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Biological research on birds of the grouse family has become increasingly related to conservation. We review trends in grouse biology, analysing the representation of species and topics in the titles of 2,788 papers published since 1930. Ruffed grouse Bonasa umbellus, the most frequently studied species before 1960, was overtaken by willow ptarmigan Lagopus lagopus in the 1970s, after which black grouse Tetrao tetrix and capercaillie Tetrao urogallus became increasingly popular until they were the most-studied species in the 2000s. The new focus on conservation ecology involves increased interest in the topics of threatened taxa, genetics and conservation. A new appreciation of the role of large, landscape-scale processes in population dynamics and conservation management is shown by an increase in publications on landscape ecology and habitat, enabled by technical advances in telemetry, genetics and mapping systems. Meanwhile, the number of papers on disease, diet, behaviour and reproduction has declined. The topics of climate change, human disturbance and pollution had few hits, but we anticipate that interest in them will increase as the current emphasis on conservation continues. This may well involve improved genetic and GIS techniques for determining dispersal patterns, habitat connectivity and population viability, along with a better understanding of how grouse survive their predators and other enemies. Better communication of experiences in management for grouse conservation is needed.
The impact of waterfowl harvest on the dynamics of duck populations remains incompletely understood. While wide-scale monitoring and management programs have been set up in North America, far less has been done in Europe where populations and harvest are essentially managed at country level with a sole focus on population size. Hence, comparing North American waterfowl populations with European waterfowl populations could be useful in suggesting flyway-scale management options in Europe. In our paper, we analyse historical capture-recapture-recoveries data for the European teal Anas crecca crecca and we compare the computed survival and harvest rates to those obtained from a North American recovery data set for the green-winged teal Anas crecca carolinensis, its sister taxon. During 1960-1976, the annual probability of survival was slightly lower in Europe (average over sexes: 0.485 ± 0.101) than in North America (0.545 ± 0.010 for both sexes). Assuming a 30% ring reporting rate, our estimate of the annual harvest rate was about three times higher in Europe (average over sexes: 0.178 ± 0.051) than in North America (average over sexes: 0.071 ± 0.014). Although the European population increased over the study period and continues to do so, such a hunting pressure may potentially reduce our flexibility in managing this population due to uncertainties such as environmental changes, and have deleterious effects in the long term. We use our results to discuss waterfowl research and management in Europe. Initiating studies to estimate ring reporting rate would be an essential first step to properly evaluate the impact of harvest on the dynamics of the teal population in Europe.
We studied the factors that determine the presence of the cinereous vulture Aegypius monachus at 134 carcasses experimentally distributed in Special Protection Areas for Birds (SPA) in western and central Spain. Our goals were to assess the use of these carcasses and by-products in order to find out the cinereous vulture's food preferences and thus provide recommendations for the management of specific vulture restaurants for this species. Our results suggest that the number of cinereous vultures that come to feed on the carcasses is related to the quantity of biomass present and to the types of pieces of the provided food. Cinereous vultures prefer individual, medium-sized muscular pieces and small peripheral scraps of meat and tendon. The time that elapses before the cinereous vultures begin to consume a carcass depends on the biomass delivered, the number of pieces into which it is divided, and the type categories of the provided food. The population density of the species in our study area and the breeding stage seem to determine the time invested in feeding at the carcasses. These results may help managers to optimise the creation of vulture restaurants and favour their use by cinereous vultures.
If the deterministic threats of fragmentation can be stopped or reversed, species may find opportunities to disperse between patches and reduce the risk of extinction. In order to realise these opportunities and apply them to conservation programmes, it is necessary to understand the dynamics involved and to estimate which capacity is high enough to sustain a population at the landscape level. In a regional population consisting of several subpopulations, the incidence function model (IFM) is a stochastic, spatially-realistic patch occupancy model which can be applied using few parameters. With this model one can simulate and manipulate a patch network for a species. In IFM, the extinction probability is assumed to be proportional to local population size which in turn is assumed to be proportional to the local patch area. Although, the basic area of patches is of importance, influence from the geometric shape of patches may be equally or more important to determine potential incidence of a species in a particular patch. Basic area measurements might overestimate the probability of occupancy and/or capacity of a certain patch network to sustain a metapopulation. One applicable method to use in dealing with regional dynamics in fragmented landscapes is metapopulation capacity; derived from metapopulation theory, this method can be used to rank different patch networks. In our study, we examine if there is any difference in occupancy level and capacity between four different area scenarios. This allows us to determine if the basic area measurement of patches can result in a biased estimation of population viability in a specific landscape. It is concluded that perimeter-area related measures of patch size combined with capacity could be a more important measure for estimation of population dynamics and impact of landscape changes compared to basic area measurement and occupancy levels.
The harvest of Brünnich's guillemots (thick-billed murres) Uria lomvia off Newfoundland and Labrador is the only legal hunt of seabirds by non-natives in Canada and the United States. Ringing programmes at Arctic breeding colonies have been used to track changes in numbers and age composition of harvested birds. In recent years, the numbers of rings reported by hunters have fallen steeply. We examined recoveries by hunters of rings from a colony in northern Hudson Bay during 1984-2006 to assess the possible reasons for the decline in recoveries. Because recoveries of common guillemots have remained stable over the same period, it seems unlikely that a change in reporting rates is involved. Instead, it appears that a combination of a reduction in hunting pressure and a change in the behaviour of the birds due to more northerly termination of the winter pack-ice boundary account for the observed reduction in recovery rates. The pattern of first year recovery rates, in particular, appears consistent with an explanation based on accommodation to ice conditions. Recovery rates of older birds appear less affected by ice conditions and in recent years, have, in any case, been very low. Our study demonstrates that under conditions of changing weather and climate, harvest management decisions may not always have the impact expected.
Predator-prey relationships are of general interest in ecology and have been studied extensively. They are also of interest for effective management and recovery of prey populations. However, quantification of these relationships in the field has remained difficult. We analysed the impact of the predation of red fox Vulpes vulpes on brown hare Lepus europaeus, grey partridge Perdix perdix and rabbit Oryctolagus cuniculus using yearly hunting bag records as population indicators in eight German provinces over a period of 41 years. Bag records were tested for deviation from properties of suitable population indicators. We quantified the association between prey and predator populations within the context of other variables such as weather and long-term trends. We used an overall regression model for each prey population and discussed three statistical approaches accounting for the time series structure of the data. Models for all prey species populations display a good fit. The fox population has a significant negative association to the hare population in all models. The results for the rabbit population show only a small effect of the fox population, though it is not significant. The effect of the fox population on the partridge population cannot be clearly distinguished from a general trend. Additionally, there is a strong long-term trend in the hare and partridge populations. This could be due to major changes in the agricultural landscapes over the last decades. It is important to note that this trend is much stronger than the association to the fox population. Our study suggests that habitat improvement could be much more effective in restoring prey populations than fox control due to the minor interactions between the fox and the prey populations.
KEYWORDS: black-footed ferret, black-tailed prairie dog, Conata Basin, home range, Mustela nigripes, space use, volume of intersection, utilization distribution
Effective conservation planning for endangered species depends on an understanding of space use patterns. Black-footed ferrets Mustela nigripes depend on prairie dogs Cynomys sp. as prey and use their burrow systems for shelter. The availability of areas with high densities of active prairie dog burrows is the major factor thought to affect their selection of sites and resources. However, we have little knowledge about how the spatial distribution of active prairie dog burrows might influence the spatial organization and home-range size of ferrets. We monitored the movements of black-footed ferrets on a black-tailed prairie dog C. ludovicianus colony in South Dakota to document ferret space use patterns. Home ranges of female ferrets were 22.9 - 95.6 ha in size (x̄ = 56.3 ha, SE = 19.7, N = 6), while male ferret home ranges were on average more than twice as large as those of females (x̄ = 128.3 ha, SE = 68.5, N = 3). The home-range size of female ferrets was correlated with mean active prairie dog burrow utilization distribution (UD) value within ferret home ranges, where home-range size decreased as active prairie dog burrow UD value increased (r2 = 0.974, P < 0.001, N = 6). Ferret space use overlapped more extensively than previously reported, with up to 43% UD overlap between a ferret and the nearest adjacent ferret of the same sex. Areas of overlap tended to have higher active prairie dog burrow UD values, suggesting that the spatial distribution of active prairie dog burrows influenced both home-range size and the amount of space use overlap between ferrets. These findings emphasize the potential influence of resource distribution on carnivore sociobiology and the importance of considering that distribution in assessing habitat for the reintroduction of specialized species.
Management of large herbivores could be improved by investing less effort in estimating absolute abundance and more effort tracking variation over time of indicators of ecological change (IEC) describing animal performance, herbivore impact on habitat, and relative animal abundance. To describe relative changes in animal abundance, monitoring trends in numbers through indices may constitute a useful and low cost method, especially at large spatial scales. Reliability of indices to detect trends should be evaluated before they are used in wildlife management. We compared population trends estimated from spotlight counts, a standard census method for deer populations, with population size estimates of a red deer Cervus elaphus population monitored using Capture-Mark-Recapture (CMR) methodology. We found a strong negative effect of conditions of observation (e.g. rainfall) on both the number of animals (-24.4%) and the number of groups (-31.6%) seen per kilometre. After controlling for observation conditions, we found that these two abundance indices were linearly correlated with CMR estimates, with the group-based index being better correlated (r = 0.75) than the individual-based index (r = 0.68). These consistent trends between indices and CMR estimates provide support in using standardised spotlight counts as an IEC describing relative changes in abundance for the monitoring and management of red deer populations.
Foraging patterns, behaviour and the distribution of animals are affected by the availability and distribution of food in the landscape. Increasing numbers of ungulates may also be in conflict with agriculture, timber, infrastructure and conservation interests. Understanding foraging habits of ungulates and how these are affected by a change in forage availability or composition are, therefore, issues of major importance both from ecological and management perspectives. Supplementary feeding (i.e. artificial supply of food) is being used to improve local habitat, and thereby affecting ungulate movements, habitat choice and migration patterns. We experimentally tested the predictions that supplementary feeding redistributes moose Alces alces during two different migration phases (early, i.e. during the onset of migration and late, i.e. in the wintering areas). We used individually marked moose and pellet group counts to investigate the effect of supplementary feeding both at the individual and population level. We monitored 30 moose with GPS-collars before, during and after the supplementary feeding experiment, corresponding to 8-10% of the moose population in two different valleys in Northern Scandinavia. During early migration, moose ignored supplementary feeding sites even though migration routes were close to the sites. At the end of the migration route, supplementary feeding affected moose movement, distribution and behaviour. In conclusion, we suggest that there is a clear difference in response to supplementary feeding by moose due to the phase of migration. We conclude that supplementary feeding can be used under certain conditions to redistribute moose in relation to browsing, or to traffic, preferably at the end-point of migration.
Due to the decreased cost and increased availability of digital camera technology, digital image analyses are rapidly replacing traditional caliper-based approaches to wildlife morphometry. The substitution of image-based measurement methods over those utilizing calipers is based on the assumption that both methods are comparable with respect to accuracy, precision, time required and inter-observer variation, yet this hypothesis has not been explicitly tested. In this article, we evaluate these aspects of each method using three life stages of the marbled salamander Ambystoma opacum. We found that digital image-based measurements were significantly more accurate, faster to obtain, and resulted in reduced inter-observer measurement variation relative to caliper measurements, yet the former was associated with reduced precision among repeated measurements relative to the latter. Based on our observations, we recommend that digital image-based measurements represent a useful alternative to caliper measurements and are particularly useful for organisms that pose risks to investigators, normally maintain non-linear body orientations, or cannot easily be removed from their habitat.
Michael S. Mitchell, Justin A. Gude, David E. Ausband, Carolyn A. Sime, Edward E. Bangs, Michael D. Jimenez, Curt M. Mack, Thomas J. Meier, M. Steven Nadeau, Douglas W. Smith
Model-based predictors derived from historical data are rarely evaluated before they are used to draw inferences. We performed a temporal validation, (i.e. assessed the performance of a predictive model using data collected from the same population after the model was developed) of a statistical predictor for the number of successful breeding pairs of wolves Canis lupus in the northern Rocky Mountains (NRM). We predicted the number of successful breeding pairs, β, in Idaho, Montana and Wyoming based on the distribution of pack sizes observed through monitoring in 2006 and 2007 (β̂), and compared these estimates to the minimum number of successful breeding pairs, βMIN, observed through intensive monitoring. βMIN was consistently included within the 95% confidence intervals of β̂ for all states in both years (except for Idaho in 2007), generally following the pattern β̂L (lower 95% prediction interval for β̂) < β̂MIN < β̂. This evaluation of β̂ estimates for 2006 and 2007 suggest it will be a robust model-based method for predicting successful breeding pairs of NRM wolves in the future, provided influences other than those modeled in β̂ (e.g. disease outbreak, severe winter) do not have a strong effect on wolf populations. Managers can use β̂ models with added confidence as part of their post-delisting monitoring of wolves in NRM.
One obvious threat to the endangered arctic fox Vulpes lagopus population in Fennoscandia is competition with the larger red fox Vulpes vulpes, which may have expanded its range towards the alpine tundra because of increased food availability in the low-alpine and subalpine region. The steady increase in the number of vacation cabins and roads, and thus also in human garbage and road-killed animals, may subsidise easily available food resources and improve red fox survival in these otherwise marginal areas. In Børgefjell National Park, Norway, 14 of 27 known arctic fox dens were used by arctic fox during 2001-2005. The dens that were used were situated at higher altitudes, farther from natural red fox habitats, than unused dens. In the best of our logistic regression models, there was also a statistical negative effect of the number of cabins within 7 × 7 km squares around the den sites. Hence, our results support the prediction that the arctic fox is less likely to use areas where human activity might be benefiting red foxes. A successful conservation strategy for the arctic fox will probably require a reduction of the driving forces behind the red fox expansion in the alpine areas.
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