Natal colony influences age-specific movement patterns of the Yellow-legged gull (Larus michahellis)

Abstract

Background: As for other life history traits, variation occurs in movement patterns with important impacts on population demography and community interactions. Individuals can show variation in the extent of seasonal movement (or migration) or can change migratory routes among years. Internal factors, such as age or body condition, may strongly influence changes in movement patterns. Indeed, young individuals often tend to move across larger spatial scales compared to adults, but relatively few studies have investigated the proximate and ultimate factors driving such variation. This is particularly the case for seabirds in which the sub-adult period is long and difficult to follow. Here, we examine migration variation and the factors that affect it in a common Mediterranean seabird, the Yellow-legged gull (Larus michahellis).

Methods: The data include the encounter histories of 5158 birds marked as fledglings between 1999 and 2004 at 14 different colonies in southern France and resighted over 10 years. Using a multi-event mark-recapture modeling framework, we use these data to estimate the probability of movement and survival, taking into account recapture heterogeneity and age.

Results: In accordance with previous studies, we find that young individuals have greater mobility than older individuals. However, the spatial extent of juvenile movements depends on natal colony location, with a strong difference in the proportion of sedentary individuals among colonies less than 50 km apart. Colony quality or local population dynamics may explain these differences. Indeed, young birds from colonies with strong juvenile survival probabilities (~ 0.75) appear to be more sedentary than those from colonies with low survival probabilities (~ 0.36).

Conclusions: This study shows the importance of studying individuals of different ages and from different colonies when trying to understand seabird movement strategies. Local breeding success and the availability of food resources may explain part of the among colony differences we observe and require explicit testing. We discuss our results with respect to the feedback loop that may occur between breeding success and mobility, and its potential implications for population demography and the dissemination of avian disease at different spatial scales.

Keywords: Capture heterogeneity; Colonial seabirds; Demography; Dispersal; Environmental quality; Migration; Multi-site mark-recapture; Prospection; Survival.

Fig. 1

Colony locations. Localization of the studied colonies in France (inset) and their associated number of ringed individuals. Camargue: A—Besson (956), B—Flamants (733), C—Banaston (183), D—Galère (869), E—Pégoulier (396). Marseille: F—Pomègues (257), G—Ratonneau (16), H—Jarron (4), I—Jarre (112), J—Congloué (63), K—Riou (385), L—Plane (707). Hyères: M—Porquerolles (277), N—Bagaud (250)

Fig. 2

Geographic resighting zones. Map of the geographic sites considered for the mark-recapture model. Zone 1: less than 50 km around the natal colony. Open symbols indicate the resighting data of marked individuals used in analyses

Fig. 3

Age-dependent movement. Estimated post-breeding movement probabilities from the natal colony (+ 95% confidence interval) for individuals from Camargue colonies according to age. Individuals that remain at zone 1 are considered sedentary

Fig. 4

Colony-dependent movement. Estimated juvenile post-breeding movement probabilities (+ 95% confidence interval) according to the natal region. Here, the colonies from the Hyères and Marseille regions have been combined, as defined by the selected model (see “Results” section)