Spring density and summer habitat use of alpine rock ptarmigan Lagopus muta helvetica in the southeastern Alps

In the Alps tourism, land-use practices and climate change may cause a loss of suitable habitat of rock ptarmigan (Lagopus muta helvetica). Hence, there is a need for basic research on population densities and habitat requirements of this species as a basis for long-term monitoring studies. So far, in the Austrian Alps, no accurate data on densities and trends of rock ptarmigan populations are available. We carried out counts of calling cocks in the southeastern part of the Austrian Alps (Nockberge National Park, Carinthia, Austria) between 31 May and 1 July 2003 and evaluated the distribution of male rock ptarmigan territories. The spring density of 5.4 territorial cocks per square kilometre was similar to densities in the Swiss Alps but higher than spring population densities in the Italian Alps and the Pyrenees. To investigate summer habitat use, we established a grid mapping of habitat parameters and rock ptarmigan signs. In total, 38 squares with signs of rock ptarmigan presence were recorded (i.e. 32% of all recorded squares). The presence of rock ptarmigan was significantly correlated with cover of rock and rock ptarmigan preferred habitat patchiness. Our study provides a useful reference for future monitoring of this species in the alpine distribution range considering the potential decrease and fragmentation of alpine habitats resulting from climate change and human impacts.     

Combs and sexual selection in black grouse (Tetrao tetrix)

We studied supra-orbital combs in lekking black grouse (Tetrao tetrix) in relation to sexual selection at five leks in Finland1991-1998 and four leks in Sweden 1992-1995. Comb size wasestimated in two ways: by observing its natural size in thefield at different behaviors ("observed comb size"), and bymeasuring the comb size from captured birds ("measured combsize"). The size of combs is highly variable, and individualscan change it within seconds. Males express their larger combsduring display, as compared to other behaviors. Observed mean comb sizes were larger on leks with a higher number of malesand a higher number of copulations. Measured and observed combsizes and copulatory success did not significantly correlatewhen all males where analyzed, but a positive and significantrelationship between observed comb size and copulatory success was found within males that achieved copulations. Measured comblength correlated positively with the amount of testosterone.While females were present on the lek, displaying and successfulmales showed the largest observed comb size. When we comparedobserved comb size during fighting between successful and unsuccessfulmales and correlated comb size of pairs of fighting males withtheir fighting activity, no significant differences in combsize were found. The result that comb size correlated significantlywith an increase in testosterone level and that larger combsize, within successful males, predicted higher copulatorysuccess suggests that combs may be a cue for females to assessmale quality. The lack of a significant relationship betweenobserved comb size and fighting behavior suggests that combsize either has minor importance in male-male signaling onthe lek or that males may express similar-sized combs duringfighting to avoid serious fights and thus risk of comb injuries.     

Locomotor development in the Svalbard rock ptarmigan (Lagopus muta hyperborea)

Juvenile animals often suffer from high levels of predation. Development of an effective and efficient locomotor system is therefore likely to be crucial towards ensuring their survival. However, our understanding of locomotor efficiency, at least in terms of energetic cost in young animals is poor. We performed this study as Svalbard rock ptarmigan, Lagopus muta hyperborea must rapidly develop the ability to locomote prior to the onset of their first winter, during which conditions are extreme. To aid survival, adult ptarmigan deposit large winter fat stores, whilst at the same time males exhibit a reduced metabolic cost of locomotion. Sub-adult males, however, are unable to fully acquire fat stores during their first winter and the maturity of their locomotor systems is unknown. Here, we investigate the energetics and kinematics of terrestrial locomotion in sub-adult male birds using flow-through respirometry and high-speed video recordings, respectively. We demonstrate that in terms of running speed and metabolic cost, sub-adult ptarmigan develop a mature functioning locomotor system prior to the onset of winter. This research indicates that achieving a mature locomotor system allows young males to emerge from the winter with the ability to compete for territories and mates during the breeding season.     

Queuing for territory positions in the lekking black grouse (Tetrao tetrix)

The importance of a central territory position as a determinantof male mating success in lekking species has been debated.The process by which a male can obtain a central territory hasbeen especially lacking a quantitative analysis. We presenta stochastic queuing model describing territory succession towardthe lek center and apply it to a 8-year sequence of territorycentrality measures on a black grouse Tetrao tetrix lek. Thelek shows a value of intermediate queue discipline, which deviatessignificantly both from strict orderly queuing and from randomranking of males. Thus, high-ranking males are partly able tomaintain their superior position over years, but queue-jumpingis not excluded; especially because highly succesful males donot attempt to change their territory position toward the lekcenter. As a result of stochastic queuing, a central territoryindicates an older than average male, as well as a male witha history of high fighting rates. These results are consistentwith the hypotheses that territory position is an honest signalof male quality and that the long-term fighting effort and survivalrequired to acquire a central territory may increase the reliabilityof the signal over that of short-term display effort. The impartialqueue discipline, however, also leaves room for other male characteristicsto play a role in determining individual mating success.     

Physiological costs enforce the honesty of lek display in the black grouse (Tetrao tetrix)

Females may use condition-dependent sexual traits as reliable cues of male “quality” if the costs of the expression of such traits vary with male “quality”, and if there is positive genetic correlation between male traits and condition. However, there are multiple ways of measuring the changes in body condition which reflect physiological costs meaning that the multifaceted nature of the physiological costs associated with the expression of sexual traits has rarely been thoroughly examined. In the lekking black grouse (Tetrao tetrix), mating success is highly skewed towards males defending central territories and having high survival rates to the following year, but the mechanisms underpinning such superior performance remain unclear. In this study, we quantified the changes in five measures of body condition before and after the mating season and related these changes to male lek performance (fighting rate, territory centrality and mating success) to understand the physiological costs of male reproductive effort. Between the two capture sessions, male body mass decreased significantly, blood parasite counts and plasma carotenoid concentration increased substantially while the total immunoglobulin concentration tended to increase. There was no overall impairment of individual body condition as the changes in the five measures of body condition were unrelated. Male fighting rate was unrelated to changes in the condition measures but males losing more body mass defended central territories and had high mating success. Therefore, females preferring central, dominant males may select males better able to afford the energetic costs of lek performance thereby effectively enforcing the honesty of male display.     

Reduced metabolic cost of locomotion in Svalbard rock ptarmigan (Lagopus muta hyperborea) during winter

The Svalbard rock ptarmigan, Lagopus muta hyperborea experiences extreme photoperiodic and climatic conditions on the Arctic archipelago of Svalbard. This species, however, is highly adapted to live in this harsh environment. One of the most striking adaptations found in these birds is the deposition, prior to onset of winter, of fat stores which may comprise up to 32% of body mass and are located primarily around the sternum and abdominal region. This fat, while crucial to the birds' survival, also presents a challenge in that the bird must maintain normal physiological function with this additional mass. In particular these stores are likely to constrain the respiratory system, as the sternum and pelvic region must be moved during ventilation and carrying this extra load may also impact upon the energetic cost of locomotion. Here we demonstrate that winter birds have a reduced cost of locomotion when compared to summer birds. A remarkable finding given that during winter these birds have almost twice the body mass of those in summer. These results suggest that Svalbard ptarmigan are able to carry the additional winter fat without incurring any energetic cost. As energy conservation is paramount to these birds, minimising the costs of moving around when resources are limited would appear to be a key adaptation crucial for their survival in the barren Arctic environment.     

Evidence for energy savings from aerial running in the Svalbard rock ptarmigan (Lagopus muta hyperborea)

Svalbard rock ptarmigans were walked and run upon a treadmill and their energy expenditure measured using respirometry. The ptarmigan used three different gaits: a walking gait at slow speeds (less than or equal to 0.75 m s(-1)), grounded running at intermediate speeds (0.75 m s(-1) < U < 1.67 m s(-1)) and aerial running at high speeds (greater than or equal to 1.67 m s(-1)). Changes of gait were associated with reductions in the gross cost of transport (COT; J kg(-1) m(-1)), providing the first evidence for energy savings with gait change in a small crouched-postured vertebrate. In addition, for the first time (excluding humans) a decrease in absolute metabolic energy expenditure (rate of O(2) consumption) in aerial running when compared with grounded running was identified. The COT versus U curve varies between species and the COT was cheaper during aerial running than grounded running, posing the question of why grounded running should be used at all. Existing explanations (e.g. stability during running over rocky terrain) amount to just so stories with no current evidence to support them. It may be that grounded running is just an artefact of treadmill studies. Research investigating the speeds used by animals in the field is sorely needed.     

Effect of suboptimal environment and host age on helminth community of black grouse (Tetrao tetrix)

Helminths have often been considered responsible in driving partially wildlife population density fluctuations; therefore more information have to be achieved when target hosts are endangered or threatened species, such as black grouse (Tetrao tetrix). During 8 years (2003–2010), we collected and analyzed 431 intestinal contents of hunted black grouse from Central Alps (Verbania), recording age, body weights, biometric measures, and the culling site to investigate (1) their helminth community structure, (2) how much infection varies in relation to age class and to prealpine and alpine origin area, and (3) if parasites may act as population destabilizing factors. The helminth community is composed by two nematodes Ascaridia compar and Aonchotheca caudinflata. A. compar is the predominant species, and a significant higher intensity of both helminths is recorded in juveniles. A. caudinflata has a negative effect on weights of all the population subjects (p?<?0.001), independently of age and origin area. Prealpine population, characterized by significantly lower weights than those of the alpine ones (p?<?0.05), is found more infected by both helminths, with also a negative impact (p?<?0.001) of A. compar recorded on prealpine adults’ weights. The negative effect noticed for A. caudinflata emphasizes its pathogenicity and shows that this infection can be considered a further stressor for the studied population. Moreover, A. compar affects essentially adults in prealpine area and this fact, together with the major infection of the entire prealpine population, supports the hypothesis that habitat characteristics play a role in the infectious process.     

Female‐biased dispersal alone can reduce the occurrence of inbreeding in black grouse (Tetrao tetrix)

Although inbreeding depression and mechanisms for kin recognition have been described in natural bird populations, inbreeding avoidance through mate choice has rarely been reported suggesting that sex‐biased dispersal is the main mechanism reducing the risks of inbreeding. However, a full understanding of the effect of dispersal on the occurrence of inbred matings requires estimating the inbreeding risks prior to dispersal. Combining pairwise relatedness measures and kinship assignments, we investigated in black grouse whether the observed occurrence of inbred matings was explained by active kin discrimination or by female‐biased dispersal. In this large continuous population, copulations between close relatives were rare. As female mate choice was random for relatedness, females with more relatives in the local flock tended to mate with genetically more similar males. To quantify the initial risks of inbreeding, we measured the relatedness to the males of females captured in their parental flock and virtually translocated female hatchlings in their parental and to more distant flocks. These tests indicated that dispersal decreased the likelihood of mating with relatives and that philopatric females had higher inbreeding risks than the actual breeding females. As females do not discriminate against relatives, the few inbred matings were probably due to the variance in female dispersal propensity and dispersal distance. Our results support the view that kin discrimination mate choice is of little value if dispersal effectively reduces the risks of inbreeding.     

Forest fragmentation due to agriculture affects the reproductive success of the ground-nesting black grouse Tetrao tetrix

We used data from the Finnish wildlife triangle censuses (1989-92) to test the prediction that the reproductive success of ground-nesting bird species is lowered in forest landscapes fragmented by the occurrence of agricultural land, presumably as a consequence of increased densities of generalist predators Our study was based on 201 wildlife triangles located in central Finland (total length 2412 km) As expected, the proportion of black grouse hens with a brood in August decreased relative to the increasing proportion of agricultural land in a landscape (100 km²) However, on a smaller spatial scale (10 8 km²), the probability of an observed hen being with a brood was higher in the vicinity of fields This finding may be explained by differences in habitat selection between hens with a brood and those without a brood We did not find any negative effect of landscape composition on brood size We conclude that increased predation pressure in forest landscapes fragmented by agriculture affects nesting success, but not the survival of black grouse chicks after hatching Our results also emphasize the importance of spatial scale in studies of landscape ecology     

Spacing behaviour and habitat use of rock ptarmigan (Lagopus mutus) at low density in the Italian Alps

Studies of rock ptarmigan Lagopus mutus in northern latitudes have shown that, in the breeding season, the majority of cocks pair monogamously and defend small territories, whilst in most populations, a small proportion of cocks are polygynous or remain unmated. Little is known, however, on spacing behaviour and habitat use of alpine rock ptarmigan populations occurring at low densities at the southern edge of the species’ range. From 1995 to 1997, we trapped, radio-tracked and observed birds in the Central Italian Alps (elevation 2,000–3,000 m) in order to investigate spacing behaviour and habitat use in alpine landscapes where habitats offering rich food and cover are patchy. Both sexes were selective in their habitat use, and cocks did not establish territories on bare ground, artificial or nutrient rich grasslands or bogs. In the breeding season, cocks had larger home ranges than hens (cocks 99 ± 57 ha, hens 50 ± 25 ha) that overlapped with the ranges of neighbouring cocks and hens. Cocks were monogamous and defended relatively large territories (core areas of home ranges: cocks 37 ± 26 ha, hens 24 ± 12 ha), which corresponded with low spring densities (0.47–2.29 cocks km⁻² and 0.35–1.60 pairs km⁻²). Territory size of individual cocks was negatively correlated with the amount of high quality habitat in the core-area. Our results suggest increased home ranges and large breeding territories in low density alpine rock ptarmigan populations, compared to populations occurring at higher densities in the central and northern alps, and on subarctic and arctic grounds at northern latitudes, confirming the predictions of models on food-based territoriality.     

Genetic impoverishment of the last black grouse (Tetrao tetrix) population in the Netherlands: detectable only with a reference from the past

We have studied a small isolated population of black grouse (Tetrao tetrix) in the Netherlands to examine the impact of isolation and reduction in numbers on genetic diversity. We compared the genetic diversity in the last extant Dutch population with Dutch museum samples and three other black grouse populations (from England, Austria and Norway, respectively) representing isolated and continuous populations. We found significantly lower allelic richness, observed and expected heterozygosities in the present Dutch population compared to the continuous populations (Austria and Norway) and also to the historical Dutch population. However, using a bottleneck test on each population, signs of heterozygosity excess were only found in the likewise isolated English population despite that strong genetic drift was evident in the present Dutch population in comparison to the reference populations, as assessed both in pairwise F(ST)and STRUCTURE analyses. Simulating the effect of a population reduction on the Dutch population from 1948 onwards, using census data and with the Dutch museum samples as a model for the genetic diversity in the initial population, revealed that the loss in number of alleles and observed heterozygosity was according to genetic drift expectations and within the standard error range of the present Dutch population. Thus, the effect of the strong decline in the number of grouse on genetic diversity was only detectable when using a reference from the past. The lack of evidence for a population reduction in the present Dutch population by using the program bottleneck was attributed to a rapidly found new equilibrium as a consequence of a very small effective population size.     

Leucocytozoon lovati infections in wild rock ptarmigan (Lagopus mutus) in Japan

Leucocytozoon lovati infections were detected in free-flying rock ptarmigan (Lagopus mutus), an endangered species that inhabits alpine areas in Japan. Eight of nine adult birds tested positive for L. lovati infection. For comparison, two captive rock ptarmigans hatched in a breeding facility at the foot of the mountains were examined. Both were negative for L. lovati infection. This is the first report of L. lovati infection in the rock ptarmigan in Japan.     

The habitat use and diet of Black Grouse Tetrao tetrix in the Pennine hills of northern England

The habitat and dietary preferences of Black Grouse were studied from 1989 to 1991 in a largely treeless habitat within a 17 km² area of the Pennine hills of northern England using radiotelemetry. Grassland habitats were preferred by 84% of 19 birds for much of the year and heather moorland was selected in winter; the other birds, all females, remained in heather habitats all year. Most females reared broods in damp, rushy grass moorlands, but one of six broods used hay fields. Diet closely reflected seasonal plant availability in selected habitats and the leaves, flowers, fruits and seeds of a wide variety of plants were eaten. Cotton-grass Eriophorum vaginatum was important in spring, grassland herbs, grasses, sedges and rushes in summer and autumn and Ling Heather Calluna vulgaris in late autumn and winter. Males fed substantially more on heather in winter than females which partially replaced heather in their diet with the leaves of grasses and herbs. Young chicks showed considerable preference for Sawfly (Symphyta) larvae. Suggested management recommendations include the regulation of sheep-grazing, encouragement of wet flush areas and the late cutting of hay fields.     

Effects of density on lek-site selection by Black Grouse Tetrao tetrix in the Alps

Capsule: The Black Grouse is a primarily lekking species, but low population density and lack of suitable habitat can lead to the establishment of non-lekking populations.

Aims: To understand if differences in density could be related to differences in the lekking system, if there were differences in lek-site selection, and if there was a direct effect of habitat on the lek size.

Methods: We compared lek sizes between two Black Grouse populations with different male population densities as estimated by distance sampling. We considered land-cover categories, landscape metrics and orographic variables and computed the Ivlev’s Electivity Index to evaluate habitat selection of males in the two study areas. A general linear model was used to assess the relationship between lek size and habitat variables.

Results: We could not demonstrate the direct effect of density on the displaying behaviour but we found strongly different patterns of lek-site selection and different effects of habitat on lek size according to the population density.

Conclusions: We concluded that habitat normally considered as high quality and habitat complexity may play different roles in selection by solitary versus lekking males when different population densities are considered.     

Spring densities and calling activities of Rock Ptarmigan ( Lagopus muta helvetica ) in the Austrian Alps

According to the European Bird Directive (Council Directive 79/409/EEC of 2 April 1979 on the conservation of wild birds), particular efforts must be made to preserve the Rock Ptarmigan (Lagopus muta helvetica) and its habitats. Protection and management of this species require basic knowledge of the current status of each of its populations. Within the Austrian distribution range of Rock Ptarmigan, only two study sites from the inner parts of the Alps have been investigated and no data on the most eastern pre-alpine populations are available. In the present study, we conducted simultaneous counts of calling Rock Ptarmigan cocks and recorded calling activities. We calculated spring densities for alpine and pre-alpine study areas and compared them. Spring densities for different habitat types in one study area were observed and compared. Spring densities and calling activities differed between study sites, even within the most eastern border of distribution. Generally, spring densities seem to be higher in alpine habitats than in pre-alpine study sites. In one alpine study area, the highest spring densities were found for habitat patches with a heterogeneous mixture of rocky surface and dwarf pine.     

Modelling habitat use of Tetrao urogallus L. in Austria for conservation issues

Loss and deterioration of habitats are major threats for Tetrao urogallus in central Europe, where forests are highly fragmented and forest practices have distinctly changed during the last decades. Habitat models are important tools for conservation planning, often relying on presence–absence data. We mapped indirect signs of Tetrao urogallus presence as well as habitat variables over a series of seven study areas in the Austrian Alps, situated on limestone and on silicate rock. We modelled habitat use of Tetrao urogallus with one parametric approach (binary logistic regression) and two machine learning classification algorithms (classification trees and random forests) for both geological substrata separately. All three modelling approaches performed equally well in terms of accuracy or predictive power, but differed in model calibration. Three variables significantly contributed to all three habitat models on limestone and on silicate substrate, respectively, i.e. the cover of field-layer, the cover of dwarf shrubs and the proportion of deciduous trees in forest stands on limestone and the cover of field-layer, the canopy cover and the occurrence of Abies alba and/or Pinus sylvestris in forest stands on silicate rock. Some variables like the cover of Rubus sp. appeared in several models, which are not frequently mentioned in other studies. There have been some explanatory variables, which would have been missed, when applying just one single modelling approach, for example the occurrence of forest edges, the availability of canopy gaps and the supply of ant hills. Our results suggest differing habitat management strategies on limestone and on silicate rock. Considering the large spatial requirements of Tetrao urogallus the necessity of active habitat management for Tetrao urogallus becomes obvious.