Avian wildlife reservoir of Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. in Norway.

Cloacal swabs from 540 wild-living birds were cultured for Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. The carrier rates detected were as follows: C. fetus subsp. jejuni, 28.4%; Yersinia spp., 1.2%; and Salmonella spp., 0.8%. All birds were apparently healthy when captured. C. fetus subsp. jejuni was isolated from 11 of the 40 bird species examined. Among birds inhabiting the city of Oslo, the highest isolation rate was found in crows (Corvus corone cornix) (89.8%), followed by gulls (Larus spp.) (50.0%) and domestic pigeons (Columba livia domesticus) (4.2%). The gulls and crows scavenge on refuse dumps. High carrier rates were also detected among the following birds from nonurban, coastal areas: puffin (Fratercula arctica) (51.3%), common tern (Sterna hirundo) (5.6%), common gull (Larus canus) (18.9%), black-headed gull (Larus ridibundus) (13.2%), and herring gull (Larus argentatus) (4.2%). The list of species harboring C. fetus subsp. jejuni also includes the Ural owl (Strix uralensis), goldeneye (Bucephala clangula), and reed bunting (Emberiza schoeniclus). The following five Yersinia strains were isolated: Y. kristensenii (two strains), Y. intermedia (two strains), and "Yersinia X2" (one strain). Four strains belonging to the genus Salmonella were isolated from three different species of gulls. These isolates were identified as S. typhimurium, S. indiana, and S. djugu. The results indicate that campylobacters are a normal component of the intestinal flora in several bird species, whereas Salmonella and Yersinia carriers are more sporadic.     

Avian wildlife reservoir of Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. in Norway

Cloacal swabs from 540 wild-living birds were cultured for Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. The carrier rates detected were as follows: C. fetus subsp. jejuni, 28.4%; Yersinia spp., 1.2%; and Salmonella spp., 0.8%. All birds were apparently healthy when captured. C. fetus subsp. jejuni was isolated from 11 of the 40 bird species examined. Among birds inhabiting the city of Oslo, the highest isolation rate was found in crows (Corvus corone cornix) (89.8%), followed by gulls (Larus spp.) (50.0%) and domestic pigeons (Columba livia domesticus) (4.2%). The gulls and crows scavenge on refuse dumps. High carrier rates were also detected among the following birds from nonurban, coastal areas: puffin (Fratercula arctica) (51.3%), common tern (Sterna hirundo) (5.6%), common gull (Larus canus) (18.9%), black-headed gull (Larus ridibundus) (13.2%), and herring gull (Larus argentatus) (4.2%). The list of species harboring C. fetus subsp. jejuni also includes the Ural owl (Strix uralensis), goldeneye (Bucephala clangula), and reed bunting (Emberiza schoeniclus). The following five Yersinia strains were isolated: Y. kristensenii (two strains), Y. intermedia (two strains), and "Yersinia X2" (one strain). Four strains belonging to the genus Salmonella were isolated from three different species of gulls. These isolates were identified as S. typhimurium, S. indiana, and S. djugu. The results indicate that campylobacters are a normal component of the intestinal flora in several bird species, whereas Salmonella and Yersinia carriers are more sporadic.     

Energy dissipation in the elastic recoil of leg tendons of Larus ridibundus

Cycles of tension and recoil were given to different tendons of black-headed gull (Larus ridibundus) in an Instron universal testing machine. It is shown that a large proportion of the energy elastically stored in straining is released upon recoil, ranging the energy lost (dissipation energy) between 8 and 13%. These results are in complete agreement with those published in the literature on mammals and birds that can be considered as the most accurate.     

Craniogenesis in the laughing gull (Larus ridibundus L.). The reconstruction of the basic plan of the bird

To contribute to the knowledge of the cranium of older bird embryos, the chondrocranium and osteocranium of the Black-headed Gull (Larus ridibundus) are described. The chondrocranium of the Black-headed Gull is compared with the chondrocranium of other bird species with special consideration of functional and phylogenetic aspects. As a result a "grundplan" of the bird chondrocranium is reconstructed. Most of the chondrocranial autapomorphies of birds are connected with the enlargement of the eyes, the development of a beak and a prokinetic skull, and the reduction of the olfactory system.     

The influence of age and sex on wing-tip pattern in adult Black-headed Gulls Larus ridibundus

A discriminant equation based on bill-depth and total head- and bill-length is provided to sex adult Black-headed Gulls Larus ridibundus . This equation is used to sex birds of known age. Relationships between age and morphometrics and between age and the black extent on the wing are then investigated both in males and females. Size of birds did not change with age but the black extent on the wing tended to decrease with age in both sexes. The tendency to become lighter with age may he an expression of senescence.     

Social stimuli, testosterone, and aggression in gull chicks: support for the challenge hypothesis

We tested the challenge hypothesis for the hormonal regulation of aggression in chicks of the black-headed gull, Larus ridibundus. Chicks of this species are highly aggressive toward conspecifics, but never to peers that hatched from the same clutch (modal clutch size is three). Therefore, in the first experiment small families were housed together in large groups (challenged condition) and compared to families kept isolated (nonchallenged condition). As expected, in the challenged condition during the initial stage of territory establishment basal levels of testosterone (T) were clearly higher than those in the nonchallenged condition. In the second experiment we tested the effect of a short social challenge on short-term T-fluctuations. The design was based on an earlier experiment, showing that after temporary T-treatment chicks become very sensitive to social challenges while having low basal T-levels. We now show that these social challenges induce brief elevations in plasma T-levels. These peaks are similar to those in previously untreated chicks but untreated chicks do not respond with aggression to a challenge. Therefore, we conclude that the initial exposure to elevated T-levels increases the sensitivity to brief changes in T induced by social challenges. In this way exposure to T, that may be detrimental for development, is minimized while birds remain able to defend territories. This is the first report showing that the challenge hypothesis as established for adult birds, is also applicable for aggressive behavior in young birds outside the sexual context. Furthermore we suggest that a phase of priming with T is necessary to obtain the high behavioral responsiveness to a challenge.     

Parent-offspring conflict and the coordination of siblings in gulls

Offspring solicit food from their parents by begging behaviours. Studies on birds suggest that these displays are 'honest signals of need' and adults provide food according to the begging level. However, siblings may compete for parental resources and the begging intensity is expected to change with brood size. Here, we show that in the black-headed gull (Larus ridibundus) an increase of the numbers of siblings can result in a decrease of individual begging cost through nestlings' synchronized signalling. This is in accordance with some mathematical models. As parents respond to the total solicitation emerging from the nest, the probability to get food increases with the number of chicks begging together. The more siblings there are, the more they coordinate their begging while decreasing the number of individual begging bouts. Intra-brood synchronization of begging enables chicks to reduce their effort and hence exerting an important role in parental-offspring negotiation.     

Should males come first? The relationship between offspring hatching order and sex in the black‐headed gull Larus ridibundus

In birds with hatching asynchrony and sexual size dimorphism, chicks hatched earlier and later in the laying sequence usually suffer different mortalities due to uneven abilities to compete for food, especially in poor years. If sexes differ in vulnerability to environmental conditions, e.g., by having different food requirements due to differential growth rates, mothers can increase fitness by allocating sex according to the laying order, producing less vulnerable sex later rather than early in the clutch. By analysing variation in primary sex ratio using a PCR-based DNA technique, we tested this prediction in black-headed gull Larus ridibundus chicks where males may be the less viable sex under adverse conditions. The overall primary sex ratio of the population did not depart from parity. However, first hatched chicks were more likely to be males whereas last hatched chicks were more likely to be females. Both egg volume and hatchling body mass decreased with laying order irrespective of sex. Time of breeding had no effect on offspring sex or hatchling sex ratios.     

Within clutch co-variation of egg mass and sex in the black-headed gull

Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the sexes, particularly in size dimorphic species. Our results show that, within clutches of black-headed gulls (Larus ridibundus) the proportion of males was positively associated with egg mass. This applied for all three laying positions, independently of the absolute egg mass. There was a significant relationship between the distribution of the sexes over the laying sequence and the egg mass change. When egg mass decreased over the sequence, first-laid eggs were male biased and last-laid eggs female biased, and vice versa. The potential adaptive value of this allocation strategy is evaluated with regard to male sensitivity to egg quality and competitive differences between the sexes.     

Effects of testosterone on growth, plumage pigmentation, and mortality in Black-headed Gull chicks

In the Black-headed Gull Larus ridibundus, sibling chicks defend small territories against conspecifics with testosterone-dependent aggressive behaviour. The energetic requirements for the performance of this behaviour may trade off against the energetic requirements for growth. There are indications that testosterone suppresses growth in birds and, therefore, regulate this trade-off. In this study, the effect of testosterone on growth and plumage pigmentation of Black-headed Gull chicks was analysed. Young chicks in small groups were treated for ten days with testosterone or sham treated. Testosterone-treated birds showed decreased growth rate (daily increase in body mass, head-bill length and tarsus-length) and a marked decrease in juvenile pigmentation of the plumage (tail-bar, back, and secondary coverts). Field measurements revealed a negative correlation between nest density, which correlates positively with aggressive behaviour of adults, and plumage coloration. Furthermore, these measurements showed an increase in mortality of chicks that had low levels of pigmentation early in life. The data suggest that chicks face a testosterone-regulated trade-off between growth and territory defence.     

Low resolution of mitochondrial COI barcodes for identifying species of the genus Larus (Charadriiformes: Laridae)

We evaluated whether cytochrome c oxidase subunit I (COI) barcodes that have been previously suggested for birds are useful for identifying species of the genus Larus, which are resident or migratory birds in Korea. We found 31 intra- or interspecific COI haplotypes from 12 of 13 Larus species in Korea. Haplotype analyses showed that the COI barcodes could not distinguish some interspecific haplotypes from 6 of 12 Larus species because there were no nucleotide substitutions among their COI haplotypes. The neighbor-joining tree formed shallow branches in the clades expected for L. saundersi, L. crassirostris, L. canus, L relictus, and L. ridbundus. In the nine Larus species, COI haplotypes were not grouped as distinct entities that were correctly assigned to their corresponding species, resulting in polytypic clades. These results indicate that the COI sequences need to be cautiously selected as a DNA barcode for identifying species of Korean Larus birds.     

The development of the genital system in Ichthyocotylurus variegatus (Trematoda: Strigeidae)

The development of Ichthyocotylurus variegatus from metacercariae to ovigerous adults in the natural definitive host (Larus ridibundus) was examined at 24 h intervals. The metacercariae develop to the adults through a somatic growth of hindbody; the gametogeny and vitellogenesis take 4-6 days. During the first day of development the pair of testes are separated from the genital anlage. The ovary differentiates one day later. Genital ducts are completely differentiated on 4th day after the beginning of spermatogenesis and cogenesis. The vitelline cells developed from 2nd to 5th day. They take an origin from the subtegumental cells of hindbody. The hind part of uterus in strigeoid adults is identical to the metraterm of other trematodes. The spermaduct along all its length works as a spermatic bladder.     

Prevalences of zoonotic bacteria among seabirds in rehabilitation centers along the Pacific Coast of California and Washington, USA

Many seabirds are rehabilitated annually by wildlife rehabilitation centers along the Pacific Coast, USA. Although various strains of zoonotic bacteria have been isolated from seabirds, risks to rehabilitators at these centers have not been well documented. From November 2001 through January 2003, we determined the prevalence of detectable enteric fauna by isolation and characterization of Gram-negative bacteria from cloacal swabs taken from 26 common murres (Uria aalge), 49 gulls (Larus spp.), and 14 other seabirds treated by rehabilitators in California and Washington (USA). At least 25 bacterial species were identified, including multiple strains of Escherichia coli, as well as Enterobacter cloacae, Citrobacter freundii, and Klebsiella pneumoniae. Antibiotic resistance was found in 13 of 19 bacterial isolates tested, including E. coli, K. pneumoniae, Acinetobacter baumanii, and Pseudomonas aeruginosa. Potential transfer of these bacteria poses a risk to wildlife rehabilitators and to seabirds in these centers, as well as to free-ranging birds.     

Structural adaptation of bird hemoglobins to high-altitude respiration and the primary sequences of black-headed gull (Larus ridibundus, Charadriiformes) alpha A- and beta/beta'-chains

Two hemoglobin components HbA (alpha A2 beta 2) and (alpha D2 beta 2) have been detected by analytical electrophoresis in the lysed erythrocytes of the adult Black-Headed Gull (Larus ridibundus). We report the complete primary structure of the alpha A- and beta-chains of the major hemoglobin component HbA. Following the chain separation and isolation of the tryptic peptides by RP-HPLC, the amino-acid sequence was established by automatic Edman degradation in spinning cup and gas-phase sequencers. The primary structures of alpha A- and beta-chains from the Black-Headed Gull HbA differ by 11 and by 6 amino-acid residues from the corresponding chains of Greylag Goose. These changes are randomly distributed over both alpha-helical and interhelical regions. The presence of beta/beta'-chains is indicated by the observation of Ile/Leu at position beta 78. An exchange at position beta 55 (D6)Leu-Asn which is known to be involved in the alpha 1 beta 1-interface with alpha 119(H2)Pro has been found. It is suggested that packing contacts in the alpha 1 beta 1-interface are important for high altitude respiration in birds.     

The impact of predation by birds on bat populations in the British Isles

The role played by predation of birds in the mortality of British bats is assessed. A review of dietary studies and anecdotal accounts revealed eleven species of bird which occasionally feed on bats–Herring Gull Larus argentatus , Black-headed Gull Larus ridibundus , Rook Corvus frugilegus , Carrion Crow Corvus corone , Little Owl Athene noctua , Short-eared Owl Asio flammeus , Kestrel Falco tinnunculus , Hobby Falco subbuteo , Merlin Falco columbarius , Peregrine Falco peregrinus and Sparrowhawk Accipiter nisus. A further three species feed more frequently on bats–Barn Owl Tyto alba , Tawny Owl Strix aluco and Long-eared Owl Asio otus. Rates of predation were very low accounting for only 00034^o_o of items taken by small hawks and falcons ( n items = 29 519) but 0035^o, of prey taken by owls ( n items = 99 479). By multiplying together the average annual prey capture rates of the predators, assessed from their energetic food requirements and direct observations of prey intake rates, the British populations of the predators and the contribution to the diet made by bats, the annual number of bats which die each year as a result of predation was estimated. The total losses of bats to predation might amount to about 201 400 bats/annum. The most significant predators are Tawny Owl ( c. 168 850 bats/annum), Barn Owl (c. 8800 bats/ annum), Long-eared Owl (c. 10 200 bats/annum) and Kestrels (c. 8400 bats/annum). This predation by avian predators would account for about 11 % of the annual mortality of British bats. An assessment of the biases involved in this calculation suggests it is probably a minimum estimate. Despite the apparent low representation of bats in the diets of predatory birds, the effects of this predation on bat behaviour and population dynamics cannot be ignored.     

Lymphoid distribution in the migratory gull Larus ridibundus

We studied the distribution of lymphocytes in the main lymphoid tissues (blood, spleen and thymus) of the gull Larus ridibundus, searching for variations that might depend on the migratory cycle. We also looked for sex- and age-associated differences in lymphoid redistribution. In L. ridibundus, lymphocytes are the most commonly observed leukocyte subpopulation in blood. Moreover, changes in the distribution of lymphocytes in the lymphoid tissue occur, depending on the migratory period. The proportion of these cells in spleen is greater in the post-migratory and pre-migratory periods compared to the non-migratory period. The percentages of circulating lymphocytes are high in the pre-migratory period, but depletion occurs in the post-migratory period. In contrast, the age or the sex of the animals did not confer any major differences on the lymphoid distribution.     

Plasmid profiles as indicators of the source of contamination of Staphylococcus aureus endemic within poultry processing plants

A total of 530 strains of Staphylococcus aureus were isolated from the defeathering machinery of a chicken processing plant and from neck skin samples of carcasses at different stages of processing in two visits 4 weeks apart. Eleven different plasmid profiles were detected in the isolates, eight being common to both visits. The plasmid profiles of the strains forming the majority of the population on the freshly slaughtered birds were rarely present in the strains isolated from the pluckers (except at the entry to the first plucker) and were present in only a small proportion of the strains isolated from carcasses after plucking. However, the profiles from the strains isolated from the pluckers on both visits were different from those forming the majority of the population on the incoming birds but formed the major part of the carcass flora after plucking, suggesting that such strains were endemic. These strains were found as a small proportion of the isolates made from the incoming birds, suggesting that this was the route by which the endemic strains were introduced into the plant. Such endemic strains exhibited a clumping growth, even in liquid shake culture, which may have made it easier for them to become established on the pluckers and to resist cleaning and disinfection. This clumping phenotype was correlated with the presence of a 7.5-megadalton plasmid.     

Plasmid profiles as indicators of the source of contamination of Staphylococcus aureus endemic within poultry processing plants.

A total of 530 strains of Staphylococcus aureus were isolated from the defeathering machinery of a chicken processing plant and from neck skin samples of carcasses at different stages of processing in two visits 4 weeks apart. Eleven different plasmid profiles were detected in the isolates, eight being common to both visits. The plasmid profiles of the strains forming the majority of the population on the freshly slaughtered birds were rarely present in the strains isolated from the pluckers (except at the entry to the first plucker) and were present in only a small proportion of the strains isolated from carcasses after plucking. However, the profiles from the strains isolated from the pluckers on both visits were different from those forming the majority of the population on the incoming birds but formed the major part of the carcass flora after plucking, suggesting that such strains were endemic. These strains were found as a small proportion of the isolates made from the incoming birds, suggesting that this was the route by which the endemic strains were introduced into the plant. Such endemic strains exhibited a clumping growth, even in liquid shake culture, which may have made it easier for them to become established on the pluckers and to resist cleaning and disinfection. This clumping phenotype was correlated with the presence of a 7.5-megadalton plasmid.     

Gastrointestinal helminths of fish-eating birds from Chiloe Island, Chile

Of four species of fish-eating birds from Chiloé Island (Chile), three were infected with eight species of helminths. Tetrabothrius sp. was found in Larus scoresbii. Tetrabothrius cylindraceus, Profilicollis antarcticus, Anomotaenia dominicanus, Stephanoprora denticulata, Capillaria sp. and P. antarcticus were found in Larus dominicanus. Contracaecum rudolphii and Corynosoma sp. infected Phalacrocorax olivaceus. With the exception of S. denticulata, C. rudolphii and Capillaria sp., the above helminths are reported for the first time from Chile.