Abstract

Migrating long distances requires time and energy, and may interact with an individual's performance during breeding. These seasonal interactions in migratory animals are best described in populations with disjunct nonbreeding distributions. The black‐tailed godwit (Limosa limosa limosa), which breeds in agricultural grasslands in Western Europe, has such a disjunct nonbreeding distribution: The majority spend the nonbreeding season in West Africa, while a growing number winters north of the Sahara on the Iberian Peninsula. To test whether crossing the Sahara has an effect on breeding season phenology and reproductive parameters, we examined differences in the timing of arrival, breeding habitat quality, lay date, egg volume, and daily nest survival among godwits (154 females and 157 males), individually marked in a breeding area in the Netherlands for which wintering destination was known on the basis of resightings. We also examined whether individual repeatability in arrival date differed between birds wintering north or south of the Sahara. Contrary to expectation, godwits wintering south of the Sahara arrived two days earlier and initiated their clutch six days earlier than godwits wintering north of the Sahara. Arrival date was equally repeatable for both groups, and egg volume larger in birds wintering north of the Sahara. Despite these differences, we found no association between wintering location and the quality of breeding habitat or nest survival. This suggests that the crossing of an important ecological barrier and doubling of the migration distance, twice a year, do not have clear negative reproductive consequences for some long‐distance migrants.

Highlights

  • Seasonal migration allows animals to exploit areas that are inhospitable at other times of the year (Alerstam, Hedenström, & Åkesson, 2003)

  • Seasonal migration is widespread throughout the animal kingdom, it is especially well developed in birds (Newton, 2010)

  • Some species migrate as far as 12,000 km one way and cross ecological barriers such as oceans, mountain ranges, and deserts, while others remain close to the breeding grounds, even if that means remaining at sub-­Arctic latitudes

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Summary

| INTRODUCTION

Seasonal migration allows animals to exploit areas that are inhospitable at other times of the year (Alerstam, Hedenström, & Åkesson, 2003). Migrating long distances requires time and energy that may entail trade-­offs with reproductive events, that is, costs are carried over from one season into the other (Alves et al, 2012; Harrison, Blount, Inger, Norris, & Bearhop, 2011; Klaassen, Lindström, Meltofte, & Piersma, 2001; Norris & Marra, 2007; Senner, Conklin, & Piersma, 2015) This effect may be enhanced when individuals need to cross ecological barriers, because they lack the opportunity to replenish energy during migration (Newton, 2010). Icelandic black-­tailed godwits (Limosa limosa islandica) wintering in Portugal arrive at their breeding sites in Iceland earlier than individuals wintering almost 2,000 km further north in Ireland and England, and have a higher reproductive success and survival (Alves et al, 2012, 2013) This emphasizes that the fitness costs of migration may be context dependent, for example, whether migration involves crossing an important ecological barrier such as the Sahara Desert Observational studies linking events during the breeding season with outspoken differences in migration strategies are still thin on the ground (but see Alves et al, 2013; Lok et al, 2011, 2015) and will help determine whether the costs and a different length of migration influences population dynamics in a declining long-­distance migratory bird

| MATERIALS AND METHODS
| DISCUSSION
Findings
15 North South
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