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SUMMARYHuman endogenous retroviruses (HERVs) are a significant component of a wider family of retroelements that constitute part of the human genome. These viruses, perhaps representative of previous exogenous retroviral infection, have been integrated and passed through successive generations within the germ line. The retention of HERVs and isolated elements, such as long-terminal repeats, could have the potential to harm. In this review we describe HERVs within the context of the family of known transposable elements and survey these viruses in terms of superantigens and molecular mimics. It is entirely possible that these mechanisms provide the potential for undesired immune responses.

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 high er 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 spe cies recovery and range expansion in relation to habitat fragmentation at both the local and regional levels.

Summary 1.The maintenance or modification of grazing regimes is frequently advocated to deliver conservation targets in pastoral landscapes, but there are few quantitative studies of the effects of grazing on upland birds. This is particularly true with respect to grazing management in agri-environment schemes. 2. Numbers of black grouse Tetrao tetrix and their breeding success were therefore monitored at 20 sites in the north of England from 1996 to 2000. Ten treatment sites included areas where grazing was reduced before and during the study to < 1·1 sheep ha − 1 in summer and < 0·5 sheep ha − 1 in winter. Each was paired with a reference site that held sheep at two (summer) to three times (winter) the density on the experimental sites. The reduced grazing sites ranged from 0·4 to 3·2 km 2 in size and most were part of existing agreements within agri-environment schemes that had been in place for 1-5 years before 1996. 3. Numbers of black grouse males displaying increased by an average of 4·6% (SE = 2·1) year − 1 at the 10 sites with reduced grazing. Displaying male trends differed significantly between treatment and normally grazed reference sites, where numbers declined annually on average by 1·7% (SE = 1·4). 4. Summer black grouse hen densities showed the greatest rate of increase where grazing was restricted on smaller areas of ground (0·4 km 2 ). Declines occurred at sites where the area of restricted grazing exceeded about 1 km 2 . The rates of change in population density, as indicated by numbers of displaying males, peaked in the early years of grazing reduction and then declined after c. 5-7 years. 5. The proportion of females that retained broods during the late chick-rearing period was 54% (SE = 0·06) at sites with reduced grazing, significantly greater than the 32% (SE = 0·06) at normally grazed reference sites. There was no difference in the size of broods between grazing treatments. 6. This study demonstrates that agri-environment schemes, which encourage extensive management of grazing land, can benefit at least some organisms of conservation importance and lead to some recovery of populations. There is a need, however, for further understanding of how such benefits can be maintained at a landscape scale and over the greater time scales involved in vegetation dynamics and bird population processes.

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