The roles of predation, food and agricultural practice in determining the breeding success of the lapwing (Vanellus vanellus) on upland grasslands.

Abstract

1. Lapwing breeding densities decreased by 74% on pastures and 56% on meadows following agricultural improvement of upland grasslands. Fledgling production was 63% lower on improved relative to unimproved areas. Three possible hypotheses to account for these decreases have been examined:
   (i) increased predation of clutches;
   (ii) a reduction in invertebrate food and/or its availability;
   (iii) a greater destruction of clutches by agricultural machinery and/or trampling by livestock.
2. Overall, 76% of clutches on improved pastures were taken by predators compared to only 47% on unimproved pastures. Increased predation largely accounted for the reduced breeding success on improved pastures relative to unimproved pastures.
3. Although land improvement resulted in decreases in several of the invertebrate groups upon which lapwings feed, reduced food availability had only minor effects on breeding success.
4. Clutch destruction during agricultural activities was almost four times higher on improved than on unimproved land and over five times higher on meadows than on pastures. On improved meadows, the higher proportion of clutches destroyed and the low proportion of clutches that were replaced accounted for the reduced breeding success.
5. The predation hypothesis was tested using simulated lapwing clutches. After 1 day of exposure to predators, almost twice as many 'clutches' were taken by predators on improved pastures as on unimproved.
6. Fledging production on improved land was insufficient to maintain numbers at current levels without recruitment from unimproved areas and this has probably caused the reduction in lapwing densities on improved land.