Dendragapus Obscurus Research Articles

Sexual and subspecific variation in the numbers of rectrices of blue grouse

We examined numbers of rectrices of all subspecies of blue grouse (Dendragapus obscurus), determined from our own studies and reported in the literature. Approximately 8% of all birds had an uneven number of rectrices, with no difference between males and females. More birds from a presumed subspecific "hybrid" population had uneven numbers of rectrices than those from "nonhybrid" samples. Of North American tetraonines, sage grouse (Centrocercus urophasianus) and blue grouse appear most variable in this character. Within subspecies, males and females had the same modal numbers of rectrices. The sexes differed, however, in the overall distribution of numbers of rectrices; most birds with submodal numbers were females and most birds with supermodal numbers, males. Males and females in one hybrid population differed in modal numbers of rectrices: males 20, and females 18. Eighty per cent of all coastal blue grouse had 18 rectrices, with no differences among subspecies. In contrast, all interior subspecies differed from each other. The two northern interior subspecies, D. o. pallidus and D. o. richardsonii, had modes of 20 rectrices, with that for pallidus weaker than that for richardsonii (70 and 81% modal, respectively). Dendragapus obscurus obscurus had a mode of 18 rectrices, not different from that for coastal birds. A small sample of D. o. oreinus was equally divided between birds with 18 and 20 rectrices, suggesting relationships with D. o. pallidus to the north and D. o. obscurus to the east. Northern interior blue grouse emerge as a distinct group with respect to modal number of rectrices, which parallels the pattern for the presence or absence of tail bands. Based on these two characteristics, coastal blue grouse appear more closely related to southern interior than to northern interior subspecies. The blue grouse is the only tetraonine with clear evidence of subspecific variation in numbers of rectrices.

Winter Use of Douglas-Fir Forests by Blue Grouse in Colorado

We studied winter use of Douglas-fir (Pseudotsuga menziesii) forests by blue grouse (Dendragapus obscurus) from 1981 to 1983 at 2 study areas in northcentral Colorado. Comparisons of used and available stands indicated grouse were concentrated spatially, but there were no consistent differences related to basal area of tree species, conifer stem densities, and topography that were common to both areas. Blue grouse used dense (2,000 stems/ha) second growth (40-75 yr old), open to dense (200-1,900 stems/ha) mature (100200 yr old), and open ( 250 yr old) stands at elevations >300 m, but also used early successional stages (520 yr old) at elevations <300 m more than expected. Hines (1987) suggested that blue grouse use a broader range of conifer habitats in winter than previously reported. Zwickel and Bendell (1972) speculated that winter habitat and food probably did not limit populations because blue grouse disperse over a wide area of conifer forests in winter after leaving the breeding range, and winter food appears abundant. This hypothesis implies that blue grouse either use a wide range of available conifer habitats or a few specific conifer types that are widespread. For species such as the blue grouse that frequently occupy different seasonal habitats, knowledge of year-round habitat requirements is imperative for formulating sound management strategies. Schroeder (1984) identified a lack of quantitative information on winter habitat use. Accordingly, we investigated winter use of Douglas-fir forests by blue grouse in Colorado with the following objectives: (1) to compare use and availability among conifer stands to determine if preferential use was related to topography, species composition, and stand structure; (2) to compare tree species and diameter classes used with availability within stands; and (3) to compare habitats used by males and females. A. L. Cade, M. W. Crosby, J. J. Jeanson, and K. A. Medve provided field assistance. The manuscript benefited from reviews by A. E. Anderson, M. J. Armbruster, D. C. Bowden, C. E. Braun, R. C. Kufeld, R. T. Reynolds, R. A. Ryder, and D. F. Stauffer. Special thanks are extended to the many landowners who allowed us access to lands under their control. This is a contribution of the Colorado Division of Wildlife, Federal Aid to Wildlife Restoration Project

Influence of Transmission Period on Primary and Relapse Patterns of Infection of Leucocytozoon spp. and Haemoproteus mansoni

Leucocytozoon sp., L. lovati and Haemoproteus mansoni infections in captive blue grouse (Dendragapus obscurus) were monitored weekly throughout primary and relapse periods. Chicks developed primary infections with L. lovati and Leucocytozoon sp. during 5- 9 wk of natural exposure, whereas H. mansoni was transmitted during a 2-3-wk period. Relapse infections of Leucocytozoon sp. and L. lovati in wild blue grouse had constant monthly prevalences (percent infected) and intensities (mean number of parasites). In contrast, prev- alence and intensity increased throughout the relapse period for H. mansoni. The patent period in infrapopulations (within one host) of H. mansoni was 5-11 wk for primary, and 11-26 wk for relapse infections. Likewise, peak intensities appeared 1-4 wk after the start of patency for primary and 5-11 wk for relapse infections. No differences were detected in the Leucocytozoon spp. Precise timing and peak intensity was selected for in H. mansoni which had a short transmission period, but not in Leucocytozoon with long transmission periods. Gametocyte production occurs for a longer period during relapse than during the primary period. This satisfies constraints imposed by a pulse vector on parasite transmission to vertebrate hosts. A model is proposed to explain the evolution of the complex intensity patterns observed in H. mansoni.

Why do grouse have ceca? A test of the fiber digestion theory.

Two predictions deduced from the theory that grouse ceca function primarily to provide a suitable environment for the fermentation of plant fiber were tested. Digestion of neutral detergent fiber in conifer needles by blue grouse (Dendragapus obscurus) varied from 7.5 to 17.3% across tree species, but, contrary to prediction, the energy potentially derivable from this fiber digestion was insufficient to make ceca energetically profitable. Variation in digestibility of fiber among birds and across species was caused by differential accessibility of fiber to the ceca as essentially all (average, 96.8%) fiber entering the ceca was digested. An allometric analysis of grouse gut lengths suggested, and a correlation analysis confirmed, that cecal lengths among species of grouse decrease in length as dietary fiber increases, also soluble and suspended particulate food components from insoluble. Ceca do act as fermentative and absorptive reservoirs for fiber, but also (and predominantly) for urine and cell soluble or suspended components previously undigested because of high rates of passage. I suggest that the adaptive significance of this strategy is to maximize the rate at which energy is obtained from poor quality foods.

Autumn Habitat of Capercaillie in Southeastern Norway

I studied autumn habitat use by radio-marked capercaillie (Tetrao urogallus) in a coniferous forest in southeastern Norway, from September to November 1984-86. I derived use of elevation, successional stage, edge, vegetation type, tree and shrub cover, and tree height by extrapolating 876 locations of 26 males and 20 females from a habitat map. Both sexes preferred old, spruce-dominated forests. Within old forests, males preferred forest interiors, and within clearcuts males preferred edges of old forests. Males were found at higher elevations than females. Commercial forestry affects capercaillie autumn habitats adversely by extensive cutting of old, bilberry (Vaccinium myrtillus)-rich natural forests, and by producing dense, managed forest stands. J. WILDL. MANAGE. 52(4):747-753 Capercaillie inhabit boreal coniferous forests in the palearctic region. When the ground is snow-covered, birds feed on pine needles; the distribution of capercaillie along the northern part of their range is almost congruent with Scots pine (Pinus sylvestris) (Seiskari 1962:46). During winter and early spring, capercaillie prefer old pine forests with thick branches and open canopy to allow birds to feed in trees and fly between them (Gjerde et al. 1985, Klaus et al. 1985, Rolstad and Wegge 1988). In summer, capercaillie consume a great variety of plant species (Semenov-Tjan-Sanskij 1960), and their affinity for old forests is less pronounced (Marcstrim et al. 1982, Rolstad et al. 1988). During the last 20-30 years, capercaillie have declined markedly throughout their range, presumably because of habitat destruction and excessive cutting of old, natural forests (Marcstrim 1979, Moss et al. 1979, Klaus 1982). Other woodland grouse (blue grouse [Dendragapus obscurus] and spruce grouse [D. canadensis]) exhibit distinct seasonal changes in habitat use (Pietz and Tester 1982, Bendell and Zwickel 1985). Capercaillie habitat use is well documented for most of the year (Rolstad and Wegge 1988), except for autumn (Unander 1980, Toverud 1984). My objective was to determine capercaillie habitat use and old forest affinity during

Nesting parameters in a high density, declining population of blue grouse

Of four nesting parameters (clutch size, egg fertility, egg hatchability, and nesting success) in a population of blue grouse, Dendragapus obscurus fuliginosus, at Hardwicke Island, British Columbia, only clutch size differed between yearling and adult females. There was no difference among years for any of the parameters considered. This population declined from very high to moderate density during the studies reported here, and clutch size, egg fertility, and hatchability were significantly lower than reported for a more stable population (Comox Burn) in the same general region. Nesting success at Hardwicke Island, however, was higher than at Comox Burn. Collectively, the parameters examined do not, by themselves, explain the observed decline. Nevertheless, they suggest that the population at Hardwicke Island differed from that at Comox Burn in some fundamental aspects of reproduction that may be symptomatic of other factors possibly involved in its decline, e.g., the survival of chicks.

Populations of Leucocytozoon gametocytes in blue grouse (Dendragapus obscurus) from Hardwicke Island, British Columbia.

Population dynamics of round and elongate gametocytes of Leucocytozoon in wild and captive blue grouse (Dendragapus obscurus (Say)) from Hardwicke Island, British Columbia, were studied from 1980 to 1982. Blue grouse chicks were sampled weekly throughout each transmission season. Three patterns in the type of gametocyte produced during primary infection were observed in naturally infected captive and wild blue grouse chicks. Such variation in the expression of the gametocyte stage within a single host population suggests a different interpretation than has been previously reported for species of Leucocytozoon. The data from the primary patterns and profiles coupled with reexposure data and the asynchronous appearance of round and elongate gametocytes can be best interpreted as infection with two concurrent species of Leucocytozoon in blue grouse. More detailed research on the life cycle is necessary to confirm if two species of Leucocytozoon exist in blue grouse.

Use of early successional, midsuccessional, and old-growth forests by breeding blue grouse (Dendragapus obscurus fuliginosus) on Hardwicke Island, British Columbia

Numbers of breeding blue grouse (Dendragapus obscurus fuliginosus) observed along standardized transects on Hardwicke Island, British Columbia, were significantly higher in early successional stages than in midsuccessional or old-growth forests. Numbers in old-growth and midsuccessional forests were not statistically different. Cover percentage of the herbaceous stratum may be an important component of the preferred habitat.

Aggressiveness, incidence of singing, and territory quality of male blue grouse

The relative aggressiveness and proportion of time spent singing (incidence of singing) were assessed for male blue grouse (Dendragapus obscurus) occupying high- and low-quality territorial sites. Playback experiments were used to assess the relative aggressiveness of males; no support was obtained for the hypothesis that males on high-quality sites are more aggressive than those on low-quality sites. Prior experience with an area may be more important than aggressiveness in determining the quality of territorial site that is obtained. In 1 of 2 years, males on high-quality sites were observed hooting (singing) a greater proportion of the time than were males on poorer sites. A greater incidence of hooting by males on high-quality sites may be one factor that results in more females being observed near these males than near males on less suitable areas, as was found in a previous study.

Survival and Reproduction of Dispersing Blue Grouse

Dispersal in a declining population of Blue Grouse (Dendragapus obscurus) was studied over four years on Hardwicke Island, British Columbia, Canada, by radio-tracking 66 individuals and reobserving or recapturing 126 banded individuals. On a 464-ha main study area, numbers of territorial males decreased from 152 to 94, breeding females from 276 to 113, and young grouse alive in late summer from 847 to 224 during the period of study. Despite this, dispersal distances did not vary between years and bore no clear relationship with adult densities in spring or density of juveniles in the previous fall. Rates of survival and reproduction for long-dispersers (grouse moving greater than the median dispersal distance) and short dispersers (grouse moving less than the median dispersal distance) were similar. Similar results were noted for grouse that left the study area (dispersers) and those that remained on the study area (non-dispersers). Overall, there was little evidence that dispersers fared poorly or that dispersal was greatly influenced by population density.

Aggressive and Spacing Behavior of Female Blue Grouse

-Female Blue Grouse (Dendragapus obscurus) on Stuart Island, Washington were found to interact aggressively with female dummies in the prelaying period when a taped cackle call was played. Interactions included: tail fanning, wing dragging, everting the white patagium feathers to display a shoulder patch, head bobbing, neck stretching, jump attacking, pecking, and diving attacks. Threatening and aggressive calls included: cackling calls with inflections, a Nee-uk call, and attack and scream whinny calls. The frequency of aggressive interactions was greatest in the latter half of April, a period when hens were selecting nesting sites. The prelaying ranges of 12 hens were mostly mutually exclusive and showed a dispersed distribution relative to each other. However, there were interspaces sufficient for other grouse to nest. We suggest that aggressive behavior and mutual avoidance of females resulted in a dispersed distribution of nest sites. Such spacing should enhance the reproductive fitness of females by reducing predation rates on hens, eggs, and young. Received 24 August 1983, accepted 16 November 1984. THERE has been disagreement among biologists on whether territoriality in birds primarily served to disperse the breeding population (Lack 1966, 1968), or whether, in addition to this spacing function, it regulated numbers by excluding some individuals from securing breeding space (Wynne-Edwards 1962). Even after 20 years, the argument continues (Davies 1978, Patterson 1981, Wittenberger 1981). Recently, the territorial limitation hypothesis has been expanded to include the mutual exclusion of yearling females by other females in polygynous Blue Grouse (Dendragapus obscurus; Zwickel 1972, 1980; Hannon and Zwickel 1979). The primary evidence for surplus nonbreeding females was that, following the removal of localized females in the prelaying period, additional yearling females occupied the vacancies created (Zwickel 1972, 1980). However, this replacement does not constitute unequivocal evidence of socially induced nonbreeding in yearling females, since these females might have bred elsewhere (cf. Watson and Moss 1970). The newcomers could have shifted their ranges to improve their fitness as proposed in the Fretwell-Lucas habitat model (Fretwell and Lucas 1969). Such redistribution is consistent with theoretical considerations that animals should space themselves to reduce predation risk (Taylor 1976). The resolution of this perennial question requires documentation of the dispersion pattern of all females in a population where emigration cannot confound results. We measured aggressiveness and described the distribution of female Blue Grouse on Stuart Island, Washington during the breeding cycle in 1975 and 1976. Our hypothesis was that social interactions between females in the prelaying period resulted in mutually spaced ranges but that the spacing and ensuing social interactions did not prevent any female from nesting. Subordinate females could either nest between the ranges of other females or delay nesting until adults were egglaying and/or incubating their eggs.

Blue Grouse—Effects on, and Influences of, a Changing Forest

Blue grouse (Dendragapus obscurus) may increase spectacularly in lowland Pacific coast forest that has been logged by clear-cutting. Locally, they may be used heavily by hunters, and more subtly, by nonconsumptive recreationsists. They can be sufficiently abundant to affect the survival of young conifers, the distribution of seeds and, perhaps, nutrient cycling. Blue grouse can represent a major component of the faunal biomass on a given area.Local populations of blue grouse change mainly as a result of forest management practices on lowland breeding ranges. Logging at higher elevations probably will not produce grouse in equivalent densities, and the implications of increased logging on winter range (at even higher elevations) are unknown.Current logging and silvicultural practices have both positive and negative effects on blue grouse. Newly logged lowlands are colonized rapidly by "surplus" grouse from nearby, established populations. They may persist in variable, but unpredictable, densities until forest canopy approaches 75% coverage. Populations decline due to non replacement of adults that die. Although clear-cutting often results in short-term, and occasionally large, increases in numbers, these persist for only about 25% or less of a planned rotation period. The productive period for occupancy by grouse may be shortened by early planting, planting everywhere, fertilization with urea, and by large, even-aged plantations. The productive period may be extended by delayed planting, a wider spacing within plantations, not planting sites of low timber productivity and, perhaps, by intensive thinning throughout the forest rotation, or cutting in small patches.An important key to continuous maintenance of breeding populations of blue grouse appears to be the presence of a well-developed and diverse understory. Alternatives to present clear-cutting practices that would leave a more open tree canopy would probably provide continuous production of grouse and many other species, albeit at a lower density than sometimes results from present programs. Experimental forests that can be manipulated in conjunction with long-term studies of the effects of these manipulations on wildlife are needed if we are to integrate forest - wildlife management practices fully. Keywords: blue grouse, Dendragapus obscurus, populations, clear-cut logging, silviculture, forest succession.

Density, movements, and breeding success of female blue grouse in an area of reduced male density

The density of male blue grouse (Dendragapus obscurus) on a 95-ha area was reduced artificially by approximately 75% in 1982. Density, movements, and breeding success of females on this area in that year were compared with those of females on the same area in 1981 (when density of males was undisturbed) and of females on an unmanipulated control area in 1981 and 1982. A reduction in male density had no apparent effect on the density of either yearling (potential recruits) or adult females, or the daily movements, timing of breeding, and breeding success of females. Home ranges of females were largest when male density was artificially reduced, but not significantly so. The larger home range sizes of females residing in an area with a very low density of males did not seem to result entirely from females searching for males with which to breed. Results of this study suggest that densities of male blue grouse have no apparent effect on densities of females or production of young, and support the hypothesis that densities of females in this species are regulated independently of males.

Seasonal changes in spatial patterns and behavior of yearling male blue grouse on the breeding range

Changes in spatial patterns and behavior of yearling male blue grouse (Dendragapus obscurus) equipped with radio transmitters were recorded during spring and summer, 1980 and 1981, on Hardwicke Island, British Columbia. Sizes of home ranges decreased and yearlings appeared to become less dispersed as the season progressed. Most birds moved off their initial home range and onto new areas on the breeding range by late summer although the timing of this movement varied among individuals. Interactions involving yearling males with females and territorial males decreased as the season advanced. Changes in spatial patterns and behavior appear to be related to seasonal changes in levels of hormones in yearling males.

Spatial Patterns of Yearling Male Blue Grouse and Their Relation to Recruitment into the Breeding Population

Abstract Movements of yearling male Blue Grouse (Dendragapus obscurus) were monitored by radio telemetry during the springs of 1980 and 1981, on Hardwicke Island, British Columbia. The locations of the birds were clumped around territories of adult males. Most birds were associated with a few occupied territories, others settled near vacant sites that had been used as territories in previous years, and a few moved widely over the breeding range. Some territories attracted more yearlings than others. Presumed costs and benefits that may be associated with different types of spatial patterns of yearling males are discussed.

REPRODUCTIVE ISOLATION IN SONORAN DESERT DROSOPHILA.

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Factors affecting the return of young blue grouse to breeding range

From 1969 to 1976, 1958 juvenile blue grouse, Dendragapus obscurus fuliginosus, were marked with patagial wing tags and(or) leg bands in east-central Vancouver Island. Return and(or) recovery records from these birds in their 2nd year of life or greater indicate no significant differences among annual cohorts, between sexes, by time of hatch, by body weight at hatch, or by age of maternal parent (yearling or adult). However, a difference in the returns of smaller and larger chicks at time of hatch approached significance (smaller, least). There was a constant and significant increase in rate of return of chicks first marked at from 1 to 10 weeks of age.

Dispersal and site fidelity in Blue Grouse

Ten years of banding and censusing data from Blue Grouse (Dendragapus obscurus) were analyzed with respect to dispersal of juveniles and site fidelity of yearlings and adults. Juvenile females dispersed farther than juvenile males. In sibling pairs of the same sex, brothers settled closer to one another than sisters. In sibling pairs with birds of opposite sex, females dispersed farther than males. Adult males first established territories close to where they had been sighted as yearlings, or nonterritorial adults, and most females returned in spring to the same general area where they had previously nested. Two-year-old females showed less fidelity to breeding sites they had used as yearlings than older females to sites they had used in previous years.

Renesting in adult and yearling blue grouse

Eight of 31 radio-tagged female blue grouse (Dendragapus obscurus) that had first nests terminated before hatch produced second clutches. Significantly more adult than yearling hens renested. All yearling hens that produced a second clutch had first nests terminated during laying or early incubation; but most yearlings did not renest. Adult females renested independently of the stage of incubation when nests were terminated. Average size of second clutches of adults are likely larger than those of yearlings and average size of second clutches of all females are likely smaller than those of first clutches. Most prenesting home ranges used during second nesting attempts were in the same general areas and of the same sizes as those used during initial nesting attempts.

Survival and delayed breeding in male blue grouse

We present an analysis of survival of male blue grouse (Dendragapus obscurus) using known-aged individuals and examine the results in terms of the evolution of delayed breeding. Males had low rates of mortality and, among 2-year-olds, mortality rates of territorial and nonterritorial birds were the same. Up to 6 years of age, males had life expectancies of at least 2 years. Males that postponed breeding and survived had a 40–45% chance of eventually obtaining a high-quality site for a territory. If males had not delayed breeding they likely would have had to settle on areas where opportunities for breeding appear to be low. Thus, survival patterns of males are consistent with the hypothesis that it is advantageous for some males to delay breeding if high-quality sites cannot be obtained.