Data from: The stress hormone corticosterone in a marine top-predator reflects short-term changes in food availability

In many seabird studies, single annual proxies of prey abundance have been used to explain variability in breeding performance, but much more important is probably the timing of prey availability relative to the breeding season when energy demand is at a maximum. Until now, intraseasonal variation in prey availability has been difficult to quantify in seabirds. Using a state-of-the-art ocean drift model of larval cod Gadus morhua, an important constituent of the diet of common guillemots Uria aalge in the southwestern Barents Sea, we were able to show clear, short-term correlations between food availability and measurements of the stress hormone corticosterone (CORT) in parental guillemots over a 3-year period (2009–2011). The model allowed the extraction of abundance and size of cod larvae with very high spatial (4 km) and temporal resolutions (1 day) and showed that cod larvae from adjacent northern spawning grounds in Norway were always available near the guillemot breeding colony while those from more distant southerly spawning grounds were less frequent, but larger. The latter arrived in waves whose magnitude and timing, and thus overlap with the guillemot breeding season, varied between years. CORT levels in adult guillemots were lower in birds caught after a week with high frequencies of southern cod larvae. This pattern was restricted to the two years (2009 and 2010) in which southern larvae arrived before the end of the guillemot breeding season. Any such pattern was masked in 2011 by already exceptionally high numbers of cod larvae in the region throughout chick-rearing period. The findings suggest that CORT levels in breeding birds increase when the arrival of southern sizable larvae does not match the period of peak energy requirements during breeding.

在诸多海鸟相关研究中，学界常采用猎物丰度的年度单一替代指标来解释繁殖表现的变异，但相较而言，猎物可获得性的时间节点与能量需求峰值出现的繁殖季的相对匹配度或许更为关键。迄今为止，海鸟的猎物可获得性季内变异仍难以量化。本研究依托巴伦支海西南部普通海鸠（Uria aalge）的主要猎物——大西洋鳕（Gadus morhua）幼体的尖端海洋漂移模型，在2009至2011年的三年周期内，清晰揭示了食物可获得性与亲代海鸠体内应激激素皮质酮（CORT）水平间的短期显著关联。该模型可实现极高空间分辨率（4千米）与时间分辨率（1天）的鳕幼体丰度与体型提取，结果显示，源自挪威北部邻近产卵场的鳕幼体始终可在海鸠繁殖群落附近被捕获，而来自更远南部产卵场的幼体出现频率更低，但体型更大。南部幼体呈批次抵达模式，其抵达规模与时间节点（进而决定与海鸠繁殖季的重叠程度）在不同年份存在差异。在南方鳕幼体出现频率较高的一周后捕获的成年海鸠，其体内CORT水平更低。该模式仅出现在2009年与2010年——这两年中南部幼体均在海鸠繁殖季结束前抵达。2011年，该区域整个育雏期的鳕幼体数量本就异常偏高，因此此类模式被掩盖。本研究结果表明，当南部体型较大的鳕幼体抵达时间与繁殖期鸟类的能量需求峰值时段不匹配时，亲鸟体内的CORT水平会升高。