Variations in Black Grouse Tetrao tetrix winter survival in a year with prolonged snow cover

Capsule Low Black Grouse survival rate in northern England during a severe winter with prolonged snow was attributed to limited availability and proximity of woodland.

Aims To compare the impact of the severe winter weather on Black Grouse in an open treeless landscape in northern England with more wooded landscapes in Scotland.

Methods We assessed the impact of severe winter conditions in relation to previous milder winters at a sample of leks counted annually in northern England and the Scottish Highlands between 2001 and 2012. In addition, following the severe winter in 2009/10 Black Grouse were surveyed at all leks in 2010 where they were surveyed the previous year. We assessed woodland habitat extent within 1 km of leks and related this to indices of Black Grouse over-winter survival.

Results Black Grouse in northern England were severely affected by the severe winter of 2009/10, declining by 38% in comparison to a 23% increase in the Scottish Highlands. Leks in northern England were at higher altitudes and had less tree cover than those in Scotland.

Conclusion The lack of woodland cover around leks in northern England implies that availability of above snow forage, shelter and cover from predators was too low for Black Grouse to survive during prolonged deep snow. Measures are required to provide emergency food sources in periods of prolonged snow, such as the provision of supplementary food at leks, the cultivation of seed-rich arable crops, and the establishment of pockets of woodland.     

The invertebrate diet of Black Grouse Tetrao tetrix chicks: a comparison between northern England and the Scottish Highlands

Capsule: Conservation programmes for Black Grouse Tetrao tetrix need to consider managements that increase invertebrates for chicks.

Aims: To compare invertebrates in chick diet between habitat and region and to relate abundance of preferred invertebrates to Black Grouse breeding success.

Methods: Chick faeces were collected from roosts in the Pennines (northern England) and Perthshire (Scottish Highlands) to identify invertebrates eaten. Larval abundance was determined by sweep netting (Pennines) and related to Black Grouse breeding success.

Results: Invertebrates were recovered out of 98 faecal samples from 63 broods. Ants were more numerous in chick diet in Perthshire, with larvae (both sawflies and moths) more numerous in the Pennines. Sawfly larval abundance was positively correlated with Black Grouse breeding success in the Pennines.

Conclusions: Management for Black Grouse should promote high invertebrate abundance to maintain high breeding success. This may be achieved through creating low-intensity grazed moorland fringes to encourage Bilberry, and associated moth caterpillars, adjacent to areas of higher grazing intensity to retain grasses and rushes that host sawfly larvae.     

Juvenile sex ratio in relation to breeding success in Capercaillie Tetrao urogallus and Black Grouse T. tetrix

We examined the relationship between breeding success and juvenile sex ratio in two gamebirds with differing degrees of sexual size dimorphism. We used breeding success as an indicator of the level of environmental stress the birds had experienced. Capercaillie Tetrao urogallus and Black Grouse T. tetrix wing samples were collected from hunters in northern Sweden during 1977-86. In both species, annual juvenile sex ratio (percentage of males) increased with annual breeding success, i.e. with reduced environmental stress. We attribute this to the higher energy requirements during growth, vulnerability to environmental stress, and mortality of juvenile males compared with females, especially under adverse conditions. Moreover, the relationship between breeding success and juvenile sex ratio was stronger in Capercaillie than in Black Grouse. This reflects the higher degree of sexual size dimorphism in Capercaillie, and consequent larger mortality difference between juvenile males and females.     

Native woodland creation is associated with increase in a Black Grouse Lyrurus tetrix population

Capsule: Black Grouse population increases were greatest where new native woodland (NNW) within 1500?m of leks comprised approximately 30% of land area and averaged 5 years old.

Aims: To examine whether change in a population of Black Grouse Lyrurus tetrix in Scotland was associated with the creation of native woodland.

Methods: We examined whether lek location, size and change in size were associated with habitat and topography surrounding leks. We also examined vegetation differences in NNW and adjacent unplanted moorland.

Results: From 2002 to 2012 the number of lekking male Black Grouse increased by 90%. Lek occurrence was positively associated with the amount of NNW edge habitat. Leks were larger where there was more adjacent NNW. Lek increases were greatest where NNW plots comprised approximately 30% land area, and were 5 years old, within a 1500?m radius. Plots aged more than approximately 20 years old were associated with Black Grouse population declines. NNW supported taller and denser important field-layer vegetation than adjacent moorland, likely due to grazing exclusion.

Conclusions: Subject to longer-term management commitments to stimulate continued regrowth of the important field layer and maintain benefits for Black Grouse, expansion of native woodland could contribute to landscape-scale recovery of Black Grouse after decades of decline.     

Golden Plover Pluvialis apricaria breeding success on a moor managed for shooting Red Grouse Lagopus lagopus

Capsule The best estimate of breeding success was a mean of 0.57 fledglings per pair, which when combined with adult survival rates, successfully explained the observed population trend.

Aims To quantify Golden Plover breeding success on a moor managed for shooting Red Grouse Lagopus lagopus.

Methods An intensive study recorded the fate of individual Golden Plover nests and, using radiotelemetry, chicks. The factors associated with mortality were examined, allowing the construction of a model of breeding success. Adult survival was estimated from return rates of colour-ringed birds.

Results Estimated rates of daily nest survival during laying (0.8636) were significantly lower than during incubation (0.9913). The daily survival rate of chicks less than nine days (0.8868) was significantly lower than for older chicks (0.9792). A population model based on these parameters overestimated the rate of nest losses, but accurately described brood survival and fledging success. Although predation rates were low, poor survival of young chicks through starvation or exposure suggest other factors were limiting breeding success at the study site.

Conclusions Predation rates of Golden Plover nests and chicks can be low on moorlands managed for shooting Red Grouse. However, in the absence of predation, other factors may still reduce chick survival and limit breeding success.     

Seasonal variation in lek attendance and lekking behaviour by male Black Grouse Tetrao tetrix

Eleven Black Grouse Tetrao tetrix leks in the Scottish Highlands were visited at dawn once every week for a year. Apart from July and three leks which were unoccupied in winter, males visited leks throughout the year. Total numbers of males attending leks peaked in March in one study area (six leks) and in April in the second (five leks). The number of males present and the proportion of leks occupied varied seasonally. The proportion of males at leks was at a maximum in April (80% of males) when all leks were attended, with a secondary peak in September when 60% of leks had males present. Males spent the most time displaying in April. The optimal conditions for attendance were calm, dry mornings just after dawn. Most reliable counts of numbers of males were those made between the last week of March and the end of the first week of May.     

Rain, breeding success and distribution of Capercaillie Tetrao urogallus and Black Grouse Tetrao tetrix in Scotland

The number of chicks reared by Capercaillie was inversely related to the number of days with rain during and just after their hatching. However, rain had no detectable effect on the breeding success of Black Grouse on the same study area. The breeding distribution of Capercaillie in Scotland is more limited than that of Black Grouse, which extends into rainier areas. It is speculated that sexual selection for large size in Capercaillie has indirectly caused their chicks to be more vulnerable to rain and, consequently, has limited their distribution to less rainy areas.     

Lek fidelity and movement among leks by male Greater Sage‐grouse Centrocercus urophasianus: a capture‐mark‐recapture approach

Males in lek mating systems tend to exhibit high fidelity to breeding leks despite substantial evidence of skewed mating success among males. Although movements between leks are often reported to be rare, such movements provide a mechanism for an individual to improve lifetime fitness in response to heterogeneity in reproductive conditions. Additionally, estimates of apparent movements among leks are potentially biased due to unaccounted variation in detection probability across time and space. We monitored breeding male Greater Sage‐grouse Centrocercus urophasianus on 13 leks in eastern Nevada over a 10‐year period, and estimated movement rates among leks using capture‐mark‐recapture methods. We expected that male movement rates among leks would be low, despite predictions of low breeding success for most males, and that detection rates would be highly variable among leks and years. We used a robust design multistate analysis in Program mark to estimate probability of movements among leks, while accounting for imperfect detection of males. Male Sage‐grouse were extremely faithful to their leks; the annual probability of a male moving away from its original lek of capture was approximately 3% (se = 0.01). Detection probabilities varied substantially among leks (range = 0.21–0.95), and among years (range = 0.30–0.76), but remained relatively constant within years at each lek. These results suggest that male Sage‐grouse dispersal is either rare, or consists primarily of dispersal of sub‐adults from their natal areas prior to the breeding season. The study highlights the benefits of robust design multistate models over standard ‘live‐encounter’ analyses, as they not only permit estimation of additional parameters, such as movement rates, but also allow for more precise parameter estimates that are less sensitive to heterogeneity in detection rates. Additionally, as these data were collected using capture‐mark‐recapture methods, our approach to estimating movement rates would be beneficial in systems where radiotagging is detrimental to the study organism.     

Designing mosaic landscapes for Black Grouse Tetrao tetrix using multi‐scaled models

With increasing pressures on land for human use, it is important to identify the habitat requirements of key species, not just in terms of a correlation with a given habitat feature, but also the relationship between species presence and its coverage, proximity to other habitat types, and importance at different spatial scales. We used maximum entropy to estimate the optimal proportions of 18 habitat types, plus elevation and habitat richness associated with the presence of leks of Black Grouse Tetrao tetrix within an 800‐km² study area in Perthshire, Scotland. We repeated the analysis at several radii (0.2–3 km) to assess how the importance of different habitats changed with proximity to lek and scale. We then examined habitat features or combinations of features that were associated with large leks or positive lek growth. Models at all radii had satisfactory predictive power. Using response curves from maxent , we constructed ideal habitat mixes for leks at each radius. At the 2‐km radius, suitability was highest with around 20% each of three moorland types and open/mixed forestry, whereas close to leks (0.2 km), higher proportions of grouse moor and lower proportions of closed‐canopy woodland were optimal. The relationship between habitat and lek size or direction of lek growth was complex, indicating that a landscape containing large or productive leks can be the result of more than one combination of habitats. This demonstrates a degree of flexibility in designing landscapes for Black Grouse conservation, so landowners can prioritize combinations of habitats that are the most practical and/or economical, while still serving the requirements of the target species.     

The Red Queen Visits Sage Grouse Leks

Coevolution between parasites and host is a sufficient althoughnot necessary condition for the evolution of secondary sexualcharacteristics. I review evidence supporting the role of parasitesin the maintenance of lek behavior in Sage Grouse (Centrocercusurophasianus). Males bearing avianmalaria (Plasmodium pediocetii)or lice (Lagopoecus gibsoni or Goniodes centrocerci) have significantlylower reproductive success than noninfected males. Malaria-infectedmales attend leks significantly less frequently and lek attendanceis highly correlated with male reproductive success. Inaddition,males with malaria secured copulations later in the breedingseason with hens that wereyounger, in poorer condition, andless successful than mates of malaria-free males. Lice createhematomas on the air sacs of males which females can detectto avoid lousy males. Results of our field studies are reinforcedby experiments; captive males given antibiotics to reduce parasiteloads are chosen more often by females in arena trials. Ourresults lend empirical support for Hamilton and Zuk's (1982)interpretation of the RedQueen's hypothesis, although many unknownsremain in our understanding of the interaction between parasitesand Sage Grouse.     

A survey and GIS-based estimate of the breeding population of Great Snipe Gallinago media in Central Norway

Capsule By using a GIS-model to identify suitable breeding habitats for Great Snipe in Central Norway, we estimated a total of 276 leks holding approximately 2700 males.

Aim To estimate the size of the Great Snipe population in central parts of the species remaining breeding areas in Western Europe.

Methods GIS-analysis identified an area of 528?km² as suitable habitat for Great Snipe in the total study area (22?000?km²). Complete surveys were made in 8% of these habitats by using a subset of 53 sampling areas.

Results A total of 28 Great Snipe leks were found within the sampling areas. Ten of these were found in previously known lek areas, while 18 leks were found in areas with no previous knowledge of leks. Extrapolating the lek density and the lek size found in the surveyed areas, resulted in a total estimate of 276 Great Snipe leks holding approximately 2700 lekking males. The leks were found on open fens along the forest edge and were mainly situated on base-rich bedrocks. Mean altitude of the leks was 570?m.

Conclusion The total population of Great Snipe in Norway was previously assumed to comprise 5000–15?000 lekking males or ‘pairs'. By extrapolating the densities of leks found in Central Norway to a national scale, we expect the true breeding population of Great Snipe to be approximately 13?500 males. Changes in the elevation of the tree limit and increased overgrowth, as a result of reduced grazing pressure and/or global warming, are possible threats that may reduce the availability of preferred Great Snipe habitats and increase population fragmentation.     

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.     

Diversionary feeding and nestling diet of Hen Harriers Circus cyaneus

Capsule: Diversionary feeding reduced Hen Harrier Circus cyaneus nestlings’ natural food intake by half. Red Grouse Lagopus lagopus scotica chicks constituted 0–4% of all nestling food items. Annually, this reduced annual grouse chick production by 0–6%.

Aim: To quantify proportions of diversionary and natural food (including grouse) delivered to Hen Harrier nestlings in relation to brood size, male status and natural prey abundance.

Methods: We recorded diversionary food provisioned to 25 Hen Harrier broods (2008–15) and studied the diet of 15 broods using observations from hides, nest cameras and regurgitated pellet analysis. Variation in nestling diet was analysed using compositional analysis.

Results: Hen Harriers took 76% of diversionary food provided. Depending on assessment method, average nestling diet was 44–53% diversionary food, 39–55% natural prey (including 24–45% passerines, 4–15% small mammals, 0–4% grouse chicks) and 0–9% unknown items. The amount of diversionary food consumed was not influenced by male status, brood size or natural prey abundance. The number of Red Grouse chicks delivered annually was 34–100% lower than expected under unfed conditions, however, the confidence intervals associated with these estimates were large.

Conclusion: Diversionary food influenced Hen Harrier nestling diet and reduced the number of Red Grouse chicks taken relative to modelled predictions. It may help reduce conflict between Hen Harrier conservation and Red Grouse shooting, but only if overall grouse productivity is thereby maintained or increased.     

Comparing methods for estimating the abundance of Western Capercaillie Tetrao urogallus males in Pyrenean leks: singing counts versus genetic analysis of non-invasive samples

ABSTRACT

Population estimates of male Western Capercaillies Tetrao urogallus were carried out during the mating season using two methods: counts of singing males and non-invasive genetic analysis. Estimates of male numbers were 50% lower using the singing counts compared to the estimates obtained through genetic analysis, and underestimates were greatest when the number of Capercaillies was lowest.     

Habitat associations of young Black Grouse Tetrao tetrix broods

Capsule: In the Scottish Highlands, Black Grouse Tetrao tetrix females with young broods selected areas rich in wet flushes, grasses and Sphagnum mosses.

Aims: To identify associations between young Black Grouse broods and habitat characteristics.

Methods: We located brood-rearing Black Grouse females in four areas of moorland-forest mosaic in the Scottish Highlands. Each brood was paired with a random reference location 100?m away. We recorded cover of different habitats and fine-scale vegetation and structure within squares of 1 and 0.25?ha, respectively. Associations between brood occurrence and habitat and vegetation variables were examined at the two scales.

Results: Black Grouse broods were positively associated with wet flushes (1?ha), and with Heather Calluna vulgaris, sedges Carex spp., grasses, Sphagnum mosses and taller vegetation with intermediate levels of height variability (0.25?ha).

Conclusions: This study highlights the importance of wet habitats for young Black Grouse chicks. In addition, relatively tall field-layer vegetation comprising Heather, sedges, grasses over a layer of Sphagnum mosses attracted brood-rearing Black Grouse females. Many management practices associated with peatland restoration, including drain-blocking, Sphagnum re-establishment and the avoidance of burning on deep peat soils, are therefore consistent with favourable habitat management for Black Grouse.     

Associations between distance to forest and spatial and temporal variation in abundance of key peatland breeding bird species

Capsule Negative forest edge effects were detected for Willow Ptarmigan (Red Grouse) Lagopus lagopus and Dunlin Calidris alpina.

Aims To investigate the effects of distance to forest on the abundance and changes in abundance of four key peatland breeding bird species, and to measure changes in predatory bird numbers, in the peatlands of northern Scotland.

Methods Bird surveys were carried out in 2000 at 34 plots, covering 197 km² of peatland, and 80 forestry point‐count sites, first surveyed in 1988. Habitat data were also collected in 2000. We used multi‐model inference to investigate the associations between forest distance and other habitat variables, and the abundance, and changes in abundance, of four bird species of economic or conservation importance: Red Grouse, European Golden Plover Pluvialis apricaria, Dunlin and Common Greenshank Tringa nebularia.

Results There was strong evidence that distance to forest was negatively associated with Dunlin abundance and changes in Red Grouse abundance, but only weak evidence for negative associations with Golden Plover abundance and changes in Dunlin abundance. There was no evidence of a forest distance effect on Greenshank. Among predatory birds, there were no significant increases either on peatland plots or in new forestry plantations.

Conclusions This study provides evidence that, for a given habitat quality, Dunlin densities are lower, and Red Grouse declines more likely, near to forest edges, but weak evidence only that Dunlin declines are more likely, and Golden Plover abundance lower, near to forests. These results suggest that for at least two key peatland breeding birds, forest removal is likely to benefit birds breeding on adjacent unafforested peatland.     

Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

Indirect Effects of an Existing Wind Energy Facility on Lekking Behavior of Greater Prairie‐Chickens

Rapid expansion of the wind energy industry has raised concerns about the potential effects of anthropogenic disturbance on prairie grouse. While efforts have been made to address the effects of wind energy facilities on measures of fitness, their effect on the behaviors of prairie grouse has been largely neglected. To address these concerns, we investigated the effects of an existing wind energy facility in Nebraska that became operational in 2005 on the lekking behavior of male greater prairie‐chickens Tympanuchus cupido pinnatus between March and May 2013. Given the potential for disturbance caused by wind turbine noise to disrupt acoustic communication and thus behavior, we predicted that males at leks close to, compared to far from, the wind energy facility would spend more time in agonistic behaviors, and less in booming displays. Given the potential for wind turbine noise to reduce the number of females attending leks (hereafter ‘female lek attendance’), we also predicted that males at leks close to the wind energy facility would spend more time in non‐breeding behaviors and less time in breeding behaviors than males farther from the facility. Although we found no effect of the wind energy facility on female lek attendance, males at leks closer to the wind energy facility spent less time in non‐breeding behaviors than those at leks farther away. However, distance from the wind energy facility had no effect on time spent performing booming displays, flutter jumps, or in agonistic behaviors. Given that lekking behaviors of males influence mating success, our results may have consequences for the fitness of prairie grouse breeding in the vicinity of wind energy facilities.     

Male‐skewed adult sex ratio,survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.     

An experimental assessment of the potential effects of human disturbance on Black Grouse Tetrao tetrix in the North Pennines,England

In the United Kingdom, Black Grouse Tetrao tetrix have declined in range and abundance during the 20th century. In England at present, birds are largely found only on the margins of managed grouse moors in the north, where more than 80% of birds are confined to the North Pennines Area of Outstanding Natural Beauty. The Black Grouse is one of a group of species potentially at risk from increased human recreational disturbance owing to their threatened status and their use of habitats to which a statutory right of human recreational access has recently been granted. To assess the likely impact of increased disturbance to Black Grouse, 77 were caught and radiotagged between 2002 and 2004, and each was randomly assigned to one of three experimental disturbance categories: no disturbance (low), fortnightly disturbance (moderate) or twice weekly disturbance (high). Birds that were disturbed more regularly flushed at greater distances, especially in spring and winter when birds exposed to high disturbance flushed at 32% greater distances than those in moderate disturbance treatments. There were no differences in fecundity (clutch size, hatching success, breeding success) or survival between disturbance treatments. Winter survival was 78% and summer survival 92%. There was no age‐related difference in survival. The disturbance regimes imposed had no discernible impact upon Black Grouse population dynamics. However, in the absence of appropriate data to indicate likely changes in patterns and levels of human recreation resulting from open access, we cannot be sure whether the levels we applied will be representative in the future. Should actual disturbance levels be higher than those we used in this study, we list visitor management options that may help reduce any conflict that arises.