Providing evidence to improve practice

Individual study: Effects of multiple grassland farmland interventions on birds, grasses and invertebrates in southern England

Published source details

Wakeham-Dawson A., Szoszkiewicz K., Stern K. & Aebischer N.J. (1998) Breeding skylarks Alauda arvensis on Environmentally Sensitive Area arable reversion grass in southern England: survey-based and experimental determination of density. Journal of Applied Ecology, 35, 635-648


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Undersow spring cereals, with clover for example Bird Conservation

A replicated, controlled study in summer 1995 on 89 fields in the South Downs, southern England (Wakeham-Dawson et al. 1998), found that the density of singing Eurasian skylarks Alauda arvensis was higher on undersown spring barley fields than on any other field type (approximately 22 birds/km2 on four spring barley fields vs. 2-15 birds/km2 on 85 other fields). Other field types were arable fields reverted to species-rich grassland (see ‘Habitat restoration and creation: Grasslands’) or permanent grassland (‘Revert arable land to permanent grassland’); downland turf (close-cropped, nutrient-poor grassland); permanent grasslands; winter wheat, barley and oil seed rape and set-aside (‘Provide or maintain set aide areas in farmland’).

 

Revert arable land to permanent grassland Bird Conservation

A replicated, controlled study in the spring and summer 1994-6 on 40 farms in southern England (Wakeham-Dawson et al. 1998) found that arable fields reverted to permanent grassland held similar densities of Eurasian skylarks Alauda arvensis as winter wheat and intensively managed permanent grassland, except in summer 1994, when they held significantly higher densities, and summer 1995, when they held lower densities than winter wheat (summer 1994: 11.9 birds/km2 on 65 reverted fields vs. 2.6 and 4.4 birds/km2 for 29 and 47 fields of permanent grassland and winter wheat, respectively; summer 1995: 2.1 birds/km2 for 15 reverted fields vs. 3.0 and 11.0 birds/km2 for seven and 26 fields of permanent grassland and winter wheat; other seasons: 5.7-9.1 birds/km2 vs. 3.6-4.0 and 8.5-13.0 birds/km2). Densities of carrion crows Corvus corone tended to be higher on reverted land, significantly so in some seasons (1.8-4.8 birds/km2 on reverted fields vs. 0-3.0 and 0-1.1 birds/km2 for grassland and wheat) and rooks C. frugilegus were never found on winter wheat. Between 65 and 82 reverted arable fields were surveyed, each sown with agricultural grass mixtures and managed under specific guidelines, whilst the 15-29 permanent grassland fields were frequently mown and fertilised. Between 38 and 47 winter wheat fields were surveyed. This study is also described in ‘Undersow spring cereals’, ‘Reduce grazing intensity on permanent grasslands’, ‘Habitat restoration and creation: Grasslands’ and ‘Provide or maintain set-aside areas in farmland’.

 

Exclude livestock from semi-natural habitat (including woodland) Farmland Conservation

A replicated, controlled trial in summer 1995 and 1996 in grassland in West Sussex, England (Wakeham-Dawson et al. 1998) found significantly more invertebrates and invertebrate taxa in 1.5 x 0.5 m cages from which grazing sheep were excluded, than in uncaged areas of sheep-grazed grassland (28-38 individuals and 9-11 invertebrate taxa in cages vs 7-15 individuals and 3-5 invertebrate taxa outside). Grass within the grazing-exclusion cages was approximately 40 cm tall, whilst outside the cages it was 2 cm tall. Twelve 10 x 4 m plots, each with one grazing-exclusion cage were established in 1995, with an additional two plots used in 1996. Invertebrates were sampled within and outside the grazing-exclusion cage using a D-Vac suction sampler.

 

Reduce grazing intensity Bird Conservation

A randomised, replicated and controlled study in spring and summer 1995-6 on 12 fields in Sussex, England (Wakeham-Dawson et al. 1998), found that Eurasian skylark Alauda arvensis densities were significantly higher on fields grazed at lower intensities (4.4-14.3 birds/km2 for six lightly-grazed fields vs. 1.3-2.4 birds/km2 on six intensely-grazed fields). The density of carrion crows Corvus corone and rooks C. frugilegus did not vary between treatments. Intensively-grazed fields were managed to keep the sward under 10 cm long, less intensively managed fields had a 15-25 cm sward. This study is also described in ‘Undersow spring cereals’, ‘Revert arable land to permanent grassland’, ‘Habitat restoration and creation’ and ‘Provide or maintain set aide areas in farmland’.

 

Convert or revert arable land to permanent grassland Farmland Conservation

A replicated, controlled study in spring and summer from 1994 to 1996 in southern England (Wakeham-Dawson et al. 1998) (same study as Wakeham-Dawson & Aebischer 1998) found that arable fields reverted to permanent grassland had similar densities of Eurasian skylarks Alauda arvensis to winter wheat and intensively managed permanent grassland, except in summer 1994 when they had significantly higher densities, and summer 1995 when they had lower densities than winter wheat. In summer 1994 there were 11.9 birds/km2 on reverted fields (65 fields) vs 2.6 and 4.4 on permanent grassland (29 fields) and winter wheat (47 fields) respectively. In summer 1995 there were 2.1 birds/km2 on reverted fields (15 fields) vs 3.0 and 11.0 on permanent grassland (seven fields) and winter wheat (26 fields); in other seasons 5.7-9.1 birds/km2 on reverted fields vs 3.6-4.0 and 8.5-13.0 on permanent grassland and winter wheat. Densities of carrion crows Corvus corone tended to be higher on reverted arable land, significantly so in some seasons (1.8-4.8 birds/km2 on reverted fields vs 0-3.0 and 0-1.1 on permanent grassland and winter wheat). Rooks C. frugilegus were never found on winter wheat. Fields on forty farms were surveyed. In 1994 and 1996 between 65 and 82 reverted arable fields each sown with agricultural grass mixtures and managed under specific guidelines were studied, as well as 15-29 permanent grassland fields which were frequently mown and fertilized, and 38-47 winter wheat fields. In 1995, 15 reverted arable fields, seven permanent grassland fields and 26 winter wheat fields were surveyed. The number and locations of singing skylarks were recorded in April-May and June-July in 1994 and 1996 and in May-June 1995. The locations of foraging carrion crows and rooks were also recorded in 1994 and 1996.

Provide or retain set-aside areas in farmland Bird Conservation

A replicated study in summer 1995 on 89 fields in the South Downs, southern England (Wakeham-Dawson et al. 1998 ), found that the density of singing Eurasian skylarks was higher on set-aside fields than on any other field type, except undersown spring barley fields (approximately 15 birds/km2 on six set-aside fields vs. 22 birds/km2 on four spring barley fields and 2-12 birds/km2 on 79 other fields). Other field types were arable fields reverted to species-rich grassland (‘Habitat restoration and creation’) or permanent grassland (Revert arable land to permanent grassland’); downland turf (close-cropped, nutrient-poor grassland); permanent grasslands; and winter wheat, barley and oil seed rape. This study is also described in ‘Reduce grazing intensity on permanent grasslands’ and ‘Undersow spring cereals’.

Undersow spring cereals, with clover for example Farmland Conservation

A replicated study in summer 1995 in southern England (Wakeham-Dawson et al. 1998) found that the density of singing Eurasian skylark Alauda arvensis was higher on undersown spring barley fields than on any other field type (approximately 22 birds/km2 on four spring barley fields vs 2-15 birds/km2 on 85 other fields). Other field types were arable fields reverted to species-rich or permanent grassland, downland turf (close-cropped, nutrient-poor grassland), permanent grassland, winter wheat, oilseed rape and set-aside. The number and location of singing skylarks were recorded in May-June 1995 on 89 fields.

Reduce grazing intensity on grassland (including seasonal removal of livestock) Farmland Conservation

A randomized, replicated, controlled study in spring and summer 1995 and 1996 in Sussex, England (Wakeham-Dawson et al. 1998), found that the densities of Eurasian skylark Alauda arvensis, grass seed heads and invertebrates were significantly higher on fields grazed at lower intensities (4.4-14.3 skylarks/km2, 155 seed heads/m2 and 17-112 invertebrates/sample on six lightly-grazed fields vs 1.3-2.4 skylarks/km2, 9.6 seed heads/m2, 10-68 invertebrates/sample and 4-16 invertebrate taxa/sample on six intensively-grazed fields). The density of carrion crows Corvus corone and rooks C. frugilegus did not vary between grazing intensities, nor did the number of invertebrate taxa in 1996 (1995: 12-17 invertebrate taxa/sample on lightly grazed fields vs 6-11 on intensively-grazed; 1996: 6-16 on lightly-grazed fields vs 4-16 on intensively-grazed). In 1996 there were significantly more individuals and taxa of spiders (Araneae) in lightly-grazed fields, but no differences in beetles (Coleoptera), flies (Diptera), bees, wasps and ants (Hymenoptera) or larvae. Twelve reverted permanent grassland fields (each field 5 ha) sown with perennial rye grass Lolium perenne, cocksfoot Dactylis glomerata and white clover Trifolium repens were studied. Sheep were used to control the grass height in fields between April and July each year: intensively-grazed fields were managed to keep the grass under 10 cm long, less intensively managed fields had a grass height of 15-25 cm. Skylarks were counted and their locations recorded every 10 days from April-June 1995 and April-July 1996. Foraging rooks were surveyed in 1995 and 1996, carrion crows were surveyed in 1996. Invertebrates were sampled at five locations/field in 1995 and 1996 using a D-Vac suction trap, and in pitfall traps in 1996.

 

Restore or create grasslands Bird Conservation

A replicated, controlled study in spring and summer 1994-1996 on 40 farms in southern England (Wakeham-Dawson et al. 1998) found that arable fields reverted to species-rich chalk grassland consistently held higher densities of Eurasian skylarks than land reverted to permanent grassland (sown with agricultural grasses), intensively managed permanent grassland or winter wheat fields (12.0-22.8 skylarks/km2 for 16-35 reverted chalk grassland fields vs. 2.6-11.9 skylarks/km2 for 16-82 fields of other types). Densities of carrion crows Corvus corone and rooks C. frugilegus were not consistently higher on any field type (1-2 crows/km2 and 0-14 rooks/km2 for chalk grassland vs. 0-2 crows/km2 and 0-89 rooks/km2 for other fields). Reverted chalk grassland fields were sown with Festuca spp. and Bromus spp. grasses.

 

Restore/create species-rich, semi-natural grassland Farmland Conservation

A replicated, controlled study in spring and summer from 1994 to 1996 in southern England (Wakeham-Dawson et al. 1998) (same study as (Wakeham-Dawson & Aebischer 1998)) found that arable fields reverted to species-rich chalk grassland consistently had higher densities of Eurasian skylark Alauda arvensis than land reverted to permanent grassland (sown with agricultural grasses), intensively managed permanent grassland or winter wheat fields (12-23 skylarks/km2 on reverted chalk grassland fields (16-35 fields) vs 3-12 skylarks/km2 on 16-82 fields of other types). Densities of carrion crows Corvus corone and rooks C. frugilegus were not consistently higher on any field type (0.5-1.9 crows/km2 and 0-14 rooks/km2 on chalk grassland vs 0-1.8 crows/km2 and 0-90 rooks/km2 on other fields). Reverted chalk grassland fields were sown with Festuca spp. and Bromus spp. grasses. The other field types studied were arable fields reverted to permanent grassland, downland turf (close-cropped, nutrient-poor grassland), permanent grassland, winter wheat, barley, oilseed rape and set-aside. Fields on forty farms were surveyed. The number and location of singing skylarks were recorded in April-May and June-July in 1994 and 1996 and in May-June 1995. The locations of foraging carrion crows and rooks were also recorded in 1994-1996.

 

Provide or retain set-aside areas in farmland Farmland Conservation

A replicated site comparison study in summer 1995 on 89 fields in the South Downs, southern England (Wakeham-Dawson et al. 1998) found that the density of singing Eurasian skylarks Alauda arvensis was higher on set-aside fields than on any other field type, except undersown spring barley fields (approximately 15 birds/km2 on six set-aside fields vs 22 birds/km2 on four spring barley fields and 2-12 birds/km2 on 79 other fields). Other field types were: arable fields reverted to species-rich grassland or permanent grassland, downland turf, permanent grassland, winter wheat, barley and oilseed rape.