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Factors that influence hunter success for waterfowl are subject to varying levels of control by managers. The relative influence of these factors is poorly understood, but such information may be valuable to guide management actions intended to promote successful hunting and communicate management decisions to constituents. We used bag-check data to investigate factors influencing hunter success for mallards Anas platyrhynchos and other dabbling ducks (tribe Anatini) during the period 1981-2000 and 2002 at Illinois public waterfowl areas. Competing models of hunter success for mallards and other dabbling ducks included a negative association with average low temperature during the duck season (uncontrollable by managers) and positive associations with estimates of local and continental duck abundance, factors which we considered partially controllable by managers. Although a certain proportion of variation in hunter success for ducks cannot be directly influenced by managers, we suggest that programs and management efforts, which promote larger continental duck populations (e.g. Conservation Reserve Program) and local duck abundance (e.g. provide quality wetland foraging habitats), may positively influence hunter success.
We evaluated the effect of the removal of hooded crows Corvus cornix on common eider Somateria mollissima nesting success using a partial Before and After Comparison of Impact (BACI) design over three years in two eider breeding colonies (Håkøya and Grindøya) in northern Norway. These breeding colonies had over the last decades been subject to severe declines in number of breeding birds and it was suspected that increasing nest predation by crows was contributing to the declines. Eider nesting success was monitored in both colonies during 2006-2008. Crows were removed by live-trapping from Håkøya in 2007 and from Grindøya in 2008. We monitored the number of nesting pairs of crows and general crow activity. Crow removal was generally successful in reducing the number of established territorial and visiting crows. Modelling of daily nesting success probabilities according to a logistic exposure model revealed that eider nests found at the start of the season had a much lower probability of success than nests found later on in the season. This is likely to be due in part to the increase in number of active nests during the first half of the season. The effect of crow removal appeared to differ between the two colonies. Eider nesting success on Håkøya increased from 61% in the pre-removal year 2006 to 80% during crow removal in 2007 and declined to 74% in the post-removal year 2008. In contrast, nesting success on Grindøya remained constantly low (38-40%) during the same period. This difference between the two colonies could be explained by a difference in predation pressure, or by a higher general disturbance level on Grindøya making unattended nests vulnerable to predation by a range of alternative predator species acting compensatory to the removal of crows. New investigations should be undertaken to clarify the interaction between crows and other nest predators in determining eider nesting success. Where compensation appears to occur, conditions for this process should be investigated. This will help to indicate when crow removal can be effective and which other actions can be employed to increase common eider nesting success.
The grey partridge Perdix perdix used to be a common and widespread species throughout the temperate zone of western Eurasia, but its populations have markedly declined in most parts of its native range since the 1950s. The Pyrenean subspecies P. p. hispaniensis is threatened by alteration of its habitat, and despite ecological and hunting interest in this subspecies, the impact of harvest on population sustainability remains largely unknown. We assessed mortality of Pyrenean grey partridge and its influence on the population growth rate during 1992-2001 in the French Pyrenees. Cause-specific mortality rates were estimated using multistate capture-recapture models based on fates of 67 radio-equipped birds. Annual recruitment was estimated as the ratio of juvenile birds to adult birds in harvested samples. Mammalian predators and raptors were each responsible for a 5% monthly mortality rate. At the peak of hunting activity (i.e. October), hunting was responsible for a 30% mortality rate in some years. Modeled population growth rates appeared stable without hunting but negative with hunting. The estimated difference in population growth rates under the two regimes was 0.46. Our estimates of population growth suggest that the population was decreasing during our study, whereas it appeared stable based on ground counts. We discuss this discrepancy and proposed management actions.
Most wolf Canis lupus studies have been conducted in inland regions and comparatively little data are available for wolves inhabiting coastal areas. We monitored four members of a coastal wolf pack on the Alaska Peninsula during 2006-2008. Habitat selection ratios indicated a strong association with the coastline, and we documented pack members and other wolves feeding on several species of marine mammals in these areas. In addition, pack members were observed foraging on offshore sea ice on multiple occasions. Observed spatial use and utilization of marine mammals suggest that marine-derived subsidies may provide an important food source to coastal wolf populations. If these subsidies constitute a significant food source for coastal wolves, they likely affect wolf demographics and predator-prey relationships in these areas.
In order to understand dispersal behaviour and its population consequences, we captured 136 raccoon dog Nyctereutes procyonoides pups (i.e. < 1 year old) in northeastern Germany (Mecklenburg-Western Pomerania). We ear-tagged all animals and additionally fitted 48 of them with radio-collars. There were findings of 59 (43.4%) animals and the mean distance from the marking point was 13.5 km ± 20.1 (SD). Dispersal mortality rate was 69.5% among young raccoon dogs. Most animals (55.9%) were recovered < 5 km from the marking place, whereas only 8.5% of the records were > 50 km from the marking point. The distances of the dispersal did not differ between sexes. Most (53.7%) records of ear-tagged young raccoon dogs were made in August and September, and only 34.1% were recorded during October-April. Hunting (55%) and traffic (27%) were the major mortality criteria. Most radio-collared young raccoon dogs dispersed between July and September. The mean natal home-range size (MCP 100) with and without excursion was 502.6 ha ± 66.4 (SD; N = 9) and 92.1 ha ± 66.4 (N = 17). There were no differences between males and females in the month of dispersal. Raccoon dogs dispersed into all directions with distances varying between 0.5 km and 91.2 km. Radio-collared, dispersing animals showed a variety of movement patterns and the impression of flexible migration behaviour was confirmed. The fact that males and females showed equal dispersing behaviour is supposed to be one of the factors contributing to the high expansion and the success of the species.
The substantial increase of deer populations in Europe and North America in recent decades has led to concerns regarding the long-term sustainability of current management from an ecosystem perspective. Key questions to be answered are how herbivore density relates to available resource levels, e.g. food availability and browsing pressure, and how this relation should be monitored and included in management. In Norway, the harvest of red deer Cervus elaphus has increased from 1,479 to 35,700 during 1960-2008. Current monitoring programmes focus on deer body mass and number of seen deer rather than on the state of the vegetation communities. In our study, we quantify browsing frequency on common shrubs and trees in two municipalities, Gloppen and Flora, in the county of Sogn and Fjordane, Norway, to document current browsing pressure levels and to evaluate the potential of using browsing frequency of indicator species as a tool in the monitoring of red deer populations. We found that several species were heavily browsed (median browsing frequency > 60%). Due to their wide availability, we analysed the spatial patterns of accumulated browsing of the highly selected rowan Sorbus aucuparia compared to the less selected bilberry Vaccinium myrtillus and birch Betula sp. We predicted less spatial variation in browsing frequency of the highly selected rowan. However, we found that the best model predicting browsing on rowan (forest type, habitat productivity, canopy cover, aspect, slope and distance to arable land) based on habitat variables was more complicated than for birch (habitat productivity and altitude) and bilberry (forest type, habitat productivity, altitude and distance from the coast). This suggests large spatial variation in browsing frequency of rowan even though the average browsing frequency of rowan was higher than for bilberry and birch. Browsing frequency for all species was positively correlated with faeces counts, but only bilberry showed additional correlation with red deer (harvest) density at the local management unit scale. Due to its wide distribution and promising link to local red deer density, bilberry stands out as the most promising species to monitor among winter browse species. However, browsing frequency on different species was not always correlated. It remains to be determined to which extent browsing on bilberry can be used as an indicator for the browsing pressure on the whole vegetation community. The documentation of high browsing frequencies clearly suggests that further focus on these issues is warranted.
We studied diet composition of red deer Cervus elaphus in the Bohemian Forest by micro-histological analysis of 207 samples of red deer faeces obtained on the Czech and the Bavarian side of the border. We carried out the research from October 2006 to February 2008, and collected samples every two months at nine monitoring plots that were situated at different altitudes (i.e. from 600 to 1,250 m a.s.l.). Our results confirmed the classification of red deer among intermediate feeders with a mixed diet of graminoids (29.4%) and concentrate food items (60.6%). Concentrate food items were dominant in their diet all year round; however, the diet composition during the winter season differed from the diet composition during the vegetation season. This change was mainly represented by the strong increase in consumption of coniferous trees (from 5.7 to 26.4%) during winter. The amount of graminoids in the diet was higher during the vegetation season, which was caused by the intensive consumption of graminoids at two top-hill plots (up to 90% per sample). Likewise bilberry, Vaccinium myrtillus, with ripe berries was identified as an important food source only at the mountain ridge (up to 33% per sample). In agreement with our prediction, the diet composition of red deer at windthrow gaps (Blatný vrch Hill and Schachtenau) differed from the diet composition at undisturbed forest sites. At the gaps, ferns were an intensively consumed food source (up to 80% per sample). Contrary to other mountain areas, ferns made up a much larger share of the diet not only during autumn and winter but also during spring and summer. At Schachtenau, red deer also fed extensively on bramble Rubus sp., which intensively proliferates at the gaps. Diet composition of red deer in the Bohemian Forest differed between seasons, between plots at the mountain ridge and plots situated at lower altitudes as well as between windthrow gaps and undisturbed forest sites. However, further research of diet selectivity is necessary to explain in detail the observed feeding patterns.
Abundance indices suggested that the moose Alces alces population in northern New Hampshire was stable despite favourable habitat and conservative harvest. Causes and rates of mortality were unknown because moose reproduction and survival was unstudied in the region. Our study was designed to investigate the dynamics of the regional population in 2002-2005. A total of 92 moose (33 cows and 59 calves) were captured and fitted with radio-collars (VHF = 83, GPS = 9). Parturition ranged from 8 May to 13 July (median = 19 May) with 78% of births occurring during 13-27 May. Calving rate of yearlings and adults (> 2 years old) averaged 30 and 85%, respectively; twinning rate was 11%. Analysis of reproductive data from harvested cows (1988-2004) indicated that the average weight of adult cows increased but their corpora lutea count declined from ∼ 1.4 to 1.2/cow. Both ovulation rate and average weight of yearling cows declined about 25 and 4%, respectively. There were 39 mortalities (49% calves) with winterkill/parasite (41%), vehicle collision (26%) and hunting (18%) as the leading causes. Major sources of mortality of radio-marked cows were human-related; survival was 0.87. Annual calf survival was 0.45. Unmarked calf (0-2 months of age) survival was 0.71 with 76% of mortality in the first month of life. Radio-marked calves (∼ 7-12 months of age) had a survival rate of 0.67; 74% of the mortality was winterkill/parasite related. Calf mortality was concentrated (88%) in late winter-early spring. The unseasonably warm and snowless fall in 2001 probably favoured high tick transmission and increased tick loads on moose that resulted in high calf mortality (0.51) and measurable cow mortality (10%) in mild winter-spring 2002. Documentation of substantial tick-related mortality of radio-marked moose calves was unique to this study. The stability of the moose population probably reflects the variation in annual recruitment and lower fecundity of yearling cows associated with heavy infestations and epizootics of winter tick. Given that fertility, calving rate and body condition of adult cows, and summer calf survival are annually high, the population should recover from tick epizootics that periodically inhibit population growth.
Time series analysis plays an important role in the detection of mechanisms that drive population fluctuations. However, long time series are rare, with ungulate data sets usually not exceeding 50 years. In this article, we describe a long-term data set of population density indices of five ungulate species obtained from the analysis of bag records collected in the Castelporziano Preserve, Rome, Italy. Hunting statistics are often used as proxies for population density; however, in the case of long time series for large mammals, there are no comparative studies to assess the validity of such data. We evaluated the ungulate time series, using two different approaches: we 1) compared hunting statistics with independent animal counts, and 2) assessed whether or not habitat composition of the drive areas was representative of habitat availability in the whole estate. Regressions between bag data and animal counts gave significant results only for three species, whereas bag data corrected for hunted area were significantly correlated to animal counts for all five species. The results suggest that use of bag records not corrected for hunting effort and without any previous validation could lead to misleading estimates of abundance indices. Finally, our analysis showed that density indices of the five species were not significantly affected by the selection of habitats where hunting drives were organised. Our data set may contribute to the understanding of ungulate ecology in the Mediterranean environment.
Dabbling ducks generally use distinct day roost and nocturnal habitats, the set of which constitute their ‘functional unit’. The rate at which these birds may switch between day roosts has never been quantified. Using resightings of nasal-saddled birds and capture-recapture modelling in the Camargue, southern France, we estimated the weekly probability that a teal Anas crecca switches from one day roost to another one nearby (transition probabilities). We also estimated the probability that a teal survives and remains in our study area, consisting of four neighbouring roosts (apparent survival). Birds were highly faithful to one specific water body if they remained in our study area (i.e. weekly rate of switching between roosts was only about 2-6%), but the probability that an individual remained within one of the four roosts from one week to the next (local weekly apparent survival rate) was only 60-70%. Intensive search efforts led to a 60% detection probability. Low local apparent survival coupled with very high site fidelity within the system suggests that two distinct strategies may coexist, i.e. frequent movement between distant winter quarters vs very high fidelity to the very same local wetland. Such strategies may be used successively by the same individuals, or may alternatively represent distinct bird categories (i.e. transients vs residents). In any case, these different strategies suggest that habitat management procedures need to be considered at both local and flyway scales simultaneously. The former may ensure that sites repeatedly used by the same individuals can provide adequate conditions to birds when they remain in a given winter quarter, while the latter will ensure transient birds find appropriate sites within the network of distant wetlands they may use as successive wintering quarters during a season.
The red fox Vulpes vulpes has traditionally been subjected to control efforts throughout much of its range. In this article, we present data on the sex and age composition of red foxes culled at bait sites in an area of southeastern Norway. While an excess of males were shot in early and mid-winter, equal proportions of males and females were shot in early spring. Apparently, females are more nutritionally stressed in March due to pregnancy and therefore visit bait sites more frequently. Culling earlier in winter will predominantly remove males and will bias the sex composition in the population towards females.
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