Black grouse range

Key finding

• Due to the limited disperal capacity of male black grouse, to meet the BAP targets of expanding the range and linking isolated populations, it may be necessary to translocate males from core to peripheral areas.

The black grouse population in the UK has declined and contracted owing in part to the direct loss, fragmentation and degradation of habitat. This has disrupted the black grouse population structure in northern England, resulting in at least two distinct sub-populations in the region, Northumberland (north of the Tyne Gap) and the North Pennines (see Figure 1).

Figure 1. Dispersal capacity of male and female black grouse and evidence of fragmentation of the black grouse population in northern England

Dispersal capacity of females
Dispersal capacity of males

Since 1996, the North Pennines Black Grouse Recovery Project has addressed this decline. In 1999, black grouse became a Biodiversity Action Plan 'Priority Species', for which we and the RSPB are lead partners. The Recovery Project has been responsible for implementing the Species Action Plan for black grouse in England, the main objectives of which are to:

• Restore the population to its 1996 level of 800 males by 2005
• In the long term (20 years), increase the range
• Prevent further fragmentation of populations
• Promote re-colonisation of formerly occupied areas by 2005

The project is achieving its short-term objectives in relation to abundance, with the population in 2002 numbering 895 males compared with 773 males in 1998. The range, however, is at best only being maintained, and localised contractions continue. Expanding this range may be difficult because of the limited dispersal powers of black grouse.

Recent radio-tracking studies have measured the dispersal distances of 48 juvenile black grouse (28 males and 20 females). The average dispersal distance of yearling males was 0.8 kilometres, whereas the equivalent distance for females was 8.0 kilometres. Similar differences between male and female dispersal have been observed during earlier studies in the North Pennines and elsewhere in Europe.

Figure 2. Dispersal distances of 28 male and 20 female black grouse in the North Pennines, 1998-2004

	Males
	Females

In continuous black grouse habitat, leks are spaced at approximately two-kilometre intervals, which is typical along the valley sides of the North Pennines. Fragmentation of habitat on a small local scale is unlikely to affect the overall population much, as females can disperse easily between fragments. However, should fragmentation occur at a landscape scale with patches separated by distances of more than 20 kilometres, then sub-populations become disconnected and genetic isolation is a possibility.

Given limited male dispersal, range expansion may prove difficult to achieve in the short and longer-term. Several sightings of females outside the current described range (based on lek locations) suggest that male absence may be limiting breeding range expansion. This hypothesis is based, however, on data gathered largely within the core of the North Pennines range and assumes that dispersal distances are similar at the margins of the range where densities of birds are lower. This assumption is reasonable given that both dispersal frequencies and distances of both black grouse and red grouse appear to be density-independent.

We therefore propose to try and extend the range by moving males from core areas of the North Pennines where there are plenty, to areas on the north and southern boundaries where there are no leks, but within range of dispersing females.