Population trends of waders on their boreal and arctic breeding grounds in northern Europe

Waders form a conspicuous part of the bird fauna in boreal and arctic areas, where they inhabit forests, wetlands, mires and tundra. These are important breeding areas for a large set of wader species, and may be particularly vulnerable to climate change. However, large-scale and systematic monitoring data from the breeding grounds of boreal and arctic waders are largely lacking. We present population trends for 22 wader species breeding in the boreal and arctic parts of Fennoscandia (Norway, Sweden and Finland) between 2006 and 2018. The trends are based on 9,713 surveys of 1,505 unique routes (6–8 km), each surveyed in at least two years, evenly distributed over an area of ~1 million km². The trends were significantly negative for three species: Red-necked Phalarope Phalaropus lobatus (–7.9% year⁻¹), Broad-billed Sandpiper Calidris falcinellus (–5.4% year⁻¹), and Whimbrel Numenius phaeopus (–1.3% year⁻¹). The trends were significantly positive for three species: Oystercatcher Haematopus ostralegus (+4.9% year⁻¹), Dunlin Calidris a. alpina (+4.2% year⁻¹) and Wood Sandpiper Tringa glareola (+0.8% year⁻¹). For the remaining species, we found no statistically significant trends. On average, as shown by a multi-species indicator, there was no general change in numbers over time. On 1,539 routes with at least one survey, wader species richness as well as total number of wader pairs increased significantly with increasing latitude. Species population trend was not correlated with breeding latitude, but population trends of long-distance migrants tended to be more negative than those of medium-distance migrants. The recent fortunes of waders breeding in northern Fennoscandia have been more buoyant than those in other parts of Europe, but the trends for some species are worrying.