Response of northern harriers and short-eared owls to grassland management in Illinois

Published source details Herkert J.R., Simpson S.A., Westemeier R.L., Esker T.L. & Walk J.W. (1999) Response of northern harriers and short-eared owls to grassland management in Illinois. Journal of Wildlife Management, 63, 517-523.
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This study is summarised as evidence for the following.

	Action	Category
	Mow or cut natural grasslands Action Link
	Use prescribed burning on grasslands Action Link

Mow or cut natural grasslands

A replicated and controlled study in 1990-1994 in two intensively managed grassland sanctuaries in southeast Illinois, USA (Herkert et al. 1999), found that short-eared owls Asio flammeus were more likely to nest on fields burned and mowed in the last 12 months than on controls (undisturbed for 12 months). Northern harriers Circus cyaneus hudsonius were less likely to. Mowing was conducted between 20^th June and 15^th July each year. This study is discussed in detail in ‘Use prescribed burning’.
Use prescribed burning on grasslands

A replicated and controlled study in 1990-1994 in two intensively managed grassland sanctuaries in southeast Illinois, USA (Herkert et al. 1999), found that northern harriers tended to nest in fields not disturbed by grassland management (burning and mowing) within the last 12 months (a total of 22 nests in unmanaged fields vs. seven in burned and grazed fields). Short-eared owl Asio flammeus nest-site selection could only be assessed in 1990: all 13 nests were in fields subject to management within the last 12 months. One study site comprised 550 ha of grassland among 10 tracts, the second 308 ha among seven tracts. Each tract comprised 3-32 ‘sub-fields’ (0.5-15 ha) usually subject to one management type (all burned or all mowed).