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Number and Distribution Records of Caspian Tern \u3ci\u3eHydroprogne caspia\u3c/i\u3e in Indonesia, with Special Reference to Sumatra
No full textWe summarize all reports of Caspian Tern Hydroprogne caspia recorded in Indonesia, with particular focus on Sumatra (1983–2019). There were 29 records in total, which together indicate that the Caspian Tern is a regular visitor to Indonesia, in contrast to previous assumptions that it is rare. This species has been recorded during the non-breeding period (September to March in Indonesia, and August to April in Sumatra) in small numbers ranging from one to 40 birds. Many potential sites for this species, particularly along east coast of Sumatra, have still not been well explored. Additional search efforts will advance our knowledge of Caspian Tern and other seabirds that occur in Indonesia
Dispersal Under the Seabird Paradox: Probability, Life History, or Spatial Attributes?
No full textManagement of avian species threatened by land use and climate change requires a thorough understanding of their site fidelity and dispersive behaviors. Among long-lived colonial seabird species, the behavior of returning to the natal colony to breed, i.e., natal philopatry, may increase the likelihood that adequate resources and mates are available, but it may also increase the potential for inbreeding, competition, and ecological traps. Successful management of seabird populations—using chick translocation to encourage colony establishment to locations having minimal threats—must also be informed by the likelihood that birds will return to the new sites. However, the extent of philopatry, and the traits that dictate variation across seabirds, have yet to be fully summarized. We evaluated whether seabirds returned to their natal colony at rates greater than those predicted by colony size and various dispersal variables, based on data gathered for 36 seabird species nesting in the British Isles and the Hawaiian Archipelago. We compiled long-term banding and census data across 663 colonies. A linear mixed-effects model was employed to determine the relationship between philopatry and colony demographics, wingspan (mobility), and spatial variables. Our results indicate that philopatric rates are higher in the Hawaiian Archipelago than in the British Isles. Additionally, our research suggests that seabird management using chick translocation will have the greatest success with Procellariiformes species
Underwater Behavior of Christmas Shearwaters \u3ci\u3ePuffinus nativitatis\u3c/i\u3e from Kure Atoll
No full textThe Christmas Shearwater Puffinus nativitatis is an aquatic, tropical shearwater. While individuals of this species are known to forage by pursuit plunging and diving, there are no published reports quantifying their sub-surface foraging behavior. We obtained diving information from eight chick-rearing Christmas Shearwaters on Kure Atoll during June–August 2017. Over the 33 days during which instruments were deployed, 1521 dives were recorded. Individual deployments lasted three to eight days and were independent of the maximum depths recorded. Individual maximum depths were 10.7–24.1 m, averaging 15.4 m. While the deepest and longest recorded dive reached 24.1 m and lasted 31 s, the majority of dives were \u3c 3.0 m deep (64%) and lasted ≤ 3.0 s (53%). Overall, deeper dives were longer. Almost all diving occurred during daylight, with peak diving activity (13%) occurring between 17h00 and 18h00 (dusk). Genetic metabarcoding identified digested prey items from regurgitations, distinguishing 11 species of fish and squid. This study highlights the way in which this species of concern uses the epipelagic foraging habitat within the Papah¯anaumoku¯akea Marine National Monument
Distribution Patterns and Population Size of the Ashy Storm Petrel \u3ci\u3eOceanodroma homochroa\u3c/i\u3e
No full textThe Ashy Storm Petrel (ASSP) Oceanodroma homochroa population has been surveyed intensively, both at sea within the California Current and on the adjacent breeding grounds. Nevertheless, colony-based estimates of breeding populations have significantly underestimated the species’ abundance, especially in the northern portion of its range compared to the southern portion. The species has been described as abundant in central-northern waters, whereas it is considered rare or uncommon in the southern portion. We analyzed aerial and ship tracks from 1980 to 2017 (~497000 km covering 91267 km2 ), to estimate total ASSP population size and at-sea distribution. Modeling the results of these formal surveys (7211 ASSPs seen) led to an estimated total population of about 13 445 ASSPs (95% confidence interval = 10128–27820), with 62% of the population frequenting the northern portion of the range, i.e., north of Point Conception (especially Monterey Bay north through the Gulf of the Farallones to Cordell Bank), compared with 38% in the south (especially waters around the northern Channel Islands). Based on over a thousand well-organized bird-watching surveys, almost the entire population can occur in a single flock in the northern portion during the California Current’s autumn Oceanic Period. These flocks occur in trophic hotspots: areas where submarine canyons cut into the shelf. Such large “molting flocks” have been shifting north from Monterey Bay to Cordell Bank since about 2007, but reasons for the northward shift remain a mystery. The apparent mismatch in at-sea vs. colony-based population sizes likely involves the non-breeding portion, which is especially difficult to estimate because it includes immature individuals as well as “floating” individuals: adults capable of breeding but denied access to breeding sites, which are limited by intraspecific competition
No Evidence of Habitat Effect on Clutch Size, Egg Quality, and Hatching Success of the Yellow-legged Gull \u3ci\u3eLarus michahellis\u3c/i\u3e at a Micro-spatial Scale
No full textIn colonial seabirds, the nest substrate that is available and, in particular, the vegetation cover around the nest, are important environmental factors that drive an individual’s nesting selection process and, ultimately, reproductive performance. Using data collected during three consecutive years in a Yellow-legged Gull Larus michahellis colony from the Bay of Biscay, Spain, we tested whether clutch size, egg volume, and hatching success covaried with the proportion of vegetation cover around nests. We found no effect of vegetation cover on breeding performance. Laying date showed a positive effect on egg volume and a negative effect on hatching success and the number of hatched eggs. Egg volume tended to be smaller in 2020 compared to 2018 and 2019, and hatching success decreased through the sampling period, with the lowest hatching success occurring in 2020. Our findings agree with a previous study in which vegetation had no or unclear effects on breeding performance in Yellow-legged Gulls; however, they contradict other seabird studies that found a positive correlation between the two variables. The role of vegetation on breeding performance could vary not only between gull species, but also geographically, with ecological drivers such as intra- and interspecific interactions and climate playing key roles in observed differences. Finally, the use of egg volume and hatching success as proxies for breeding output could be used for the long-term monitoring of the relationship between breeding performance and factors such as landfill management, fishing, or climate change in the Yellow-legged Gull and other gull species
Mercury Contamination in the Endocrine Glands of Black-tailed Gulls \u3ci\u3eLarus crassirostris\u3c/i\u3e on Kabushima (Kabu Island), Japan
No full textA colony of about 30 000 pairs of Black-tailed Gull Larus crassirostris nest on Kabushima (Kabu Island), which is located on the northeast mainland coast of Japan (Sanriku Coast, Honshu Island). There, the surface-water Hg concentration is higher than in the North Pacific Ocean. We collected carcasses from the breeding colony to assess the level of mercury (Hg) contamination. We measured Hg concentrations in 10 body tissues, including the endocrine glands. The relative mercury concentrations in the tissue samples (µg/g dry weight) were as follows: adrenal glands \u3e livers \u3e kidneys \u3e blood \u3e pituitaries \u3e gonads \u3e breast muscles \u3e thyroid glands \u3e pancreases \u3e brain stems. Correlations existed between blood mercury levels and all body tissues except for the adrenal glands. Based on these results, we suggest that mercury levels in blood may not be a good indicator for hypothalamic-pituitary-adrenal axis impacts in Black-tailed Gulls