Herring Gull Population Research Articles

Identifying spatial drivers of long-term population growth in three large gull species: the importance of mink farms and urban areas

Population growth generally shows extensive spatial variation within species, but the proximate and ultimate drivers of this variation are often poorly understood. For highly mobile colonial breeders, population growth is expected to be linked to resource availability within a considerable radius of the colony. We analyzed the relationship between population growth over the period 2000–2020 and resource availability for three large gull species in several hundred colonies in Denmark. Colony growth rates showed strong spatial autocorrelation for Herring Gull <em>Larus argentatus</em>, whereas no such relationship was apparent for the other two species (Great Black-backed Gull <em>L. marinus</em> and Lesser Black-backed Gull <em>L. fuscus</em>). Colony growth rates of Herring Gulls were correlated with relevant proxies of food availability within species-specific foraging ranges, including the extent of urban and subtidal foraging habitats, and the number of mink farms. No such correlations were found for the other two species. The positive relationships of Herring Gull colony growth with the number of mink farms and the extent of built-up area were particularly interesting, as they highlighted the strong dependency of this species on human-associated food sources. Furthermore, Denmark closed all mink farms in late 2020 because of concerns about the spread of SARS-CoV-2 virus between farms and between minks and humans, culling approximately 17 million minks. This dramatic change in food availability is expected to have a negative impact on the Danish Herring Gull population, which in recent years has fared better than in the neighboring countries.

Ecosystem change and population declines in gulls: Shifting baseline considerations for assessing ecological integrity of protected areas

In Lake Superior's Pukaskwa National Park (PNP) in northern Ontario, Canada, herring gull (Larus argentatus) population size is used as an indicator of ecological integrity. Since the 1970s, gull populations have declined by 70% suggesting deteriorating park conditions. However, most other rated park indicators show stable or positive trends. Here, we focus on reconciling these seemingly disparate trends through a better understanding of factors regulating PNP gull populations. Lake-wide declines in surface-schooling prey fish may be limiting aquatic food resources for PNP gulls. To investigate this, we examined gull population trends in different parts of the park in the context of food availability. Gull diets were assessed using regurgitated pellets, egg stable isotopes (nitrogen, carbon) and fatty acids. Population declines were more severe in southern PNP compared to northern PNP and inter-region differences in bird diets likely contributed to these population trends. Gulls in the south relied to a greater extent on dwindling aquatic food resources, i.e., prey fish, while birds in northern PNP supplemented their diets with anthropogenic foods, i.e., garbage. Recognizing that regional declines in aquatic food availability have occurred across eastern Lake Superior is important for the interpretation of PNP gull population trends. Wide-scale ecological changes affecting PNP suggest that factors limiting PNP's herring gull population are not park-specific but, instead, reflect broader ecosystem-wide changes. Defining an appropriate threshold based on current knowledge of ecological conditions on Lake Superior is critical for using herring gull populations as an indicator of park ecological integrity.

Status of Greenland Populations of Great Black-Backed Gull (Larus marinus), Lesser Black-Backed Gull (Larus fuscus) and Herring Gull (Larus argentatus)

Abstract. Great Black-backed (Larus marinus), Lesser Black-backed (L. fuscus) and Herring (L. argentatus) gulls have all shown population increases and range expansion in Greenland in recent decades, but in very different ways. Great Black-backed Gulls increased from at least the 1960s from an established, local population. Lesser Black-backed Gulls immigrated from Iceland in the 1980s, spread rapidly over most of the southern part of Greenland and are common and abundant today. Herring Gulls also immigrated in the 1980s, but only established a small, scattered, and, at many sites, irregular breeding population. Here, we present the most recent information on the status and trends of Great Black-backed Gull, Lesser Black-backed Gull and Herring Gull populations in Greenland.

Colony- and age-specific seasonal dispersal of Herring Gulls Larus argentatus breeding in The Netherlands

The Herring Gull population in The Netherlands went through phases of exploitation, protection, persecution and again (partial) protection during the nineteenth and twentieth centuries. The numbers of breeding pairs peaked in the 1980s at approximately 90,000 pairs, at which point a colour-ringing campaign was organised to evaluate dispersal and distribution patterns. Herring Gulls were ringed as chicks, predominately near-fledglings, in 12 colonies in 1986 (1,247 individuals), 13 colonies in 1987 (1,354 individuals) and 14 colonies in 1988 (1,396 individuals). Between 1986 and 2009, of the 3,997 Herring Gull chicks colour-ringed, 3,124 individuals (78.2%) were seen and reported at least once, while 453 (11.3%) were recovered dead. In total, 86,247 ring-readings of living gulls were received and processed, originating from 1,358 locations by 868 observers. One-fifth (20.5%) of all sightings originated from the home-ranges (areas within a radius of 5 km around the ringing place). Only 691 sightings (0.8%) were reported at over 300 km from the natal colony (10.7% at 6–10 km, 8.9% at 11–25 km, 17.7% at 26–50 km, 22.9% at 51–100 km, 14.4% at 101–200 km and 4.1% at 201–300 km). Colony-specific differences in travelling distance, dispersal rate and direction of movements suggest a grouping of colonies in three areas: (1) eastern Wadden Sea islands (Rottumeroog–Vlieland), with significantly higher dispersal rates and movements mostly towards the south-west to south-east; (2) Texel and the four colonies along the mainland coast (Callantsoog–Wassenaar), with shorter mean range and movements mostly to the south; (3) colonies in the Delta area (Europoort–Saeftinghe), with rather short range movements and dispersal in many directions. The maximum distance travelled did not vary much between adults, immatures and juveniles, but the timing of outward and return movements was different for each of these age categories. Adult birds reached their greatest mean distances on average 1 month earlier than immatures, which in turn arrived at this point 1 month earlier than juveniles. These age-specific differences were enhanced in the spring, when birds were moving towards the (natal) colonies, but when adults moved on average closer and 2 months ahead of immatures, which in turn moved earlier and closer to the natal home-range than juveniles. With reference to findings from other studies in other European countries, Herring Gulls breeding in The Netherlands occupies a mid-position between dispersive and sedentary tendencies.

Genetic Variation in Mitochondrial DNA of North American Herring Gulls, Larus argentatus

The herring gull ( Larus argentatus), which is one of the most abundant gulls in temperate North America, is used as an important bioindicator species, but little is known about its patterns of genetic variation. This study examines DNA sequence diversity in the cytochrome b gene of mitochondrial DNA (mtDNA) from herring gull colonies in the Great Lakes basin and from a site in the Maritimes. A 307-bp fragment of the gene was analyzed using a rapid mutation screening procedure coupling directed termination PCR (DT-PCR) with single-stranded conformation polymorphism (SSCP). Seven mtDNA haplotypes were revealed in 224 specimens with a common haplotype dominating all populations. Direct sequencing of a 1063-bp fragment of the cytochrome b gene identified 8 additional haplotypes, but the sequence divergence among all 15 haplotypes was very low (average 0.24%). These data suggest that herring gulls experienced a bottleneck during the last glaciation that is now reflected in their low levels of genetic divergence. The geographic distribution of mtDNA haplotypes indicates that gene flow among herring gull populations is sufficient to ensure genetic homogeneity in the Great Lakes, but insufficient to homogenize genetic variation between the Great Lakes and the Maritimes. Meanwhile, a comparison analysis of frozen egg specimens suggests a possible shift in the genetic composition of the Great Lakes populations over the last 15 years.

Genetic Structure Among Breeding Herring Gulls ( Larus argentatus) from the Great Lakes and Eastern Canada

Herring gulls ( Larus argentatus) have been used as sentinel species for exposure to toxic chemicals since the 1960s. Reference populations in these studies have never been characterized to determine whether genetic differences might explain some of the effects seen in gulls at contaminated locations. Previously it was shown that there were higher rates of germline minisatellite DNA mutation rates in herring gulls colonizing sites located near steel industries in urban areas in the Great Lakes. It was suggested that population substructuring among gull colonies could account for differences in the mutation rates observed as a result of surveying different minisatellite loci. Here this explanation is dismissed by showing that genetic exchange among herring gull populations within the Great Lakes appears to be sufficient to ensure genetic homogeneity of these populations; in contrast, differences exist at the minisatellite loci scored between the gulls in the Great Lakes and the Maritimes. It is suggested that reference samples for future Great Lakes herring gull studies be selected from within the Great Lakes, and that potential genetic divergence from Maritime gulls should be investigated in more detail.

Relationship between cod fishery activities and the population of herring gulls on the North Shore of the Gulf of St Lawrence, Québec, Canada

The history of herring gull (Larus argentatus) populations nesting along the North Shore of the Gulf of St Lawrence and the commercial fishing activities there are closely related. Coastal cod (Gadus morhua) supply the main fishery in this part of the Gulf and traditionally have resulted in significant amounts of fish offal being discarded at sea and in fishing ports. Using commercial catch data of cod landings, and information from herring gull surveys conducted in the migratory bird sanctuaries on the North Shore from 1925 to 1993, the relationship between the cod fishery and herring gull populations was investigated. Between 1925 and 1975 the fisheries harvested a mean of 5 234 t of cod annually, with high and low catches of 11 000 and 1 700 t, respectively. During the same period, the herring gull population in the sanctuaries increased from 650 to 8 000 pairs. After 1975, and until 1993, the annual mean harvest was 5771 t peaking in 1983 at 11 500 t. There was then a steady decline until a complete fishery collapse in 1993. During the same period, the herring gull population increased from 8 000 pairs in 1975 to 14 000 pairs in 1988, but then dropped dramatically in most sanctuaries and was estimated at only 3000 pairs in 1993. This general decline of gulls appears to be related to the decrease in commercial fishing activities in the region, but not uniformly so.

Dynamique de population du goéland argenté en Bretagne application à la gestion de l’espèce

The population dynamics of the Herring Gull population of Brittany is briefly summarized. Following its steady increase between 1955 and 1978, the population started levelling off, but began colonizing new sites further south. The number of fledglings per pair was 1.3 ± 0.2 in 1983-84. The yearly survival rate of adult breeders was 0.91 ± 0.02, and the survival rate of birds during their first year of life was 0.71 ± 0.10.

The feeding ecology of five species of gulls (Ayes: Larini) in the inner Bristol Channel

The relative importance of different feeding sites to gulls in the inner Bristol Channel was determined by an analysis of chick regurgitations during the breeding season (1973–76), and by direct counts of birds at feeding sites during the winter (1973–77). About 70% of the local Herring gull population fed at refuse tips throughout the year. Tips were also of considerable importance to Lesser black‐backed gulls in summer and winter, and to Great black‐backed gulls in winter (c. 45% of birds). Common and Black‐headed gulls fed mainly on fields (c.90% and 70% of birds, respectively) and these areas were also used by about 50% of Lesser blackbacked gulls in winter. Littoral and inshore areas were utilized mainly by Great blackbacked gulls throughout the year (c. 50% of birds) and by Lesser black‐backed gulls in summer (c. 20% of birds). Foods provided directly or indirectly by man were clearly of major importance to all species. These findings are discussed in relation to the partitioning of food resources by gulls, their increasing populations and possible control measures.

Reproductive Parameters and Egg Contaminant Levels of Great Lakes Herring Gulls

Poor reproductive success and declines in colony size of herring gulls (Larus argentatus) have occurred in Lake Ontario at a time that dramatic increases of this species have been reported on the Atlantic seaboard. In 1975 herring gull productivity on Scotch Bonnet Island, Lake Ontario, was 0.15 chicks per pair of adults, one-tenth the productivity of colonies studied on Lakes Erie, Huron and Superior. Reduced nest site defense and decreases in eggs found, egg hatchability and chick survival were observed in the Lake Ontario colony. The major causes of egg failure were disappearance and embryonic death. Hatching success of Lake Ontario eggs by artificial incubation was 23-26 percent compared to 5379 percent for eggs from other areas. Analyses of eggs from 9 gull colonies for organochlorine contaminants indicated that the pattern of relative contamination was: Lakes Ontario > Michigan > Superior > Huron > Erie. Mirex levels were nearly 10 times higher in Lake Ontario than in the other lakes. Movements of herring gulls within the Great Lakes basin are offered as an explanation of variation in individual egg residues in each colony and the moderately high levels of chemical residues in some Lake Superior eggs. J. WILDL. MANAGE. 41(3):458-468 Recent declines have been noted in several herring gull colonies in Lake Ontario (Quilliam 1973, Canadian Wildlife Service unpublished data) and Lake Michigan (Ludwig and Ludwig 1969, J. J. Hickey personal communication). In contrast, herring gull populations have increased since the early 1900's along the eastern seaboard of both the United States (Kadlec and Drury 1968) and Canada (Haycock and Threlfall 1975). Reproductive success (the number of chicks fledged per pair of breeding adults) in 6 Lake Ontario herring gull colonies between 1972 and 1974 was reported as 0.1 to 0.44 (Gilbertson 1974, Teeple 1977, R. D. Morris personal communication). This is in contrast to the range in herring gull productivity (0.5-1.5) reported from other areas (reviewed by Kadlec and Drury 1968). The poor reproductive success of Lake Ontario herring gulls is the result of excessive embryonic mortality and egg disappearance, and poor survival of hatched chicks. Attention has been focused on organochlorine contaminants as causative a ents (Keith 1966, Ludwig and Tomoff 1966, Gilbertson 1974, Teeple 1977). The herring gull consumes a large variety of foods including fish and other aquatic organisms, insects, garbage, small rodents, and the young of other birds. Its capacity for accumulating organochlorine compounds has been well documented (Hickey et al. 1966, Anderson and Hickey 1976). Reproductive success and eggshell quality of herring gulls nesting in Lakes Superior, Huron, Erie and Ontario are reported in this paper. Seasonal movements and levels of several environmental contaminants in eggs are presented for herring gulls nesting in all 5 Great Lakes. In addition, the 458 J. Wildl. Manage. 41(3):1977 This content downloaded from 207.46.13.106 on Wed, 15 Mar 2017 18:01:31 UTC All use subject to http://about.jstor.org/terms REPRODUCTION AND CONTAMINANTS OF HERRING GULLS Gilman et al. 459

Timing of primary moult in adult Herring Gulls and Lesser Black-backed Gulls

Timing of primary moult in relation to the breeding cycle is presented for 113 actively moulting adult Herring Gulls and 79 Lesser Black-backed Gulls from Walney Island, England. Moult in both species occurred about when the eggs hatched in mid-May. The entire Herring Gull population began to moult the primaries within a period of 50 days. Lesser Black-backed Gulls started to moult 10 days later than Herring Gulls but many birds were not yet moulting as late as 5. August when I left the study area. It is suggested that the population of Lesser Black-backed Gulls consists of residents and migrants and that the former begin to moult earlier than the latter.

Effects of Human Disturbance on the Breeding Success of Gulls

DRENT, R., G. F. VAN TETS, F. TOMPA, AND K. VERMEER. 1964. The breeding birds of Mandarte Island, British Columbia. Can. Field-Nat. 78:208-263. EMLEN, J. T., JR. 1956. Juvenile mortality in a Ring-billed Gull colony. Wilson Bull. 68:232238. GILLETT, W. H. 1973. The effect of model gull orientation and movement on the responses of a Glaucous-winged Gull to the model. M.A. Diss., Andrews University. HARRIS, M. P. 1964. Aspects of the breeding biology of the gulls Larus argentatus, L. fuscus, and L. marinus. Ibis 106:432-456. HAYWARD, J. L. 1974. Orientation and sequences of behavior during aggressive communication by the Glaucous-winged Gull (Larus glaucescens). M.A. Diss., Andrews University. KADLEC, J. A., AND W. H. DRURY, JR. 1968. Structure of the New England Herring Gull population. Ecology 49:644-676. KADLEC, J. A., W. H. DRURY, JR., AND D. K. ONION. 1969. Growth and mortality of Herring Gull chicks. Bird-Banding 40:222-223. LUDWIG, J. P. 1966. Herring and Ring-billed Gull populations of the Great Lakes 1960-1965. Pub. No. 15, Great Lakes Res. Div., Univ. Michigan, pp. 80-89. PALUDAN, K. 1951. Contributions to the breeding biology of Larus argentatus and Larus fuscus. Ejnar Munksgaard, Copenhagen. PAYNTER, A. 1949. Clutch-size and egg and chick mortality of Kent Island Herring gulls. Ecology 30:146-166.

The Current Status of the Herring Gull Population in the Northeastern United States

The Current Status of the Herring Gull Population in the Northeastern United States

Structure of the New England Herring Gull Population

Measurements of the rates of population increase, reproduction, and mortality together with an observed age ratio, were used to analyze the population of the Herring Gull in New England. Data from sporadic censuses prior to this study, aerial censuses by the authors, and National Audubon Society Christmas Bird Count indicated that the New England breeding population has been doubling every 12 to 15 years since the early 1900's. This increase has involved founding new colonies and expanding the breeding range There is evidence that 15 to 30% of the adults do not breed in any given year. Sixty—one productivity measurements on 43 islands from 1963 through 1966, involving almost 13,000 nests, showed that from 0.8 to 1.4 young/breeding pair/year is the usual range of rate of production. The age distribution in the population was determined by classifying Herring Gulls by plumage category on an aerial census of the coast from Tampico, Mexico, to Cape Sable, Nova Scotia. Of the 622,000 gulls observed, 68% were adults, 17% were second— and third—year birds, and 15% were first—year birds. Mortality rates derived from band recovery data were too high to be consistent with the observed rate of population growth, productivity, and age structure. Loss of bands increasing to the rate of about 20%/year 5 years after banding eliminates most of the discrepancy. The age structure and rate of population increase indicate a mortality rate of 4 to 9% for gulls 2 years old or older, compared with the 25 to 30% indicated by band recoveries. The population structure we have developed fits everything we have observed about Herring Gull population dynamics, except mortality based on band recoveries.