Seasonal variation in Whimbrel abundance across sub-Arctic habitats of varying succession stage

The increase in temperature in Arctic regions is driving significant changes in hydrology and nutrient availability, with consequences at all ecosystem levels, ranging from habitats to populations. Disruption of the ecological succession by natural and/or anthropogenic causes has the potential to alter ecosystem functioning and habitat composition, influencing population dynamics of species. Iceland is a global stronghold for breeding populations of several waders such as the Icelandic Whimbrel Numenius phaeopus islandicus, which breeds on a gradient of abundance in habitats at early to mid-succession stages. The species provides a suitable system to investigate variation in abundance across habitats at different stages of ecological succession and throughout the season. We counted adult Whimbrels for three years at 14 sites in three habitats at early to mid-succession stages. Highest and lowest abundance was found in habitats of early succession throughout the breeding season. During pre-incubation, an increase in abundance was reported in all habitats, which stabilized during incubation. During post-incubation, abundance decreased in moss heath and remained stable in heathland and river plain. Our findings show consistent differences in overall abundance and progression of numbers through the breeding season between habitats at different succession stages. This has important implications for conservation strategies of the Whimbrel population and for habitat management, as it shows high variation in overall abundance and also suggests that the importance of some habitats for Whimbrel varies during the season.