Foraging habitat selection by breeding Common KestrelsFalco tinnunculuson lowland farmland in England

Abstract

Capsule Breeding Common Kestrels prefer to forage over recently cut grass than all other habitat types on farmland. Aims To identify foraging habitat and prey of Common Kestrels during the breeding season. Methods We observed seven pairs of Common Kestrels during the breeding season over three years, using fixed vantage point observations. We recorded foraging attempts, and habitat and prey data for where the birds chose to forage. Compositional Analysis was used to establish use of each habitat category relative to that habitat's availability within the Kestrels' observed foraging ranges. Results We found that Kestrels select habitats non-randomly, with cut grass (≤5cm, all cut less than two weeks previously) being the most used relative to availability. Prey taken varied with grass height: the ratio of mammals to invertebrates was greater on cut grass (4.36 mammals: 1 invertebrate) than on longer, uncut grass swards (1.73 mammals: 1 invertebrate). Conclusion Our results highlight the importance of areas of long and short grass in close juxtaposition, to provide conditions suitable for prey and access to them, respectively. The creation and maintenance of such small-scale habitat heterogeneity will be the key to maximizing the benefits of English agri-environment schemes for Common Kestrels.

Creating ephemeral resources: how long do the beneficial effects of grass cutting last for birds?

“…earthworms Lumbricus spp. Similarly, Kestrels also showed a trend for greater occurrence on shorter swards in line with previous studies (Sheffield et al 2001, Aschwanden et al 2005, Whittingham & Devereux 2008, Garratt et al 2011. Kestrels are diurnal hunters (Village 1990) which either hover over or perch overlooking grass in order to visually detect their prey, most commonly small mammals such as voles Microtus spp., and small birds (the latter particularly in June/July).…”

“…These earlier studies showed that corvids, pigeons and Kestrels preferred short grass swards (Perkins et al 2000, Atkinson et al 2005, Whittingham & Devereux 2008, Garratt et al 2011), but did not investigate the time period over which the effects of grass cutting attract foraging birds. The key result reported here is the rapid drop off in field use by many bird species after cutting (Fig.…”

Should We Stay or Should We Go Now? What Happens to Small Mammals When Grass is Mown, and the Implications for Birds of Prey

“…Previous work has shown that kestrels foraging on farmland prefer short grass above all other habitats available to them (Ashwanden et al 2005, Whittingham & Devereux 2008, Garratt et al 2011, presumably as it increases accessibility to their prey. The same association has also been shown for other raptors (Baker & Brooks 1981, Aschwanden et al 2005.…”

“…If wide and densely vegetated, grass margins should enhance numbers of small mammals on arable farmland (Shore et al 2005, Aschwanden et al 2007), a key resource for many birds of prey (Cavé 1968, Glue 1974, Korpimäki 1984, Village 1990, Korpimäki & Norrdahl 1991, Redpath & Thirgood 1999, Koks et al 2007. However, in the UK some farmland specialist raptors such as the barn owl Tyto alba and the kestrel Falco tinnunculus are still declining (Risely et al 2010, Garratt et al 2011. These continued declines may indicate that the quality of grass margins in AESs can be improved to further benefit raptors that rely on small mammals.…”

“…62 000 ha in the area of grassland on farms in England since the mid1980s (Grice et al 2007, Garratt et al 2011. If wide and densely vegetated, grass margins should enhance numbers of small mammals on arable farmland (Shore et al 2005, Aschwanden et al 2007), a key resource for many birds of prey (Cavé 1968, Glue 1974, Korpimäki 1984, Village 1990, Korpimäki & Norrdahl 1991, Redpath & Thirgood 1999, Koks et al 2007.…”