A comparison of Herring Gull Larus argentatus and Lesser Black-backed Gull Larus fuscus nest sites: their characteristics and relationships with breeding success

Nest sites used by Herring Gulls and Lesser Black-backed Gulls in a mixed colony were compared. Correlations between features surrounding a nest and breeding success at different stages of the breeding cycle are presented. Lesser Black-backed Gulls nested on more vegetated and flatter areas than did Herring Gulls, even though the latter species had a lower hatching success at less vegetated sites. The difference in the general topography of nest sites between the species suggests that the Lesser Black-backed Gull, through an individual defence strategy, may be better adapted to use sites which are accessible to ground predators than the Herring Gull. The fledging success of Lesser Black-backed Gulls tended to increase with an increased proportion of relatively tall vegetation close to the nest. The Lesser Black-backed Gull may therefore be able to leave its young unattended and rely on their concealment for protection against predators. In contrast, the Herring Gull may rely more on parental vigilance to protect young. More frequent attendance by adult Herring Gulls at the nest site during chick rearing compared with Lesser Black-backed Gulls supports this hypothesis.     

Nonbreeding and nests without eggs in the Lesser Black-backed Gull Larus fuscus

Estimates of the number of breeding Lesser Black-backed Gulls Larus fuscus at the Tarnbrook Fell gullery, Lancashire, have been made from annual counts of nests since 1981. During all of these surveys, the mean percentage of nests which did not contain eggs has been remarkably constant from year to year (54%± 1.9%). A study of specific nests at the colony in 1992 showed that the great majority of these "empty" nests did not subsequently receive eggs. in 1993, a study of a sample of territory-holding gulls was made on a 0.41-ha study plot to investigate and to quantify the occurrence of empty nests. Of the 62 pairs that defended a territory and constructed a complete nest, 27% subsequently failed to produce eggs. These birds attended their territory as a pair significantly less frequently than pairs that produced clutches and achieved significantly fewer apparently successful mountings. Sixty percent of pairs constructed more than one nest, and 58% of all nests built received no eggs. The construction of empty nests was not found to be related to the density of nesting gulls. Since 1981, estimates of the number of gulls in the colony have been based on the assumption that one nest represents one pair of gulls. This has been shown not to be the case, and a correction multiplier of 0.61 must be applied to counts of nests at the colony to obtain an estimate of the number of breeding gulls.     

Sex-biased mortality in the Lesser Black-backed Gull Larus fuscus during the nestling stage

Theory predicts that skewed progeny sex ratios should be relatively common in vertebrate populations. In most birds this has proved hard to substantiate due to the difficulties associated with identifying the sex of large samples of chicks. This study reports the success of a new molecular DNA technique in determining the sex of 601 newly-hatched Lesser Black-backed Gulls Larus fuscus
There was no evidence of any adaptive sex ratio within broods. Male chicks were found to be disproportionately large and to grow at a faster rate than females. The overall sex ratio changed significantly from 0.484 (male/male + female) at hatching to 0.399 by fledging, probably due to male susceptibility to starvation. Mortality also increased significantly with hatching order, an effect often observed in species like the Lesser Black-backed Gull where hatching is asynchronous. I discuss the possibility that hatching asynchrony may in fact be a strategy employed to prevent excessive skews developing in progeny sex ratio whenever variable differential mortality is likely.
The results appear to vindicate Fisher's (1930) hypothesis which predicts the overproduction of the 'cheaper' sex. However, as the skewed sex ratio may be determined more by unpredictable environmental factors, such as food supply and weather conditions rather than parental strategy, this interpretation should be treated with caution.     

Difficulties in the ageing of the Herring Gull and Lesser Black-backed Gull

Annual Report Of The Edward Grey Institute

Report On The Nest Record Scheme, 1956, by J. F. Burton

Buzzard Survey, by N. W. Moore     

Lesser Black-backed Gulls Larus fuscus thriving on a non-marine diet

Capsule: Lesser Black-backed Gulls Larus fuscus breeding 30?km from the coast in the Netherlands focussed entirely on terrestrial food sources and reached relatively high breeding success.

Aim: To gain insight in the foraging ecology, habitat use and breeding performance of inland-breeding Lesser Black-backed Gulls.

Methods: We received data from seven birds fitted with global positioning system (GPS) loggers. The colony was frequently visited to collect pellets and boluses and to monitor reproductive success, mortality and growth rate of chicks.

Results: The GPS data revealed that mainly terrestrial habitats were used, 98% of these GPS positions were within 25?km of the colony. Refuse dumps were the most preferred sites, but also agricultural fields and freshwater bodies were often visited. Only two of the 710 recorded trips were directed to the North Sea. The pellet and bolus analyses confirmed the GPS data: no marine food remains were found. Breeding success of birds in the enclosure was relatively high, with 90% of eggs hatched and 51% of chicks fledged (1.6 chicks/pair).

Conclusions: Relying on terrestrial food is feasible when sources are available in the vicinity of the colony. We conclude that Lesser Black-backed Gulls could theoretically shift towards inland breeding after a fishery discards ban.     

Parent-Offspring Conflict over Independence in the Herring Gull (Larus argentatus)

Observations on 24 focal nests revealed that, at the time when parental investment in feeding fledging chicks declined, chicks showed a marked increase in begging, particularly in larger broods, whilst parents became less responsive to begging. That chicks suffer a cost from early termination of investment is indicated by the fact that third-hatched chicks, who had attempted (unsuccessfully) to initiate more feeds, were absent from the territory first, rather than the more mature first- and second-hatched chicks. Taken together, these results and related inter- and intra-brood contrasts in behaviour are interpreted as offering support for Trivers ' theory of parent-offspring conflict over the termination of investment.     

Experimental evidence for the relationship between food supply, parental effort and chick survival in the Lesser Black-backed Gull Larus fuscus

We studied breeding success, chick growth, parental effort and chick behaviour in two groups of Lesser Black-backed Gulls Larus fuscus whose chicks were provided with additional food until 7 days after hatching or until fledging. These data were compared with those from control pairs which we studied simultaneously to test the hypotheses that food was in short supply during the chick stage at the colony site and that in such circumstances the behaviour of adults and young is mainly responsible for the low success. Pairs whose chicks were fed with additional food until fledging showed a higher fledging success than control pairs (intermediate for pairs of first experimental group). During the first week after hatching, experimental adults of both groups were present together at the territory for longer than control pairs. In adult females of experimental pairs, the length of feeding trips was shorter than in females of control pairs, whilst the rate of chick feeding was more frequent in the experimental broods. After the chicks were 7 days old, differences were significant only for the experimental pairs whose chicks were provided with additional food until fledging. Chicks fed until fledging showed a higher daily mass and wing-length increments and reached a higher fledging mass at an earlier age than both control chicks and chicks which were provided with additional food until day 7. Starvation occurred only in control chicks and in chicks of the first experimental group after we had stopped providing food. When food was in short supply, fledging success of gulls was adversely affected as a result of both starvation (because of the lower feeding rates of chicks) and a higher predation rate (arising from changes in behaviour of both adults and chicks).     

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. Received: 27 January 2000 / Accepted: 18 September 2000     

Age Dynamics of Helminth Fauna of the Herring Gull (Larus argentatus) in Kola Bay,Barents Sea

Biology Bulletin - The influence of host age on the helminth fauna of the Herring Gull (Larus argentatus) captured in breeding colonies in Kola Bay in the Barents Sea was studied. The fauna of...     

Arterial system of the Herring gull (Larus argentatus)

Fourteen specimens of the Herring gull ( Larus argentatus ) were dissected and diagrams of the arterial system were prepared. Little individual variability in the larger arteries were noted; the origin, course, and number of smaller arteries, however, showed noticeable variation. In the neck and thorax region, the following arteries were relatively constant in origin and course: the common carotid, internal carotid, subclavian, sternoclavicular, ascending oesophageal, axillary, internal mammary (inner), pectoral, syringeobronchial, cervical cutaneous, comes nervi vagi, and subscapular artery. Individual variability was noted in the vertebral, accessory sternoclavicular, thyroid, and accessory oesophageal artery. In other regions of the body, as in the neck and thorax, the smaller arteries exhibited great individual variations. Additional studies are needed to clarify the phylogenetic significance of the vascular system in birds.     

Biochemical genetic variation in populations of Larus argentatus and Larus fuscus in northwestern Europe

The techniques of biochemical population genetics were used to examine the relationships between two apparently closely related species and their component subspecies which form the Larus argentatus/fuscus species complex in northwest Europe. The systematics and taxonomy of these populations in this part of the circum-polar ring are complex and it was thought that this type of analysis might clarify the taxonomic relationships. Samples were obtained from breeding colonies along a transect from northern France (47°N), through Britain to arctic Norway (70°N), with additional samples from the Camargue on the Mediterranean coast (42°N). Twenty-one enzyme systems were examined using starch gel electrophoresis. No interspecific differences were found and only one locus (glutamate oxaloacetate transaminase) was polymorphic. There were no allelic differences within geographical groups of populations, although there were some differences between some of the subspecies. The low levels of heterozygosity ( H = 0.0081 and H = 0.0031) are considered to arise from a combination of two factors: the low levels of heterozygosity which appear to be characteristic of birds and population effects. Furthermore, no interspecific differences were detected ( I = 0.999) indicating the morphological changes rather than changes at structural gene loci may have been more important in speciation.     

The sympatric breeding of Larus fuscus, L. cachinnans and L. argentatus in western France

An opportunity to study the validity of the species Larus cachinnans , considered by some authors as merely a group of races related to either L. fuscus or L. argentatus , is given by its sympatric breeding with these species. Both of these latter species have recently extended their breeding range southwards, while Mediterranean representatives of the cachinnans group have spread northwards, and the three forms now breed side by side over c. 350 km along the Atlantic coast of France, where their breeding biology was studied from 1983 to 1990. L. cachinnans is very territorial, some pairs holding territories almost all year round; argentatus pairs may defend territories from mid-winter; and the supposedly migratory fuse us are on their territories for only a short period before laying. L. cachinnans is an early breeder, laying from late March to early May, while fuscus lay from May into June, and argentatus has a protracted breeding season overlapping the other two. Interbreeding occasionally occurs; it can be productive in the case of fuscus x argentatus whereas fuscus x cachinnans attempts did not produce any young. No cachinnans x argentatus pair has been observed. This indicates strong reproductive isolation, evidence that L. cachinnans must be considered a good species.     

Residues of DDE and PCB in Eggs from Herring Gull (Larus Argentatus) and Common Gull (Larus Canus) in Norway

In 1969 294 eggs from herring gull were collected from eight different localities in Norway. The eggshell thicknesses were measured, and 10 eggs from each locality were analysed by gas liquid chromatography for organochlorine insecticides and polychlorinated biphenyls (PGB). Residues of DDE were demonstrated in all eggs, the concentrations varying from 0.2 to 5.4 p.p.m. in herring gull, and from 0.2 to 3.5 p.p.m. in common gull. DDT occurred only in four eggs from herring gull and then only in concentrations of from 0.1 to 0.3 p.p.m. Other organochlorine insecticides were not detected. Residues of PGB were found in all eggs from herring gull in concentrations of from 0.2 to 3.8 p.p.m. PGB 10, and in six out of nine eggs from common gull, from trace to 0.8 p.p.m. PGB 10. The analysed material showed a positive correlation between amounts present of DDE and of PGB. There was a significant difference between localities concerning the contents of DDE and PGB in eggs from herring gull. This variance may be taken into consideration by using the herring gull as an indicator organism, since this bird, especially in the northern part of Norway, is migratory. The residue concentrations of DDE and PGB were markedly higher in eggs from herring gull than in eggs from common gull. It is suggested that this may be related to the difference between these species in their feeding habits. The residues of organochlorines demonstrated in this investigation do not seem to have had any effect on eggshell thickness in herring gull.     

Lithium Transport in the Kidney of the Herring Gull Larus argentatus: Induction of Renal Li+ Net Secretion by a Salt Loading

To find out whether salt loading can induce Li⁺ net secretion in the kidney of the birds that have an extrarenal organ (the salt gland) for excretion of NaCl excess (earlier, such effect was revealed in the pigeon and chicken, the birds that do not have the salt gland), the effect of intravenous NaCl injections (4–5 injections of 14–20 mmol/kg at 20–30-min intervals) on Li⁺ transport in the gull kidney was studied. Prior to the salt loading, above 99% of the filtered Li⁺ were reabsorbed in the kidney: fractional excretion of Li⁺ (FE_Li) was 0.0024 ± 0.0007 (mean ± SD), the Li⁺ reabsorption occurring not only in the proximal, but also in the distal tubule. Under conditions of the salt loading, two essentially different regimes of the kidney functioning were observed: net Li⁺ reabsorption (FE_Li = 0.63 ± 0.26) and net Li⁺ secretion (FE_Li = 1.26 ± 0.12). In the absence of the salt loading, Li⁺ (due to its distal reabsorption) does not fit requirements of an indicator of proximal reabsorption of Na⁺ and water. However, in the regimes of the salt net reabsorption and the salt net secretion, FE_Li probably can serve as an indicator of delivery of these substances to the end of the proximal tubule (the lithium clearance method). If this suggestion is correct, transition from the net Li⁺ reabsorption (FE_Li < 1) to its net secretion (FE_Li > 1) with rise of the salt loading indicates the appearance of net Na⁺ secretion in the proximal tubule under these conditions. A comparison of the results for the gull and the chicken has shown that although the presence of the salt gland did not prevent transition of the kidney to the net Li⁺ secretion, its duration in the gull was significantly shorter. The comparative data are presented on parameters of renal function in the regimes of net Li⁺ secretion and net Li⁺ reabsorption. In both regimes, a linear correlation was observed between FE_Li and FE_Na; however, regression coefficients considerably differed. An abrupt break of the curve occurred at FE_Li 1.     

Adoption of Strange Chicks by Herring Gulls,Larus argentatus L

Adoption of young by unrelated adults is expected to be rare in natural populations, yet a high incidence was observed in a population of Herring Gulls on the Isle of May, Scotland. The means whereby rejection was avoided, and the resulting costs and benefits to adopting parents and adopted chicks, are described.