No abstract

The natural valleys of large rivers provide suitable nesting and foraging sites for many bird species. In this study, we assess the effects of water fluctuations during the breeding season on Common Sandpipers’ nest survival on a semi-natural section of the Vistula River, and evaluate which tactics this species can adopt to minimise the effects on a long-term scale. Birds can avoid losses due to flooding by adjusting the timing of nesting to avoid the occurrence of extreme water conditions, and/or by choosing a safe nesting location. We found that nest location is a direct response to periodic high water, and the threat of flooding seems to be one of the important determinants of Common Sandpiper nest placement. The choice of nest location is not random, as 70% of pairs nested above a height that provides an 80% chance of avoiding flooding of the nest. For the lowest-lying nests found in this study, nesting success was reduced up to 92% because of inundation. Birds choose more elevated places, even during the second half of the season when the threat of flooding is lower. Their preference for nesting above a certain height does not change over the breeding season, which corresponds to the very small impact of the date of first egg laying on breeding success. Those who breed earlier in the season have a slightly higher risk of being flooded, but nesting in more elevated places reduces this risk much more than shifting the time of breeding.