Wang Sara Y, Zavalaga Carlos, Gonzales-DelCarpio Diego, Irigoin-Lovera Cinthia, Díaz-Santibañez Isabella, Polito Michael J
Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
Unidad de Investigación en Ecología y Conservación de Aves Marinas, Universidad Científica del Sur, Lima, Peru.
PLoS One. 2025 Mar 18;20(3):e0320161. doi: 10.1371/journal.pone.0320161. eCollection 2025.
Intraspecific competition can lead to sexual segregation of diets or foraging behaviors in seabirds, and in some species the resulting niche partitioning is facilitated by sexual dimorphism. However, environmental stochasticity can mediate intraspecific competition and thus the extent of sex-based partitioning. The Peruvian booby (Sula variegata) is a sexually dimorphic seabird endemic to the Humboldt Current System (HCS), a highly variable environment due to El Niño Southern Oscillation. To determine the extent of sexual partitioning in this species, we quantified the foraging and trophic niches of breeding Peruvian boobies at Isla Guañape Norte, Peru in two years with different oceanographic conditions and nesting propensity. Morphometrics, GPS-tracked foraging behaviors, diets via regurgitates, and isotopic niches were compared between sexes and years where sample sizes permitted. Although females were larger and in better body condition than males, breeding Peruvian boobies in our study did not exhibit sex-specific foraging or isotopic niche partitioning and had few differences in diet. Anchoveta (Engraulis ringens) dominated diets in both years, reflecting Peruvian boobies' dependence on this prey. Overall, while oceanographic conditions in 2016 were unfavorable enough to reduce nesting propensity, these effects did not qualitatively translate to foraging or dietary niche partitioning between the sexes for those individuals who opted to breed. In combination, our results suggest weak intraspecific competition during our study period, and highlight how the foraging strategies of Peruvian boobies have adapted to the variable environmental conditions found in the HCS.
种内竞争会导致海鸟在饮食或觅食行为上出现性别隔离，在某些物种中，由此产生的生态位划分会因两性异形而得到促进。然而，环境随机性可以调节种内竞争，从而影响基于性别的划分程度。秘鲁鲣鸟（Sula variegata）是洪堡海流系统（HCS）特有的两性异形海鸟，由于厄尔尼诺南方涛动，该系统环境变化很大。为了确定该物种的性别划分程度，我们在秘鲁的瓜尼亚佩北岛对繁殖期的秘鲁鲣鸟的觅食和营养生态位进行了量化，研究时间为两年，这两年的海洋学条件和筑巢倾向不同。在样本量允许的情况下，我们比较了不同性别和年份之间的形态测量数据、GPS跟踪的觅食行为、反刍食物的饮食情况以及同位素生态位。尽管雌性比雄性体型更大、身体状况更好，但我们研究中的繁殖期秘鲁鲣鸟并未表现出特定性别的觅食或同位素生态位划分，饮食上也几乎没有差异。这两年的饮食中秘鲁鳀（Engraulis ringens）都占主导地位，这反映了秘鲁鲣鸟对这种猎物的依赖。总体而言，2016年的海洋学条件不利，足以降低筑巢倾向，但对于那些选择繁殖的个体来说，这些影响并没有在性别间的觅食或饮食生态位划分上产生质的差异。综合来看，我们的结果表明在研究期间种内竞争较弱，并突出了秘鲁鲣鸟的觅食策略是如何适应HCS中多变的环境条件的。
