Laurence N. Ellison’s research while affiliated with Office National de la Chasse et de la Faune Sauvage and other places

We examined seasonal movements of radio-marked Black Grouse (Tetrao tetrix) in the southern French Alps during 1990-1996. Many hens migrated between summer and winter ranges, whereas males exhibited strong attachment to a single area. Average distance traveled from the winter range to the summer range differed significantly according to sex (males: 1.5 km, females: 2.95 km), and age (yearlings: 4 km, adults: 1.36 km). Birds of all ages displayed strong site fidelity to winter and summer areas. We found no statistical difference between median date of fall dispersal of juveniles (26 October) and median date of migration of birds older than 12 months from summer to winter areas (19 October). Similarly, spring dispersal of yearlings and spring migration of adults from their winter area occurred at the same time (14 April vs. 18 April). Furthermore, dates of movements, including dispersal, were highly repeatable for a given individual. Thus, timing of movements along with data on site fidelity support the view that dispersal and migration are tightly linked in Black Grouse. This is the first study in any Eurasian grouse species demonstrating that migratory movements of adults retrace the spring dispersal route taken when they were 9-11 months old.

Understanding the effects of climate on avian life history traits is essential if we wish to predict the demographic consequences of expected climatic changes. We investigated the influence of weather conditions on the reproductive success of Rock Ptarmigan Lagopus muta in the eastern French Pyrenees, one of the southernmost areas inhabited by the species. Reproductive success was estimated in early August between 1997 and 2006 by counting adults and well-grown chicks with pointing dogs. The number of young per adult varied from 0.08 to 0.72. Using Poisson regression and Akaike's information criterion, we selected the best model explaining the effect of weather (date of snowmelt and, for both laying/incubation and post-hatching periods, mean minimum and maximum temperatures, monthly rainfall and number of days with rain) on the proportion of young in August. Reproductive success was positively associated with early appearance of snow-free ground, and date of snowmelt alone was the model that best explained annual variation in reproductive success. Other models, which included a negative effect of rainfall, particularly after hatching, also had some support. Hence, both pre-laying and post-hatching weather conditions influenced reproductive success of Rock Ptarmigan in the eastern French Pyrenees. On a continental scale, reproductive success of alpine populations of Rock Ptarmigan is consistently lower than that of northern populations. This difference in productivity may be partly correlated with climatic conditions observed along an arctic–alpine gradient, the amount and variation of rainfall being greater in southern alpine areas than elsewhere in the species’ range.

Understanding the effects of climate on avian life history traits is essential if we wish to predict the demographic consequences of expected climatic changes. We investigated the influence of weather conditions on the reproductive success of Rock Ptarmigan Lagopus muta in the eastern French Pyrenees, one of the southernmost areas inhabited by the species. Reproductive success was estimated in early August between 1997 and 2006 by counting adults and well-grown chicks with pointing dogs. The number of young per adult varied from 0.08 to 0.72. Using Poisson regression and Akaike's information criterion, we selected the best model explaining the effect of weather (date of snowmelt and, for both laying/ incubation and post-hatching periods, mean minimum and maximum temperatures, monthly rainfall and number of days with rain) on the proportion of young in August. Reproductive success was positively associated with early appearance of snow-free ground, and date of snowmelt alone was the model that best explained annual variation in reproductive success. Other models, which included a negative effect of rainfall, particularly after hatching, also had some support. Hence, both pre-laying and post-hatching weather conditions influenced reproductive success of Rock Ptarmigan in the eastern French Pyrenees. On a continental scale, reproductive success of alpine populations of Rock Ptarmigan is consistently lower than that of northern populations. This difference in productivity may be partly correlated with climatic conditions observed along an arctic-alpine gradient, the amount and variation of rainfall being greater in southern alpine areas than elsewhere in the species' range.

We compared the body mass of adult rock ptarmigan Lagopus mutus shot in autumn in the French Pyrenees (Ariège), the French Alps (Hautes-Alpes) and the Italian Alps (Province of Verbania). Mean body mass of adults was greater in the Ariège than in the Hautes-Alpes both for cocks (466 vs 433 g) and hens (429 vs 406 g), with the body mass of Italian birds being intermediate (cocks 448 g, hens 418 g). The relatively large mass of rock ptarmigan in the Pyrenees contrasts with the geographic trends found in capercaillie Tetrao urogallus and grey partridge Perdix perdix in France. For the last two species, birds in the Pyrenees are smaller than those further north. The site differences that we observed in body mass of rock ptarmigan may be related to differences in availability of high quality foods, particularly ericaceous shrubs. However, at the continental scale within Europe, the body mass of rock ptarmigan appears to be greatest in northern latitudes.

Faune Sauvage n°265 /mars 2005 Comprendre comment les populations sont organisées dans l'espace est essentiel dans une perspective de gestion. Les études réalisées par le CNERA Faune de montagne de l'ONCFS sur le Tétras-lyre et le Lagopède alpin permettent de mieux cerner l'intérêt et les limites de l'outil moléculaire dans le cadre de cette problématique. Elles montrent comment et pourquoi deux espèces écologiquement proches peuvent néanmoins présenter des structures génétiques profondément différentes à des échelles spatiales emboîtées.

We investigated the association of habitat fragmentation with genetic structure of male black grouse Tetrao tetrix. Using 14 microsatellites, we compared the genetic differentiation of males among nine localities in continuous lowland habitats in Finland to the genetic differentiation among 14 localities in fragmented habitats in the Alps (France, Switzerland and Italy). In both areas, we found significant genetic differentiation. However, the average differentiation, measured as theta, was more than three times higher in the Alps than in Finland. The greater differentiation found in the Alps is probably due to the presence of mountain ridges rising above natural habitats of the species, which form barriers to gene flow, and to a higher influence of genetic drift resulting from lower effective sizes in highly fragmented habitats. The detection of isolation by distance in the Alps suggests that gene flow among populations does occur. The genetic variability measured as gene diversity HE and allelic richness A was lower in the Alps than in Finland. This could result from the higher fragmentation and/or from the fact that populations in the Alps are isolated from the main species range and have a lower effective size than in Finland. This study suggests that habitat fragmentation can affect genetic structure of avian species with relatively high dispersal propensities.

Alpine species may be losing habitat because of global warming. Setting management priorities for such species is thus urgent and cannot be achieved without data on population structure. We studied the structure of rock ptarmigan (Lagopus mutus) populations in the Pyrenees, Alps and Norway, using six microsatellites. We found that rock ptarmigan in the Pyrenees were genetically impoverished compared with those in the Alps and Norway, and displayed a greater divergence (Pyrenees vs. Alps or Norway: theta(ST) = 0.16, Alps vs. Norway, theta(ST) = 0.04). In the Alps, despite a weak genetic differentiation between localities up to 200 km apart (theta(ST) = 0.011), a significant isolation-by-distance (IBD) effect was detected. When computed for each sex separately this IBD effect was significant for males but not for females, suggesting that males are highly philopatric.

Data on dispersal distances of juveniles are important for understanding the genetic structure of populations, population regulation processes and the effects of landscape ecology on metapopulation dynamics. We studied dispersal in juvenile Black Grouse Tetrao tetrix in the French Alps between 1990 and 1998, by radiotracking 39 young grouse captured in August or autumn in a study area of 836 ha. Natal dispersal occurred in two discrete phases, autumn (October) and spring (mid-April to early May), with periods of reduced mobility between. The mean distance travelled by females exceeded that of males in autumn but not in spring. The natal dispersal distance of females was greater than that of males, and resulted in 81% of females leaving the study area to nest 5–29 km from their site of capture. This emigration must have been compensated for by immigrants because the number of hens in the study area increased during the study. Males were more philopatric. By the summer after capture, only 9% had emigrated from the study area. Despite the longer dispersal distances of females, there was no difference in the survival functions of the sexes between the ages of 6 weeks and 13 months.

Allelic variation at eight microsatellite loci was used to assess the levels of genetic differentiation between seven natural populations of black grouse (Tetrao tetrix) in the French Alps spaced along a 250 km south-north transect. Whatever the population or locus, genotype frequencies did not deviate significantly from expected Hardy-Weinberg frequencies and no significant between-locus linkage desequilibrium was detected. Observed levels of genotypic variation were statistically significant with maximum Fst values reaching 10% for the most distant populations (250 km). An isolation-by-distance effect was detected suggesting, as expected from data on marked birds, that black grouse populations in the French Alps are interconnected by dispersal.