COMPARATIVE NESTING AND FEEDING ECOLOGY OF SKYLARKS ALAUDA-ARVENSIS ON ARABLE FARMLAND IN SOUTHERN ENGLAND WITH SPECIAL REFERENCE TO SET-ASIDE

1. A study Of skylark Alauda arvensis L. breeding ecology in relation to crop type was carried out from April to August 1992 on arable land in southern England. Set-aside land was included in this comparative s tudy. 2. Territory density averaged 0.15 ha(-1). It was 2-3 times high er in fields of set-aside and grass, especially permanent pasture, tha n in winter and spring-sown cereals. 3. Territory size was nearly twic e as large in fields of winter cereals (4.5 ha) than in other crop typ es (2.5 ha). Where set-aside was present on one farm, territory size i n set-aside (1.7 ha) was a third lower than in cereals and grass. 4. N esting began in set-aside and permanent pasture in April and peaked in late May. Nesting was not detected in spring barley until late May an d in silage grass until early June. The density of successful nests in set-aside fields was more than double that in any of the arable crop types. 5. Average clutch size at hatching was 3.91 eggs in fields of s et-aside, over 15% higher than in silage grass (3.40) and in spring ba rley (3.27). 6. Fledging success did not differ according to crop type , but productivity, expressed as the number of fledglings produced per hectare, was 0.50 in set-aside, 0.13 in silage grass, and 0.21 in spr ing barley. Nests with chicks were not found in fields of winter cerea ls. The causes of chick death were thought to be predation in set-asid e fields, farming practices in silage grass fields, and suspected star vation in spring cereals. 7. The potentially high nesting success of s kylarks in set-aside implies that sympathetic set-aside management cou ld play an important part in reversing its decline across the European Union.