Agri-environment schemes and foraging of barn owls Tyto alba

Plant trees on farmland

A replicated, site comparison study in 2003–2004 in an agricultural area in Yorkshire, UK (Askew et al. 2007) found that farm woodland had similar numbers of small mammals compared to uncultivated field margins and set-aside. There was no significant difference in the annual average numbers of small mammals caught in farm woodland (2.4–2.8 individuals), 2-m-wide field margins (2.9–4.4), 6-m-wide field margins (2.5–3.6) and set-aside (1.6–2.0). In the first year, more wood mice Apodemus sylvaticus were caught in farm woodland (1.4 individuals) and in 6-m-wide margins (1.1) than in set-aside (0.5), but fewer common shrews Sorex arenaeus were in farm woodland (0.6 individuals) or set-aside (0.6) than in 2-m-wide margins (1.4). No other species differences between treatments were found. Farm woodland comprised young trees (age not stated), fenced and with grass generally uncut. Field margins, sown with grass, were 2 m wide (cut every 2–3 years) or 6 m wide (cut every 1–3 years). Set-aside areas were fallow for ≥5 years, with ≥90% of the area cut annually. Twelve small mammal traps were set in each of 20 plots/treatment (1 m from the habitat boundary) for four days in November–December in each of 2003 and 2004.

(Summarised by: Nick Littlewood)

Provide or retain set-aside areas on farmland

A replicated, site comparison study in 2003–2004 in Yorkshire, UK (Askew et al. 2007) found that set-aside had similar numbers of small mammals compared to uncultivated field margins and farm woodland. There was no significant difference in the annual average numbers of small mammals caught in set-aside (1.6–2.0), 2-m margins (2.9–4.4 individuals), 6-m margins (2.5–3.6) and farm woodland (2.4–2.8). In the first year, fewer common shrews Sorex arenaeus were caught in set-aside (0.6) or farm woodland (0.6) than in 2-m margins (1.4 individuals) and fewer wood mice Apodemus sylvaticus were caught in set-aside (0.5) than in 6-m margins (1.1) and farm woodland (1.4). No other species differences between treatments were found. Set-aside areas were fallow for ≥5 years, with ≥90% of the area cut annually. Field margins, sown with grass, were 2 m wide (cut every 2–3 years) or 6 m wide (cut every 1–3 years). Farm woodland comprised young trees (age not stated), fenced and with grass generally uncut. Twelve small mammal traps were set in each of 20 plots/treatment (1 m from the habitat boundary) for four days in November–December in each of 2003 and 2004.

(Summarised by: Nick Littlewood)

Create uncultivated margins around intensive arable or pasture fields

A replicated, site comparison study in 2003–2004 in Yorkshire, UK (Askew et al. 2007) found that uncultivated field margins hosted similar numbers of small mammals compared to set-aside and farm woodland. There was no significant difference in the annual average numbers of small mammals caught in 2-m margins (2.9–4.4 individuals), 6-m margins (2.5–3.6), set-aside (1.6–2.0) and farm woodland (2.4–2.8). In the first year, more common shrews Sorex arenaeus were caught in 2-m margins (1.4 individuals) than in set-aside (0.6) or farm woodland (0.6) and more wood mice Apodemus sylvaticus were in 6-m margins (1.1) and farm woodland (1.4) than in set-aside (0.5). No other species differences between treatments were found. Field margins, sown with grass, were 2 m wide (cut every 2–3 years) or 6 m wide (cut every 1–3 years). Set-aside areas were fallow for ≥5 years, with ≥90% of the area cut annually. Farm woodland comprised young trees (age not stated), fenced and with grass generally uncut. Twelve small mammal traps were set in each of 20 plots/treatment (1 m from the habitat boundary) for four days in November–December in each of 2003 and 2004.

(Summarised by: Nick Littlewood)

Plant grass buffer strips/margins around arable or pasture fields

A replicated study in 2003 and 2004 in England, UK (Askew et al. 2007) found that sown grass field margins tended to have higher numbers of small mammals than set-aside. Numbers of captured small mammals were highest in 2 m margins (2.9-4.4 individuals), followed by 6 m margins (2.5-3.6) and set-aside (1.6-2.0). Numbers of small mammals captured were correlated with sward height in 2 m margins. In 2003, significantly more common shrews Sorex arenaeus were captured in 2 m margins (1.4 individuals) than set-aside (0.6) and more wood mice Apodemus sylvaticus were found in 6 m margins (1.1) than set-aside (0.5). The trend was similar for bank voles Clethrionomys glareolus in 2004: 6 m margins (1.6), 2 m margins (1.4) and set-aside (0.5). Species richness did not differ significantly (1.7-2.0). Species richness, total number of small mammals captured, and the number of bank voles and common shrews captured was higher in 6 m margins cut every 2-3 years compared to those cut annually, although this was only significant for common shrews in 2003. Following establishment, 2 m margins were cut at 2-3 year intervals. For 6 m margins, eight 2 m strips at the edges of margins were cut annually and 12 were cut every 2-3 years. Twelve small mammal traps were set within 20 plots per treatment (1 m from the habitat boundary) for four days in November-December 2003-2004. Mammals were individually fur-clipped and released.

Provide or retain set-aside areas in farmland

A replicated site comparison study of agri-environment scheme habitats in arable farmland in England (Askew et al. 2007) found that set-aside tended to have lower numbers of small mammals than sown grass margins. Numbers of small mammals caught in permanent set-aside (fallowed for five years or more, annual cutting of at least 90%: 1.6-2.0 mammals/plot) were lower than in 2 m grass field margins (2.9-4.4 mammals/plot) and 6 m margins (2.5-3.6 mammals/plot). In 2003, significantly fewer common shrew Sorex araneus and wood mouse Apodemus sylvaticus were captured in set-aside (shrews: 0.6; mice: 0.5) than grass margins (shrews: 0.9-1.4; mice: 0.7-1.1). The trend was similar for bank voles Myodes glareolus in 2004 (set-aside: 0.5 voles/plot; margins: 1.4-1.6 voles/plot).  Species richness did not differ significantly between treatments (1.7-2.0 species). Twelve small mammal traps were set within 20 plots per treatment (1 m from the habitat boundary) for four days in November-December 2003-2004. Mammals were individually fur-clipped and released. Results from farm woodlands are not included here.