Papers by Francisco Cruz-Delgado
The Gala´pagos petrel (Pterodroma phaeopygia) is endemic to the Gala´pagos archipelago, where it ... more The Gala´pagos petrel (Pterodroma phaeopygia) is endemic to the Gala´pagos archipelago, where it is known to breed only on five islands. The species has been listed as critically endangered due to habitat deterioration and predation by introduced mammals. Significant morphological and behavioural differences among petrels nesting on different islands suggest that island populations may differ genetically. Furthermore, nesting phenology suggests that genetically differentiated seasonal populations may exist within at least one island. We analysed variation in six microsatellite loci and part of the mitochondrial ATPase 6/8 gene in 206 Gala´pagos petrels sampled from all five islands. No evidence of genetic structuring within islands was found, although statistical power was low. In contrast, significant differences occurred among island populations. For the microsatellite loci, private alleles occurred at all islands, sometimes at high frequency; global and pairwise estimates of genetic differentiation were all statistically significant; Bayesian analysis of genotypes frequencies provided strong support for three genetic populations; and most estimates of migration between populations did not differ significantly from zero. Only two ATPase haplotypes were found, but the geographic distribution of haplotypes indicated significant differentiation among populations. For conservation purposes, populations from Floreana, Santa Cruz, San Cristo´bal and Santiago should be regarded as separate genetic management units. Birds from Isabela appear to be derived recently from the Santiago population, and the population on San Cristo´bal appears to be a mixture of birds from other populations. However, considering ecological and behavioural differences among birds from different islands, we recommend that all five populations be protected.
Bird Conservation International, 2010
The Galapagos Petrel Pterodroma phaeopygia is endemic to the Galapagos Archipelago, where it nest... more The Galapagos Petrel Pterodroma phaeopygia is endemic to the Galapagos Archipelago, where it nests on only five islands. The species is considered 'Critically Endangered', mostly due to the effects of alien invasive species, which impair its reproductive success. During 2002-2003 we studied the breeding biology of the petrels nesting on San Cristó bal island. The study revealed particular characteristics of the San Cristó bal petrel population and differences compared to those of other islands, mostly related to nesting habitat, phenology, reproductive success and causes of mortality. On San Cristóbal, petrel nests were primarily located along ravines, in areas of dense vegetation cover formed by the endemic shrub Miconia robinsoniana and a wide variety of native ferns. Over 90% of the nests on the island were located on private agricultural land. The petrel population has a prolonged reproductive period covering 10 months. Laying dates occurred mostly from May to October, with a peak during August, although eggs may be occasionally laid between November and March. The incubation period averaged 50.8 days (range: 46-53), and parental care 103.7 days (range: 98-108). Overall reproductive success was 23.6%; 63.8% for eggs and 37.1% for chicks. Predation by rats was the primary cause (72.2%) of nest failure. Rat control campaigns and clearing of exotic plant species in areas of high density of petrel nests, as well as promoting cooperation agreements between conservation authorities and landowners of the properties where nests are located, are suggested among other critical management measures intended to reduce nest mortality and ensure the survival of the San Cristóbal petrel population. Resumen El Petrel de Galápagos Pterodroma phaeopygia es un ave endémica del Archipiélago de Galápagos, donde anida en só lo cinco islas. La especie está considerada como En Peligro Crítico, principalmente debido al impacto de las especies exó ticas invasoras que limitan seriamente su éxito reproductivo. Durante los añ os 2002-2003 estudiamos la biología reproductiva de los petreles que anidan en la isla San Cristóbal. Nuestro estudio reveló características particulares y diferencias con las poblaciones de otras islas, principalmente relacionadas con el hábitat de cría, la fenología, el éxito reproductivo y las causas de mortalidad. En San Cristóbal, los petreles hacen sus nidos en las encañ adas, en zonas con vegetació n densa dominada por el arbusto endémico Miconia robinsoniana y una amplia variedad de helechos nativos. Más del 90% de los nidos de la isla se encuentran en fincas agrícolas privadas. La población local de petreles tiene un período reproductivo bastante prolongado, que se extiende a lo largo de 10 meses. La mayoría de las puestas tuvieron lugar de mayo a octubre, con un pico durante agosto, aunque algunos huevos fueron puestos ocasionalmente entre noviembre y marzo. El período de incubació n promedio fue de 50.8 días (rango: 46-53) y el cuidado parental se extendió por 103.7 días (rango: 98-108). El éxito reproductivo global fue del 23.6%, siendo del 63.8% para los huevos y del 37.1% para los pichones. La depredación por ratas fue la principal (72.2%) causa de fracaso reproductivo. La realizació n de campañ as perió dicas de control de ratas y la eliminació n de plantas exó ticas en las zonas con alta densidad de nidos, así como la formalización de acuerdos de colaboración entre las autoridades de conservació n y los propietarios de las fincas privadas que albergan nidos, se sugieren como las medidas de manejo prioritarias para lograr reducir el fracaso reproductivo y asegurar la supervivencia de la població n de petreles de San Cristó bal.
Biodiversity and Conservation, 2010
We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy dev... more We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy development recently constructed in the highlands of San Cristóbal Island, Galapagos. Trained observers recorded the movements of petrels at dusk and dawn from the wind project site, and from control sites located along ravines that host nesting colonies. Collision mortality was also assessed by monitoring circular plots and transect lines located under human-made structures. Petrel flight activity showed a bimodal pattern, with the majority of the movements recorded in the hours previous to sunrise. Most petrels (96%) moved along major ravines that descend from the highlands to the south-southeastern coast of the island. Significant differences in passage rates were found between the project and control sites, with only five petrels recorded on the site selected for turbine installation. Although our data suggest that wind farms will not be more detrimental to petrels than other existing man-made structures, a word of caution is made because even very low levels of additional mortality might be significant for a species with such low productivity and slow maturation rates. Moreover, some other possible indirect effects on habitat change and disturbance might occur that were not assessed in our study. A post-construction monitoring program should be implemented to adequately assess long-term effects on petrels and to enable these uncertainties to be satisfactorily addressed.
Biodiversity and Conservation, Oct 6, 2009
We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy dev... more We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy development recently constructed in the highlands of San Cristóbal Island, Galapagos. Trained observers recorded the movements of petrels at dusk and dawn from the wind project site, and from control sites located along ravines that host nesting colonies. Collision mortality was also assessed by monitoring circular plots and transect lines located under human-made structures. Petrel flight activity showed a bimodal pattern, with the majority of the movements recorded in the hours previous to sunrise. Most petrels (96%) moved along major ravines that descend from the highlands to the south-southeastern coast of the island. Significant differences in passage rates were found between the project and control sites, with only five petrels recorded on the site selected for turbine installation. Although our data suggest that wind farms will not be more detrimental to petrels than other existing man-made structures, a word of caution is made because even very low levels of additional mortality might be significant for a species with such low productivity and slow maturation rates. Moreover, some other possible indirect effects on habitat change and disturbance might occur that were not assessed in our study. A post-construction monitoring program should be implemented to adequately assess long-term effects on petrels and to enable these uncertainties to be satisfactorily addressed.
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Papers by Francisco Cruz-Delgado