Nazca Booby Sula granti

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Demography and Populations

The Malpelo Island holds the largest colony of Nazca boobies with an estimated population of approimately 24,000 individuals but believed to reach 50000 or more individuals (García & López-Victoria, 2007). Two other large populations are established in the Galápagos islands and in La Plata island in Ecuador (Estela & Anderson, 2013). Smaller populations occur in Clipperton and San Benedicto islands (Mexico). The demographic trends have not been evaluated.

A recent tracking study shows a significant overlap in the foraging ranges of adults belonging to different populations, suggesting that there may be genetic flow and dispersal from natal populations in these trips, in spite of the high philopatry levels of the species (Estela & Anderson, 2013). Additionally, gene flow and population mixing may occur in the highly mobile juvenile phase, where individuals from different populations concentrate around the coasts of Guatemala and El Salvador (Estela & Anderson, 2013).

Genetic analyses revealed that there are three distinct populations of Galápagos Nazca boobies: San Cristobal population, Genovesa and Española population and Darwin and Wolf population; population differentiation is very likely to be due to strong natal philopatry and low disperal (Levin and Parker, 2012). There is evidence for recent bottlenecks in the Española, Genovesa and San Cristobal colonies, may be due to El Niño Southern Oscillation event of 1986-1987 that raised the sea surface temperature affecting fish availability for bird’s colonies (Levin and Parker, 2012).

Recommended Citation

Nazca Booby (Sula granti), In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/nazboo1