Development of new nuclear markers and characterization of single nucleotide polymorphisms in kelp gull (Larus dominicanus)

The present study seeks to develop nuclear markers for the kelp gull (Larus dominicanus). We hereby report the characterization of 12 independent nuclear introns, where 104 single nucleotide polymorphisms (SNPs) in 8138 sequenced base pairs were observed. These SNP markers are the first to be designed for genotyping a gull species. The markers will provide useful tools for understanding which processes act or acted upon kelp gulls to cause their low genetic variability in mitochondrial DNA. In addition, these markers open a new opportunity for population genetic and evolutionary studies in the Laridae group.     

Determinants of local recruitment in a growing colony of Audouin's gull

1. Local recruitment of Audouin's gull ( Larus audouinii Payraudeau) was studied between 1988 and 1997 at the Ebro Delta colony (north-western Mediterranean). Since its establishment in 1981, the colony has dramatically grown to include, in 1997, 65% of the total world population. Several hypotheses were tested, involving the effects of a badger predatory event in 1994, and sex, age and cohort (year of birth) on recruitment.
2. Results supported the prediction that colony size influenced recruitment: the probability for any individual to have previously bred increased throughout the study, together with colony size. At the end of the study, 90% of breeders aged 4 years had already been recruited at age 3, the age of first reproduction by Audouin's gulls. As expected by the dramatic increase of breeding numbers, most local recruitment occurred at very young ages, especially when compared with other Laridae.
3. Neither food availability nor reproductive success affected recruitment. Recruitment was not affected by high nest predation by the badger, although after the event, the proportion of Ebro Delta birds nesting on the nearby Columbretes Islands tripled.
4. Probability of first reproduction depended on age: it was the highest at ages 3 and 4, and then decreased sharply with age to stabilize beyond age 6 to a value depending on the year and cohort but always very low (< 5%). Cohort and sex did not influence local recruitment.
5. Annual resighting rates ranged between 35% and 82%, and were higher for females. This may represent a sex-dependent suspension of breeding, probably as a trade-off between early recruitment and future survival.     

Genetic and morphological similarity of two California gull populations with different life history traits

California Gulls nesting at Mono Lake (ML) have a modal clutch size of two eggs, while at Great Salt Lake (GSL) the mode is three. We used starch gel electrophoresis to determine whether the populations are genically different. Average individual heterozygosity at ML averages 2.67% and at GSL 2.95%, both slightly below the average for other birds. The average number of alleles per locus is 1.2 for both sites. Variation between sites is insignificant, with a genetic distance of 0.001 and an F_ST of 0.0044. Therefore, the clutch size differences are without genic correlates. In fact, at the loci studied, the two samples are indistinguishable from two random samples drawn from a panmictic unit. Five morphological characteristics also exhibited little between-site difference, in agreement with the electrophoretic analysis. A marked historical reduction (bottleneck) in the Mono Lake population seems not to have affected levels of genetic variation. We conclude that the clutch size differences are either recently evolved, and determined by loci not surveyed by us, or they are environmentally induced. At the population level, these gulls are similar to passerines in terms of heterozygosity and among population differentiation.     

Status,trends, and patterns of covariation of breeding seabirds at St Lazaria Island,Southeast Alaska, 1994–2006

Aim We examined patterns of covariation among piscivorous and planktivorous seabirds breeding at St Lazaria Island in order to evaluate their responses to interannual changes in sea surface temperature, a variable that affects marine food webs. In addition, we evaluated seabird population trends for responses to decadal‐scale changes in the marine ecosystem. Location St Lazaria Island, Sitka Sound, Alaska. Methods Established seabird monitoring protocols for the Alaska Maritime National Wildlife Refuge were followed in estimating population trends, the timing of nesting events and the reproductive success of eight species of seabirds between 1994 and 2006. Results  Population increases were noted for storm‐petrels (Oceanodroma furcata and O. leucorhoa), rhinoceros auklets (Cerorhinca monocerata) and glaucous‐winged gulls (Larus glaucescens). We found no population trend for pelagic cormorants (Phalacrocorax pelagicus), but it appeared that populations of common (Uria aalge) and thick‐billed (U. lomvia) murres and of tufted puffins (Fratercula cirrhata) declined. We detected no linear trends in either breeding chronology or reproductive success over the study period for any seabird. All species of piscivorous seabirds apparently responded similarly to environmental cues as there was a positive covariation among species in the timing of nesting. Piscivores tended to nest earlier, and most species had higher rates of reproductive success in years with relatively warm spring sea temperatures. In contrast, planktivorous Leach’s storm‐petrels (O. leucorhoa) tended to nest earlier when spring and summer sea temperatures were relatively cool. Clearly, seabirds at St Lazaria were responding to interannual changes in sea temperatures near the breeding colony, probably as a result of effects on the food webs. Main conclusions Every seabird species we monitored at St Lazaria exhibited significant population trends between 1994 and 2006. For most species there appeared to be a relationship between both the timing of nesting and reproductive rates and spring or summer sea surface temperatures. Responses at both decadal (populations) and interannual (timing and reproductive success) scales make seabirds useful candidates for helping to monitor change in the marine environment.     

Demographic impact of landfill closure on a resident opportunistic gull

The management of mixed municipal waste can have an impact on wildlife and ecosystems. Previous studies have investigated how opportunistic species like gulls can react very fast to new landfills; however, the impact of landfill closure on bird populations is less investigated. Yet, there is a need to understand how fast and to what extent, animal populations can be adapted to new scenarios where the waste will not be deposited in landfill sites anymore. The aim is to determine the influence of landfill closures on apparent survival of a resident Yellow-legged Gull (Larus michahellis) population, used as a model species showing short-distance foraging movements, and with a high dependence on local food subsidies. Complementarily, we built some basic population growth models in order to determine how potential changes in survival (before/after landfill closure) will impact on population growth rate. Using a data set of 4,437 Yellow-legged Gull chicks ringed in four colonies over a period of 13 years, we obtained evidence supporting that the apparent survival was affected by landfill closure, especially if the landfill was located within a buffer of 10 km around the colony. Landfill closure affected the survival of first-year gulls (with a mean decrease of ~ 0.5–0.36), but not of older birds. Consequently, we did not detect a remarkable effect of landfill closures on population growth rate, probably due to the lack of effect on adult survival rates except for one of the surveyed colonies, where we found an annual decline of 7%.     

基于贝叶斯二项式模型分析棕头鸥种群多度与环境因子间的关系

传统的种群多度调查方法由于默认观察率 p 等于 1,因此极有可能低估种群大小,进而误判种群多度与环境因子间的关系。为了了解禽流感爆发后青海湖棕头鸥种群与环境因子间的关系,为棕头鸥管理提供有效依据,于 2010 年和 2011 年的 4 ～6 月调查了青海湖保护区 23 个观测点的棕头鸥种群数量及环境因子。通过包含观察率的贝叶斯二项式混合模型分析棕头鸥种群多度与环境因子间的关系,采用 DIC 准则进行因子筛选。结果表明: 种群数量亚模型包含取样面积、放牧强度、距公路距离和植被盖度 4 个参数,种群数量随取样面积、距公路距离和植被盖度的增加而增加,随放牧强度的增加而减少; 观察率亚模型包含观察经验和棕头鸥的行为月节律 2 个参数,观察率随观察月的递增而降低,随观察经验的增加而升高,高经验观察者平均每千米观察到 18. 1 只棕头鸥,低经验观察者可以平均观察到 13. 7 只。天气状况不影响观察率,这可能与棕头鸥的觅食栖息地距岸边较近,不影响观察者的观察有关。