Rails: secretive life between water and land

The three small rail species Spotted Crake, Little Crake and Baillon’s Crake are patchily distributed in central Europe, their core ranges lying further to the east. Their habitat – wetlands such as marshes, flooded sedge meadows, and silted-up areas – has been drained and reduced in size in the past 200 years. Mires lost 82 % of surface area in Switzerland between 1900 and 2010, alluvial plains 36 %. The remaining wetlands are scattered and exposed to a number of adverse influences. Still today, low water levels during the breeding season due to ditches and other drainage measures lead to the degradation of many potential breeding sites in Switzerland. Suitable habitats do not necessarily have to be large in size, as all three species can colonise wetlands of less than 1 ha if conditions are favourable.

Singing activity in suitable habitats is generally an indication of individuals looking for a mate, as rails rarely sing during migration. In 2013–2016, 9–13 Spotted Crake territories and 1–2 Little Crake territories were recorded annually in Switzerland. As for the Baillon’s Crake, only one territory was found in 2012 and in 2017; in 2016, there was a single observation during the breeding season. How many territories might have been overlooked?

On the one hand, these secretive marsh birds are rare and irregular visitors; on the other hand, recording them by visual or acoustic means is a challenge. Visual observations mainly take place during migration, when all three species use the edges of reedbeds as stopover sites. During the breeding season, they generally remain well hidden in dense vegetation. Singing activity mostly takes place at dusk and during the night. In some larger wetlands where the birds are regularly recorded, observers annually conduct 1–2 evening surveys beginning at dusk. But in the rest of the 90 wetlands that are systematically monitored and at other potential breeding sites, there are no such special surveys. Monitoring is further complicated by the fact that males only sing regularly until they have found a mate or the eggs have been laid.

The current methods probably only enable us to detect a part of the actual territories. More intensive monitoring, for instance by means of standardised nocturnal surveys or using acoustic recording devices, would improve our understanding of the extent to which these species occur.