Skull deformity in a herring gull chick (Larus argentatus)

A skull deformity resulting in death of a herring gull chick (Larus argentatus) is described in detail. The bones of the skull and upper jaw were twisted, asymmetrical and of unusual size or absent. The lower jaw had an almost "spoon-like" external appearance and lacked normal articular surfaces.     

Sex of the first hatched chick influences survival of the brood in the herring gull (Larus argentatus)

Differences in the growth rate of male and female offspring can result in different parental rearing costs for sons and daughters. Such differences may also influence the survival chances of male and female offspring when conditions are unfavourable. In birds, hatching asynchrony leads to hierarchical competition for food between siblings. Therefore, the sex of the chick in the first hatched position in the brood may influence breeding success by affecting the extent to which the later hatched chicks can compete for resources. The interaction between brood sex composition and chick performance in the herring gull Larus argentatus was examined under different environmental conditions. When environmental conditions were relatively good, chick survival within broods was better when a female was first to hatch, an effect that was most obvious later in the season. When conditions were poorer however, sex of the first hatched chicks was not related to brood survival. In neither situation did the overall primary sex ratio differ from equality. However in the year of relatively good food availability, the first chick in the brood was more likely to be male early in the season, which was when the disadvantageous effects on brood survival of males being in this position are weakest.     

Hybridization of glaucous gull (Larus hyperboreus) and herring gull (Larus argentatus) in Iceland: mitochondrial and microsatellite data

Large white-headed gulls provide an interesting group of birds for studies of hybridization. The group is composed of 20 species of recent origin, often with weak reproductive barriers. Here we report the results from a study on the glaucous gull Larus hyperboreus, an Arctic species which has been breeding in Iceland for centuries, and the herring gull Larus argentatus which has a wide distribution in Europe but colonized Iceland in 1920s. Previous studies, based on morphological variation indicated hybridization between the two species in Iceland, have been questioned as it may just reflect variation within the species. Here we evaluate whether hybridization has occurred between the two species in Iceland by studying variation in microsatellites and mtDNA. The analysis is based on feathers taken from wings sampled in Iceland over a period of 40 years. The results are compared with samples obtained from East Greenland and published sequences of samples obtained throughout Europe. The genetic analysis reveals a distinctive grouping of the two species, although they present a shallow genealogy and an extensive sharing of the genetic variants between the two species. Several individuals show admixture for molecular markers, which may result from an incomplete lineage sorting although geographical patterns of both mtDNA haplotypes and microsatellites strongly indicate a recent hybridization in Iceland.     

The blood vascular system in the head of the herring gull (Larus argentatus)

The structure and development of the blood vascular system in the head of the herring gull (Larus argentatus) have been studied using injection techniques and histological sections. Three different but interconnected divisions of the arterial system are recognized in the adult: the cerebral carotid artery system, the external ophthalmic artery system, and the external carotid artery system. Embryologically, the arterial system is characterized by changes in the relative development of these three divisions; the cerebral carotid system being the most prominent in the first half of the embryonic period. The venous system is divided into two parts, the rostral cephalic system and the caudal cephalic system, which drain separate regions of the head. The Rete ophthalmicum, which is an arteriovenous network associated with the external ophthalmic artery system, can be identified from the fifth day of incubation, and its development appears to be coupled with changes in the arterial supply to the eye. The possibility of a homology between the Rete ophthalmicum of birds and the Rete caroticum of mammals is briefly discussed.     

Seasonal dynamics of the trematodes fauna in herring gull (Larus argentatus Pontopp.) of Kola Bay

Trematode fauna of the herring gulls from Kola Bay (Barents Sea) was investigated in March, May, June, and September 2005. The data on the trematode species composition and indices of the invasion of gulls with trematodes are given for each season. It was established, that trematode species composition is increased from spring to summer, and intensity of the gulls' invasion with some trematode species is increased from summer to autumn. Ecological factors causing seasonal differences of the trematode fauna in gulls are discussed.     

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.     

Hematologic and hematochemical characteristics of the herring gull (Larus argentatus) and the buzzard (Buteo buteo)

Some hematological and hematochemical parameters in eight herring gulls (Larus argentatus) and in six buzzards (Buteo buteo) were checked. The buzzards were fed with ovine meat exclusively, while the herring gulls were fed with fish and ovine meat. Considerable differences between the two species were noted, particularly as far as the hematological and lipidic parameters are concerned. These differences are probably related to the aquatic life of the herring gull.     

An ultrastructural study of the body wall muscles of the pentastomid Reighardia sternae dies. 1864 parasitic on the herring gull Larus argentatus pontopp

Summary The fine structure of the body wall muscle of the pentastomid Reighardia sternae is described. The muscle fibres are separated from one another and form two layers, circular and longitudinal. They are cross-striated with approximately 11 actin filaments surrounding each myosin filament. The T-system consists of simple in-pushings of the sarcolemma. The SR is also simple and forms both dyadic and triadic contacts with the T-system tubules and dyadic contacts with the sarcolemma. Electron-dense inclusions occur, usually in the vicinity of the Z-lines, and it is suggested that these may be composed of unsaturated lipids.     

An experimental investigation of a direct life-cycle in Reighardia sternae (Diesing, 1864), a pentastomid parasite of the herring gull (Larus argentatus).

A direct life-cycle in Reighardia sternae, a cephalobaenid pentastomid of gulls was investigated: the work was prompted by a report of eggs and larvae recovered from the stomach and intestine of a naturally infected gull. Infective pentastomid eggs were obtained by surgically transplanting maturing female Reighardia, taken from freshly shot wild gulls, into captive recipients. Faecal material from birds thus artificially infected was collected daily and examined for eggs. Eggs were force fed to 33 hand-reared (from eggs or nestlings) juvenile gulls which were selected at random and sacrificed at intervals thereafter and examined for pentastomids. One hour after infection, primary larvae appear in the body cavity where they moult immediately. They grow steadily and by 27-35 days are sexually differentiated, and by 66 days have copulated. Fertilized females take a further 116 days to produce eggs by which time they are 7-6 cm long. The complex migrations undertaken by developing larvae in the gull, and the problems of the mechanism of direct transmission, are discussed.     

The influence of fasting on blood and plasma composition of herring gulls (Larus argentatus).

Populations of scavenging seabird species in the North Sea may fluctuate with an artificial food source: the availability of fishery waste. To document this impact, it is necessary to assess the birds' nutritional status during periods with decreased fishing activity. Reference data for this purpose was collected from 22 herring gulls investigated during laboratory fasting. After 6 d of food deprivation and body mass losses exceeding 15%, the first birds entered starvation phase 3. Comparatively, this is a rather weak fasting capacity. Plasma levels of total protein and thyroid hormones decreased and beta-hydroxybutyrate increased with fasting duration. The leucocyte proportions were shifted from lymphocytes to heterophils. After 3 d of refeeding, most of the fasting changes were reversed. Plasma enzyme activities increased and hematocrit, hemoglobin, and erythrocyte numbers decreased in both fasting and control birds, most likely as a result of experimental stress and repeated blood sampling. Glucose, cholesterol, monocytes, basophils, and glycosylated hemoglobin remained fairly constant. Triglycerides, free fatty acids, uric acid, and urea varied significantly, but changes were not as clearly a result of fasting. Therefore, total protein, beta-hydroxybutyrate, triiodothyronine, thyroxine, and lymphocyte and heterophil percentages may be the most reliable indicators of the nutritional status and the condition of free-living herring gulls.     

An outbreak of type C botulism in herring gulls (Larus argentatus) in southeastern Sweden

From 2000 to 2004, over 10,000 seabirds, primarily Herring Gulls (Larus argentatus), died from an undetermined cause in the Blekinge archipelago in southeastern Sweden. In June 2004, 24 affected Herring Gulls were examined clinically, killed humanely, and 23 were examined by necropsy. Seven and 10 unaffected Herring Gulls collected from a local landfill site and from Iceland, respectively, served as controls. All affected birds showed similar neurologic signs, ranging from mild incoordination and weakness to severe flaccid paralysis of legs and wings, but generally were alert and responsive. All affected gulls were in normal nutritional condition, but were dehydrated and had empty stomachs. No gross or microscopic lesions, and no bacterial or viral pathogens were identified. Type C botulinum toxin was detected in the sera of 11 of 16 (69%) affected gulls by mouse inoculation. Type C botulism was the proximate cause of disease in 2004. Sera from 31% of birds tested from outbreaks in 2000 to 2003 also had detectable type C botulinum toxin by mouse inoculation. No large-scale botulism outbreak has been documented previously in this area. The source of toxin, initiating conditions, and thus, the ultimate cause of this outbreak are not known. This epidemic might signal environmental change in the Baltic Sea.     

A histochemical comparison of fibre types in the M. pectoralis and M. supracoracoideus of the great skua Catharacta skua and the herring gull Larus argentatus with reference to kleptoparasitic capabilities

Skuas, which are closely related to gulls, frequently use a specialized feeding method (kleptoparasitism) by which they rob other seabirds of their food. This paper tests the idea that skuas have evolved as specialist kleptoparasites.
The fibre type composition of the M. pectoralis, M. supracoracoideus and M. iliofibularis of a great skua Catharacta skua (Brünn.) and a herring gull Larus argentatus (Pontopp.) was determined by three enzyme histochemical methods commonly used for mammalian fibre classification; the reactions for alphaGPDH, NADH-TR and mATPase activity.
In both species slow fibres were present only in the M. iliofibularis, and fast twitch glycolytic fibres were not present in any of the muscles. The M. pectoralis and M. supracoracoideus of both species consisted entirely of the fast twitch oxidative-glycolytic fibres.
The overall metabolic enzyme activities of the muscles were assessed in terms of the proportions of fibres with high, intermediate and low metabolic enzyme activity. The overall levels of oxidative and glycolytic enzyme activity were significantly higher in the M. pectoralis than in the M. supracoracoideus and significantly higher in both of these than in the M. iliofibularis. This was true of both species.
The oxidative and glycolytic activities of all three muscles of the great skua were significantly higher than those of the homologous muscles of the herring gull. This was particularly true of the M. pectoralis and M. supracoracoideus. It is suggested that this difference between great skuas and herring gulls enables the former to be more effective aerial kleptoparasites than the latter.     

Effects of early incubation constancy on embryonic development: An experimental study in the herring gull Larus argentatus

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In many birds, parental nest attendance in early incubation is variable, with eggs incubated only intermittently. The effect of this on chick hatching success is unknown.     

Dynamics of physiological parameters in the nestling of black-backed gull Larus marinus experimentally infested by the cestode Microsomacanthus ductilus (Cestoda: Hymenolepididae)

The effect of the invasion with the cestode Microsomacanthus ductilus on physiological and biochemical processes in black-backed gull Larus marinus was examined. Experimental invasion of the gull nestling by the cestodes has been performed. Dynamics of the protein, lipid, and carbohydrate metabolism in the time history of the invasion was observed, in comparison with noninfested nestling. Increasing of the content of alpha-globulins and decreasing of the content of protein and albumin in the blood plasma of experimentally infested birds were registered to 4th day after invasion. To 7th day after invasion the level of general lipids and phospholipids decreases, while the content of gamma-globulins and modified form of albumin increases. To 10th day after invasion symptoms of intoxication were observed, but some parameters proved to be reverted to normal condition. So, it can be assumed, that the most intensive reorganization of the metabolism in infested birds takes place in the period between 4th and 7th days after infestation. Possible causes of the observed phenomena are discussed.     

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...     

Community structure of lice (Insecta: Phthiraptera) from two sympatric gull species: kelp gull (Larus dominicanus) and Franklin's gull (Larus pipixcan) in Talcahuano, Chile

A total of 1,177 lice of four species were collected from 124 kelp gulls (Larus dominicanus) and 137 lice of the same four species from 60 Franklin's gulls (Larus pipixcan). The louse Saemundssonia lari (O Fabricius) (Phthiraptera: Philopteridae) was the most numerous on both gull species, with infestation rates of 4.9 on kelp gulls and 1.8 on Franklin's gulls. The second most abundant louse was Quadraceps punctatus (Burmeister), with a high infestation rate but low prevalence on kelp gulls; those parameters were much lower among lice from Franklin's gulls. The composition and community structure of the lice were similar on both host species, but not their infestation rates. In addition, the feather mite Zachvatkinia larica Mironov (Acari: Avenzoariidae) is recorded from kelp gulls and Franklin's gulls for the first time, while the gamasid mite Larinyssus sp. is recorded from kelp gulls, also for the first time. The population parameters of all species of ectoparasites are discussed.