Action: Create open patches or strips in permanent grassland
- Two studies (both randomized, replicated and controlled) investigated the effects of creating open strips in permanent grassland. One trial from the UK found that more Eurasian skylarks used fields containing open strips, but variations in skylark numbers were too great to draw conclusions from this finding. One trial from Scotland found insect numbers in grassy headlands initially dropped when strips were cleared.
Open patches and strips in permanent grassland can be used, in a similar way to skylark plots (see ‘Create skylark plots’) to provide short, open swards for ground-nesting birds.
Supporting evidence from individual studies
A randomized, replicated, controlled trial in winter 1995-1996 in southern England (Wakeham-Dawson & Aebischer 1998) found more Eurasian skylarks Alauda arvensis on seven fields with open strips than in seven control fields without strips, but the variation in numbers was so great that these differences were not significant (2-55 skylarks/km2 on treated fields vs 0 on controls). Open strips were created in a grid pattern, 25 m apart, using a tine-cultivator in November 1995. Experimental fields were still significantly more open in May 1996, but the swards had closed entirely by February 1997. The number of skylarks was recorded on three visits/month from December 1995 to February 1996 on 14 fields.
A randomized, replicated, controlled trial in 1997 and 1998 in Scotland, (Haysom et al. 2000) found that conservation management of permanent pasture field headlands (protection from summer grazing and clearing strips in the sward using herbicides) substantially increased the number of chick-food insects. The study measured the effect of different combinations of grazing and herbicide strip treatments on the numbers of true bugs (Heteroptera), sawfly larvae (Symphyta) and caterpillars (Lepidoptera). Treatments began in 1997, and insects were sampled in June and July in 1997 and 1998. By 1998, headlands protected from summer grazing had 19-32 times more chick-food insects (609 true bugs, 75 sawflies and 18 caterpillars, on average per 10 samples) than grazed headlands (19 true bugs, 2 sawflies and 1 caterpillar). Clearing strips in the sward (to allow birds easier access to insects) initially reduced the numbers of caterpillars and sawflies, but they recovered by 1998, when vegetation in bare areas had regrown.
- Wakeham-Dawson A. & Aebischer N.J. (1998) Factors determining winter densities of birds on environmentally sensitive area arable reversion grassland in southern England, with special reference to skylarks (Alauda arvensis). Agriculture, Ecosystems & Environment, 70, 189-201
- Haysom K.A., McCracken D.I., Roberts D.J. & Sotherton N.W. (2000) Grassland conservation headlands: a new approach to enhancing biodiversity on grazing land. Grazing Management: the Principles and Practice of Grazing, for Profit and Environmental Gain, within Temperate Grassland Systems: Proceedings of the British Grassland Society Conference, 29 February-2 March, 2000, Harrogate, UK, 159-160.