Northern Prairie Wildlife Research Center
The popular belief is that sharptails are simply responding to an increase in woody vegetation which has increased due to a lack of management (mowing, burning) and possibly a series of recent wet years. Have prairie chickens declined and sharptails increased because of woody vegetation, some antagonistic relationships between the two closely related species, or possibly both?
It is instructive to consider the early history of sharptails and prairie chickens in relationship to land use changes. Hatch (1892:163) recalled conversations with Rev. Gear, a chaplain at Ft. Snelling (Twin Cities, Minnesota) in about 1839 who stated, "the prairie hens (prairie chickens) were seldom seen at the first, but after the country began to become settled considerably, they increased in numbers perceptibly from year to year. The Blackfoot Grouse (Pediocoetes phasinanellus (Linn.), were the dominant grouse-kind of the territory, and very well represented in the openings, and wherever there was much brush-lands but were never found on the open, uncultivated prairies."
Coues (1874:410) discussed the occurrence of sharptails and prairie chickens in extreme southeast South Dakota along the Missouri River in the early 1870s: "In this stretch of seventy-five miles along the Missouri, the normal dividing-line runs somewhere -- the two species interdigitating, however, to such an extent that it cannot be precisely fixed. How many sharp-tailed, if any, are still found about Yankton, I cannot say; but there the Pinnated is the prevailing form, and so numerous that I have known them to be trapped and used instead of tame Pigeons in a shooting-match. Starting up the river they accompany us part of the day, till suddenly one of the "White-bellies" whirs up from the roadside, and we are soon fairly among them. At Fort Randall they are the prevailing species; so nearly exclusively, that in the course of my six months' residence there, I never became aware of the occurrence of the other, excepting in three instances, although officers and others, beside myself, did a good deal of shooting. The Cupidones (prairie chickens) are unquestionably creeping up the Missouri, just as the Quail have already done, although they have not, apparently, as yet progressed quite so far; and with their advance, the Sharp- tailed are probably receding along this line as elsewhere. There may be some antagonism, or other incompatibility, between the two species; but more probably the different conditions of environment, induced by the settling of the country, are the main cause of the change--what the Pinnated likes best being not to the taste of the other. Just as the Quail is a "home bird", loving the stubble-field and hay-rick near the owner's house, so the Pinnated prefers to glean over cultivated fields, while the wilder Sharp-tailed clings to its native heath (shrubby areas). The railroad will take the former along and warn away the latter."
Ammann (1957:111) quoting Bent (1932), the range of the sharptail "... is becoming more and more restricted as the Central West becomes more thickly settled and more land comes under cultivation. In some places it is decreasing in numbers where prairie chickens are increasing." Johnson and Knue (1989) citing Webb (1872), "Usually, during the first few years of settlement, it (prairie chickens) increases rapidly, and is often a nuisance to pioneer farmers."
Why did cultivation favor prairie chickens more than sharptails? Were woody habitat components needed by sharptails reduced by settlement activities such as building construction and wood burned as fuel? Were prairie chickens simply better adapted to living with early agriculture and simply "out produced" the less-adapted sharptails?
Apparently sharptails retreated from and prairie chickens advanced with early cultivation of the prairies and, farther east, the clearing and cultivation of the forest. As fields in cleared forest areas were abandoned and plant succession reclaimed the openings, sharptails replaced prairie chickens. Ammann (1957) observed for many years in Michigan, the interactions between prairie chickens and sharptails and felt brush encroachment favored sharptails to the detriment of prairie chickens.
Has woody vegetation become more widespread in the SNG? Assuming that it has, based on interviews with local residents and Forest Service personnel, how could this change favor sharptails over prairie chickens?
Sharptails can tolerate (prefer?) a greater amount of woody vegetation in nesting cover than prairie chickens which gives them greater flexibility in certain settings. If residual grassy cover is limited, due to mowing, burning or grazing, sharptails will readily nest in brushy cover, especially willows (Salix spp.) and buckbrush (Symphoricarpos occidentialis) (Len McDaniel, personal commun.; Kohn 1979:38). This could favor sharptails being more successful with first nests than prairie chickens and thus contribute more young to the population since first clutches are larger (John Toepfer, personal commun.). Grosz and Kirby (1986:23) found 13 of 20 (65%) sharptail nests situated in buckbrush communities in a grazing/wildlife study near Streeter, ND and suggested that buckbrush "may be the only vegetative component that provides sufficient cover for spring nesting on the grazing treatments." Newell (1987) found SNG prairie chickens produced more young from renests which was perhaps due to a lack of adequate residual cover available for secure first nests. Len McDaniel (personal commun.) in over 25 years of observing prairie chickens and sharptails on the Valentine National Wildlife Refuge in north central Nebraska, believes sharptails tolerate heavy grazing better than prairie chickens and this could be partially explained by the preceding scenario. Also, heavy grazing tends to increase buckbrush and favors sharptails in that way (John Toepfer, personal commun.).
Glen Moravek has been a biologist at the Ft. Pierre National Grasslands in south central South Dakota for 9 years. Both prairie chickens and sharptails occur there (70/30 ratio) but Moravek feels (personal commun.) that it's better prairie chicken habitat than sharptails because of limited woody vegetation and that 20% of the landscape is interspersed with high energy crops (sorghum, corn, wheat, sunflowers). They have reduced stocking rates 20% at the Ft. Pierre Grasslands and prairie grouse have increased over 50%. This supports the notion that chickens do better than sharptails if there is less brush and that both do better if there is more residual cover.
The association between sharptails and woody vegetation could partially explain why they persist longer in unmanaged grasslands than prairie chickens. Kirsch et al. (1973:452) in analyzing prairie grouse and land use changes in central North Dakota suggested that, "sharp-tailed grouse apparently are more tolerant of loss of vigor and succession changes in the vegetation than are prairie chickens. This may also explain why sharptails survived on the (Lostwood National Wildlife) Refuge after prairie chickens disappeared and why they survived on the Soil Bank lands until they were plowed." They described pasture lands in that study area as moderately to heavily grazed with an invasion of Kentucky bluegrass (Poa pratensis) and some dominated by buckbrush. Some idle areas were also dominated by bluegrass and buckbrush. John Toepfer (personal commun.) believes sharptails can use "chicken habitat" better than prairie chickens can use "sharptail habitat" at the SNG.
Food, particularly during the winter when snow covers waste grains, could also be a factor favoring sharptails at the SNG. Sharptails are well known to utilize buds as winter food (Schmidt 1963, Coues 1874); prairie chickens much less so. Rumble et al. (1988) found shrubs comprised only 0.2 to 2.7% of the winter (Dec., Jan., Feb.) diet of SNG prairie chickens. At the SNG there is considerable buckbrush, trembling aspen, willow, and many large cottonwoods along roadways, ditches, and old farm sites. Coues (1874:418) writes of the heavy winter use made by sharptails of the "immense cottonwoods" along the Missouri River in North Dakota. Birds spent a considerable amount of time perched in these large cottonwoods and apparently fed some there as well; "... the food of the grouse is readily ascertained; in the dead of winter it consists chiefly of the berries of the cedar, and buds of the poplar or cottonwood and willow..." (Coues 1874:418). Prairie chickens will readily perch in trees, but close observation indicates very little feeding activity (John Toepfer, personal commun.). How attractive to sharptails are the SNG cottonwoods for food and perching sites?
Taxonomy and habitat preference
It is interesting to speculate why sharptails do not have a greater presence within the prairie chicken range in western Minnesota where many tracts have a significant component of woody vegetation and probably should be burned twice as frequently as current manpower permits. Certainly, the SNG is less "brushy" (small trees, high shrubs) than many of the Minnesota areas having a predominance of prairie chickens. However, the SNG may have more shrubs, especially buckbrush, and that may be the difference. Minnesota sharptails are considered to be the prairie subspecies (Tympanuchus phasinellus campestris) and the SNG sharptails are plains sharptails (T. p. jamesi) (Aldrich 1963), and there may be some differences in habitat preference. Perhaps the prairie subspecies requires even more woody vegetation than that present in some of the Minnesota range.
In western Wisconson, Toepfer (1988) compared seasonal habitat use locations for prairie chickens (n = 3,311) and sharptails (prairie subspecies) (n = 3,054) and found prairie chickens used agricultural areas more than sharptails (52.1% vs 33.2%). Sharptails, on the other hand, used shrubs and grass-shrub habitats more than twice as much as prairie chickens (25.1% vs 12.0%) as well as trees (16.8% vs 6.9%).
Another question that can be posed is whether the SNG sharptails could have more affinities with the prairie subspecies of Minnesota than with the plains sharptail of western North Dakota. Certainly the presettlement range of sharptails would have been continuous from the Dakotas into Minnesota and only within the last 100 years or so have the SNG sharptails become somewhat ecologically isolated from Minnesota sharptails by intensive agriculture.
Ammann (1957), while feeling that plant succession was the primary factor shifting the balance to sharptails, noted that in some situations, the replacement occurred more rapidly and more completely than would be expected if habitat change alone were responsible. He noted some locations in Michigan where a complete changeover from prairie chickens to sharptails occurred in 5 or 6 years after the first appearance of sharptails.
Ammann (1957) also discussed the role of interbreeding as a possible factor in favoring one species over the other. Apparently, interbreeding occurs whenever the ranges overlap and particularly when the number of one species is much less than the other (Fred Hamerstrom, personal commun.). Sparling (1979) studied the hybridization question in northwest Minnesota and believed that hybridization is most likely to occur when a female has a difficult time finding a male of her species. This is supported by the 2 instances of known interspecific matings. Fred Hamerstrom (personal commun.) and Svedarsky and Kalahar (1980) observed sharptail females mating with prairie chickens. In these cases, a female of the rarer species mated interspecifically. Ammann (1957) suggested that if a prairie chicken hen copulated with a sharptail and produced a brood of hybrids, the reproductive rate of the sharptail population would not be affected, but prairie chickens would lose an entire brood. Presumably the likelihood of this occurring would be greater where the number of sharptail dancing grounds and males exceeded those of prairie chickens, which could develop at the SNG.
Sparling (1981) found no difference in mating phenology between the 2 species and documented that behavioral characteristics ordinarily prevent interbreeding. When it occurs, hybrids are fertile as are backcrosses. Sharptail males showed stronger discriminating abilities than prairie chicken males suggesting that they would be less apt to mate with a prairie chicken hen than with a sharptail. Since males mate with more than one female, the key question is the discriminating ability of the females. Sparling found females of both species showed strong preferences for males of their species on mixed leks and in captivity. Hybrid and backcross hens initially preferred prairie chicken territories in captivity but most eventually mated with sharptail males. This tendency would favor an increase in the proportion of sharptail genes within a mixed population. While the dynamics of sharptail/prairie chicken hybridization are not completely understood, it could pose an additional threat to the viability of the SNG prairie chicken population should the balance continue to shift towards sharptails.
Another possible factor favoring sharptails could be direct antagonism towards prairie chickens. Both are comparable in size but Kobriger (1965) felt sharptails were more aggressive than prairie chickens in his observations in the Nebraska sandhills. Sharp (1957) observed interactions between prairie chickens and pheasants, and pheasants and sharptails. Pheasants always dominated prairie chickens but sharptails always dominated pheasants; by inference, sharptails should dominate prairie chickens.
Toepfer (1988), observing mixed populations in Wisconsin, noted that on mixed display gounds, sharptails usually dominated prairie chickens. On common feeding areas he observed sharptails dominate prairie chickens 55 out of 59 times.
A natural question is how did species distinction develop in the first place since some degree of spatial isolation is generally required. Toepfer (1988) suggested that deep persistent, snow and the inability of prairie chickens to subsist entirely on browse may have been the barrier which ecologically isolated the 2 species in their evolution.