Species

The Caucasian black grouse Tetrao mlokosiewiczi is endemic to the Caucasus region in Armenia, Azerbaijan, Georgia, Iran, Turkey and Russia (Kutubidze 1961, Vitovic 1986, Potapov & Flint 1989, Baskaya 1997). Its range is highly fragmented and probably contracting. Estimates of the total population size vary within 10,000–100,000 birds, but the rate of decline is unknown. Habitat degradation due to cattle grazing and shepherding, predation by feral and shepherd-dogs, and illegal hunting are believed to be major threats to the species (Klaus, Bergmann, Marti, Müller, Vitovic & Wiesner 1990, S. Baskaya, A. Gavashelishvili, S. Klaus & A. Solokha, pers. comm.). Its status is insufficiently clarified; therefore, it is currently listed as data deficient (Hilton-Taylor 2000).

The Chinese Grouse Bonasa sewerzowi is endemic to central China (Sun 1995, Bergmann, Klaus, Müller, Scherzinger, Swenson & Wiesner 1996, Sun 1996, Lu 1997) . Its range is contracting and highly fragmented. The population is declining and is currently estimated at >10,000 birds (Y-H. Sun, pers. comm.). Major threats are habitat loss and deterioration related to increasing land use and forest exploitation, particularly large-scale clear-cutting (Bergmann et al. 1996, Klaus, Scherzinger & Sun 1996, Li 1996, Y-H. Sun, pers. comm.).

The Siberian grouse Falcipennis falcipennis occurs in a limited area in far-eastern Russia (Potapov & Flint 1989, Hafner & Andreev 1998). The range is fragmented and probably contracting. The population has been estimated at one million birds. The species probably has been declining since the 1970s. The major cause of decline is forest exploitation, particularly large-scale clear-cutting (Klaus, Lieser, Suchant & Andreev 1995, Hafner & Andreev 1998, F. Hafner & S. Klaus, pers. comm.).

The Gunnison sage grouse Centrocercus minimus in southwestern Colorado and southeastern Utah has recently been recognised as a new species separate from the common sage grouse C. urophasianus (Braun & Young 1995, Young, Braun, Oyler-McCance, Quinn & Hupp 2000, American Ornithologists' Union 2000). The Gunnison sage grouse is listed as endangered (IUCN 1994) in the 2000 IUCN Red List of Threatened Species (Hilton-Taylor 2000) because of low population sizes (<5,000 birds spread over eight disjunct populations), restricted range (occupied area <500km²), ongoing population decline, and habitat degradation, loss, and fragmentation related to livestock grazing, agriculture, housing development and road construction (see Connelly & Braun 1997, Oyler-McCance 1999, Oyler-McCance, Kahn, Burnham, Braun & Quinn 1999).

Subspecies

Subspecies are generally not considered in the IUCN 2000 Red List of Threatened Species (Hilton-Taylor 2000), although the IUCN red-list categories and criteria can be applied to any taxonomic unit at or below species level (IUCN 1994). According to these criteria, two subspecies of grouse are globally threatened: Attwater's prairie chicken Tympanuchus cupido attwateri and the Cantabrian capercaillie Tetrao urogallus cantabricus.

Attwater's prairie chicken is critically endangered (IUCN 1994). The total population remaining in the wild in 1999 was 46 birds in two isolated populations in Texas that were largely supported by releases of captive-reared birds (N. Silvy, pers. comm.). Major causes of decline were agriculture, urban development and other human land use activities (Silvy, Griffin, Lockwood, Morrow & Peterson 1999, N. Silvy, pers. comm.).

The Cantabrian capercaillie (Castroviejo 1967) qualifies to be listed as endangered (IUCN 1994). It inhabits a severely fragmented 6,000 km² range in the Cantabrian mountains of northern Spain. The population is estimated at <1,000 birds; numbers have been declining by an estimated 25–50% over the past 10–15 years (J. Obeso, pers. comm.). The major causes of decline are seen in habitat loss, fragmentation, and degradation related to forestry and tourism, illegal hunting and disturbance by human outdoor activities (J. Castroviejo, pers. comm.).

Table 1.

Conservation status of the 18 species of grouse at the global level according to the 2000 IUCN Red List of Threatened Species (Hilton-Taylor 2000) and the 1996 IUCN Red list of Threatened Animals (IUCN 1996), and at the national level according to national red data books. Listing at state (USA) or province (Canada) level is noted in brackets. * No information for a few countries; therefore the list may not be complete.

Populations

At regional, national and local scales, many populations of grouse are declining and threatened with extinction. This is particularly true of grouse inhabiting regions densely populated by humans, e.g. western and central Europe, eastern and central North America, and parts of eastern Asia. Fourteen of the 18 species of grouse (78%) are included in the national red-data books of at least one country (Table 1). Only two of the 18 species, the blue grouse Dendragapus obscurus and the ruffed grouse Bonasa umbellus, are neither red-listed at global, national, nor state (US) or provincial (Canada) level.

Based on the questionnaire and published information, assumed population trends of grouse by country and species were distinguished as increasing, stable, declining or unknown. Among a total of 165 ‘national populations’ (by country and species), only two were reported to increase: black grouse Tetrao tetrix in Romania and Slovenia; 58 national populations were considered to be stable. A decline was reported for 53 populations, and for 52 the trend was unknown. The tundra grouse, i.e. white-tailed Lagopus leucurus, rock L. mutus, and willow ptarmigan L. lagopus (Potapov & Flint 1989, Braun, Martin & Robb 1993, Holder & Montgomerie 1993, Hannon, Martin & Eason 1998), still occupy most of their original ranges; they are best protected by their often remote habitats. All national populations were believed to be stable, or trends were unknown (Fig. 1). For the forest edge, i.e. black and Caucasian black grouse (Klaus et al. 1990), and the forest grouse, i.e. capercaillie Tetrao urogallus, black-billed capercaillie Tetrao parvirostris (Klaus, Andreev, Bergmann, Müller, Porkert & Wiesner 1989), Chinese and hazel grouse Bonasa bonasia (Bergmann et al. 1996), ruffed grouse (Atwater & Schnell 1989, Rusch, DeStefano, Reynolds & Lauten 2000), blue grouse (Zwickel 1992), Siberian grouse (Hafner & Andreev 1998), and spruce grouse Falcipennis canadensis (Boag & Schroeder 1992), the largest proportion of declining national populations was reported. This is related to the ongoing changes in forest habitats worldwide (see below). Among the prairie grouse (see Fig. 1), negative trends were reported for sage grouse and Gunnison sage grouse; the sharp-tailed grouse Tympanuchus phasianellus and the prairie chickens were believed to be currently stable. However, the prairie grouse have lost major parts of their original ranges in the past (e.g. Braun, Martin, Remington & Young 1994, Schroeder & Robb 1993, Connelly, Gratson & Reese 1998, Giesen 1998).

Figure 1.

Based on 125 country-by-species questionnaires from 38 countries and published information, the assumed current population trends of grouse were classified as positive, stable, negative or unclear by country and species. The results from a total of 165 national populations are summarised by habitat type. The species are grouped in the following ways: tundra grouse = white-tailed, rock, and willow ptarmigan; forest edge species = black and Caucasian black grouse; forest species: black-billed capercaillie, capercaillie, blue, Chinese, hazel, ruffed, Siberian and spruce grouse; prairie grouse = sage, Gunnison sage and sharp-tailed grouse, greater and lesser prairie chicken.

Habitat degradation, loss and fragmentation

Habitat change is considered as the major threat to grouse populations worldwide. Degradation is here understood as a decline in species-specific habitat quality that leads to reduced survival and/or reproductive success in a population, e.g. related to changes in food availability, cover or climate. Habitat loss means that an area completely loses its suitability for a particular species. Fragmentation is a likely consequence of habitat loss, e.g. clear-cuts result in habitat loss, but also fragment the remaining forest.

Figure 2.

Relative importance of various types of threats to grouse populations by continent, based on questionnaire results per country and species. A total of 115 questionnaires which reported on threats to grouse at a national level were included in the analysis and all 18 grouse species were represented.

Grouse can tolerate a certain degree of human impact on the habitat. However, where industrialised farmland, timber production forests and urban areas dominate the landscape, grouse populations are likely to decline and disappear. Habitat change has also been identified as the main cause of the extinction of the heath hen Tympanuchus cupido cupido in Massachusetts (Schroeder & Robb 1993), the black grouse in parts of central Europe (Loneux & Ruwet 1997), and the decline and extinction of prairie chicken populations in the USA (Schroeder & Robb 1993, Westemeier, Brawn, Simpson, Esker, Jansen, Walk, Kershner, Bouzat & Paige 1998).

Agriculture: The conversion of natural habitats into farmland and settlements is the process that likely has led to the largest range contractions of grouse (see del Hoyo, Elliott & Sargatal 1994). In temperate Eurasia, forests were cleared on a large scale in the middle ages and before; somewhat later, moors and heathlands were drained and fertilised (e.g. Küster 1995). In North America, the conversion of forests and grasslands to cropland started with the European settlers in the middle of the 19th century (see Braun et al. 1994). For grouse, the results were considerable habitat loss and fragmentation. Both prairie grouse (e.g. Schroeder & Robb 1993, Braun et al. 1994, Connelly et al. 1998, Giesen 1998) and forest grouse (e.g. Rolstad & Wegge 1987, 1989, Rolstad 1991, Kurki & Lindén 1995) are likely to become extinct during the transition from a natural landscape with islands of farmland to a farming-dominated landscape with scattered islands of habitat suitable for grouse. In general, grouse cannot survive in farmland because most crops are not suitable, or only during short periods, for nesting, feeding or cover, and because of increasing risk of predation (see e.g. Mckee, Ryan & Mechlin 1998).

Grazing: Intensive grazing can affect the structure, height and species composition of the vegetation and thus destroy or degrade cover, nesting and feeding habitats of grouse (e.g. Baines, Sage & Baines 1994, Baines 1996). Trampling and erosion are additional problems. Excessive livestock-grazing is known to negatively impact prairie grouse populations on North American rangelands (e.g. Schroeder & Robb 1993, Braun et al. 1994, Connelly et al. 1998, Giesen 1998), black grouse and Caucasian black grouse populations on Eurasian heaths and treeline habitats (e.g. Klaus et al. 1990), as well as some capercaillie (Klaus et al. 1989) and hazel grouse populations (Bergmann et al. 1996) in central European forests. Deterioration of grouse habitats may also result from high densities of deer or other wild ungulates which may reduce the ground vegetation to a few centimetres in height (e.g. Baines et al. 1994, Baines 1996). Some moderate grazing can be compatible with grouse. Livestock herding may even improve grouse habitats, e.g. in the Alps, where pasturing has significantly increased the area suitable for black grouse (Glänzer 1980, Magnani 1988). Also capercaillie may profit from a moderate degree of grazing if cattle and deer contribute to maintain open forest structures (Klaus et al. 1989).

Forestry: Forestry may lead to significant changes in the structure and the temporal and spatial dynamics of forests. Because each forest grouse species has a different habitat preference, silvicultural operations may affect them in different ways (Klaus 1991, Swenson & Angelstam 1993). At the forest stand scale, grouse seem to be flexible with regard to species-composition and stand age, but are sensitive to structural changes such as the loss of the ground vegetation or understorey (e.g. Baines 1995, Storch 1995, Swenson 1995). At the landscape scale, forest grouse are susceptible to habitat fragmentation, and tend to decline rapidly as the patches of suitable habitat become too small and scattered (see e.g. Rolstad & Wegge 1987, 1989, Rolstad 1991, Wegge, Rolstad & Gjerde 1992, Zwickel 1992, Aberg 1996, Storch 1997).

Urban, infrastructure and tourism development: The extent of grouse habitats lost to settlements, roads, power-lines or ski-stations is more limited. However, infrastructure development increases the accessibility of an area and opens habitats and grouse populations to exploitation (e.g. Potapov & Flint 1989, Forman & Alexander 1998). Areas frequented by humans, e.g. for sport and leisure activities, may virtually be lost as grouse habitats, even if the habitat structure remains unchanged (e.g. Ménoni & Magnani 1998, Zeitler & Glänzer 1998). Locally, collisions with features such as power-lines (Bevanger 1995), deer fences (Baines & Summers 1997), and ski-lift cables (Miquet 1986, A. Zeitler, pers. comm.) may cause significant mortality among grouse.

Pesticides and pollution: Herbicide or insecticide- treatment of rangeland or forests may result in the loss of nesting, brood and resting cover, and may reduce the abundance of invertebrate chick food. Increased mortality due to pesticides may occur, either directly through poisoning or indirectly due to increased susceptibility to predation. Pollutants transported through wind and rain may result in soil eutrophication and lead to vegetation changes that are disadvantageous to grouse (e.g. Porkert 1991, Bergmann & Klaus 1994a,b, Klaus & Bergmann 1994, Schroeder & Robb 1993, Connelly et al. 1998, Hannon et al. 1998, Giesen 1998).

Small population size

In parts of the range, e.g. in western and central Europe, loss, fragmentation and deterioration of habitats have resulted in small isolated grouse populations. Small populations generally show a high risk of extinction due to chance environmental or demographic events (Shaffer 1987, Klaus 1994). Chances of recovery are low, even if the habitat is suitable. There are several well documented examples of small grouse populations that became extinct, or are close to extinction despite major conservation efforts, e.g. black grouse in Denmark (Holst-Jørgensen 1995), Belgium, Germany (Loneux & Ruwet 1997) and the Netherlands (Niewold 1990), capercaillie in Germany (Klaus & Bergmann 1994) and prairie chickens in the USA (Schroeder & Robb 1993, Westemeier et al. 1998). It is likely that conservation efforts were made too late. An isolated grouse population should probably number at least several hundred birds (Storch 1995, Grimm & Storch 2000) in order to have good long-term survival chances (Shaffer 1987). Therefore, it is important to maintain connectivity within spatially structured populations (see Martin 1998).

There is evidence that reduced genetic variability might be an additional problem for the survival of small grouse populations: in an isolated population of prairie chickens, hatching success decreased as the population declined. This loss in fertility might have resulted from reduced genetic heterogeneity, and the fertility increased again after birds from elsewhere had been translocated into the population (Westemeier et al. 1998).

Predation

Parallel to land-use changes, the predation pressure on grouse regionally has increased during the past three decades (Reynolds 1990, Wegge, Gjerde, Kastdalen, Rolstad & Storaas 1990, Hudson 1992, Bergman & Klaus 1994a,b Klaus & Bergmann 1994, Fujimaki 1995). In the boreal forest, clear-cutting has resulted in higher numbers of generalist predators and increased mortality of grouse (Andrén & Angelstam 1988, Andrén 1992, Wegge et al.1990, Kurki, Helle, Lindén & Nikula 1997) . In temperate Europe, fertilisation of farmland, availability of anthropogenic food sources, relaxed persecution (e.g. Hudson 1992) and vaccination of foxes Vulpes vulpes against rabies (e.g. Vos 1995) have contributed to increasing predator densities and negative effects on the survival rates of prey species such as grouse are likely to follow (e.g. Klaus et al. 1990, Reynolds 1990). In addition, domestic dogs and cats are a potential problem for grouse near settled or in recreational areas (A. Zeitler & F. Zwickel, pers. comm.). Predation by shepherd-dogs has locally become a threat to the Caucasian black grouse (Klaus et al. 1990, A. Gavashelishvili, pers. comm.).

Predators can have major influence on the population density of grouse, as has been shown in experimental and in empirical studies (Parker 1984, Marcström, Kenward & Engren 1988, Reynolds 1990, Hudson 1992, Kurki et al. 1997). However, there also is evidence that suitable habitat conditions may allow grouse to survive well despite high predator numbers (Baines 1996). Predation is unlikely to become a critical threat for a grouse population in a relatively undisturbed or natural landscape (e.g. Klaus et al. 1990). Many examples of populations that are considered to be threatened by predation come from severely fragmented and degraded habitats in landscapes intensively used by humans (e.g. Bergmann & Klaus 1994a,b, Klaus & Bergmann 1994, Loneux & Ruwet 1997, Weiss 1998). Accordingly, predation was named as a threat most frequently in questionnaires from European countries (see Fig. 2).

Exploitation

Because of the pronounced and often unpredictable fluctuations of many populations, grouse are susceptible to over-harvesting (Baines & Lindén 1991, Ellison 1991). Over-exploitation often appears to be related to insufficient enforcement of hunting regulations. Birds may be shot in excess of the legal hunting bags or outside the season. In the questionnaire, poaching has been reported most frequently from regions with poor rural economics (parts of Asia and eastern Europe), or from regions that combine relatively poor law enforcement with a high trophy or sport value of grouse (parts of southern Europe). The lekking species are particularly susceptible to over-exploitation. Birds at leks are easy targets and leks may be extirpated with little effort. Also, the spring hunt of displaying capercaillie and black grouse males at the leks, which is traditional throughout central Europe, involves a high risk of disturbing the social system at the lek, and may result in reduced reproductive success (see Baines & Lindén 1991).

Human disturbance

In many countries with wealthy societies, high human population densities and urban life-styles, the growing popularity of outdoor activities increases the potential for conflicts between the interests of recreationists and the needs of wildlife. Regionally, e.g. in Japan (Y. Fujimaki, pers. comm.) and in western and central Europe (e.g. Ménoni & Magnani 1998, Zeitler & Glänzer 1998), recreationists have become one of the main concerns in grouse conservation, particularly with regard to leks, in winter habitats and during chick-rearing and moulting (Meile 1982, Baydack 1998, Ménoni & Magnani 1998, Zeitler & Glänzer 1998). Effects can be direct and indirect. The escape of a flushed grouse is energy-consuming, may expose the bird to predators and reduces the time available for foraging. Frequent presence of humans may expel grouse from otherwise suitable habitats. Individual response and population-level effects of human disturbance of birds may vary with a large number of inter-related variables, such as the number, sex and age of the birds, the proximity, type, intensity and cumulative number of human activities, and the temporal and spatial availability and distribution of food and cover (Hockin, Ounsted, Gorman, Hill, Keller & Barker 1992, Stalmaster & Kaiser 1998, Storch 1998).