The decline of the Whinchat and Northern Wheatear on Dutch heath land relates to decline of ground beetles

The Dwingelderveld National Park, located in the province of Drenthe in the north-eastern part of the Netherlands, is a heath and woodland reserve of 3,700 hectares, with 1500 ha of wet heath land, which makes it the largest wet heath land in western Europe. Sjouke van Essen surveyed the ground beetles (Coleoptera : Carabidae ) on 38 locations in the Dwingelderveld reserve in 1991 and 2008, in exactly the same manner, and observed a massive decline in the number of caught ground beetles, from 45,000 (94 species) in 1991 to 15,000 (79 species) in 2008. Within the same period there was a dramatic decline of the insectivorous Whinchat Saxicola rubetra (from 35 pairs in 1989 to 6-14 pairs in 1998-2003) and Northern Wheatear Oenanthe oenanthe (from 33 pairs in 1993 to just 3 in 2003) in the Dwingelderveld reserve.

Sources:
Lustenhouwer I en Vermeulen R (2009) Wat loopkevers vertellen. Nationaal Park Dwingelderveld Informatiebulletin Veldspraak 13:11
Ministerie Landbouw, Natuur en Voedselkwaliteit (Dutch Ministry of Agriculture, Nature and Food Quality). Natura 2000 gebiedendocument- Natura 2000 gebied 30 - Dwingelderveld, November 2006