Fast fuelling but light flight in Broad-billed Sandpipers Limicola falcinellus : stopover ecology at a final take-off site in spring (Sivash, Ukraine)

We studied phenology, staging time and refuelling in Broad-billed Sandpipers Limicola falcinellus stopping over during spring migration in the Sivash (Black Sea, Ukraine) in May 1991-94. In the study area, peak staging numbers of 2000-2500 individuals occurred in the third week of May. In May 1993, 460 birds were marked with a yellow dye and 126 of these were colour-ringed. Before 28 May no departure of birds dyed yellow could be detected; by 3 June all birds had departed. Colour-ringed adults in mid May 1993 staged for a minimum of 8.2 days. After the observed departure of large flocks (24 May and later) the staging time of colour-ringed birds decreased significantly with body mass at the time of capture. Of birds mist-netted in 1991-94, 99.3% were in full summer plumage and 89% were adults. In second-year birds, fuel deposition rate (measured between individuals) was 0.44 g/day. In adults caught from early May to 24 May, overall fuel deposition rate was 1.04 g/day (3.4% of lean body mass). Mean adult body mass in early May was 34.8 g, increasing to 45.5 g after 24 May. Estimated body mass at departure was 51 g. Departure body mass and flight range estimates suggest that although birds refuelled quickly, fuel loads are only just sufficient for an unbroken flight to Scandinavia and the Kola Peninsula. We suggest that Broad-billed Sandpipers use the Sivash as a crucial final take-off stopover site, and that they follow a 'jumping' migration strategy, performed under narrow time constraints.