Seabirds allocate different amounts of energy to reproduction throughout the breeding season, depending on the trade-off between their own needs and those of their chicks and/or changes in environmental conditions. Provisioning parents therefore modulate their foraging behaviour and diet accordingly. However, for diving seabirds, many studies have extrapolated from individuals monitored over a short period and then assumed the observed patterns were representative of the birds’ foraging activity over the entire breeding stage/season. To address this shortcoming, we monitored continuously the diving performance of ten male little penguins from incubation to chick fledging. Simultaneously, isotopic composition was examined using δ¹⁵N and δ¹³C values from whole blood samples collected every 3 weeks. Birds dived more frequently but performed shallower and shorter dives as the season progressed. The guard period was especially different, with birds spending a consistently smaller proportion of time at the bottom and performing fewer prey pursuits, compared to other periods. Isotopic composition varied less within the season, although there was a slight tendency for δ¹⁵N values to decrease through time. Finally, isotopic values were highly repeatable within individuals, suggesting that individuals specialized on different prey and in different areas. Diving was less repeatable within individuals but still explained a small but significant part of the variance in blood isotopic values. Our results suggest that it is important to take into account individual variability over the course of the breeding season, as well as timing of bio-logger deployment within a stage when designing bio-logging studies.

海鸟在整个繁殖季节要分配不同量的能量用于繁殖，这取决于它们自己与雏鸡的需求之间的权衡和/或环境条件的变化。因此，养父母会相应地调节他们的觅食行为和饮食。但是，对于潜水海鸟，许多研究都是从短期内监测的个体中推断得出的，然后假定观察到的模式代表了整个繁殖阶段/季节中鸟类的觅食活动。为了解决这个缺点，我们连续监测了十只雄性小企鹅从孵化到雏鸡出没的潜水表现。同时，同位素组成，使用δ检查¹⁵ N和δ ¹³每3周收集一次全血样品的C值。随着季节的发展，鸟类的潜水次数会增加，但潜水次数却会变浅和变短。后卫时期尤其不同，与其他时期相比，鸟类在谷底花费的时间比例一直较小，而对猎物的追求较少。同位素组成的季节内变化少，虽然有对δ的轻微趋势¹⁵N值随时间减少。最后，同位素值在个体内是高度可重复的，这表明个体专门研究不同的猎物和不同的区域。潜水在个体内的重复性较差，但仍然可以解释血液同位素值变化中的一小部分但很重要的部分。我们的结果表明，在设计生物测井研究时，必须考虑繁殖季节过程中的个体差异以及在一个阶段内部署生物测井仪的时机，这一点很重要。