Abundance, population structure and sex ratio of the Brown Booby Sula leucogaster (Pelecaniformes: Sulidae) at Sao Pedro and Sao Paulo Archipelago, Brazil

作者：Barbosa Filho Roberto Cavalcanti; Vooren Carolus Maria

来源：Ararajuba, 2010, 18(3): 157-163.

• Sula leucogaster
• population
• Sao Pedro and Sao Paulo Rocks
• dynamic
• demography

Abundance, population structure and sex ratio of the Brown Booby Sula leucogaster (Pelecaniformes: Sulidae) at Sao Pedro and Sao Paulo Archipelago, Brazil. Censuses of the Brown Bobby population at St. Peter and St. Paul Archipelago (00 degrees 55' 10"N, 29 degrees 20' 33"W) were made during six research expeditions between September of 2001 and July of 2002 through counts of the birds present on the ground and on man-made structures. Bird numbers varied with the time of the day, with a maximum at 05h30 (381) and minimum at 13h30 (265). There were no significant variations in the population size between seasons of the year and between years. The final estimates of the population, of all life stages combined, were of 377 birds in 2001 and of 381 birds in 2002. Among the adults the abundance of females was higher than the males at all times, with average sex ratio of 1.3 females/males. The age structure, with an average 81% of adults, did not changed throughout the year. Of the total population number, 88% occurred at Belmonte Islet, where 13% had settled on man-made structures. The population densities ranged from 0.003 to 0.402 birds/m(2), with highest value in Belmonte breeding colony. The mean density in the study area was 0,022 birds/m(2). The results are discussed here in relation with factors affecting the population and may support actions for its conservation and management.

• 出版日期2010-9