Individual Black-tailed Godwits do not stick to single routes: a hypothesis on how low population densities might decrease social conformity
Loonstra, A.H.J.; Verhoeven, M.A.; Zbyryt, A.; Schaaf, E.; Both, C.; Piersma, T. (2019). Individual Black-tailed Godwits do not stick to single routes: a hypothesis on how low population densities might decrease social conformity. Ardea 107(3): 251-261. https://dx.doi.org/10.5253/arde.v107i3.a11
In: Ardea. Nederlandse Ornithologische Unie: Arnhem & Leiden. ISSN 0373-2266; e-ISSN 2213-1175, more
The miniaturization of tracking devices is now rapidly increasing our knowledgeon the spatiotemporal organization of seasonal migration. So far, most studiesaimed at understanding within- and between-individual variation in migratoryroutines focus on single populations. This has also been the case for continentalBlack-tailed Godwits Limosa l. limosa (hereafter Godwits), with most workcarried out on individuals from the Dutch breeding population, migrating in relativelylarge numbers in the westernmost part of the range. Here we report themigratory timing and routes of four adult individuals of the same subspeciesfrom the low-density population in eastern Poland and compare this with previouslypublished data on Godwits breeding in The Netherlands. During northwardmigration, the birds from Poland departed and arrived later from their winteringand breeding grounds. However, on southward migration the Polish breedingGodwits departed earlier, but arrived one month later than the Dutch birds ontheir wintering grounds in sub-Saharan Africa. Despite the small sample size oftracked birds from Poland, we find a significantly higher between-individual variationin timing during southward migration in Polish Godwits as compared to theDutch Godwits. Furthermore, not only did migratory routes differ, but the fewPolish Godwits tracked showed a higher level of between- and within-individualvariation in route choice during both southward and northward migration. Toexplain this remarkable discrepancy, we propose that the properties of transmissionof social information may be different between Godwits from a high-densitypopulation (i.e. the one in The Netherlands) and a low-density population (inPoland) and that this leads to different levels of canalization. To examine thishypothesis, future studies should not only follow individuals from an early ageonwards, but also quantify and experimentally manipulate their social environmentsduring migration.
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