Publications

volatile fatty acids and metabolizable energy derived from cecal fermentation in the willow ptarmigan.		1976	177
the pectoral muscles and the development of thermoregulation in chicks of willow ptarmigan (lagopus lagopus).		1976	3317
the shivering pattern in an arctic (willow ptarmigan) and a tropical bird (bantam hen).		1976	3318
hind gut function in the grouse (lagopus lagopus).		1976	5245
thermoregulation and muscular development in cold exposed willow ptarmigan chicks (lagopus lagopus l.).		1976	9239
the occurrence of gapeworm (syngamus trachea) in willow grouse.	21.4% of the willow grouse (lagopus lagopus) examined from a coastal locality in northern norway were infected with syngamus trachea. none of the willow grouse examined from an inland locality with colder and longer winters were infected with the parasite. it is suggested that the parasite may influence survival of the grouse population.	1975	124787
studies of louping-ill virus (flavivirus group) in wild red grouse (lagopus lagopus scoticus).	studies were made to find evidence of louping-ill virus infection in free-living red grouse and relate this to their breeding success. in areas where ticks were abundant 61 (84%) adult grouse had antibody to the virus compared with 1 (10%) in areas where ticks were relatively scarce. of 162 chicks tested 25 were shown to be viraemic. infected chicks were of significantly less weight than comparably aged uninfected birds and the probability that they died was much greater than that of uninfected ...	1978	212479
metabolic thermoregulatory responses in eggs and chicks of willow ptarmigan (lagopus lagopus).		1975	237680
micromorphological studies on the small intestine and caeca in wild and captive willow grouse (lagopus lagopus lagopus).		2004	506873
a comparison of the microbiological conditions in the small intestine and caeca of wild and captive willow grouse (lagopus lagopus lagopus).		1979	506874
vitamin c deficiency in growing willow ptarmigan (lagopus lagopus lagopus).	willow ptarmigan chicks raised on a diet containing 265 mg ascorbic acid/kg develop scury-like symptoms and die by 4 weeks of age. if blueberry plants are given as an ad libitum supplement to this diet, the malady is prevented. we have described the clinical, pathological and histological changes which accompany this malnutrition and conclude that they are in accord with the description of scurvy in guinea pig and man. biochemical determination of ascorbic acid synthesis in the kidney of ptarmig ...	1979	512712
tachycardia during egg-hypothermia in incubating ptarmigan (lagopus lagopus).	incubating birds regulate the egg temperature by varying their posture and the distance between eggs and brood patch. in the present study, we show that this homeostatic process is further assisted by varying the brood patch blood flow according to the temperature of the eggs. when female ptarmigan resume incubation of cooled eggs (e.g. after a period of foraging), they immediately develop pronounced tachycardia (4 times noraml in wild, 2-3 times in captive birds). tachycardia is maintained, alt ...	1979	539457
uric acid metabolism in the caeca of grouse (lagopus lagopus) [proceedings].		1978	569701
social rank, mating and egg fertilization in willow ptarmigan (lagopus lagopus lagopus).	when captive ptarmigan were allowed to choose their mates freely, the social rank of the male and female correlated significantly. when mates were allocated by the experimenter, without regard to similarity in social rank, fertility was low. when birds of similar social rank were paired, the fertility was high. it is suggested that fertility in captive ptarmigan may be increased if the relative social rank of mating birds is considered.	1977	605022
atrophy of a breast muscle with a single fibre type (m. pectoralis) in fasting willow grouse, lagopus lagopus (l.).	the willow grouse (lagopus lagopus) are arctic gallinaceous birds with small fat stores and large muscles. in winter, these birds may starve for periods of several days. it was important to know which energy reserves were utlized during periods of starvation. body composition of female willow grouse and bantam hens was studied before and after fasting. grouse have much larger breast muscles than do bantams, but reproductive organs are larger in hens. the relative amounts of adipose tissue are ab ...	1978	681910
haematology, weight and condition of captive red grouse (lagopus lagopus scoticus) infected with caecal threadworm (trichostrongylus tenuis).	red grouse infected with the caecal threadworm trichostrongylus tenuis developed a mild anaemia. haemoglobin and albumin levels in the blood fell but there were no significant changes in the number of red blood cells or their size. in infected birds the numbers of circulating eosinophils and heterophils increase, as did the concentration of alpha, beta and gamma globulin. body weights did not change but muscle masses shrank. birds that subsequently died had the lowest concentration of haemoglobi ...	1978	749086
listeriosis among willow grouse (lagopus lagopus) in captivity.		1975	803676
"emotional" bradycardia: a telemetry study on incubating willow grouse (lagopus lagopus).		1977	888715
the effects of castration on concentrations of luteinizing hormone in the plasma of photorefractory red grouse (lagopus lagopus scoticus).		1977	892416
proceedings: seasonal variations in plasma luteinizing hormone levels in male red grouse (lagopus lagopus scoticus).		1975	1133531
pulmonary phycomycosis in captive rock ptarmigan (lagopus mutus) and willow ptarmigan (lagopus lagopus) chicks.		1975	1136901
thermoregulatory behavior and body temperature in chicks of willow grouse (lagopus lagopus lagopus).	clocal temperatures (tcl) of outdoor living captive willow grouse chicks (lagopus lagopus lagopus) were found to increase from 39.4 +/- 0.5 degrees c. the first day to 40.3 +/- 0.5 degrees c. the twelfth day after hatching. average tcl of adults was 40.7 +/- 0.3 degrees c. when left alone for 30 min. in a controlled test environment providing temperatures ranging from 21 degrees c. to 46 degrees c., the one day old chicks preferred significantly higher ambient temperatures than eight day old bir ...	1975	1161703
regulation and grinding ability of grit in the gizzard of norwegian willow ptarmigan (lagopus lagopus).	fluctuations in grit composition in the gizzards of willow ptarmigans and the grinding ability of various grit assortments from wild ptarmigans were examined. we confirmed reports of other investigators that larger, fewer and rounder stones were present in the winter than in the autumn. experiments showed that ptarmigans prefer stones with diameters between 2-5 mm. birds on a constant diet maintained a constant stone intake throughout the year. the composition of gizzard grit was influenced by t ...	1975	1228713
multilocus dna fingerprints in gallinaceous birds: general approach and problems.	multilocus profiles were investigated in five different species of galliformes (ring-necked pheasant phasianus colchicus, indian peafowl pavo cristatus, japanese quail coturnix coturnix japonica, domestic chicken gallus gallus, and red grouse lagopus lagopus scoticus) using two human multilocus probes (33.6 and 33.15) in combination with each of four restriction enzymes (alui, ddei, haeiii or hinfi). all the species show a dna fingerprint-like pattern using at least one restriction enzyme in com ...	1992	1612925
factors affecting the establishment of the caecal threadworm trichostrongylus tenuis in red grouse (lagopus lagopus scoticus).	the resistance of captive reared red grouse to trichostrongylus tenuis was measured as the proportion of ingested infective 3rd-stage larvae which failed to develop to adult worms. individual grouse showed wide, repeatable variations in resistance. seasonal variations may also have occurred. red grouse acquired little or no effective immunity to reinfection after challenge with a single dose of infective larvae. in trickle-dosed grouse, however, adult worms weakly inhibited the establishment of ...	1989	2594417
development and survival of the free-living stages of trichostrongylus tenuis, a caecal parasite of red grouse lagopus lagopus scoticus.	in the laboratory, yields of infective 3rd-stage larvae of trichostrongylus tenuis were determined by temperature when moisture was adequate. on the moor, eggs in caecal faeces did not develop to infective larvae during the winter. in summer, development did occur and yields of infective larvae were related to temperature: greatest yields were obtained when mean monthly soil surface temperatures ranged between 7.6 and 10.3 degrees c. rainfall was unimportant, as was desiccation. during summer th ...	1989	2797866
arrested development of trichostrongylus tenuis as third stage larvae in red grouse.	worms were counted in red grouse (lagopus lagopus scoticus) in north east scotland in march, april, august, september, november and december 1986. immature worms occurred as third (l3) and fourth (l4) stage larvae throughout. two kinds of evidence suggest that l3 larvae spent much of the winter in a state of arrested development. first, recently acquired l3 larvae could be distinguished by the fact that they retained outer l2 cuticles for a few days; these were present only in the august and sep ...	1988	3194598
physiological aspects of freezing behaviour in willow ptarmigan hens.	when threatened, wild willow ptarmigan (lagopus lagopus lagopus) hens displayed freezing behaviour, i.e. motionless, crouched with head down and eyes open. but while non-incubating hens showed increased heart (hr) (from 229 +/- 18 to 254 +/- 33 beats min-1) and ventilation rates (vr) (from 25 +/- 2 to 31 +/- 4 breaths min-1), incubating hens showed bradycardia (from 208 +/- 40 to 102 +/- 13 beats min-1) and reduced vr (from 25 +/- 2 to 10 +/- 2 breaths min-1), which could be maintained for as lo ...	1988	3227948
endocrine changes in photostimulated willow ptarmigan (lagopus lagopus lagopus) and svalbard ptarmigan (lagopus mutus hyperboreus).	changes in plasma luteinizing hormone (lh), testosterone, thyroxine (t4), and triiodothyronine (t3) and the height of supraorbital combs were compared in captive willow ptarmigan (lagopus lagopus lagopus) and svalbard ptarmigan (lagopus mutus hyperboreus) exposed to an artificial annual cycle of daylength simulating that at 70 degrees n. plasma lh and testosterone and comb height increased more slowly in svalbard than in willow ptarmigan as daylength increased. in both species, plasma lh and tes ...	1988	3371650
electrophoretic separation of serum esterases in willow ptarmigan (lagopus lagopus lagopus).		2012	3436830
the effect of trichostrongylus tenuis on the caecal mucosa of young, old and anthelmintic-treated wild red grouse, lagopus lagopus scoticus.	the caecal mucosa of wild young and adult grouse infected naturally with trichostrongylus tenuis was examined by means of scanning electron microscopy and compared with adult grouse which had been treated with an anthelmintic. the caecal mucosa of young red grouse with low worm burdens possessed longitudinal plicae and exhibited little damage. the caeca from adult grouse, most of which carried high worm burdens, showed a localized depression of plicae and atrophy and cell disruption in areas of ...	1987	3588017
appropriate and inappropriate hypothalamic cold thermosensitivity in willow ptarmigan.	hypothalamic thermosensitivity has been investigated in conscious willow ptarmigan (lagopus lagopus lagopus) provided with chronically implanted hypothalamic perfusion thermodes. the birds were exposed to either cold (ta - 10 degrees c) or warm (ta + 25 degrees c) ambient conditions while hypothalamic temperature (thy) was clamped for periods of 20 min at different set levels between 28 degrees c and 43 degrees c. the responses of the animals to hypothalamic thermal stimulation were classified b ...	1987	3673613
changes in aromatase activity in the neuroendocrine tissues of red grouse (lagopus lagopus scoticus) in relation to the development of long-day refractoriness.	changes in aromatase activity in the neuroendocrine tissues of captive male and female red grouse (lagopus lagopus scoticus) were measured during a photo-induced breeding cycle. the gonads enlarged and subsequently regressed, as a consequence of the development of long-day refractoriness, within 84 days of transferring photoinsensitive birds from a non-stimulatory to a stimulatory daylength. the object of the study was to determine whether long-day refractoriness is related to an increase in aro ...	1986	3944533
the influence of ascorbic acid on the occurrence of tibial dyschondroplasia in young broiler chickens.	two distinctly different basal diets were used to test the influence of supplementary ascorbic acid on the occurrence of tibial dyschondroplasia. addition of either .1 or .25% ascorbic acid to these diets did not alter the occurrence of tibial dyschondroplasia in 25-day-old broiler chickens. however, supplementary ascorbic acid did increase the amounts of ascorbic acid present in blood plasma. also, individual differences in circulating ascorbic acid were not associated with this disease. furthe ...	1985	4011557
orienting and freezing responses in incubating ptarmigan hens.	behavior studies and telemetric recordings of heart and respiration rates were performed on five wild and two captive, incubating, willow ptarmigan hens (lagopus lagopus lagopus) and on four wild, incubating, svalbard ptarmigan hens (lagopus mutus hyperboreus). sounds and sight of approaching humans, egg predators, or dogs near the nests elicited behavior in the hens which we have interpreted as an orienting response (or) followed by freezing behavior. during both types of behavioral responses, ...	1985	4059382
variation in the visceral characteristics of the willow ptarmigan (lagopus albus) and common ptarmigan (lagopus mutus) in the taimir peninsula.		1974	4843924
the digestion of heather (calluna vulgaris) by red grouse (lagopus lagopus scoticus).		1972	5015248
the response of three grouse species (tetrao urogallus, lagopus mutus, lagopus lagopus) to louping-ill virus.		1980	6253539
clostridium perfringens type a toxins in relation to nephritis and uric acid diathesis in captive willow ptarmigan (lagopus l. lagopus).		1982	6295118
effects of different diets on viability, and gut morphology and bacteriology in captive willow ptarmigan chicks (lagopus l. lagopus).		1984	6464926
the development of photorefractoriness in castrated willow ptarmigan (lagopus lagopus lagopus).	changes in plasma lh levels were observed in castrated willow ptarmigan exposed to different lighting patterns to determine whether they become photorefractory. lh levels did not increase in long-term castrated birds exposed to a natural (70 degrees n) increase in daylength and did not fall abruptly in june when intact birds become photorefractory. plasma lh levels in naturally photostimulated, long-term castrates fell gradually during the summer and fall. plasma lh levels increased steeply when ...	1984	6735157
yersinia pseudotuberculosis infection in captive black grouse (tetrao lyrurus) and willow ptarmigan (lagopus l. lagopus).		1982	6762820
seasonal prevalence of hematozoa in willow ptarmigan (lagopus lagopus) from northwestern british columbia.		1981	6787186
development of photorefractoriness in willow ptarmigan (lagopus lagopus lagopus) and red grouse (lagopus lagopus scoticus) exposed to different photoperiods.		1982	7067969
plasma thyroxine and triiodothyronine levels during the development of photorefractoriness in willow ptarmigan (lagopus lagopus lagopus) exposed to different photoperiods.		1982	7084662
annual cycle of plasma concentrations of growth hormone in red grouse (lagopus lagopus scoticus).		1982	7152243
parental nutrition and chick production in captive willow ptarmigan (lagopus l. lagopus).		1982	7168429
nephritis and uric acid diathesis in captive willow ptarmigan (lagopus l. lagopus). effect of feed protein concentration and grass meal admixture.		1982	7180788
chick nutrition and mortality in captive willow ptarmigan (lagopus l. lagopus).		1982	7180789
effect of natural feed, antibiotics, tannin, diphenyliodoniumchloride and salicylic acid supplement on plasma uric acid concentration in captive willow ptarmigan (lagopus l. lagopus).		1982	7180790
caecal decomposition of uric acid in captive and free ranging willow ptarmigan (lagopus lagopus lagopus).	urine entering the caeca of birds contains significant amounts of uric acid. the discovery of great numbers of bacteria utilizing uric acid in the caeca has encouraged the discussion about nitrogen recycling in birds. in this work caecal decomposition of uric acid in wild and captive willow ptarmigan has been investigated using radioactively labelled uric acid injected directly into one of the caeca. the appearance of radioactive co2 in the expired air was taken as an indication of uric acid bre ...	1981	7282388
a comparison of the responses of captive willow ptarmigan (lagopus lagopus lagopus), red grouse (lagopus lagopus scoticus), and hybrids to increasing daylengths with observations on the modifying effects of nutrition and crowding in red grouse.		1981	7286635
on caecal synthesis and absorption of amino acids and their importance for nitrogen recycling in willow ptarmigan (lagopus lagopus lagopus).	the willow ptarmigan has two large caeca housing dense populations of microorganisms. urine, containing uric acid, is transported from the cloaca into the caeca when these are filled. here the uric acid is rapidly broken down, suggesting that the caeca take part in a recycling of excretory nitrogen. in this work it is shown that ammonia produced by the uric acid decomposition is incorporated into new amino acids in a glutamic dehydrogenase catalyzed reaction. we have, however, not been able to d ...	1981	7348031
seasonal changes in the concentrations of plasma luteinizing hormone and testosterone in willow ptarmigan (lagopus lagopus lagopus) with observations on the effects of permanent short days.		1980	7353781
the roles of day length and the testes in the regulation of plasma lh levels in photosensitive and photorefractory willow ptarmigan (lagopus lagopus lagopus).		1980	7409453
the development of photorefractoriness in willow ptarmigan (lagopus lagopus lagopus) after the suppression of photoinduced lh release with implants of testosterone.		1980	7409454
age-dependent accumulation of cadmium and zinc in the liver and kidneys of norwegian willow ptarmigan.		1993	8219593
host specificity of trichostrongylus tenuis from red grouse and northern bobwhites in experimental infections of northern bobwhites.	the red grouse (lagopus lagopus scoticus) and northern bobwhite (colinus virginianus) are parasitized by the cecal nematode, trichostrongylus tenuis. our objective was to determine if t. tenuis from red grouse is infective in bobwhites. we inoculated bobwhites with infective-stage t. tenuis larvae that originated from red grouse in northern england and bobwhites in florida. we also inoculated domestic chickens with larvae from the same sources. none of the 6 bobwhites inoculated with larvae from ...	1993	8331474
caecal threadworms trichostrongylus tenuis in red grouse lagopus lagopus scoticus: effects of weather and host density upon estimated worm burdens.	trichostrongylus tenuis eggs were counted in faeces from individually marked wild red grouse for 8 years. egg counts varied seasonally and annually. in some years, a sudden increase in mid-april was consistent with delayed maturation of larvae which had overwintered in the birds in a hypobiotic state. a more gradual increase in summer was probably due to uninterrupted maturation of larvae ingested then. despite 30-fold year-to-year variation in mean egg counts, relative differences in egg counts ...	1993	8414674
hypobiosis of trichostrongylus tenuis in experimentally infected grey partridges.	storage of infective larvae (l3) of trichostrongylus tenuis at +4 degrees c for six weeks before being given as single infections to grey partridges (perdix perdix) did not increase the proportion of worms subsequently found to be hypobiotic. however, after repeated infections, hypobiotic larvae were numerous. three infections given over three weeks resulted not only in the presence of many hypobiotic larvae, but also in the coincident loss of most adult worms. this indication of the role of imm ...	1993	8460270
the effect of parasites on wildlife.	populations of animals which live in the wild are regulated by many biotic and abiotic factors. parasites are one of the biotic factors. parasites may influence their hosts in different ways. they may cause the death of the host due to a direct lethal effect or an indirect effect. direct lethal effects may occur if killing is a part of the life cycle of the parasite or if hosts and parasites have not developed an equilibrium. the introduction of hosts or parasites into a new environment with sui ...	1996	8933697
isolation and characterization of hypervariable microsatellites in the red grouse lagopus lagopus scoticus.		1997	9004522
transmission dynamics and host-parasite interactions of trichostrongylus tenuis in red grouse (lagopus lagopus scoticus).	two components of the transmission dynamics of trichostrongylus tenuis in red grouse are examined and quantified, namely parasite transmission rate and density-dependent reductions in egg production. age-intensity data for birds of known age suggest that the rate of parasite uptake increases during the first 6 mo of a bird's life and this increase reflects an increase in feeding rate with age and exhibits no signs of self-cure. analysis of these age-intensity curves permits us to estimate the tr ...	1997	9105295
efficacy of acaricidal tags and pour-on as prophylaxis against ticks and louping-ill in red grouse.	this paper examines the efficacy of 10% lambdacyhalothrin-impregnated plastic tags and a deltamethrin pour-on preparation in protecting red grouse chicks from parasitism by ticks and subsequent infection with the louping-ill virus. in 1995, ten red grouse hens (lagopus lagopus scoticus) in a free-living population in north-east scotland were fitted with lambdacyhalothrin-impregnated plastic tags, glued to radio transmitters. chicks of more than 10 days of age from a further ten untreated radio-c ...	1997	9430120
the epidemiology of louping-ill, a tick borne infection of red grouse (lagopus lagopus scoticus).	the epidemiology of louping-ill in red grouse was studied in northern britain concentrating on the possible role of other species and mechanisms of disease persistence. this tick borne viral disease caused heavy mortality in red grouse, particularly chicks. louping-ill induced mortality reduced the strength of the density dependence that generates the tendency of grouse populations to cycle and in some populations may cause population sinks. four routes of transmission were examined and non-vira ...	1997	9802086
local genetic structure in red grouse (lagopus lagopus scoticus): evidence from microsatellite dna markers.	allelic variation at seven hypervariable tri- and tetranucleotide microsatellite loci was used to determine levels of population differentiation between 14 populations of red grouse (lagopus lagopus scoticus) in northeast scotland, uk. despite the potential for long-distance dispersal in grouse, and a semicontinuous habitat, significant population divergence was observed (mean rst = 0.153; p < 0.01) and an isolation-by-distance effect detected (mantel test: p < 0.001). examination of the spatial ...	1998	9859199
cestodiasis in the red grouse in scotland.	little is known about the cestode parasites of red grouse lagopus lagopus scoticus. the carcasses of 71 free-living and grouse collected from northeastern scotland (uk) between june 1991 and september 1992 were examined for the cestode paroniella urogalli. over 70% of young and old birds were infected in summer and winter. cestode abundance ranged from 0 to 29 (mean +/- se = 5.54 +/- 0.81) worms per host and did not differ significantly between young and old grouse, or between seasons. cestode i ...	1999	10231751
cospeciation and horizontal transmission of avian sarcoma and leukosis virus gag genes in galliform birds.	in a study of the evolution and distribution of avian retroviruses, we found avian sarcoma and leukosis virus (aslv) gag genes in 26 species of galliform birds from north america, central america, eastern europe, asia, and africa. nineteen of the 26 host species from whom aslvs were sequenced were not previously known to contain aslvs. we assessed congruence between aslv phylogenies based on a total of 110 gag gene sequences and aslv-host phylogenies based on mitochondrial 12s ribosomal dna and ...	2000	10756010
habitat loss and raptor predation: disentangling long- and short-term causes of red grouse declines.	the number of red grouse (lagopus lagopus scoticus) shot in the uk has declined by 50% during the 20th century this decline has coincided with reductions in the area of suitable habitat and recoveries in the populations of some avian predators. here we use long-term records of shooting bags and a large-scale manipulation of raptor density to disentangle the effects of habitat loss and raptor predation on grouse populations. the numbers of grouse harvested on the eskdale half of langholm moor in ...	2000	10821608
matrilineal genetic structure and female-mediated gene flow in red grouse (lagopus lagopus scoticus): an analysis using mitochondrial dna.	dna sequence variation at the hypervariable 5' end of the mitochondrial control region was examined in 247 individuals to detect genetic divergence among 14 populations of red grouse (lagopus lagopus scoticus) in northeastern scotland. ten haplotypes were resolved, several of which were shared among populations. analysis of molecular variance, nei's gamma st, and a cladistic estimate of the amount of gene flow indicated a lack of overall population differentiation. patterns of overall panmixia a ...	2000	10937204
evolution of the mitochondrial dna cytochrome b gene in tetraonidae birds].	mitochondrial fragments containing the cytochrome b gene (1020 bp in size) of four bird species belonging to four genera of the family tetraonidae (tetrao parvirostris, bonasa umbellus, lagopus lagopus scoticus, and falcipennis falcipennis) were directly sequenced. of the 1020 nucleotide positions, 186 were variable and uniformly distributed over the gene and only 46 were parsimony informative. most substitutions were synonymous. replacement substitutions were detected for 15 out of 340 amino ac ...	2000	10994496
role of small mammals in the persistence of louping-ill virus: field survey and tick co-feeding studies.	louping-ill (li) is a tick-borne viral disease of red grouse, lagopus lagopus scoticus lath. (tetraonidae: galliformes), and sheep, ovis aries l. (bovidae: artiodactyla), that causes economic loss to upland farms and sporting estates. unvaccinated sheep, grouse and mountain hares, lepus timidus l. (leporidae: lagomorpha), are known to transmit li virus, whereas red deer, cenrus elaphus l. (cervidae: artiodactyla), and rabbits, oryctolagus cuniculus l. (leporidae: lagomorpha), do not. however, th ...	2000	11016435
analysis of aggregation, a worked example: numbers of ticks on red grouse chicks.	the statistical aggregation of parasites among hosts is often described empirically by the negative binomial (poisson-gamma) distribution. alternatively, the poisson-lognormal model can be used. this has the advantage that it can be fitted as a generalized linear mixed model, thereby quantifying the sources of aggregation in terms of both fixed and random effects. we give a worked example, assigning aggregation in the distribution of sheep ticks ixodes ricinus on red grouse lagopus lagopus scoti ...	2001	11393830
generation of periodic waves by landscape features in cyclic predator-prey systems.	the vast majority of models for spatial dynamics of natural populations assume a homogeneous physical environment. however, in practice, dispersing organisms may encounter landscape features that significantly inhibit their movement. we use mathematical modelling to investigate the effect of such landscape features on cyclic predator-prey populations. we show that when appropriate boundary conditions are applied at the edge of the obstacle, a pattern of periodic travelling waves develops, moving ...	2002	11886619
platinum group elements in the feathers of raptors and their prey.	platinum (pt), palladium (pd), and rhodium (rh) concentrations were determined in the feathers of three raptor species in sweden, the sparrowhawk ( accipiter nisus), the peregrine falcon ( falco peregrinus), and the gyrfalcon ( falco rusticolus), as well as the main prey of the sparrowhawk (the house sparrow, passer domesticus) and the gyrfalcon (the willow grouse, lagopus lagopus). the analysis of feathers from 1917-1999 revealed a clear temporal trend, with significantly higher rh concentratio ...	2002	11910463
the effect of aggressiveness on the population dynamics of a territorial bird.	a central issue in ecology lies in identifying the importance of resources, natural enemies and behaviour in the regulation of animal populations. much of the debate on this subject has focused on animals that show cyclic fluctuations in abundance. however, there is still disagreement about the role of extrinsic (food, parasites or predators) and intrinsic (behaviour) factors in causing cycles. recent studies have examined the impact of natural enemies, although spatial patterns resulting from r ...	2003	12610624
standard sampling techniques underestimate prevalence of avian hematozoa in willow ptarmigan (lagopus lagopus).	a total of 68 willow ptarmigan (lagopus lagopus l.) was collected during september 1995 from two localities in troms county, northern norway. thin blood smears were prepared and examined for blood parasites. of the 68 willow ptarmigan examined, 94% harbored one or more species of hematozoa. there were four (6%), 44 (65%), 16 (24%), and four (6%) birds infected by zero, one, two, and three species of parasites, respectively. prevalences at the coastal locality, kattfjord (n = 43), were leucocytoz ...	2003	12910763
the role of non-viraemic transmission on the persistence and dynamics of a tick borne virus--louping ill in red grouse ( lagopus lagopus scoticus) and mountain hares ( lepus timidus).	there exist many tick borne infections that are of either economic or public health interest. mathematical models have previously been used to describe the dynamics of these infections. however it has recently come to light that there is an alternative mechanism for the transmission of these diseases that has not been considered in a modelling framework. this is transmission through ticks co-feeding on non-viraemic hosts. this paper extends a simple mathematical model to include this alternative ...	2004	14745507
faecal egg counts provide a reliable measure of trichostrongylus tenuis intensities in free-living red grouse lagopus lagopus scoticus.	the reliability of different egg counting methods for estimating the intensity of trichostrongylus tenuis infections in red grouse, lagopus lagopus scoticus, was investigated in the autumn, when grouse may harbour high parasite intensities. possible limitations to the use of these methods were also examined. faecal egg counts were found to accurately estimate t. tenuis worm intensities, at least up to an observed maximum of c. 8000 worms. two egg counting methods (smear and mcmaster) gave consis ...	2004	14972040
rising burden of immature sheep ticks (ixodes ricinus) on red grouse (lagopus lagopus scoticus) chicks in the scottish uplands.	the sheep tick ixodes ricinus (l.) (acari: ixodidae) is an ectoparasite of major economic and pathogenic importance in scotland. its distribution in the scottish uplands is assumed to be governed by the abundance and distribution of its definitive hosts (deer and sheep) and climatic variables such as temperature and rainfall. as the numbers of its major host in scotland, red deer, have increased dramatically and climatic conditions have become more favourable, the level of parasitism could have ...	2004	15009449
willow ptarmigan (lagopus lagopus) as a biomonitor of environmental metal levels in norway.	the purpose of this study was to examine the potential of a native wild bird, lagopus lagopus, as a monitor of environmental metal levels, in particular with respect to the influence of atmospheric deposition of metals from long-range transport. specimens of willow ptarmigan were collected from ten different locations in norway. the concentrations of cadmium, zinc and copper were determined in kidneys of birds from all sites. mean cadmium levels in adult ptarmigan kidney ranged from 6.6 to 48.5 ...	1994	15091659
lead exposure of small herbivorous vertebrates from atmospheric pollution.	concentrations of pb in livers of willow grouse (lagopus lagopus), black grouse (tetrao tetrix), and hare (lepus timidus) were determined in samples collected during the period 1990-92 from 77 locations distributed across norway. our objective was to elucidate the impact of long-range atmospheric transport on the pb exposure of the animals. the moss hylocomium splendens was measured for atmospheric pb deposition and pb in soil at 60-cm depth was determined to reflect the natural geochemical back ...	2000	15093005
weak compensation of harvest despite strong density-dependent growth in willow ptarmigan.	ptarmigan and grouse species (lagopus spp.) are thought to be able to compensate for a modest harvest because there is a surplus of breeding birds that are prevented from breeding by territory holders. to estimate the degree of harvest-mortality compensation reliably we experimentally harvested 0%, 15% and 30% of the willow ptarmigan (lagopus lagopus) on 13 estates ranging from 20 to 54 km2 in size during four hunting seasons in norway according to a regional block design. population overwinter ...	2004	15101697
ticks need not bite their red grouse hosts to infect them with louping ill virus.	for pathogens transmitted by biting vectors, one of the fundamental assumptions is often that vector bites are the sole or main route of host infection. here, we demonstrate experimentally a transmission route whereby hosts (red grouse, lagopus lagopus scoticus) became infected with a member of the tick-borne encephalitis virus complex, louping ill virus, after eating the infected tick vector. furthermore, we estimated from field observations that this mode of infection could account for 73-98% ...	2004	15252984
comparative tissue distribution of metals in birds in sweden using icp-ms and laser ablation icp-ms.	cadmium, copper, lead, palladium, platinum, rhodium, and zinc profiles were investigated along feather shafts of raptor and other bird species by laser ablation inductively coupled plasma mass spectrometry (la-icp-ms). the distribution of external versus internal metal contamination of feathers was investigated. the species examined were peregrine falcon (falco peregrinus), sparrowhawk ( accipiter nisus), willow grouse (lagopus lagopus), and house sparrow (passer domesticus) in sweden. for habit ...	2004	15386152
population biology of trichostrongylus tenuis, a parasite of economic importance for red grouse management.	the caecal nematode, trichostrongylus tenuis, is associated with dramatic decreases in the density of red grouse (lagopus lagopus scoticus) resulting in a significant loss of sporting income to many upland estates in the uk. in this article peter hudson and andrew dobson describe the dynamics of the grouse-t. tenuis system, show that the parasites can cause population crashes and present preliminary findings from the development of new control methods.	1989	15463233
testosterone and autumn territorial behavior in male red grouse lagopus lagopus scoticus.	in many bird species, males exhibit territorial aggression outside the breeding season, when testosterone concentrations are low and may not regulate territorial behaviors. the hormonal regulation of aggression at this time of year has only been studied in passerine birds. here, we investigated the role of testosterone in the regulation of aggression in a non-passerine bird, the red grouse lagopus lagopus scoticus. male red grouse are aggressive in early spring when breeding starts, in autumn wh ...	2005	15811360
interactions between population processes in a cyclic species: parasites reduce autumn territorial behaviour of male red grouse.	the causes of population cycles fascinate and perplex ecologist. most work have focused on single processes, whether extrinsic or intrinsic, more rarely on how different processes might interact to cause or mould the unstable population dynamics. in red grouse (lagopus lagopus scoticus), two causal mechanisms have been supported: territorial behaviour (changes in autumn aggressiveness) and parasites (parasite induced reduction in fecundity). here, we report on how these two regulatory processes ...	2005	15891828
lead concentrations in ruffed grouse, rock ptarmigan, and willow ptarmigan in québec.	between 1996 and 1998, ruffed grouse, spruce grouse, willow ptarmigan, and rock ptarmigan harvested by hunters in québec were examined for lead contamination. on examination of the gizzards of these birds, lead shot was found only in ruffed grouse (1.2%). the probability of ingestion of lead shot by grouse and ptarmigans is low. analyses of the lead concentrations in the wing bones of grouse and ptarmigans and in the muscle tissue of ptarmigans were conducted. although differences were observed ...	2005	15959706
demographic consequences of age-structure in extreme environments: population models for arctic and alpine ptarmigan.	organisms living in arctic and alpine environments are increasingly impacted by human activities. to evaluate the potential impacts of global change, a better understanding of the demography of organisms in extreme environments is needed. in this study, we compare the age-specific demography of willow ptarmigan (lagopus lagopus) breeding at arctic and subalpine sites, and white-tailed ptarmigan (l. leucurus) breeding at an alpine site. rates of egg production improved with age at the alpine and ...	2005	16010534
separating behavioral and physiological mechanisms in testosterone-mediated trade-offs.	testosterone often mediates trade-offs between reproduction and other life-history traits, which are usually investigated using testosterone implants. however, this approach does not distinguish between the physiological and behavioral effects of testosterone. we studied a wild game bird, the red grouse lagopus lagopus scoticus, and took a new approach to investigate mechanisms linking elevated testosterone to increased parasite intensity. we caught males in autumn, removed their parasites, impl ...	2005	16032571
organochlorines and trace elements in upland game birds harvested in canada.	american woodcock, common snipe, two species of ptarmigan (willow and rock), and three species of grouse (ruffed, spruce, and sharp-tailed) were collected from 21 locations between 1991 and 1994 as part of a nationwide survey of contaminants in game birds harvested in canada. breast muscle was analysed for organochlorines (chlorobenzenes, hexachlorocyclohexanes, chlordane-related compounds, ddt metabolites, mirex, dieldrin, and pcbs) and trace elements (hg, cd, se, and as). the concentrations of ...	2006	16055172
interactions between intrinsic and extrinsic mechanisms in a cyclic species: testosterone increases parasite infection in red grouse.	field studies of mechanisms involved in population regulation have tended to focus on the roles of either intrinsic or extrinsic factors, but these are rarely mutually exclusive and their interactions can be crucial in determining dynamics. experiments on red grouse lagopus lagopus scoticus have shown that population instability can be caused both by the effects of a parasitic nematode, trichostrongylus tenuis, on host production or by changes in testosterone influencing aggressive behaviour and ...	2005	16191643
vector-borne parasites decrease host mobility: a field test of freeze or flee behaviour of willow ptarmigan.	transmission mode has been suggested to be a strong predictor of virulence. according to theory, the transmission of vector-borne parasites should be less dependent on host mobility than directly transmitted parasites. this could select for increased exploitation of host resources in parasites transmitted by vectors, which may be manifested as higher virulence. here, we test the prediction that there is an association between transmission mode and the effect on host mobility by comparing parasit ...	2006	16696980
accumulation of heavy metals in circumpolar willow ptarmigan (lagopus l. lagopus) populations.	a circumpolar survey of heavy metals in willow ptarmigan liver and kidney revealed considerable variations in cd content in canada and scandinavia. the cd content in central canada was comparable with that in scandinavia and russia, at least for kidney. however, in both liver and kidney the median for canada as a whole was much higher than in the other countries. some canadian locations had exceptionally high levels, several birds having >50 mg kg(-1) in liver and >400 mg kg(-1) in kidney. in no ...	2006	17055034
cadmium concentrations in tissues of willow ptarmigan (lagopus lagopus) and rock ptarmigan (lagopus muta) in nunavik, northern québec.	willow and rock ptarmigan were obtained from northern québec. willow ptarmigan were found to have mean cadmium concentrations of 179.7 microg/g (dw) in the kidneys and 25.8 microg/g (dw) in the liver; these levels were three times higher than those found in the rock ptarmigan. the cadmium levels in the ptarmigan were below the threshold above which adverse effects can be observed in birds. the difference between the two ptarmigan species in cadmium content is explained by the diet. a comparison ...	2007	17223236
nematode parasites reduce carotenoid-based signalling in male red grouse.	carotenoids determine the yellow-red colours of many ornaments, which often function as signals of quality. carotenoid-based signalling may reliably advertise health and should be particularly sensitive to parasite infections. nematodes are among the commonest parasites of vertebrates, with well-documented negative effects on their hosts. however, to date, little is known about the effects that these parasites may have on carotenoid-based signalling. tetraonid birds (grouse) exhibit supra-orbita ...	2007	17264052
territory occupancy rate of goshawk and gyrfalcon: no evidence of delayed numerical response to grouse numbers.	two recent studies on territory occupancy rates of goshawk accipiter gentilis and gyrfalcon falco rusticolus report a 2-3-year-delayed numerical response to grouse numbers, which is a requirement for a hypothesis of predator-generated grouse cycles. the time lags were assumed to reflect the average age of sexual maturity in the raptor species. in southern norway, however, subadult (two-year-old) goshawk hens occupied only 18-25% of territories where occupancy was not recorded in the preceding ye ...	2007	17549523
ornamental comb colour predicts t-cell-mediated immunity in male red grouse lagopus lagopus scoticus.	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 ...	2008	17898979
sensitivity to assumptions in models of generalist predation on a cyclic prey.	ecological theory predicts that generalist predators should damp or suppress long-term periodic fluctuations (cycles) in their prey populations and depress their average densities. however, the magnitude of these impacts is likely to vary depending on the availability of alternative prey species and the nature of ecological mechanisms driving the prey cycles. these multispecies effects can be modeled explicitly if parameterized functions relating prey consumption to prey abundance, and realistic ...	2007	18027760