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Sea turtle populations have declined globally and are of conservation concern. We investigated the effects of nest management methods on hatching success and egg/hatchling predation rates of hawksbill turtles Eretmochelys imbricata on Cousine Island, Seychelles. We determined the effectiveness of two different crab-barrier methods (netted and fenced) on hatching success and predation rates. We examined the relative influence of nest-site cover (full sun, partial sun or full shade) and location (zones of high risk or low risk of predation) on hatching success and predation rates. We also examined temperature disparity between netted and control nests to estimate potential effects on sex ratios and measured typical beach-substrate temperatures in the different nesting habitats. We compared data from 40 netted, 40 fenced and 40 control nests during the 2014/2015 breeding season. Overall, hawksbill turtle hatching success was not significantly affected by treatment or cover; however, netted nests and nests incubating in full sun had the highest mean hatching success. Predation rate was generally low but variable, and the rates differed significantly between the three treatments. Nest temperatures differed significantly between the netted and control nests, with netting used to protect nests having a substantial cooling effect. Hatchling sex ratios for natural nests were skewed towards females and those for netted nests skewed towards males. With climate change and increasing ambient temperatures imminent, a better understanding of how the spatial distribution of nests and variations in environmental factors influence hawksbill turtle hatching success and the levels of predation on eggs and hatchlings will assist future conservation measures. [ABSTRACT FROM AUTHOR]

Populations of the Critically Endangered hawksbill turtle Eretmochelys imbricata in the Seychelles showed significant declines in the past. They have since recovered and nesting numbers are increasing because of increased protection and management intervention. Data on their nesting ecology on Cousine Island were collected and analysed for the breeding seasons from 2004/2005 to 2013/2014 with the aim of improving management methods. The findings indicate that the number of nesting individuals increased during the study period (from x̅ = 34.3 nesters between 2004 and 2009, to x̅ = 55.4 nesters between 2010 and 2014); however, the clutch frequency was relatively low compared with other study areas. Night-time nesting increased, most likely because of increased disturbances across the study period. Clutch sizes decreased significantly across the nesting season, and there was a significant drop in hatching success in clutch sizes exceeding 200 eggs. The predation rate and infertility rate each showed an increasing trend over time. Nests incubating in full sun showed the highest mean hatching success rate and had the shortest mean incubation duration. The present study provides insight into the species' nesting ecology on Cousine Island and will better inform management decisions aimed at increasing hatching success and minimising threats such as beach erosion and predation. [ABSTRACT FROM AUTHOR]

Common white ternsGygis albalay a single egg balanced on rocks or branches and consequently are at risk of low nesting success. A novel technique of hollowing out coconut husks and providing artificial nest sites was developed on Cousine Island, Seychelles. Our study aimed to critically assess whether common white tern nesting success differed between artificial and natural nest sites. For natural nest sites, nesting success and the stage of nest failure were also compared between seasons, nest heights, and tree species. Finally, we compared results from our study to those of a study conducted 10 years ago on the same island. Nesting success differed significantly between artificial nests and natural nests, with the success of artificial nests nearly double that of natural nests. Hatching success was similar for artificial and natural nests (65% and 52% respectively), suggesting coconut husks do not reduce egg losses, but rather provide secure perches for young chicks. Most natural nest failures occurred during the egg phase (70%), followed by the youngest chick phase (21%). Of the eggs that hatched in natural nests, 61% fledged successfully. Tree species and season significantly influenced nesting success for natural nests and nest height varied significantly between tree species. Higher nesting success was observed during the mixed seasonal period (50%) followed by the cooler, windier and drier South-East Monsoon season (33%). The hotter and more humid North-West Monsoon period had the lowest nesting success (20%). Comparisons of nesting success at natural and artificial nest sites with the earlier study did not differ significantly, despite a smaller population of common white terns being present on the island at that stage. Our results support the use of artificial nest sites to improve nesting success for this species and serve as a model for similar species currently under threat. [ABSTRACT FROM AUTHOR]