Traditional Fish Pond Management Provides Reliable Foraging Opportunities for Migrating Black Storks in Romania

Abstract

Migrant water birds such as Black Storks Ciconia nigra have progressively started capitalizing on man-managed ecosystems during migration. Behavioural and ecological studies at stopovers are thus key to deliver comprehensive conservation policies. To be able to improve stopover potential for one of the main Black Stork fall passage sites in central Romania, the Dumbraviţa fishing complex, we analysed the species' foraging behaviour in relation to management of water levels and human activities. Afternoon feeding sessions were recorded weekly during two consecutive autumn migration periods in August–September 2017 and 2018. We used focal and scan sampling methods to quantify behavioural patterns based on 168, 10-minute feeding bouts between 16:00 and 18:00. The selection of foraging areas was contingent upon drainage practices and biased towards vegetated sectors of ponds. The time at which the storks started foraging was strongly correlated with the cessation of the daily fish harvest. Hunting strategies involved grabbing (visual) and water probing (tactolocation), the first prevailing in terms of frequency and time allotment and the latter mainly being used in shallow, muddy areas. Until now, traditional fish farming has unintentionally catered to Black Stork feeding preferences. We put forward several long-term management suggestions to secure the stopover potential for Black Storks at Dumbraviţa.