Hatching date in Northern Wheatears, as a proxy of nest site selection, shows a longitudinal gradient in the white dunes and occurs earlier in older males in the grey dunes on Norderney

Vollständiger Abstract

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Abstract Understanding species’ nest site selection is essential for successful species conservation, because it allows to identify critical areas, allocate resources efficiently, and formulate effective measures. One indirect way to assess this for migratory birds is by examining breeding timing, considering that higher-quality habitats are occupied earlier, while controlling for extrinsic and intrinsic factors. However, how site- and individual-level factors jointly correlate with the nest site selection remains unclear. This study examined the population of Northern Wheatears ( Oenanthe oenanthe ), a long-distance migratory songbird, nesting in burrows from introduced rabbits on the German island Norderney. Using data from 321 nests monitored between 2021 and 2025, we assessed the influence of nest site- (habitat type, longitude, distance to paths, and streets) and individual-level (male age) characteristics on hatching date. We found a longitudinal gradient in hatching dates of the juveniles in white dunes, with earlier hatching in the east of the island, where rabbit density is highest, as shown in previous studies. In grey and vegetated dunes, hatching dates were primarily influenced by the age of the males, with chicks of older males hatching earlier. Habitat type and distance to paths and streets had no significant effect. These findings suggest a different timing of nesting related site- and individual-level characteristics. Habitat areas of the Wadden Sea National Park with short vegetation and rabbit burrow availability are critical breeding sites for Northern Wheatears on the island. Conserving natural habitats, maintaining rabbit population, and not expanding anthropogenic grassland areas are key actions to sustaining suitable habitat conditions for the Northern Wheatear population.