Habitat partitioning in endangered Cantabrian capercaillie Tetrao urogallus cantabricus

The endangered Cantabrian capercaillie (Tetrao urogallus cantabricus) lives at the southern edge of tetraonids’ distribution range, in entirely deciduous forests. Its conservation planning has been always lek-centred. There is very little information about the specific habitat requirements of hens and broods, even though reproductive success appears to be a limiting factor. We analysed summer surveys from 1997 to 2004, carried out to estimate the reproductive success of the population. We compared the habitat characteristics at different spatial scales of hens with broods, broodless hens, and cocks in summer, with the better known spring habitat in display areas. Summer habitat showed higher proportion of open areas and was associated with more rugged zones at moderate spatial scales (78 ha) than spring habitat at display areas. Cocks and hens showed summer habitat partitioning; hens were associated with higher proportions of open and shrubby habitats. Furthermore, broodless hens preferred areas with higher slope variability than the display and summer areas preferred by cocks. These differences may reflect the sexual dimorphism of the species in reproductive role, energetic demands and conspicuousness. At larger spatial scales a previously developed habitat suitability model performed well to predict good brood-rearing areas. Hens with broods were located in the best-preserved areas in the range, mainly characterized by higher proportion of forest cover at a large (50 km²) scale. We suggest that these characteristics indicate refuge habitats where Cantabrian capercaillie can still breed successfully.     

Subspecies Cantabrian capercaillie Tetrao urogallus cantabricus endangered according to IUCN criteria

The Cantabrian capercaillie Tetrao urogallus cantabricus, a subspecies of the western capercaillie, is endemic to the Cantabrian Mountains of northwest Spain. The range is separated from its nearest neighbouring capercaillie population by a distance of more than 300 km. High genetic differentiation compared to capercaillie elsewhere qualifies the subspecies as an Evolutionarily Significant Unit. An assessment according to the IUCN Red List categories and criteria showed that the subspecies qualifies as Endangered due to rapid population declines, small population size, and severely fragmented range. The implementation of a range-wide recovery plan is vital for the survival of this subspecies.     

Habitat and diet of young grouse broods: resource partitioning between Capercaillie (Tetrao urogallus) and Black Grouse (Tetrao tetrix) in boreal forests

We compared habitat use and diets of young Capercaillie and Black Grouse broods in a boreal forest in southeast Norway. We used pointing dogs to search for broods (N = 83) in mature “natural” forest types and examined the crop content of 66 chicks 1–9 weeks old. We also measured the abundance of insects in the habitats where broods were found. Although overlapping substantially in both habitat and diets, there were notable differences: Capercaillie broods were more frequently recorded in bilberry-dominated forest types, whereas Black Grouse preferentially used pine bog forest, a more open habitat with little bilberry. Capercaillie chicks ate proportionally more insects, particularly lepidopteran larvae, and insects dominated their diet for a longer period of time (until age 28–29 days) than in Black Grouse (14–15 days). After reaching their peaks, the quantity of insects in the crops declined rapidly especially in Capercaillie, and in one of 2 years this occurred at a time when insects, including larvae, were still abundant in the habitats. Among plant foods, both species ate large amounts of Bilberry (Vaccinium myrtillus) and Bog Whortleberry (V. uliginosum). The main difference between species was a large proportion of both over-wintered and new, not yet ripe, berries of Cranberry (Oxycoccus quadripetalus) in Black Grouse, and a higher proportion of the forb Melampyrum sylvaticum in Capercaillie. The difference in diets reflected their differential use of habitats; the Vaccinium-preferred habitats of Capercaillie were richer in insects, particularly larvae, than the pine bog habitat preferred by Black Grouse. Because insects, especially larvae, comprised a larger proportion of the diet of Capercaillie chicks and chicks of this species need more food to sustain their rapid growth, Capercaillie is likely to be more sensitive to variation in insect food than Black Grouse. Also, by reducing the abundance of bilberry, the main host plant of larvae chick food, clearcutting forestry has negative effects on the brood habitat quality of both species.     

Genetic diversity, structure and conservation of the endangered Cantabrian Capercaillie in a unique peripheral habitat

Populations at the rear edge of the species’ range are often at a high risk of extinction due to their isolation, fragmentation and small population sizes. However, these populations also play a relevant role in the conservation of biodiversity since they may represent a valuable genetic resource. The endangered Cantabrian Capercaillie (Tetrao urogallus cantabricus) inhabits deciduous forests of the Cantabrian Mountains of Spain, at the southwestern limit of the species’ range. Recently, nine Cantabrian Capercaillie leks were discovered in Pyrenean oak forests of the southern slope of the Cantabrian range, where the subspecies historically occurred. To elucidate if the origin of this peripheral population nucleus is the result of a historical range contraction or a recent re-colonization from the core population, we sampled moulted feathers from all the known leks in the southern peripheral forests and from the adjacent main core population, based on nine microsatellite loci genotypes. No significant genetic differentiation was detected between main core and peripheral forests suggesting that gene flow is not interrupted between these nuclei. Contrary to expected, peripheral forests did not represent sink populations, since gene flow mainly occurred from southern peripheral to northern main core forests. Therefore, the origin of these birds inhabiting the peripheral nucleus seems not to be a recent colonization but relicts from the former distribution range that have remained unnoticed in a drier and warmer environment than described so far for the species. Cantabrian Capercaillie faces a high risk of extinction in the southernmost forests of its distribution, not only because of its peripheral location but also due to its small population size, low genetic diversity and low incoming gene flow. According to our results, this peripheral nucleus could represent an expanding edge for the population if Pyrenean oak forests continue to spread out southwards and consequently stress the need for conservation programs to preserve habitat availability and forest connectivity.     

Vorkommen des Auerhuhns (Tetrao urogallus major C. L. Brehm, 1831) am Athos (Greichenland)

Summary At the Mount Athos the Capercaillie is spread in the montane high forests at an altitude between 1140 m and 1340 m above sea level. This isolated occurrence at the southern boundary of the species area and 140 km to the south of the breeding place in the Rhodope Mountains is the southernmost occurrence recorded so far. In former times, the Capercaillie presumably was widespread in the mountain forests of Central and Northern Greece.     

Infrasound in the capercaillie ( Tetrao urogallus )

We examined the sounds made by displaying male capercaillies on a lek in the Black Forest for infrasonic components. Vocalizations did not contain infrasound, whereas flutter jumps produced substantial low-frequency sound energy, with regularly spaced frequency peaks and maximum energy below 20 Hz. This pattern was found in recordings from different distances and for all tested individuals. Nonvocal infrasound may be significant in territorial behavior or orientation of capercaillie.     

Factors affecting breeding habitat selection in a cliff-nesting peregrine Falco peregrinus population

We studied factors affecting breeding habitat selection in a population of cliff-nesting peregrines Falco peregrinus across multiple spatial levels (cliff site, cliff context and land-use of the surrounding landscape), over a 2,100 km² study area in the Alps (Italy and Switzerland). We detected 30 breeding pairs (density: 1.43 territorial pairs/100 km²), whose territories were uniformly distributed over the study area. We compared 15 habitat features characterising occupied cliffs and 30 randomly selected unoccupied cliffs by means of stepwise forward logistic regression and hierarchical partitioning. The logistic regression analysis showed that occupied cliffs were longer (horizontal length), steeper, and had a greater extension of urban areas in the surrounding landscape compared to non-occupied cliffs. The model had a discrimination ability of 0.95. Hierarchical partitioning indicated that the logistic regression model was appropriate. Neither the distance of cliffs to the nearest site occupied by a potential competitor and predator, the eagle owl Bubo bubo, which occurred at a low density (0.67 pairs/100 km²), nor the distance to the nearest site occupied by peregrines had any effect on the cliff suitability model. Therefore, habitat selection in cliff-nesting peregrines was mainly influenced by cliff site features and surrounding landscape characteristics, whereas the proximity to conspecifics and to an intraguild predator had no apparent effects on peregrine settlement in our study population.     

The bacterial microbiota in the ceca of Capercaillie (Tetrao urogallus) differs between wild and captive birds

The diet of wild capercaillie differs strongly between seasons. Particularly during winter, when energy demands are high and the birds forage solely on coniferous needles, microbial fermentations in the ceca are considered to contribute significantly to the energy requirement and to the detoxification of the resinous diet. Here, we present the first cultivation-independent analysis of the bacterial community in the cecum of capercaillie, using the 16S rRNA gene as a molecular marker. Cloning and fingerprinting analyses of cecum feces show distinct differences between wild and captive birds. While certain lineages of Clostridiales, Synergistetes, and Actinobacteria are most prevalent in wild birds, they are strongly reduced in individuals raised in captivity. Most striking is the complete absence of Megasphaera and Synergistes species in captive capercaillie, which are characterized by a large abundance of Gammaproteobacteria closely related to members of the genus Anaerobiospirillum, bacteria that are commonly connected with intestinal dysfunction. The community profiles of cecum content from wild birds differed between summer and winter season, and the cecum wall may be an important site for bacterial colonization. Our results corroborate the hypothesis that the bacterial community in the ceca of tetraonid birds changes in response to their highly specialized seasonal diets. Moreover, we propose that the observed differences in community profiles between wild and captive capercaillie reflects a disturbance in the bacterial microbiota that compromises the performance of the cecum and may be responsible for the high mortality of captive birds released into nature.     

Infrasound in the flutter jumps of the capercaillie (Tetrao urogallus): apparently a physical by-product

We have tested our assumption that infrasound from flutter jumps of displaying cocks is significant for capercaillie (Tetrao urogallus) orientation. Seven captive females were used for playback experiments during a period when they were extremely disposed to mating and thus expected to respond intensively to signals from males. However, no behavioural response was found, neither to infrasound nor to the audible sound from flutter jumps. We suggest that flutter jumps have only visual functions and that infrasound is nothing but a physical by-product. In large mammals, also, the role of infrasound for communication is as yet uncertain.     

Viability and Management of an Endangered Capercaillie (Tetrao urogallus) Metapopulation in the Jura Mountains, Western Switzerland

The populations of Capercaillie (Tetrao urogallus), the largest European grouse, have seriously declined during the last century over most of their distribution in western and central Europe. In the Jura mountains, the relict population is now isolated and critically endangered (about 500 breeding adults). We developed a simulation software (TetrasPool) that accounts for age and spatial structure as well as stochastic processes, to perform a viability analysis and explore management scenarios for this population, capitalizing on a 24 years-long series of field data. Simulations predict a marked decline and a significant extinction risk over the next century, largely due to environmental and demographic stochasticity (average values of life-history parameters would otherwise allow stability). Variances among scenarios mainly stem from uncertainties about the shape and intensity of density dependence. Uncertainty analyses suggest to focus conservation efforts on enhancing, not only adult survival (as often advocated for long-lived species), but also recruitment. The juvenile stage matters when local populations undergo extinctions, because it ensures connectivity and recolonization. Besides limiting human perturbations, a silvicultural strategy aimed at opening forest structure should improve the quality and surface of available patches, independent of their size and localization. Such measures are to be taken urgently, if the population is to be saved.     

Influence of nesting habitat selection on Mallard (Anas platyrhynchos) nesting success

Summary In the Marismas of the Guadalquivir (SW Spain), the nesting season of the Mallard extends from late January to late May. The relative importance of different nesting habitats changed throughout this period. Nesting habitats primarily used were those in which the nesting success was highest.

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Einfluß des Neststandes auf den Bruterfolg der Stockente (Anas platyrhynchos)

Zusammenfassung Die Brutzeit der Stockente dauert in den Marismas des Guadalquivir (SW-Spanien) von Ende Januar bis Ende Mai. Die relative Bedeutung des Nisthabitats ändert sich während dieser Zeit. Die jeweiligen Neststandorte werden bevorzugt so gewählt, daß der Bruterfolg am höchsten ist.

     

Coexistence of carnivores in a heterogeneous landscape: habitat selection and ecological niches

Understanding distributional patterns and mechanisms used by species for habitat selection is crucial to adopt effective land management policies in terms of biodiversity conservation. A heterogeneous landscape may allow coexistence of species. That coexistence will be dependent on the availability of the resources in the habitat that has to be sufficient to fulfil their basic needs. The present study aimed to investigate habitat selection, niche breadth and niche overlap of three sympatric carnivore species (Vulpes vulpes, Genetta genetta and Martes foina) in a typically fragmented landscape from Central Portugal, using camera-trapping techniques. The results obtained revealed that the investigated species use the available habitats differently and in a non-random way. The red fox showed the most specialized behaviour, positively selecting coniferous forests. The common genet preferred eucalyptus, avoiding old-growth mixed woodland, in contrast with stone marten that exhibited a strong preference for this late habitat, avoiding eucalyptus. Concerning the niche breadth, the genet had the highest value while the red fox had the lowest one. The results obtained at the camera-trap level showed that the highest niche overlap occurred between the genet and the stone marten which suggests that these species can coexist and share the available resources. Regarding the habitat level, the greatest niche overlap was found for the stone marten and the red fox, indicating the exploration of the same general habitat conditions by both species. The results obtained in the present study support the concept that landscape complexity allows coexistence between species within the same trophic level.     

The role of habitat selection behavior in population dynamics: source–sink systems and ecological traps

Ecological traps, poor-quality habitat that nonetheless attract individuals, have been observed in both natural and human-altered settings. Until recently, ecological traps were considered a kind of source–sink system, but source–sink theory does not model maladaptive habitat choice, and therefore cannot accurately represent ecological traps or predict their population-level consequences. Although recent models of ecological traps addressed this problem, they used patch-based models containing only two habitats that were very different from one another, but were internally homogeneous. These sorts of patch models may not apply to many real populations, and using them for populations in landscapes with mosaic or gradient habitat structures may be misleading. I developed models that treat source–sink dynamics and ecological traps as special cases of a single process, in which the attractiveness and quality of the habitat are separate variables that can be either positively or negatively related, and in which habitat quality varies continuously throughout the landscape. As expected, sinks are less detrimental to populations than ecological traps, in which preferential use of poor habitat elevates extinction risk. Furthermore, ecological traps may be undetected, and may even appear to be sources, when population sizes are large, but may still prevent recovery in spite of the availability of high-quality habitat when populations drop below threshold levels. Conservation biologists do not routinely consider the possibility that apparent sinks are actually traps, but since traps should be associated with the rapidly changing and novel habitat characteristics primarily produced by human activities, ecological traps should be considered an important and potentially widespread conservation concern.     

Genetic effects of habitat fragmentation and population isolation on Etheostoma raneyi (Percidae)

The use of genetic methods to quantify the effects of anthropogenic habitat fragmentation on population structure has become increasingly common. However, in today’s highly fragmented habitats, researchers have sometimes concluded that populations are currently genetically isolated due to habitat fragmentation without testing the possibility that populations were genetically isolated before European settlement. Etheostoma raneyi is a benthic headwater fish restricted to river drainages in northern Mississippi, USA, that has a suite of adaptive traits that correlate with poor dispersal ability. Aquatic habitat within this area has been extensively modified, primarily by flood-control projects, and populations in headwater streams have possibly become genetically isolated from one another. We used microsatellite markers to quantify genetic structure as well as contemporary and historical gene flow across the range of the species. Results indicated that genetically distinct populations exist in each headwater stream analyzed, current gene flow rates are lower than historical rates, most genetic variation is partitioned among populations, and populations in the Yocona River drainage show lower levels of genetic diversity than populations in the Tallahatchie River drainage and other Etheostoma species. All populations have negative F_IS scores, of which roughly half are significant relative to Hardy–Weinberg expectations, perhaps due to small population sizes. We conclude that anthropogenic habitat alteration and fragmentation has had a profoundly negative impact on the species by isolating E. raneyi within headwater stream reaches. Further research is needed to inform conservation strategies, but populations in the Yocona River drainage are in dire need of management action. Carefully planned human-mediated dispersal and habitat restoration should be explored as management options across the range of the species.     

Significance of habitat type for the genetic population structure of Panonychus citri (Acari: Tetranychidae)

Restricted migration and habitat fragmentation promote genetic differentiation between populations: Because most of the hosts of Panonychus citri are woody plants, mainly citrus trees that are usually planted at intervals of several metres, this mite likely faces more risks (e.g., starvation) by dispersing between host plants, compared to other spider mite species that infest both herbaceous and woody plants, such as Tetranychus urticae. Such a limited gene flow between patches (host plants) can lead to differentiation of populations even within a small area. Therefore, we hypothesize that P. citri populations are genetically differentiated not only between distant populations but also within small areas, such as within a grove. To test this hypothesis, we investigated the divergence of P. citri populations in Japanese citrus groves according to a hierarchical arrangement of geographical distance, ranging from distant populations (10 groves distributed throughout different areas in two major Japanese islands; this level of analysis is referred to as ‘geographic’) to local populations (different trees in a specific grove; ‘local’). Three molecular markers were used an esterase locus, one microsatellite and a point mutation in the mitochondrial cytochrome oxidase subunit I. At a local level acaricide susceptibility tests were also performed using two acaricides: fenpyroximate (25 ppm) and etoxazole (3.33 ppm). At a broad geographic level the gene diversity decreased with decreasing area size and distance between populations. By contrast, at the local level, populations maintained a significant level of variation between trees within groves, and the divergence within groves was higher than between groves. Whereas no statistical difference of the mortalities was detected among groves for the two acaricides tested, the difference was statistically significant among trees within groves in fenpyroximate (ANOVA, p < 0.025) and=" marginal=" in=" etoxazole="><>p < 0.05). we=" concluded=" that=">P. citri populations maintain a higher level of variation between trees (or patches of trees) within groves than between groves at the local level, though the gene diversity tended to be smaller with decreasing distance between populations at the geographical level. Results are discussed in relation to the dispersal behaviour of spider mites.     

Diet selection by hares (Lepus europaeus) in arable land and its implications for habitat management

Populations of European hares (Lepus europaeus) have experienced a dramatic decline throughout Europe in recent decades. European hares are assumed to prefer weeds over arable crops, and weed abundance was reduced by the intensification of agriculture. Therefore, modern agriculture has been blamed as a major factor affecting European hare populations. However, it is questionable whether European hares select weeds at all, as previous studies had major methodological limitations. By comparing availability and use of plants with Chesson’s Electivity Index, we investigated whether the European hare actually feeds selectively on different plants in arable land. Food availability and use were dominated by cultivated crops (e.g. winter wheat, spring barley and sugar beet). Diet selection analysis revealed that in autumn and winter, European hares predominantly preferred cultivated crops (winter wheat) and food items provided by hunters (tubers of sugar beet and carrot). In spring and summer, apart from soy, only weeds (e.g. clover and corn poppy) were positively selected, especially after cereal crops were harvested. We suggest that the decline in European hare populations throughout Europe was facilitated by the decrease in weed abundance. Wildlife-friendly set-asides in arable land have the potential to reconcile the European Union’s Common Agricultural Policy with wildlife conservation.     

Nest-site habitat selection by Lesser Rheas ( Rhea pennata pennata ) in northwestern Patagonia, Argentina

Selection of nest-site habitat by a population of wild Lesser Rheas (Rhea pennata pennata) was studied in the northwestern Patagonia steppe, Argentina, during two reproductive seasons (2004/2005 and 2005/2006). Nest spatial distribution was compared with randomly selected points in the study area. Contrary to observations in other ratite species, nest distribution showed an aggregate pattern associated with “mallín” (meadow) areas, which are habitats of higher productivity in the Patagonia steppe. Moreover, similar to observations made on the Greater Rhea (Rhea americana), vegetation cover was higher in nest sites than in randomly selected sites, probably because higher vegetation provides concealment from predators and protection from the strong westerly winds that frequent in this region. Our results reinforce the importance of “mallín” areas for the reproduction and conservation of this threatened ratite species.     

Fine-scale population differentiation and gene flow in a terrestrial salamander (Plethodon cinereus) living in continuous habitat

Several recent studies have shown that amphibian populations may exhibit high genetic subdivision in areas with recent fragmentation and urban development. Less is known about the potential for genetic differentiation in continuous habitats. We studied genetic differentiation of red-backed salamanders (Plethodon cinereus) across a 2-km transect through continuous forest in Virginia, USA. Mark-recapture studies suggest very little dispersal for this species, whereas homing experiments and post-Pleistocene range expansion both suggest greater dispersal abilities. We used six microsatellite loci to examine genetic population structure and differentiation between eight subpopulations of red-backed salamanders at distances from 200 m to 2 km. We also used several methods to extrapolate dispersal frequencies and test for sex-biased dispersal. We found small, but detectable differentiation among populations, even at distances as small as 200 m. Differentiation was closely correlated with distance and both Mantel tests and assignment tests were consistent with an isolation-by-distance model for the population. Extrapolations of intergenerational variance in spatial position (sigma(2)<15 m(2)) and pair-wise dispersal frequencies (4 Nm < 25 for plots separated by 300 m) both suggest limited gene flow. Additionally, tests for sex-biased dispersal imply that dispersal frequency is similarly low for both sexes. We suggest that these low levels of gene flow and the infrequent dispersal observed in mark-recapture studies may be reconciled with homing ability and range expansion if dispersing animals rarely succeed in breeding in saturated habitats, if dispersal is flexible depending on the availability of habitat, or if dispersal frequency varies across the geographic range of red-backed salamanders.