Field-layer management trials for black grouse at Corrimony

Project objectives
Work planned or underway
Results
Who to contact
Partners
Funding

Male black grouse displaying

Vegetation recovered rapidly on flush habitats following cutting, but not on wet and dry heath, where vegetation remains shorter and more open three years after cutting. Common heather is the only plant species/taxa to show a major reduction in cover following cutting, with only moderate recovery two to three years on.

Vegetation growth rates increase after cutting relative to those on control plots on both dry and wet heath habitats, but (surprisingly) on flush habitats growth rates are as high on control plots as they are on cut plots. The continued, progressive, increase in vegetation height on control plots on all habitats (but particularly on flush) suggests that vegetation at Corrimony may still be responding to the low deer densities on this site, and that at some stage vegetation may become too tall and rank to be suitable for black grouse (in the absence of management).

Vegetation height, rather than growth rate, is the major effect on both overall invertebrate abundance and caterpillar abundance (as measured by sweep netting); caterpillars being a key food of black grouse chicks. Therefore, there is little suggestion that cutting of field-layer vegetation increases the abundance of chick food, although it may increase availability, particularly given the continued increase in the height of the field-layer vegetation at Corrimony.

Preliminary analyses provide no evidence for greater usage of cut plots by black grouse (as determined by the occurrence of droppings).

Project objectives

To determine the effects of cutting of field-layer on vegetation composition and structure
Abundance of invertebrate foods of black grouse chicks
Use by black grouse

Work planned or underway

Data collection began in autumn 2004, with management beginning in winter 2004/05. Post-management data have been collected in 2005 – 07 and in 2009. Analyses of these data are in progress, but have yet to incorporate the latest information from 2009.

Results

Vegetation has shown a rapid recovery on flush habitats following cutting, but not on wet and dry heath, where vegetation remains substantially shorter and more open two years after cutting. Common heather is the only plant species/taxa to show a major reduction in cover following cutting, with only moderate recovery two years on.

The overall invertebrate abundance (as measured by sweep netting) was lower on cut than uncut plots on dry heath, but did no differ between cut and uncut plots on wet heath and flush habitats. However, the abundance of caterpillars (often a key food for chicks) was lower on cut plots on dry heath and flush habitats two years after cutting, although there was no such difference between cut and uncut plots on wet heath.

Data on black grouse usage remain to be analysed.