Occupancy reliably reflects territory quality in a long-lived migratory bird, the white stork

Patterns of territory occupancy were studied in the population of ca. 200 pairs of white stork Ciconia ciconia breeding in central Poland from 1994 to 2011. We tested whether occupation rate in this species correlated with different indices of territory quality and reproductive performance of nesting birds. Territory occupancy deviated significantly from random pattern, as nearly half of the territories were occupied for over 75% of all breeding seasons. It was found that white storks returning to breeding grounds in spring settled earlier in the territories of higher occupancy. There was a positive association between territory occupancy and productivity of storks, which could be explained by the lower prevalence of brood reduction in the longer occupied territories. Finally, we demonstrated that occupancy positively correlated with the share of high‐quality habitats (wetlands) in the foraging territories of storks. All these relationships indicate that territory occupancy may be used to reliably assess attractiveness of particular nesting territories and to identify key areas for white storks. We also suggest that the application of this simple measure of territory quality could well enhance conservation efforts directed at long‐lived migratory birds.