ABSTRACT: Studying the at-sea movements and behaviour of juvenile seabirds is logistically challenging, but new technologies now allow tracking birds on their first migration, giving a more complete picture of population-level spatial ecology. We investigated the post-fledging migration of juvenile northern gannets Morus bassanus from the world's largest colony, at Bass Rock, Scotland. We first examined the movements and survival of 38 juveniles over their initial days at sea with GPS precision for up to 53 d post-fledging. We then compared their migration journeys with those of 35 adults tracked with geolocators. Almost one-third of juveniles died within 2 mo of leaving the colony, and this mortality was often associated with apparent uncertainties in their direction of migration, including marked, abrupt and often repeated changes in bearing within the North Sea. Both juveniles and adults then migrated as far as the Canary Current Large Marine Ecosystem (CCLME) off the Atlantic coast of West Africa, initially taking both clockwise and counter-clockwise routes around the UK. Juveniles covered a distance each day similar to that of adults, but they reached the CCLME much more quickly, mainly because they travelled more directly, staying close to the coast throughout most of their migration, whereas adults additionally spent long periods over relatively restricted areas of ocean further offshore. The CCLME is a hotspot of unregulated fishing activity, and our findings highlight the importance of this region across different age-classes of birds, echoing previous calls that the regional strengthening of marine conservation should be a high priority.

中文翻译：

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幼年北方塘鹅的后迁徙、死亡率和迁徙

摘要：研究幼年海鸟的海上运动和行为在后勤方面具有挑战性，但新技术现在允许跟踪鸟类的第一次迁徙，从而更全面地了解种群水平的空间生态。我们调查了幼年北方塘鹅Morus bassanus的后迁徙来自世界上最大的殖民地，位于苏格兰的巴斯岩。我们首先使用 GPS 精度检查了 38 只幼鱼在海上最初几天的活动和存活情况，最长可达 53 天。然后，我们将他们的迁徙历程与使用地理定位器追踪的 35 名成年人的迁徙历程进行了比较。几乎三分之一的幼鱼在离开殖民地 2 个月内死亡，这种死亡通常与迁移方向的明显不确定性有关，包括北海内方位的显着、突然和经常重复的变化。幼鱼和成鱼随后迁徙至西非大西洋沿岸的加那利洋流大型海洋生态系统 (CCLME)，最初沿英国顺时针和逆时针路线迁移。少年每天行走的距离与成年人相似，但他们到达 CCLME 的速度要快得多，主要是因为他们的旅行更直接，在大部分迁徙过程中都靠近海岸，而成年人则在更远的近海相对受限的海洋区域中度过了很长时间。CCLME 是不受管制的捕鱼活动的热点，我们的研究结果强调了该地区对不同年龄级别鸟类的重要性，呼应了之前的呼吁，即区域加强海洋保护应成为高度优先事项。