Diverse migration strategies with similar investments in movement

In several species of birds, migration strategies may differ greatly even within a single population. Migration is often assumed to be a costly endeavour, especially for long distance migrants and these costs are presumably compensated for by better survival conditions in the non-breeding area. One way to assess the cost of alternative strategies is to study the investment in movement within the context of the entire annual cycle. In this study we compare trade-offs associated with several migration strategies in a generalist seabird. We used GPS tracking data to quantify lesser black-backed gulls’ movement throughout their annual cycle. The annual cumulative distance travelled by long distance migrants wintering in west Africa, thousands of kilometres from their breeding colony, did not differ significantly from individuals of the same breeding colony wintering only a few hundred kilometres away. Within a year, birds travelled approximately 30,000 km across all migrations strategies. Short distance migrants returned earlier than long distance migrants. Maximum range, cumulative distance travelled or timing of arrival at the breeding area were not correlated with sex and wing length. Individuals spent only a small proportion of their time in flight and generally spent < 20% of their time at sea throughout an annual cycle, suggesting a reliance on inland resources for many individuals. Studying movement throughout the annual cycle may change our perspective when considering the consequences of different migration strategies.