Larus Marinus Research Articles

Monitoring Nesting Seabirds: Reply to a Commentary by Ian C. T. Nisbet

Johnson and Krohn (2001) addressed the importance of timing when conducting surveys, and the effect of this variable on the ability of a monitoring program to statistically detect trends in numbers of breeding seabirds. However, Nisbet's commentary on our paper concentrates in general on the use of counts based on aerial photographs as a reliable survey measure, and on the precision and accuracy of gull counts that were conducted as part of our study. While comparisons of different survey techniques and associated accuracy assessments are important, this was not the subject of our paper. Our focus was on the temporal variability in numbers of nesting Double-crested Cormorants (Phalocrocorax auritus), Great Blackbacked Gulls (Larus marinus) and Herring Gulls (Larus argentatus) in coastal Maine across the breeding season, and the potential effect that survey protocols (e.g., conducting surveys at different times of year, for different survey windows or for different island sample sizes) could have on the ability of a survey program to detect long-term population trends.

Reliability of Aerial Photography for Detecting Population Trends in Gulls

Johnson and Krohn (2001; hereafter,J&K) reported on a series of aerial photographic surveys of breeding colonies of Herring Gulls (Larus argentatus), Great Black-backed Gulls (L. marinus) and Double-crested Cormorants (Phalacrocorax auritus) in Maine. Although their paper was primarily addressed to the timing of surveys, they concluded that ... aerial photos taken during the first few weeks of June can be used to reliably detect population trends in all three species (p. 31). I believe that this claim was not adequately supported by the information presented either in the paper byJ&K (2001) or in the Ph.D. thesis by Johnson (1998) on which it was based. This information did not

Häckfagelfaunan i östra Smålands ytterskärgård 1990—2000

The numbers of breeding birds were surveyed in the Baltic archipelago of Småland, southeastern Sweden, during 1984 and 1990—2000. The species included in the survey were Podiceps cristatus, Phalacrocorax carbo, Ardea cinerea, swans, ducks and geese (Anatidae), waders (Haematopus ostralegus and Charadridae), skuas, gulls and terns (Laridae), auks (Alcidae) and the passerine Anthus petrosus. The surveyed area is a narrow belt in the outer archipelago. It is 90 km long and ranges from Mönsterås in the south to Västervik in the north. Breeding birds were recorded from 54 islands or groups of islands. On average, 7,572 pairs were recorded each year from a total of 39 breeding species. The species population trends were analysed for the period 1990—2000. Three species showed a significant increase in number of pairs: Mergus serrator, Larus marinus, and Sterna caspia. Ten species showed a significant decrease in number of pairs: Tadorna tadorna, Melanitta fusca, Haematopus ostralegus, Arenaria interpres, Larus canus, Larus fuscus, Sterna paradisaea, Cepphus grylle, Alca torda and Anthus petrosus.

Effects of cleaning a tidal river of sewage on gull numbers: a before-and-after study of the River Tyne, northeast England

For most of the 20th century, the tidal reaches of the River Tyne in northeast England were used as an open sewer for organic wastes from almost a million people. This produced anaerobic conditions in the river, but supplied an appreciable source of food for five species of gulls. Observations on the number of gulls using the river were made in 1969/70 to establish the situation before a sewage treatment scheme was implemented. By 1994, the volume of untreated sewage discharged into the river had been reduced by 97% and by 86% in the study area, and a second survey was carried out to evaluate the effect of the clean-up on gull numbers. Overall, gull numbers showed a significant decrease of 37% between the two study periods. The decrease in winter was 38% and was also significant, while the decline in summer was 33%, but not significant. Considering individual species, numbers of Common and Great Black-backed Gulls declined by 93% and 91% respectively. In both these cases this is presumed to be due to the decline in available food. Black-headed Gull numbers did not change significantly and it appears they have been able to find alternative feeding sites such as mud flats exposed at low tide and the outfall where treated effluent is discharged. Numbers of Lesser Black-backed Gulls and Kittiwakes rose dramatically as a result of increases in breeding numbers in the area. Neither species feeds along the river. Numbers of Herring Gulls did not change significantly — it is likely that the effect of the decline in food availability was masked by the increase in breeding numbers in towns along the river banks. The different response of each of the species of gulls indicates the differences in their ecology and breeding status in the area.

Relationships Between Black-Legged Kittiwake Nest-Site Characteristics and Susceptibility to Predation by Large Gulls

Abstract We quantified the relationship between Black-legged Kittiwake (Rissa tridactyla) nest-site characteristics and risk of predation by Great Black-backed (Larus marinus) and Herring (L. argentatus) Gulls at Gull Island, Newfoundland, Canada, during 1998 and 1999. We monitored kittiwake nesting cliffs to identify nest sites attacked by large gulls and compared characteristics of attacked and successful nests among four study plots. We also examined which nest sites were attacked by Herring or Great Black-backed Gulls during calm (≤10 km hr−1) or windy conditions (>10 km hr−1). We found that kittiwake nests on plots with fewer nests were more likely to be attacked by gulls and less likely to fledge young. Nest density and nest location relative to the cliffs' upper edges significantly affected the risk of gull predation. Breeding success was correlated with nest density and ledge width and differed significantly among plots. Regardless of wind conditions both gull species were more likely to attack ne...

The Importance of Survey Timing in Monitoring Breeding Seabird Numbers

-We conducted weekly aerial surveys of islands along the central Maine coast from April-June of 19931997 and used aerial photographs to determine peak nest count dates for Double-crested Cormorants (Phalacrocorax auritus), Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus). These data also were used to determine the potential effect of survey timing on the ability to detect long-term trends in the abundance of these species. The number of cormorant nests in the study area peaked in mid-June, while Great Black-backed and Herring gulls peaked in late May and earlyJune, respectively. Peak nesting dates generally were consistent for each island across years, but varied by up to a month between islands during a given year. A 10-year monitoring program using annual surveys conducted between 23 May and 23June, or biennial surveys conducted from 2-17June, would have an 80% probability of detecting annual changes of ?5% for all three species in this region. Received 1 November 2000, accepted 4 December 2000.

Delayed capelin (Mallotus villosus) availability influences predatory behaviour of large gulls on black-legged kittiwakes (Rissa tridactyla), causing a reduction in kittiwake breeding success

During 1998 and 1999, the impact of predation by herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus) on breeding success of black-legged kittiwakes (Rissa tridactyla) at Gull Island, Witless Bay, southeastern Newfoundland, was quantified in relation to the timing of the annual arrival of capelin (Mallotus villosus) to spawn. The frequency of predation attempts by large gulls on kittiwakes was compared among three periods: before the mean hatching date for herring gulls, between the mean hatching date for herring gulls and the arrival of the capelin, and following capelin arrival. The frequency varied significantly among the three periods, being highest after gull chicks hatched but before the capelin arrived. The frequency of gull predation was significantly correlated with the percentage of kittiwake eggs and chicks that disappeared each week. We estimated that 43 and 30% of kittiwake eggs and chicks at Gull Island were taken by gulls in 1998 and 1999, respectively. Kittiwakes have been indirectly (through increased predation by gulls) affected by the delayed arrival and lower abundance of capelin in recent years, which underlines the need to understand multispecies interactions when interpreting the effects of human alteration of the marine environment.

Characteristics of Predators and Offspring Influence Nest Defense by Arctic and Common Terns

Nest defense is a critical aspect of parental care that entails both costs and benefits. The purpose of this study was to examine patterns of nest defense in a colony of Arctic and Common Terns (Sterna paradisaea and S. hirundo, respectively) using observations of natural predators: Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus). Tern nest-defense scores were higher for hunting gulls than for overflying gulls and for gull flights closer to the ground. Defense scores also were significantly higher during the chick stage than during the egg stage. Within the chick stage, response score initially increased with age, but then declined. The results of this study indicate that terns vary their defense in relation to characteristics of predators and offspring that influence the costs and benefits of defense.

Characteristics of Predators and Offspring Influence Nest Defense by Arctic and Common Terns

Abstract Nest defense is a critical aspect of parental care that entails both costs and benefits. The purpose of this study was to examine patterns of nest defense in a colony of Arctic and Common Terns (Sterna paradisaea and S. hirundo, respectively) using observations of natural predators: Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus). Tern nest-defense scores were higher for hunting gulls than for overflying gulls and for gull flights closer to the ground. Defense scores also were significantly higher during the chick stage than during the egg stage. Within the chick stage, response score initially increased with age, but then declined. The results of this study indicate that terns vary their defense in relation to characteristics of predators and offspring that influence the costs and benefits of defense.

Seabird migration in the Canadian northwest Atlantic Ocean: moulting locations and movement patterns of immature birds

All seabirds in the northwest Atlantic Ocean migrate, but timing and routes are not well understood. We evaluate existing knowledge on seabird migration with data from the Programme intégré de recherches sur les oiseaux pélagiques (PIROP) data base, using observations of immature and moulting seabirds to track migration of the following species: Northern Fulmar (Fulmarus glacialis), Greater Shearwater (Puffinus gravis), Northern Gannet (Morus bassanus), Herring Gull (Larus argentatus), Iceland Gull (Larus glaucoides), Glaucous Gull (Larus hyperboreus), Great Black-backed Gull (Larus marinus), Black-legged Kittiwake (Rissa tridactyla), and Thick-billed Murre (Uria lomvia). The distributions of immature and moulting birds show strong seasonal patterns in the northwest Atlantic, and new transition zones and clear biological borderlines for seabird distribution were found. New data on timing and location of moulting Thick-billed Murres are presented. The southern Labrador Banks and Grand Banks (Thick-billed Murre, Northern Fulmar) and southeast Newfoundland and Georges Bank (Greater Shearwater) were identified as moulting grounds. In terms of marine conservation the following areas seem to be important for part of the life cycle of the species named: western Greenland, Cape Cod, Grand Banks, Labrador Banks, southwest Newfoundland, and the Grand Manan area.

Effects of winter fishery activities on resting numbers, food and body condition of large gulls Larus argentatus and L. marinus in the south-eastern North Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 194:241-247 (2000) - doi:10.3354/meps194241 Effects of winter fishery activities on resting numbers, food and body condition of large gulls Larus argentatus and L. marinus in the south-eastern North Sea O. Hüppop*, S. Wurm Institut für Vogelforschung ŒVogelwarte Helgoland¹, Inselstation, PO Box 1220, 27494 Helgoland, Germany *E-mail: o.hueppop-ifv@t-online.de ABSTRACT: C Influences of fishery activities on herring gulls and great black-backed gulls (Larus argentatus, L. marinus) wintering on the island of Helgoland, south-eastern North Sea, were studied. When cod fishery discards were available close to the island, 83 to 87% of the gulls¹ pellets contained fishery discard remains and 70 to 73% of all pellets consisted exclusively of these. At times when no nearby trawling took place (Christmas/New Year), numbers of herring gulls dropped by up to 86% and numbers of great black-backed gulls by up to 80%. Similar declines were observed during a trawling moratorium in February 1998. Adults of both gull species had a significantly lower body mass during periods of no fishing around the island (13 and 24% less, respectively). Retraps of single gulls support these findings. The results show for the first time a strong influence of discard availability on numbers and body condition of large gulls wintering in the south-eastern North Sea. Effects on gull winter mortality and thus on population dynamics can be assumed. KEY WORDS: Fisheries · Herring gull · Great black-backed gull · Resting numbers · Food · Fishery discards · Body condition · North Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 194. Publication date: March 17, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

Metals in Herring and Great Black-Backed Gulls from the New York Bight: the Role of Salt Gland in Excretion

We examined the tissue distribution ofmetals in the herring (Larus argentatus) andgreat black-backed (Larus marinus) gullsobtained near the John F. Kennedy Airport, on LongIsland, New York, to determine whether there werespecies differences and whether levels in the saltgland were sufficiently high to suggest that thisorgan may be serving an excretory function. For mostorgans, herring gulls had significantly higher levelsof lead (except for liver), but significantly lowerlevels of mercury (except in the salt gland) thangreat black-backed gulls. For all metals exceptarsenic, there were significant differences inconcentrations among tissues for both species. Greatblack-backed gulls had much higher concentrations ofcadmium in kidney than in any other organ and this wasmuch higher than the level in herring gulls; herringgulls had much higher levels than black-backs of leadin salt glands. For both species, concentrations inkidney, liver and salt gland were generally higherthan in heart muscle or pectoral muscle. For herringgulls, the concentrations of all metals in the saltglands were not significantly different from the organwith the highest values (liver or kidney). For greatblack-backed gulls this was true only for lead,selenium, chromium, and mercury. We examined theratio of metals in all organs to the liverconcentration. Very low ratios ( 2) included lead (2.75:1) and cadmium(14.3:1) in kidney of black-backs. In greatblack-backs the kidney:salt gland ratio was >1.5:1except for mercury (1.31:1) and chromium (0.83:1),while in herring gulls all ratios were between 0.7 and1.2, except for mercury (0.46:1), reflecting therelatively higher concentrations of metals in the saltgland of this species. We suggest that most heavymetals seem to be concentrating in the salt glands ofgulls, within an order of magnitude of the kidneyconcentration, and that salt glands may be serving asignificant excretory function for these cations.

CHARACTERISTICS OF PREDATORS AND OFFSPRING INFLUENCE NEST DEFENSE BY ARCTIC AND COMMON TERNS

Abstract Nest defense is a critical aspect of parental care that entails both costs and benefits. The purpose of this study was to examine patterns of nest defense in a colony of Arctic and Common Terns (Sterna paradisaea and S. hirundo, respectively) using observations of natural predators: Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus). Tern nest-defense scores were higher for hunting gulls than for overflying gulls and for gull flights closer to the ground. Defense scores also were significantly higher during the chick stage than during the egg stage. Within the chick stage, response score initially increased with age, but then declined. The results of this study indicate that terns vary their defense in relation to characteristics of predators and offspring that influence the costs and benefits of defense.

The use of energy, fat, and protein reserves by breeding Great Black-backed Gulls

Changes in mass (adjusted for body size) and in nutrient reserve levels were examined in adult male and female Great Black-backed Gulls (Larus marinus), from arrival at the colony to 1 week prior to the fledging of young. During the prelaying period, males lost approximately as much of their prebreeding fat reserves as females gained in mass, suggesting that males contributed substantial energy to the reproductive investment of the pair. We did not analyze prebreeding females for fat or protein but, based on the mass-fat correlation, females likely put on fat during prebreeding that was to be allocated for egg formation. However, their overall loss in mass was equal only to the accumulation prior to laying, suggesting that increased body reserves serve breeding directly, as capital costs for clutch formation. In contrast, males did not regain prebreeding mass until prefledging, suggesting that costs associated with prebreeding activity by males were larger than those for females. Once the clutch was completed, both sexes carried comparable reserves; neither sex fully regained prebreeding levels during incubation. Female mass at the end of the chick-rearing period was lower than during or before incubation, while males recovered their prebreeding mass (adjusted for body size).

Using Radio-Transmitters to Improve Estimates of Gull Predation on Common Eider Ducklings

We quantified the efficacy of using pellet numbers to estimate predation rates on Common Eider (Somateria mollissima) ducklings by Great Black-backed Gulls (Larus marinus) by using eider ducklings fitted with radio transmitters. Ducklings fitted with radio-transmitters were no more vulnerable to gull predation than were other ducklings. The recovery of radio-transmitters attached to eider ducklings and subsequently retrieved from Great Black-backed Gull pellets suggests that traditional methods of estimating the number of eider ducklings eaten by gulls from the remains found in pellets at gull nests and loafing areas underestimates the true number eaten by gulls by a factor of 5-17. Previous low estimates of eider duckling mortality on the Wolves Archipelago, Bay of Fundy cannot be explained by movements of broods to the mainland coast.

Restoration of a multi-species seabird colony

Nesting herring and great black-backed gulls ( Larus argentatus and Larus marinus) were removed from a recently abandoned tern ( Sterna sp.) colony through a combination of poisoning and shooting. Following gull control, all three species of tern that had nested in the colony prior to the arrival of the gulls returned and nested in increasing numbers. In addition to the restoration of the terns, removal of the gulls led to colonization and/or significant increases in populations of four other seabirds. Gull numbers were greatly reduced by initial poisoning efforts, but continued immigration from surrounding colonies has required an on-going program of shooting to eliminate territorial birds nesting in areas utilized by terns and other species. In situations calling for active management we advocate rapid, focused intervention, and stress the importance of inter-organizational cooperation, and an active program of public education.

Status and Productivity of Common Eiders in Relation to Great Black-Backed Gulls and Herring Gulls in the Southern Bay of Fundy and the Northern Gulf of Maine

-The breeding population of Common Eiders (Somateria mollissima) in the Bay of Fundy has remained stable over the last decade, ranging from 8,000 to 10,000 breeding pairs. However, the number of ducklings surviving to fledging in the Bay of Fundy decreased from >14% of the adult breeding population prior to 1991 to <10% between 1995 and 1998. Although the breeding population in the Grand Manan Archipelago decreased over the decade, these colonies produced more ducklings that survived to fledgling in the Bay of Fundy between 1995 and 1998 and represented an important source of potential recruits (44-87%) to the eider population. Higher duckling production in the Grand Manan Archipelago cannot be attributed to higher hatch success, but may reflect lower predation rates by Great Black-backed Gulls (Larus marinus). The number of ducklings observed during aerial surveys was not correlated with commercial catches of herring (Clupea harengus), an alternative food source for predatory gulls. Duckling survival to fledgling was higher for a local breeding population in the Gulf of Maine (12%) than in the Bay of Fundy (6%). The relatively large number of ducklings associated with a two-island archipelago within the Petit Manan National Wildlife Refuge accounted for a large proportion of the surviving ducklings and may reflect lower predation rates by Great Black-backed Gulls as a result of gull control measures. The current populations of Herring Gulls (L. argentatus) and Great Black-backed Gulls breeding in the Bay of Fundy in New Brunswick are estimated at 5,367 pairs (5,011-7,282: 95% CI) and 1,771 pairs (1,685-1,868: 95% CI) respectively. Assuming that the age structure of gulls in this region is similar to that of the expanding New England population, the total number of individual gulls in the Bay of Fundy probably exceeded 56,393 (54,173-62,289: 95% CI) in 1998. Received 30 November 1998, accepted 27January 1999.

Results of a Seven Year Effort to Reduce Nesting by Herring and Great Black-Backed Gulls

-In 1992, as part of an integrated Piping Plover (Charadrius melodus) recovery plan, the U.S. National Park Service initiated a long-term gull control program to reduce nesting by Herring and Great Black-backed gulls (Larus argentatus and L. marinus) at Breezy Point, western Long Island, New York. An estimated 600 pairs of the two species nested in an area of about 50 acres. Gull management included discharging pyrotechnics to harass gulls and keep them off the nesting areas prior to the onset of breeding, and the physical destruction of all gull nests and eggs in the colony. This program was non-lethal to adult gulls. From 1993 to 1996, we found no evidence that discharging pyrotechnics at the colony site prior to egg-laying reduced the daily numbers of loafing gulls. Gulls appeared to habituate to the pyrotechnics and to our activities as the day (morning to evening) and season progressed. The physical destruction of nests and eggs was an effective method to eliminate the production of fledglings and eventually, starting three years after gull management began, reduced the number of nesting attempts 60%, from 742 total clutches in 1994 to 282 in 1998. Destroying gull clutches was an effective (albeit slow) method to control and reduce nesting by Herring and Great Black-backed gulls but, since about 40 percent of the colony remains, nest destruction will need to continue for several more years if the colony is to be eliminated. Received 8 February 1999, accepted 15 April 1999.

Seabird Breeding Performance during Two Years of Delayed Capelin Arrival in the Northwest Atlantic: A Multi-Species Comparison

-Breeding performance and timing of breeding of six seabird species breeding in the northwest Atlantic were compared during 1992 and 1993 when oceanographic anomalies and changes in fishing practices provided an opportunity to compare effects of reduced food availability at a multi-species level. The inshore spawning migration of capelin (Mallotus villosus), a major prey for five of the six species considered here, was delayed by one month in 1992 and 1993, and a ground fisheries moratorium eliminated the production of fish offal, an important alternative food source for Larus gulls and Black-legged Kittiwake (Rissa tridactyla). Inshore, surface-feeding piscivores, kittiwake and Herring (L. argentatus) and Great Black-backed (L. marinus) gulls, had lower breeding success than did pursuit-diving Atlantic Puffin (Fratercula arctica) and Common Murre (Uria aalge). Breeding performance of Leach's Storm-Petrel (Oceanodroma leucorhoa), an offshore, surface-feeding planktivore, appeared unaffected by nearshore perturbations. Hatching, fledging and breeding success of inshore surface-feeders were much reduced while those of pursuit divers were similar to previous years when ocean conditions were normal. Later breeding in 1993 than in 1992 for kittiwakes and Herring Gulls resulted in more chicks of these species hatching after mature capelin became available, with subsequent higher breeding success. Results support the hypothesis that inshore surface feeders are more sensitive to changes in food availability than are pursuit-divers and offshore surface-feeders, and demonstrate the importance of timing of breeding in relation to temporal changes in prey availability. Received 23June 1998, accepted 31 October 1998.

The use of energy, fat, and protein reserves by breeding Great Black-backed Gulls

The use of energy, fat, and protein reserves by breeding Great Black-backed Gulls