Population dynamics of Common Sandpipers Actitis hypoleucos in the Peak District of Derbyshire - a different decade

摘要

Capsule A report of the failure of a population to recover from a catastrophic snow storm. Aims To examine why our study population of Common Sandpipers failed to recover from a sharp drop in 1989, caused by a severe late April snowstorm, when it had recovered from a similar event in 1981. Methods Populations were censused weekly, with extra visits to ring adults and chicks. Hatching was assumed to have occurred if adults alarmed, and fledging if alarming continued for three weeks. Data from 1989-99 and 1979-88 were compared. Results The recruitment of new adults to the population was much lower, but these recruits mostly came from other breeding areas, and the local recruits appeared to go elsewhere. Median dispersal distance is estimated as 3.3 km, sufficient to take,most locally produced young adults outside the study area. Conclusions We do not know if poorer breeding in the source populations for our birds, or poorer survival of first year birds over winter in West Africa, is the cause of the failure of this population to recover in the 1990s.