BODY-MASS CHANGES IN WADERS (CHARADRII) IN A HIGH ARCTIC AREA AT NORTHERN TAIMYR, SIBERIA

Body mass data were collected for 5 species of tundra waders during 6 breeding seasons to study variation in nutrient reserves relative to h igh arctic climatic conditions and the stage of reproduction. Structur al size was accounted for by the Ist Principal Component of external l inear measurements: wing length, bill length and tarsus length. Sandpi pers Calidris spp. were on average lighter in phenologically late seas ons, while mass of Turnstones (Arenaria interpres) was similar in all years. Mass of waders was lower during brood-rearing than during incub ation. Body mass during pre-nesting was most variable between years, r eflecting the unpredictable weather conditions in this period. Monogam ous species (Knots Calidris canutus and Turnstones) began to breed ear lier, and were on average, as heavy during the pre-nesting period as d uring incubation. In contrast, species with a proven or suspected rapi d double-clutch breeding system (Little Stints C, minuta and Sanderlin gs C. alba) began to breed later and had during the laying period mass es close to those of adults attending broods, and lower than during in cubation. Body mass of the two latter species and Curlew Sandpipers (C alidris ferruginea) varied during incubation, reaching peak at 7 to 13 days after clutch completion.