Potential causes of an apparent decline in blue-footed boobies in the Galápagos Islands

• Main Author: Cruz, Larisa Lee
• Published: University of Leeds 2010
• Subjects: 598.43
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610900

The Galapagos Islands arc considered a hotspot in terms of biodiversity, but an increase in tourism over the past 30 years and its consequential human immigration is posing new threats to the wildlife. Blue-footed boobies Sula nebouxii breed in Galapagos and its population is considered to be one of the largest for the species in the world, but there is some indication that it has declined. I studied blue-footed boobies at two breeding colonies (San Cristobal and North Seymour) to look at potential causes of decline; specifically low food availability at sea and poor health status. Additionally, I examined how impacts differ between the sexes in relation to sexual size dimorphism. Low provisioning parameters and low chick growth and survival, particularly at North Seymour, suggest that blue-footed boobies in Galapagos are facing low food availability compared to colonies elsewhere in the eastern Pacific Ocean. Blood parasite prevalence was high in adults and chicks at both sites, and higher on adults at North Seymour than at San Cristobal. Provisioning was not affected by blood parasites, but infected female chicks at North Seymour had lower asymptotic size. Physiological condition (evaluated using haematological variables) was lower for adults and chicks at North Seymour. Differences between the sexes were found on levels of parental care and isotopic segregation during non-breeding at San Cristobal, but not at North Seymour. Male and female adults also differed in their immune response to parasites. Male and female chicks differed in the nitrogen and carbon isotopic values of feathers and blood, suggesting differences in physiological processes between the sexes during growth. Physiological parameters did not show repeatability within individuals, between members of a pair or between parents and chicks, suggesting that it is more influenced by environmental factors than by genetic effects.