, the lesser black-backed gull Larus fuscus, and its association with different prey

The lesser black-backed gull Larus fuscus is a typical surface-feeding seabird with a widespread, patchy distribution in the SE North Sea. During the 1990s, breeding numbers along the German North Sea coast increased exponentially. Analyses of a multiple-year data set revealed changes in the at-sea distribution that seemed to reflect an increase in the numbers of breeding birds. Detailed recordings of feeding and resting behaviour at sea revealed area utilisation by the lesser black-backed gull. Observations at sea and dietary analysis revealed that swimming crabs Liocarci- nus spp. are a major dietary item of this gull species. This natural food source was primarily captured close to the shore; at longer distances from the coast the gulls mainly fed on other natural prey items or discarded fishes from trawlers and avoided competition with other breeding gull species. During July and August 1990 to 1995 L. fuscus abundance was significantly correlated with fishing effort, while in May and June there was no such correlation. Time of day was the main environmental vari- able influencing the gulls' flight activity and indicated an association between activity and availabil- ity of their major natural prey, swimming crabs. Distinct patterns and changes in the at-sea distribu- tion and foraging behaviour of L. fuscus in the SE North Sea reflect anthropogenic and natural influences in their habitats.

Carotenoids and egg quality in the lesser blackbacked gull Larus fuscus: a supplemental feeding study of maternal effects.

Egg quality is a phenotype of, and can profoundly influence fitness in, both mother and offspring. However, the physiological mechanisms that underlie this maternal effect are poorly understood. Carotenoids are hypothesized to enhance antioxidant activity and immune function, and are responsible for the pigmentation of egg yolk. The proximate basis and consequences of this maternal investment, however, have not previously been studied in wild birds. In this supplemental feeding study of lesser black-backed gulls, Larus fuscus, carotenoid-fed females are shown to have increased integument pigmentation, higher plasma concentrations of carotenoids and antioxidant activity, and lower plasma concentrations of immunoglobulins (Igs) in comparison with controls. In turn, carotenoid-fed females produced eggs containing high carotenoid but low Ig concentrations (i.e. passive immunity), whereas control females produced eggs containing low carotenoid but high Ig concentrations. Within-clutch patterns of these resources varied over the laying sequence in a similar manner in both carotenoid-fed and control nests. Our results suggest that carotenoids could be one resource responsible for egg quality maternal effects in birds. We discuss the possible implications of carotenoid-mediated effects on phenotype for fitness in mothers and their offspring.

British Ornithologists’ Union Records Committee: 28th Report (October 2001)

British Ornithologists’ Union Records Committee: 28th Report (October 2001)

Changes in the waterbird community of the Lake Sevan–Lake Gilli area, Republic of Armenia: a case for restoration

Waterbird species richness (Gaviiformes, Podicipediformes, Pelecaniformes, Ciconiiformes, Phoenicopteriformes, Falconiformes, Anseriformes, Gruiformes, Charadriiformes, Passeriformes) has been significantly affected by a 19.5 m lowering of the water level in Lake Sevan (1933–2000), and the complete draining of nearby Lake Gilli (1960–2000) in the Republic of Armenia. Twenty-three former breeders are currently nonbreeders in the area. Four former breeders (black stork Ciconia nigra, glossy ibis Plegadis falcinellus, white-winged scoter Melanitta fusca, little crake Porzana parva) have been extirpated from the area. Four former nonbreeders (cattle egret Bubulcus ibis, red-breasted goose Branta ruficollis, sociable lapwing Chettusia gregaria, lesser black-backed gull Larus fuscus) have been absent from the area for at least 20 years. The red-breasted merganser Mergus serrator is the only former nonbreeder discovered breeding in the Lake Sevan basin. We recommend that management plans of the 1960s and 1970s be used to further develop and enact new efforts to increase the water level of Lake Sevan by at least 6 m, and that Lake Gilli and its surrounding wetlands be restored as a means of increasing waterbird species richness overall, and protecting regional populations of globally threatened or near-threatened species (Dalmatian pelican Pelecanus crispus, red-breasted goose Branta ruficollis, ferruginous pochard Aythya nyroca, white-headed duck Oxyura leucocephala, corn crake Crex crex, great snipe Gallinago media, black-winged pratincole Glareola nordmanni, white-tailed eagle Haliaeetus albicilla).

Maternally derived androgens and antioxidants in bird eggs: complementary but opposing effects?

Maternally derived traits, such as within-clutch variation in the amount of testosterone deposited in egg yolks, may have profound effects on offspring fitness. Offspring with elevated levels of testosterone may benefit from increased competitive ability through effects on aggression and growth rate. However, elevated levels of testosterone are also associated with costs of increased peroxidative damage from free radicals and consequent oxidative stress. Diet-derived antioxidants, such as vitamin E and various carotenoids, provide protection against the deleterious effects of oxidative stress. Here we show that within-clutch variation in yolk testosterone is the opposite to that of yolk antioxidant concentration in the lesser black-backed gull Larus fuscus. We provide evidence that suggests that these two direct maternal effects are, in fact, complementary and, in conjunction with an indirect maternal effect (the onset of incubation), may provide an adaptive mechanism for parental favoritism in response to environmental variability. The potential implications of these findings with respect to previous investigations on variation in yolk testosterone concentrations and on the understanding of intrafamilial dynamics are discussed.

The cost of egg production: increased egg production reduces future fitness in gulls

Measurements of costs of reproduction are essential for our understanding of the evolution of reproductive effort. While in birds the effects of increased chick‐rearing effort on subsequent survival and fecundity have been relatively well studied experimentally, costs associated with increased egg‐production effort have received relatively little attention. We experimentally increased the egg‐production effort of individually marked Lesser Black‐backed Gulls Larus fuscus and followed their breeding performance in the next year. In the season following increased egg production, females, but not males, were less likely to be resighted in the study plot and those that did return were less likely to produce a clutch compared to control birds. It is unclear whether the observed effect on local return rate represents differential survival, differences in breeding propensity or differences in dispersal between experimental and control females. In any event, all of these would adversely affect the fitness of experimental females. In addition, those experimental females that did breed invested less in egg production the following season, which again is likely to affect breeding performance. Thus, this study provides evidence that there is an inter‐brood trade‐off between current egg‐production effort and future fitness in birds.

Genetic affinities within the herring gull Larus argentatus assemblage revealed by AFLP genotyping.

To date, the taxonomic status of circumpolar breeding populations of the Herring Gull Larus argentatus, the Lesser Black-backed Gull Larus fuscus, and the closely related Yellow-legged Gull Larus cachinnans has been based on differences or similarities in phenotype, morphology, and feeding and premating behavior. To shed some new light on the many taxonomic uncertainties surrounding these taxa, we describe the results of a large DNA study based on comparing the distribution of 209 biallelic markers among 109 gulls, representing 11 gull taxa of the Herring Gull assemblage and the Common Gull Larus canus. A detailed phylogenetic analysis failed to show clustering of individuals into groups representing either geographic origin or phenotype. Alternatively, birds were grouped into taxa defined on the basis of phenotype and geographic origin or phenotype alone. Genetic analyses revealed significantly different genetic distances between all pairs of taxa. However, based on these genetic distances, again no consistent phylogenetic tree could be constructed. Analysis of molecular variance indicated that about 77% of the total genetic variability among these gulls could be explained by within-taxon differences. Only 23% of the total genetic variability was due to genetic differences between taxa, irrespective of their species or subspecies status. Although this seems to challenge the current taxonomic treatment of the herring gull assemblage, our results are too premature and too incomplete to recommend a drastic change.