Philip Warren

Dispersal, survival and causes of mortality in black grouse Tetrao tetrix in northern England

Between autumn 1998 and spring 2000, 70 black grouse Tetrao tetrix (48 poults and 22 adults) were equipped with radio transmitters in the North Pennines, England. We recorded timing and distances of dispersal, survival rates and causes of death. First-year survival rates differed between years, but in each year were highest in late autumn prior to dispersal, when predation by stoats Mustela erminea and raptors accounted for three-quarters of deaths. First-year grouse survival was lower than that of adult birds owing to predation in the autumn and winter by raptors and stoats. The annual adult survival rate of 0.72 was higher than those found in most other European studies. By contrast, breeding success was low. Dispersal was confined to first-year hens, with distinct dispersal periods in late autumn (mean 10.3 km) and again in early spring (mean 5.8 km). Natal dispersal resulted in none of the first-year hens breeding within the study area. Adults of either sex and first-year cocks showed high site fidelity. This has practical repercussions when considering prescriptive management to aid species recovery and range expansion in relation to habitat fragmentation at both the local and regional levels.

Abundance of male Black Grouse Tetrao tetrix in Britain in 2005, and change since 1995-96

Capsule There was a non-significant decline in the number of displaying males in Britain between 1995–96 and 2005, with a significant decline in Scotland. Aims To estimate the number of displaying male Black Grouse in Britain in 2005, and to compare this with the 1995–96 estimate. Methods Surveys were carried out in a stratified sample of 1-km (Wales) and 5-km (Scotland and England) squares throughout the known range, using similar methods to the 1995–96 survey. Results There were an estimated 5078 displaying males in Britain in 2005 (95% CI 3920–6156). This estimate is 22% less than the 1995–96 estimate of 6506, although these estimates are not significantly different. In Scotland, numbers fell by 29% overall, comprising large and significant declines of 49% and 69% in southwest and southeast Scotland, respectively, but small and non-significant declines in north (16%) and northeast Scotland (9%). In England, there was a non-significant decline of 11%, while in Wales numbers rose by 39%. Where numbers have declined there has been a decrease in the number, but not the size, of display groups. Display sites in Britain were at higher altitudes (median 400 m) in 2005 than in 1995–96 (median 340 m). Conclusion Although Black Grouse numbers in Wales increased, this survey provides evidence of a large decline in southern Scotland. The causes of this decline are not fully understood, and further research is urgently required to reveal the underlying mechanisms and implement appropriate conservation measures.

Variations in the Vital Rates of Black Grouse Tetrao tetrix in the United Kingdom

Abstract In the United Kingdom, black grouse Tetrao tetrix are in severe decline with only 6,500 displaying males in 1995-1996 and a range retraction of 28% between 1972 and 1991. Recent declines have been greatest in central and southern Scotland and parts of Wales and contrast with relative stability in northern England. We compare the demography of black grouse in three regions: North Wales, northern England and the Scottish Highlands. Patterns in annual fecundity, measured as fledglings per breeding female, were correlated between regions, suggesting that annual weather patterns common across regions may be a key determinant of breeding success. Site related effects such as habitat quality or management were also significant in northern England and North Wales. Male population growth rates at leks were positively correlated with fecundity in the previous year. Fecundity was highest in North Wales and the Scottish Highlands at 1.7 chicks per female in August compared to 1.3 in northern England. Variations in the annual fecundity of radio-tagged females were linked to differences in brood survival rather than clutch survival, which did not differ among years. We found a non-significant trend for juvenile survival to be lower in North Wales (0.18) than in either northern England (0.65) or the Scottish Highlands (0.56). Similarly, annual adult survival also tended to be lower in North Wales (0.44) than in either northern England (0.70) or the Scottish Highlands (0.66). Predation was the main cause of death in all regions, with red fox Vulpes vulpes and raptors being the chief predators in North Wales and the Scottish Highlands and stoat Mustela erminea in northern England. The last 10 years have seen the implementation of a series of black grouse recovery projects in the UK. An understanding of the limiting demographic stage in each project area is critical before appropriate remedial management prescriptions can be implemented.

Current status and recent trends in numbers and distribution of Black Grouse Tetrao tetrix in northern England

Capsule Surveys of Black Grouse in northern England in 1998, 2002 and 2006 show population recovery in the form of increases in both numbers and range. Aims To quantify the population size and range of Black Grouse in northern England. Methods Male black grouse attending leks were surveyed in 1998, 2002 and 2006. These results were put in context with a longer-term trend in northern England, using annual counts from a non-random sample of leks in the North Pennines between 1989 and 2006. Results Numbers of males increased from 773 in 1998 to 1029 in 2006. Range increased from 74 occupied 5-km grid squares in 1998 to 93 in 2006. Conclusion The English Black Grouse population is increasing in both numbers and range, but has become fragmented into two subpopulations, one in North Northumberland, the other in the North Pennines.

Impact of nest visits by human observers on hatching success in Lapwings Vanellus vanellus: a field experiment

Capsule Increased nest visits during incubation did not reduce Lapwing clutch survival whereas nesting in pastures with high Black-headed Gull Larus ridibundus abundance did.

Expanding the range of black grouse Tetrao tetrix in northern England through translocating wild males

Black grouse were once widespread in England, but have declined over the past 150 years due largely to habitat changes. In 1998, 773 males remained and following the instigation of conservation measures population size increased to 1029 in 2006, but population range remained similar. We hypothesized that range expansion was limited by the short dispersal ranges of males (up to 1 km) relative to females (up to 19 km), resulting in yearling females dispersing into areas without males. We tested this hypothesis by moving males to establish new leks and to stimulate range expansion. Three release sites were chosen beyond the southern edge of the male range, but were within the perceived dispersal distance of females, and where habitats were considered suitable and generalist predators were controlled. Between 2006 and 2010, 17 males were released at the first site, and a further 18 and 27 respectively at two sites between 2011 and 2014. Males were caught at night, fitted with radio-transmitters and hard released. In the first spring following translocation, 98% of males were observed displaying. Males displayed an average 3.6 km (range 0.6 to 27.1 km) from their release point. Leks were established at all sites, with 14 different leks occupied in spring 2015 contributing to the re-colonisation of seven 10 km grid squares. Mean annual survival in the first year following translocation was 0.77 (0.63–0.86, 95% CL) and was similar to that of birds measured in previous studies in the core northern England range. This suggests that under appropriate circumstances translocation can be a helpful conservation tool in stimulating range expansion.

The extent and impact of shooting on black grouse Tetrao tetrix in northern England

Abstract In northern England, 95% of black grouse Tetrao tetrix leks occur on the fringes of managed grouse moors. Recognising the threatened conservation status of black grouse in northern England, most grouse moors have refrained from deliberate shooting for more than a decade. Despite this, black grouse are unintentionally shot in mistake for red grouse Lagopus lagopus scoticus. We assessed the circumstances and frequency of shooting in northern England and its potential impact on population recovery from three independent sources, annual shooting returns as part of the Game and Wildlife Conservation Trusts (GWCT) National Gamebag Census (NGC), incidents of shooting reported independently to the North Pennines Black Grouse Recovery Project (NPBGRP) and losses of radio-tagged black grouse to shooting. Moors contributing to the NGC between 1998 and 2008 reported 110 black grouse shot from 13 of 23 moors, averaging 1.2% of the estimated post-breeding population. From 2001 to 2008, 152 black grouse from 28 moors were reported shot independently to the NPBGRP, equivalent to an annual 1.0% of the post-breeding population. The majority appeared unintentional (78%), with females (68%) more frequently shot. Out of 244 radio-tagged black grouse on 15 estates, four adult females were shot (1.6%). The voluntary restraint from harvesting black grouse in northern England appears effective, with incidents of shooting infrequent. Continued effort to minimise shooting incidents, particularly on the fringe of the range to encourage settlement of dispersing females, may contribute to increasing numbers and range.