Seasonal changes in body size and mass of Red Knots Calidris canutus during autumn migration through southern Baltic

Body size and mass of 1,458 juvenile 558 adult Knots were measured during autumn migration in Puck Bay, Poland, between 1983 1999. The measurements fit well with those gathered along the route Siberian Calidris c. canutus. All linear adults, except body adjusted for size, significantly higher than juveniles. Shorter wing juveniles adults seems to be a general rule regardless geographical region. Adult females migrated ahead males, confirmed by decreasing mean measurements. Juveniles carried larger relative energy stores adults. Bay may an emergency feeding place Knots, whereas use it as one many stop-over sites. smaller, but had mass, late September earlier, indicating behavioural difference early birds preceding stages migration. Late probably follow time-minimising strategy fuel fewer sites, passing August migrate very small energetic reserves, making only short flights stops.