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A series of diets containing different proportions of heather was fed to red grouse. Heather is the bird's main natural food and contains much fiber; the rest of each diet was a relatively low-fiber, grain-based formulation. With increasing heather and associated fiber contents, food intake increased and overall digestibility of heather was only 9.4%, but, when heather was eaten as the sole food by wild red grouse, its digestibility was 46%. Adaptations to diets containing more heather included increases in the size of the digestive system. Gizzard weight increased linearly with food intake. Lengths of intestines and particularly ceca also increased with intake, but not linearly. Up to an intake of about 50 g dry matter/day no significant change occurred. Above 50 g/day, gut size increased rapidly. Bulk may have started to limit intake at about 50 g/day. One can think of galliform digestion functioning in two modes: 1) a low-fiber mode, in which bulk does not limit intake and fiber digestion is unimportant; and 2) a high-fiber mode, in which bulk limits intake and fiber digestion may well be important. Most studies on avian digestion have been of captive galliforms, most of which probably function in low-fiber mode all the time. Wild galliforms seem to function in high-fiber mode for much of the time, but this has been studied little.

Sympatric populations of tetraonid birds tend to fluctuate in synchrony, at least on local scales. If shared parasites among sympatric populations of different tetraonid species are to operate as a local, synchronizing factor for population fluctuations at least two conditions should be met: i) the host species should share the same (or similar) parasite species, and ii) geographical location should contribute significantly more to the variation in the parasite species composition and abundance than differences among host species. We examined these conditions among subpopulations of sympatric willow ptarmigan and rock ptarmigan and found that host species shared a common pool of parasite species, and geographic location was more important than host species in determining parasite abundance across locations. There was no time lag between density oscillations in the two hosts, suggesting a symmetrical pattern of transmission and maintenance of parasites within habitats governed by the density of hosts and the environment. These findings are consistent with the idea that parasites may play a role in generating synchronous density fluctuations, but large scale experiments are needed to verify this hypothesis. [ABSTRACT FROM AUTHOR]

The long-term decline of the black grouse population throughout Europe is influenced by many factors that affect populations differently depending on the distribution range, from Central Europe to the Scandinavian countries. Therefore, we analyzed available literature sources to describe the main reasons for the population decline of this species and to suggest conservation measures. In total, 228 pieces of literature from 1955 to 2024 were analyzed for this study. Based on the literature analysis, it is clear that the drivers of population decline differ across the distributional range. In Central Europe, where the population is declining rapidly, habitat loss and forest fragmentation are crucial factors, as is the negative impact of tourism. In Scandinavia, where the population is gradually declining, decreasing breeding success and increasing chick mortality rates are generally considered the main negative factors. However, these factors also affect black grouse populations in Central Europe. It is crucial to acknowledge that a significant proportion of the contributing factors, such as predation and habitat loss, can be attributed to human activities. Therefore, it is necessary to emphasize that environmental protection should work hand in hand with wildlife managers to improve the situation. [ABSTRACT FROM AUTHOR]

Background: Spatial scale is important when studying ecological processes. The Greater sage-grouse (Centrocercus urophasianus) is a large sexually dimorphic tetraonid that is endemic to the sagebrush biome of western North America. The impacts of oil and gas (OAG) development at individual leks has been welldocumented. However, no previous studies have quantified the population-level response. Methods: Hierarchical models were used to estimate the effects of the areal disturbance due to well pads as well as climatic variation on individual lek counts and Greater sage-grouse populations (management units) over 32 years. The lek counts were analyzed using generalized linear mixed models while the management units were analyzed using Gompertz population dynamic models. The models were fitted using frequentist and Bayesian methods. An information-theoretic approach was used to identify the most important spatial scale and time lags. The relative importance of OAG and climate at the local and population-level scales was assessed using information-theoretic (Akaike's weights) and estimation (effect size) statistics. Results: At the local scale, OAG was an important negative predictor of the lek count. At the population scale, there was only weak support for OAG as a predictor of density changes but the estimated impacts on the long-term carrying capacity were consistent with summation of the local impacts. Regional climatic variation, as indexed by the Pacific Decadal Oscillation, was an important positive predictor of density changes at both the local and population level (particularly in the most recent part of the time series). Conclusions: Additional studies to reduce the uncertainty in the range of possible effects of OAG at the population scale are required. Wildlife agencies need to account for the effects of regional climatic variation when managing sage-grouse populations. [ABSTRACT FROM AUTHOR]

The cestode Hymenolepis microps is an intestinal parasite of tetraonid birds, including the willow ptarmigan (Lagopus lagopus). This parasite is able to maintain a high prevalence and intensity throughout the year, even in a subarctic environment in bird populations with relatively low host densities, indicating effective transmission routes. Willow ptarmigan consume mainly vegetal material and active consumption of invertebrates is confined to the first two or three weeks of life. Ptarmigan are infected by different species of ectoparasites, of which two species of feather lice, Lagopoecus affinis and Goniodes lagopi, are the most abundant. In this study, we explored the hypothesis that feather lice may be suitable intermediate hosts for H. microps. We applied histological techniques and light microscopy to investigate lice for the presence of larval cestode stages (cysticercoids). We found 12 cysticercoid-like structures inside chewing lice collected on L. lagopus hosts harbouring H. microps. In addition, a polymerase chain reaction (PCR) screening of Ischnocera lice DNA, targeting the 18S rRNA gene of the cestode, showed positive results for two different short fragments of the 18S rRNA gene of H. microps which were sequenced from lice collected on birds. Both independent lines of evidence support the hypothesis that Ischnocera lice might be suitable intermediate hosts in the life cycle of H. microps in L. lagopus. [ABSTRACT FROM AUTHOR]

Phenolic compounds (phenolics) are secondary metabolites ubiquitous across plants. The earliest phenolics are linked to plants' successful transition from an aquatic to a terrestrial environment, serving as protection against damaging ultraviolet (UV) radiation, and as antioxidants to reduce oxidative stress in an atmosphere with an increasingly high O2:CO2 ratio. In modern plants, phenolics are best known for the defense against fungal and bacterial pathogens and as antifeedants that deter herbivory. Phenolics also play a role in seed dormancy, delaying germination, and lengthening viability in the seed bank. Many plants' seeds are endozoochorous – dispersed by animals, like birds, who eat and later excrete the seeds. Plants send visual signals to attract birds with UV‐sensitive (UVS) vision for pollination and seed dispersal. As fruits ripen, antioxidant activity and phenolic content decrease. The waxy cuticle of fruits increases in UV reflection as phenolic rings, which absorb UV light, degrade. The UV contrast that birds detect may act as an honest signal, indicating nutritional changes in the fruit. However, there is little evidence to support the evolution of UV coloration during ripening being driven by frugivore selection. Antioxidant properties of fruit phenolics may be dually adaptive in plants and avian frugivores. [ABSTRACT FROM AUTHOR]

Wild vertebrates usually avoid ground disturbed by humans with uncertain effects on their distribution and density. We report on a natural experiment that confirms and extends previous conclusions about how the local distribution of capercaillie is affected by track‐based disturbance. We surveyed the birds' droppings in two periods, before and after a predicted increase in disturbance adjacent to an expanding Scottish village, and model the probability of finding droppings in relation to period plus two disturbance gradients – distance to a much disturbed 'entry zone' with a high density of tracks lying adjacent to the village, plus distance to the nearest track. Throughout the study, no droppings were found within the entry zone and their density was depressed up to 400 m from it. Density of droppings was also depressed within 100–120 m of tracks but, compared to a notional scenario without tracks, was threefold greater on ground 120–250 m from tracks. Although the number of cocks counted at the lek in spring showed a small increase, there was an almost threefold decline in the probability of finding capercaillie droppings on and within about 40 m of tracks. We infer that, after the development, birds were less likely to use or cross tracks in pursuit of their daily living requirements, with unknown consequences for their population dynamics and vital rates. Our results have implications for refuge design. Birds on roughly half of a 50 ha refuge should be undisturbed by direct effects of track‐based activities. However, birds shifting away from tracks may themselves cause local increases in density and associated, indirect disturbance such that a refuge would need to be over 300 ha to keep half of it undisturbed. [ABSTRACT FROM AUTHOR]

Simple Summary: Bird mortality resulting from collisions and electrocutions with overhead lines (such as power lines and phone lines) has contributed to the decline of various avian species globally. Specifically, overhead line collisions pose a significant threat to the conservation of the Canarian houbara bustard (Chlamydotis undulata fuertaventurae), an endangered subspecies endemic to the Canary Islands. This study focuses on postmortem findings from Canarian houbara bustards that collided with overhead lines. We describe the necropsy findings of Canarian houbara bustards found dead near overhead lines, and we investigated, using a forensic approach, whether the animal survived the initial trauma. The mortality of birds resulting from collisions and electrocutions with overhead lines, such as power lines and phone lines, among others, has been implicated in the decline of various avian species globally. Specifically, overhead line collisions pose a significant threat to the conservation of the Canarian houbara bustard (Chlamydotis undulata fuertaventurae), an endangered subspecies endemic to the Canary Islands. This study centers on the postmortem findings of Canarian houbara bustards that have collided with overhead lines, providing insights into the post-collision outcomes for these birds. A complete standardized necropsy of nine Canarian houbara bustards revealed that trauma was the cause of death in all cases. The most notable gross lesions associated with trauma included bone fractures, soft tissue lacerations, hemorrhages, luxations, and hemocoelom. The inguinal area, chest, and wings were the body regions more frequently affected. A histopathology, immunohistochemistry, and entomology analysis confirmed that numerous birds survived the initial trauma. We concluded that when a houbara bustard collides with an overhead line, it frequently survives the initial trauma, with a survival time ranging from minutes to hours. The histopathology, immunohistochemistry, or entomologic analysis may be helpful to approximate the timing interval between trauma and death. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Variation in the distribution and abundance of animals in space and time are key concepts of population ecology. We studied these variations in a population of red foxes ( Vulpes vulpes) in the tundra and taiga of northern Sweden. We analysed 12 years (1974-1985) of snow tracking data from a large area of 65,375 km. Specifically, we evaluated to what extent the distribution of red foxes was explained by the presence of prey and how this interacted with snow depth and altitude. We also tested for temporal linear trends in the distribution and abundance of red foxes during the study period. The distribution of red foxes was explained by the presence of rodents, hares, tetraonid species, and ungulates (i.e. carcasses). Snow depth had a negative effect on the impact of small prey on the distribution of the red foxes, whereas it had a positive effect on the impact of ungulates. The influence of hares increased with altitude. Neither distribution nor abundance of red foxes showed a positive or negative linear trend, suggesting a stable population in northern Sweden during our study. This study showed that the distribution of red foxes was not only influenced by the presence of their main prey (rodents), but also by interactions between alternative prey, altitude, and snow depth. This study also emphasizes the importance of ungulate carcasses for red foxes and for wildlife management. [ABSTRACT FROM AUTHOR]

Copyright of Ardeola is the property of Sociedad Espanola de Ornitologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  Sexual ornaments might reliably indicate the ability to cope with parasites and diseases, and a better ability to mount a primary inflammatory response to a novel challenge. Carotenoid-based ornaments are amongst the commonest sexual signals of birds and often influence mate choice. Because carotenoids are immuno-stimulants, signallers may trade-off allocating these to ornamental colouration or using them for immune responses, so carotenoid-based ornaments might be particularly useful as honest indicators of immuno-compentence. Tetraonid birds, such as the red grouse Lagopus lagopus scoticus, exhibit supra-orbital yellow–red combs, a conspicuous ornament which functions in intra- and inter-sexual selection. The colour of combs is due to epidermal pigmentation by carotenoids, while their size is testosterone-dependent. In this study, I investigated whether comb characteristics, and in particular, comb colour, indicated immuno-competence in free-living male red grouse. I assessed T-cell-mediated immunity using a standardised challenge with phytohaemagglutinin. Red grouse combs reflect in the red and in the ultraviolet spectrum of light, which is not visible to humans but that grouse most likely see, so I measured comb colour across the whole bird visible spectrum (300–700 nm) using a reflectance spectrometer. I found that males with bigger and redder combs, but with less ultraviolet reflectance, had greater T-cell-mediated immune response. Comb colour predicted T-cell-mediated immune response better than comb size, indicating that the carotenoid-based colouration of this ornament might reliably signal this aspect of male quality. [ABSTRACT FROM AUTHOR]

1. Among the commonest sexual signals of birds are the red-yellow traits pigmented by carotenoids, but how they reliably advertise individual quality remain poorly understood. Here we tested the hypothesis that carotenoid-based signalling is enhanced by testosterone but reduced by parasites, and that the dual action of testosterone on ornament expression and parasite resistance ensures reliable signalling. 2. Tetraonid birds such as the red grouse Lagopus lagopus scoticus have bright red combs pigmented by carotenoids, which function in intra- and inter-sexual selection. In separate experiments, we manipulated a main nematode parasite, Trichostrongylus tenuis (using deparasitation and re-infection) and testosterone (using testosterone or combined Flutamide/ATD treatments) in free-living males and investigated effects on plasma carotenoids and comb colour. 3. In untreated males, comb redness positively correlated with plasma carotenoids, testosterone concentration and condition. Plasma carotenoids and comb redness both negatively correlated with T. tenuis abundance. 4. Plasma carotenoids decreased in response to a challenge from T. tenuis, but increased when parasites were reduced. Testosterone enhanced comb redness, but tended to deplete plasma carotenoids. Combined Flutamide and ATD treatment had no significant effects on comb colour or plasma carotenoids, indicating that testosterone effects might be direct. 5. Our experiments show contrasted effects of testosterone and nematode parasites on carotenoid-based ornamentation. Testosterone and parasites have well documented interactions in the study model. These, together with the opposite effects that testosterone and parasites have on carotenoid availability and use, would shape optimal levels of signalling, depending on individual quality, and might ensure reliable signalling. 6. Carotenoid-based and testosterone-dependent traits have rarely been linked. Our study provides such a connection and shows that investigating how parasites, testosterone and carotenoids interact helps in the understanding of the evolution and maintenance of honest carotenoid-based signals of health. [ABSTRACT FROM AUTHOR]