| Summary: | In our seasonal world, animals face a variety of environmental conditions in the course of the year. To cope with such seasonality, animals may be phenotypically flexible, but some phenotypic traits are fixed. If fixed phenotypic traits are functionally linked to resource use, then animals should redistribute in response to seasonally changing resources, leading to a ‘phenotype-limited’ distribution. Here, we examine this possibility for a shorebird, the bar-tailed godwit (Limosa lapponica; a long-billed and sexually dimorphic shorebird), that has to reach buried prey with a probing bill of fixed length. The main prey of female bar-tailed godwits is buried deeper in winter than in summer. Using sightings of individually marked females, we found that in winter only longer-billed individuals remained in the Dutch Wadden Sea, while the shorter-billed individuals moved away to an estuary with a more benign climate such as the Wash. Although longer-billed individuals have the widest range of options in winter and could therefore be selected for, counterselection may occur during the breeding season on the tundra, where surface-living prey may be captured more easily with shorter bills. Phenotype-limited distributions could be a widespread phenomenon and, when associated with assortative migration and mating, it may act as a precursor of phenotypic evolution. Percentage of energy (AFDM) in dietPercentage of energy content (AFDM g) in diet of bar-tailed godwits (Limosa lapponica) per month based on observations and dropping analysis. Dataset includes mean burying depth of lugworms (cm), mean bill length (mm) of Dutch Wadden Sea birds only and the mean PEIR (predicted energy intake rate).Percentage_AFDM_in_Diet.txtBill lengths of first and consequent catchesBill lengths of bar-tailed godwits (Limosa lapponica) at time of first capture and bill lenghts of birds recaptured (> 1 yr).retrap.txtPredicted Energy Intake Rate (PEIR)Prey burying depth per month and year, energy and density per m2, the predicted a (exp.a; area ...
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