Different migration strategies used by two inland wader species during autumn migration, case of Wood Sandpiper Tringa glareola and Common Snipe Gallinago gallinago

Waders generally follow two alternative strategies.The ‘B-strategy’ or ‘energy minimization’ strategy is to initiate migration late in the season, start moulting at the breeding grounds and migrate slowly in small steps, whereas the ‘S-strategy’ or ‘time minimization’istomigrateimmediatelyaftertheendofthebreedingperiodandmoulton the wintering grounds after a migration with only a few stopover sites.We studied Wood Sandpipers Tringa glareola and Common Snipes Gallinago gallinago at the Polish Jeziorsko reservoir.Adult and juvenile Wood Sandpipers migrate during different peri- ods, and showed no signs of moult.In contrast, both age groups of Common Snipe mi- grate during the same period, and up to 30% of ringed adult Common Snipes had started their post-breeding moult at the reservoir.Wood Sandpipers stayed 4-5 days at the reser- voir,wheretheyfattenedatarateof1.15g/day(whichwaspositivelycorrelatedwiththeir length of stay, r = 0.21), and left with 21% of fat (% of LBM), allowing themto cover dis- tances exceeding 2,500 km (which enables them to reach the coast of the Mediterranean Sea).In contrast, Common Snipes stayed 11 days, fattening 0.3 g/day, and left the reser- voir independently of their fat reserve.Common Snipes stored a significantly smaller fat reserve than Wood Sandpipers, and their reserve was predicted to allow maximally 1,500 km of constant flight.Our findings support the hypothesis that, under common feeding conditions at Jeziorsko reservoir, Common Snipes behave according to the energy minimization strategy whereas Wood Sandpipers use a time minimization strategy.

R. Wlodarczyk, P. Minias, K. Kaczmarek, T. Janiszewski & A. Kleszcz, Ornis Fennica 84:119-130. 2007