We studied the post‐juvenile dispersal of 18 radiotagged juvenile Hazel Grouse Bonasa bonasia (14 males, four females) in an expanding population in the southeastern French Alps between 1998 and 2001. The mean dispersal distances between the capture sites of juveniles in September–October and the centre of the home range in the following spring was 4 km for males (range 0.1–24.9 km) and 2 km for females (range 0.2–5.6 km). The distances recorded for two long‐dispersing males (15 and 24.9 km) are greater than those reported to date for Hazel Grouse. Using our radiotracking data, we interpret the pattern of range expansion that has been occurring since the 1950s around our study area. Barriers to dispersal included rocky ground and other alpine habitats above 2000 m and over 1 km wide, but Hazel Grouse did cross open agricultural land at lower elevation. Two patterns of dispersal movements were recognized in juveniles: erratic movements that led to settlement on or near the natal site, and direct movements to a new range relatively far from the natal area. We discuss the adaptive consequences of these different behaviour patterns.
By use of radio-tracking, we studied hazel grouse Bonasa bonasia in the south eastern French Alps from 1998 to 2002. The Kaplan-Meier annual survival rate of adult males (N = 41) was 0.72 (95% C.I.: 0.59 -0.85), and 0.60 for adult females (N = 15; 95% C.I.: 0.40 -0.91). For juveniles (sexes combined; N = 29) the survival over nine months (15 September-15 June) was 0.74 (95% C.I.: 0.58-0.90). The seasonal pattern of survival was different for the two sexes. Adult male survival during November-April (S = 0.76; N = 38) was lower than dur ing May-October (S = 0.95; N = 41). Only three of 16 male deaths (ages com bined) occurred in summer. Female survival (ages combined) during No vember-April (S = 0.90; N = 16) was higher than during May-October (S = 0.70; N = 16). Five of six females died between May and July, i.e. during egg lay ing, incubation or brood rearing. Raptors, red foxes Vulpes vulpes or pine martens M artes martes accounted for most mortality of adults. The estimated annual survival rates were high compared to those reported for more northern popu lations, and the difference may be due to an extensive, dense and well-structured habitat that reduces the ability of raptors to kill hazel grouse. The high survival rates may explain the range expansion currently occurring in the south eastern French Alps.
Loss, fragmentation and decreasing quality of habitats have been proposed as major threats to biodiversity world-wide, but relatively little is known about biodiversity responses to multiple pressures, particularly at very large spatial scales. We evaluated the relative contributions of four landscape variables (habitat cover, diversity, fragmentation and productivity) in determining different components of avian diversity across Europe. We sampled breeding birds in multiple 1-km 2 landscapes, from high forest cover to intensive agricultural land, in eight countries during 2001−2002. We predicted that the total diversity would peak at intermediate levels of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; forest and open-habitat specialists would show threshold conditions along gradients of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; resident species would be more strongly impacted by forest cover and fragmentation than migratory species; and generalists and urban species would show weak responses. Measures of total diversity did not peak at intermediate levels of forest cover or fragmentation. Rarefaction-standardized species richness decreased marginally and linearly with increasing forest cover and increased non-linearly with productivity, whereas all measures increased linearly with increasing fragmentation and landscape diversity. Forest and open-habitat specialists responded approximately linearly to forest cover and also weakly to habitat diversity, fragmentation and productivity. Generalists and urban species responded weakly to the landscape variables, but some groups responded non-linearly to productivity and marginally to habitat diversity. Resident species were not consistently more sensitive than migratory species to any of the landscape variables. These findings are relevant to landscapes with relatively long histories of human land-use, and they highlight that habitat loss, fragmentation and habitat-type diversity must all be considered in land-use planning and landscape modeling of avian communities.
Habitat suitability models (HSMs) are widely used to plan actions for species of conservation interest. Models that will be turned into conservation actions need predictors that are both ecologically pertinent and fit managers’ conceptual view of ecosystems. Remote sensing technologies such as light detection and ranging (LiDAR) can describe landscapes at high resolution over large spatial areas and have already given promising results for modeling forest species distributions. The point‐cloud (PC) area‐based LiDAR variables are often used as environmental variables in HSMs and have more recently been complemented by object‐oriented (OO) metrics. However, the efficiency of each type of variable to capture structural information on forest bird habitat has not yet been compared. We tested two hypotheses: (1) the use of OO variables in HSMs will give similar performance as PC area‐based models; and (2) OO variables will improve model robustness to LiDAR datasets acquired at different times for the same area. Using the case of a locally endangered forest bird, the capercaillie (Tetrao urogallus), model performance and predictions were compared between the two variable types. Models using OO variables showed slightly lower discriminatory performance than PC area‐based models (average ΔAUC = −0.032 and −0.01 for females and males, respectively). OO‐based models were as robust (absolute difference in Spearman rank correlation of predictions ≤ 0.21) or more robust than PC area‐based models. In sum, LiDAR‐derived PC area‐based metrics and OO metrics showed similar performance for modeling the distribution of the capercaillie. We encourage the further exploration of OO metrics for creating reliable HSMs, and in particular testing whether they might help improve the scientist–stakeholder interface through better interpretability.
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