Monitoring wader productivity during autumn passage in Iceland

From mid July to early September 2005, age-proportions of 10,884 waders in 439 flocks were recorded in S and W Iceland. The aim was to provide current information about the timing of migration of age groups of high arctic and Icelandic breeding waders and to investigate the feasibility of using age proportions of waders in Iceland in autumn as a productivity monitoring tool. Juveniles of the high arctic species began to arrive in early to mid August whereas fledged juveniles of most resident species were already present in small numbers when the survey started. Potential sources of bias, like the effects of habitat, spatial and temporal scales and flock sizes on the proportion of juveniles recorded, are addressed. The differences between measuring juvenile proportions during passage and in winter are discussed.