Vieyra Leticia, Velarde Enriqueta, Ezcurra Exequiel
Oriente 257 Number 165, Col. Agrícola Oriental, México, D.F. C.P. 08500, Mexico.
Ecology. 2009 Apr;90(4):1084-94. doi: 10.1890/07-2009.1.
Parental age, body condition, and food availability have been found to influence breeding parameters in seabirds, such as clutch size, number of chicks hatched and fledged, hatching, fledging, and reproductive success. In this paper we analyze the influence of parental age and body condition estimated by body mass, and food availability estimated from catch per unit effort (CPUE) statistics for Pacific sardine (Sardinops caeruleus) + northern anchovy (Engraulis mordax) by the local fishing fleet, on the breeding parameters of the Heermann's Gull (Larus heermanni; a vulnerable species according to Mexican federal law) nesting in Isla Rasa, Gulf of California, Mexico. Results are based on data from 1123 recaptures of known-age individuals, ranging from 4 to 13 years of age, during seven observation years between 1989 and 1997. Ages of mated male and female gulls were positively correlated. Breeding parameters showed their lowest values in 1992, an El Niño year in which the birds also showed significantly lower individual masses for both males and females, and in which the local CPUE of sardine + anchovies was lowest. All breeding parameters increased significantly with parental age and were highest at 10-12 years. No significant statistical interactions were found between food availability and parental age on the breeding parameters. Through a path analysis we found that there is a strong chained relationship between variables: food availability, which is strongly driven by oceanographic conditions, affects both the survival of eggs into hatchlings and the survival of hatchlings into fledglings. This external factor and parental age, a biological factor intrinsic to each nesting couple, explain 41% of the observed between-nest variation in fledgling success.
已发现亲鸟年龄、身体状况和食物可获得性会影响海鸟的繁殖参数，如窝卵数、孵化和出飞的雏鸟数量、孵化率、出飞率以及繁殖成功率。在本文中，我们分析了亲鸟年龄和通过体重估算的身体状况，以及根据当地捕鱼船队对太平洋沙丁鱼（Sardinops caeruleus）+ 北鳀（Engraulis mordax）的单位捕捞努力量渔获量（CPUE）统计数据估算的食物可获得性，对在墨西哥加利福尼亚湾拉萨岛筑巢的黑背鸥（Larus heermanni；根据墨西哥联邦法律为易危物种）繁殖参数的影响。结果基于1989年至1997年七个观察年份中对1123只已知年龄个体（年龄在4至13岁之间）的重捕数据。配对的雄鸟和雌鸟的年龄呈正相关。繁殖参数在1992年显示出最低值，这是一个厄尔尼诺年，当年鸟类的雌雄个体体重也显著降低，且沙丁鱼 + 鳀鱼的当地CPUE最低。所有繁殖参数均随亲鸟年龄显著增加，在10 - 12岁时最高。在繁殖参数方面，未发现食物可获得性和亲鸟年龄之间存在显著的统计交互作用。通过路径分析，我们发现变量之间存在很强的链式关系：受海洋学条件强烈驱动的食物可获得性，既影响卵孵化成雏鸟的存活率，也影响雏鸟成长为幼鸟的存活率。这个外部因素和亲鸟年龄（每个筑巢配偶固有的生物学因素）解释了观察到的巢间幼鸟出飞成功率差异的41%。
