Lesser Prairie-Chicken Range-wide Conservation Plan: Background and Life History
By: W.E. Van Pelt, S. Kyle, J. Pitman, D. Klute, G. Beauprez, D. Schoeling, A. Janus, and J. Haufler
Western Association of Fish and Wildlife Agencies December 2013
The Lesser Prairie-Chicken Range-wide Conservation Plan
BACKGROUND AND LIFE HISTORY
The LPC is a North American grouse species that occupies sand sagebrush (Artemisia filifolia), sand shinnery oak (Quercus havardii) and mixed grass vegetation communities of the southern Great Plains within portions of Colorado, Kansas, New Mexico, Oklahoma and Texas.
During the breeding season (primarily mid-March through May), male LPC congregate on lek sites and perform courtship displays to attract females for mating. Nests are initiated mid- April through late May, typically within two weeks of lek attendance and copulation (Bent 1932, Copelin 1963, Snyder 1967, Merchant 1982, Haukos 1988, Behney et al. 2010). Hatching peaks in late May through mid-June throughout the range (Copelin 1963, Merchant 1982). Re-nests (following nest depredation or abandonment of the initial clutch) are initiated mid-May through early June, with hatching mid-June through early July (Merchant 1982, Pitman et al. 2006). After hatching there is a period of time during which chicks are brooded by the female. This means the critical reproduction period for LPC range-wide is from March 1-July 15, with some variation due to latitude. In autumn and winter, birds assemble into mixed flocks, feeding primarily in sand sagebrush, sand shinnery oak, or mixed-grass prairies, but also often in waste grain fields (Hagen and Giesen 2005). Habitat components necessary to fulfill LPC life history needs include nesting habitat, brood-rearing and summer habitat, and autumn/winter habitat.
LPC have high fidelity to lek sites (Campbell 1972) and males often use traditional leks sites year after year. Females tend to select traditional leks rather than newer or temporary leks (Haukos and Smith 1989). However, new leks will form, especially with an expanding population, as reported for greater prairie-chickens (Tympanuchus cupido pinnatus) (Hamerstrom and Hamerstrom 1973).
Lek sites are characterized by sparse, low vegetation [less than 4” (10 cm)] and are often located on a knoll, ridge, or grama-grass (Boutela spp.) flat (Jones 1963, Copelin 1963, Cannon and Knopf 1979, Taylor and Guthery 1980a, Giesen 1991). Disturbed areas such as roads, abandoned oil and gas well pads, areas around livestock watering facilities, herbicide treatments, and prairie dog towns (Crawford and Bolen 1976a, Davis et al. 1979, Sell 1979, Taylor 1979, Ahlborn 1980, Locke 1992, Bidwell et al. 2003) may also be used as lek sites. Jones (2009) reported a lek being established in a sand sagebrush site one year after a burn. A study conducted by Jarnevich and Laubhan (2011) indicated that areas with slight topographic relief are favored as lek sites.
Monitoring of lek locations is an important component of the RWP. Generally, there are sufficient areas with appropriate conditions for lek development to meet this LPC habitat requirement. Lek sites are therefore not considered limiting to LPC populations, and habitat management to specifically provide for lek sites is not considered to be necessary. However, monitoring leks is very important in management for LPC, as data help wildlife managers understand the distribution and trends of LPC in an area, and indicate where birds are finding nesting habitat. Leks also provide a valuable index of LPC population status in an area over time.
Furthermore, lek locations provide valuable information about where maintenance and improvement of nesting and brood rearing habitat will be most effective. The presence of stable to increasing birds on leks over 5 to 10 year periods, which will capture fluctuations brought on by climatic conditions, reveals that at least minimum quality habitat exists in the area and that birds are present to respond to habitat improvements. Because LPC exhibit strong site fidelity, they are susceptible to continued occupation of habitat that has degraded below suitable levels for population maintenance and growth (i.e. sink population); therefore, the mere presence of birds at lek sites does not correlate strongly with habitat quality unless trends are known. However, the presence of birds, whether declining or not, to respond to habitat improvements and/or removal of negative impacts should hasten local population recovery and expansion. Lek locations are therefore considered an important consideration in developing management plans for specific sites or for siting projects within the LPC range.
Nesting success and brood survival are two of the most critical population parameters for LPC sustainability (Hagen 2003, Pitman et al. 2006, Hagen et al. 2009 and Grisham 2012), and are considered two of the most critical habitat components for this species. Shrub and herbaceous cover are key components influencing nest fate of LPC (Davis et al. 2008). In sand sagebrushgrasslands, nests are most often in sand sagebrush or in tall native bunchgrasses (Giesen 1994, Pitman et al. 2005, 2006). Further, successful nests are typically associated with greater heights and cover of shrubs and/or tall perennial grasses (e.g., native bluestems) (Davis et al. 1979, 1981; Riley et al. 1992, Patten et al. 2005a, Davis 2009, Lyons et al. 2011, Hagen et al. in review).
Typically the height and density of shrubs, forbs, or residual grasses are greater at the nest site than in the surrounding rangeland, and are greater at successful nests than at unsuccessful nests (Riley 1978, Davis et al. 1979, Wisdom 1980, Haukos and Smith 1989, Riley et al. 1992, Pitman et al. 2005, Patten et al. 2005a, Davis 2009, Lyons et al. 2011, Hagen et al. in review). In southwestern Kansas, LPC that nested in areas with denser cover were more successful in hatching nests than females with less cover (Hagen et al. 2007b). A maximum height selection for grasses and shrubs appears to be around 18-20 in. (46-51 cm) (Lyons et al. 2011). Grasses were found to be taller at successful nests (average height = 26 in., (66 cm)), than unsuccessful nests (average height = 14 in., (36 cm) n = 26; Riley et al. 1992). Nesting habitat producing the relatively highest nest success rates in sand sagebrush communities would have >60% absolute cover of shrubs, grasses, and forbs, and where feasible should support grasses >20 in. (51 cm) in height (Hagen et al. in review). Elmore et al. 2009 suggested that habitat patches should maintain average grass heights greater than 15” (38 cm) in order to provide enough taller vegetation to provide preferred nest sites. Residual litter should be maintained and bare ground minimized (Davis 2009, Grisham 2012, Hagen et al. in review). In sand shinnery oak, nesting habitat has been reported to have lower total vegetation cover (>35% absolute cover desired), but should strive to support grasses >20 in. (51 cm) in height and maintain a high level (>30%) residual cover of litter (Haukos and Smith 1989, Riley et al. 1992, Davis 2009, Grisham 2012, Hagen et al. in review).
In the Conservation Reserve Program (CRP) grasslands planted to mixed, native warm-season grasses, nests are predominately found in mid- and tall grasses such as little bluestem (Schizachyrium scoparium), big bluestem (A. gerardi), switchgrass (Panicum virgatum), and in some locations western wheatgrass (Pascopyrum smithii), where clumps of tall residual vegetation from the previous growing season are common (Fields 2004). Nests have been found in CRP planted to Old World bluestems (Bothriochloa spp.) (Wolfe et al. 2003), but such stands are generally thought to offer poorer quality nesting habitat compared to native warm season grass stands due to less concealment, herbaceous species diversity, reduced nest success, etc. Female LPC typically nest within two miles of leks (Suminski 1977, Riley 1978, Giesen 1994). Pitman et al. (2006) reported that the majority of hens they monitored nested within one mile of a lek, but not necessarily the lek where they were captured. Thus, locations of leks can serve as an indicator of where existing nesting habitat is located, and indicate prime areas for potential improvements to nesting habitat.
Juxtaposition and interspersion of nesting and brood habitat is important (King 1938), and so are generally found within two miles of lek sites. As broods have limited mobility, especially at early ages, quality brood habitat needs to be close to nesting habitat. Giesen (1998) suggested approximately 1000 ft. (300 m.) as a desirable maximum distance for brood movement. Pitman (2003) reported one female that moved 35 mi (58 km) from its capture site to where it nested. Jamison (2000), in a study conducted in southwestern Kansas, reported movements that averaged 806 ft. (246m) per day [n = 14, range 634 – 1,411 ft. (193 – 430 m)] for broods less than 14 days of age and 1,040 ft. (317m) per day [n = 8, range 605 – 2,139 ft. (184 – 652 m)] for broods 14 to 60 days of age (Jamison 2000). A mosaic of nesting and brood habitat provides the optimal combination of conditions for LPC. Hagen et al. (in review) suggested that approximately 1/3 of an area should be in brood habitat and 2/3 in nesting habitat for quality LPC habitat. Thus, interspersion of nesting and brood habitat is important in providing optimum habitat conditions.
Brood habitat typically has a higher amount of forb cover and less grass cover than nesting sites (Ahlborn 1980, Applegate and Riley 1998. Hagen et al. in review). Brood-rearing locations are usually associated with higher levels of insect abundance (Jamison et al. 2002b, Hagen et al. 2005) and where chicks can move easily on the ground (Bidwell et al. 2003). Grisham (2012) reported that brood survival from 0-14 days post-hatch was the primary limiting factor to LPC in the Southern Great Plains, and that lack of forbs that could support greater numbers of insects was a primary factor. Active sand dunes with shrubs, especially within sand shinnery oak or sand sagebrush vegetation types, are common in brood-rearing habitat. Jones (2009) reported male LPC and females with broods used sand sagebrush areas one and two years following a burn. Greater forb density was found in these areas.
Burning of LPC habitat (both sand sagebrush and sand shinnery oak communities) tends to temporally reduce shrub and grass cover while increasing forb cover for one to two years postfire, and has been found to increase grasshopper densities (Boyd and Bidwell 2001). Following this, the shrub and grass component recovers and the forb cover is reduced (Davis et al. 2008).
Thus, brood habitat is improved for a few years following a burn while nesting habitat is lowered in quality, but this is a temporary change as grasses and shrubs respond following the burn and typically return to their higher cover and density within several years. Grisham (2012) compared brood habitat selection in areas in New Mexico that had either been grazed or were ungrazed combined with being treated or untreated with herbicide (tebuthiuron) to reduce sand shinnery oak. He found that broods used areas that were either grazed or had received herbicide treatment over areas that were ungrazed or not treated with herbicide, further supporting the selection of broods for more disturbed areas.
Shrubs and shinnery oak have been reported to be used for shade in summer (Copelin 1963, Donaldson 1969, Bell 2005 Larsson et al. 2012) for thermoregulation during high temperatures (Bell et al. 2010, Larsson et al. 2012), not only for broods, but for adults as well. At higher temperatures, LPC broods in New Mexico selected locations with more overhead cover and taller plant heights (Bell et al. 2010). There was also evidence that sand shinnery oak was preferred habitat irrespective of temperature (Bell et al. 2010). Woodward et al. (2001) suggested that shrubland communities provide year round food and cover and are less influenced by climate and grazing than herbaceous dominated communities.
LPC typically range across larger areas during the autumn and winter months, occupying the same general vegetation types as are used for nesting and brood-rearing (Giesen 1998). Boal and Pirius (2012) reported that 97% of bird locations in the non-breeding season for 23 birds they monitored in west Texas were within one mi (1.7 km) of a lek. Kukal (2010) studied over-winter habitat use of LPC in the northeastern Panhandle of Texas, and found that 98% of the locations for the birds were within three mi (5 km) of the lek where they were captured, and within 1.4 mi (2.4 km) of a known lek. As these findings represent similar distances for locations of overwintering birds as reported for distances from leks for nesting and brood rearing birds, these results indicate the general overlap in nesting, brood, and autumn/winter habitat use.
Taylor and Guthery (1980a) found LPC use mixed-grass, sand sagebrush, or sand shinnery oak for resting and roosting. The birds fed in these vegetation communities, or congregated in agricultural fields with waste grains as long as they are located in close enough proximity to rangelands that provide adequate cover for resting and concealment (Jones 1964, Crawford and Bolen 1976b, Ahlborn 1980, Taylor and Guthery 1980b, Jamison 2000). Sand shinnery oak provides leaves, catkins, acorns, and insect galls as seasonal food resources. Pirius (2011) and Boal and Pirius (2012) described overwinter habitat use in sand shinnery oak ecosystems in west Texas, and found that birds in this location selected for grasslands mixed with sand shinnery oak while not selecting for sand sagebrush-dominated areas, whether these had grasses present or not. Kukal (2010) described overwinter habitat use in the panhandle of Texas and found the LPC there preferred grasslands with <15% shrub cover, and emphasized the need to maintain good quality grasslands for over-winter habitat use. Kukal (2010) did not observe birds using agricultural fields. Because of the overlap in autumn and winter habitat requirements with nesting and brood habitat, specific management for autumn and winter habitat is not considered to be necessary as long as good quality nesting and brood habitat is present.
The USFWS (2012a) provided a review of foods of LPC. They noted that most food habitats studies have been conducted in sand sagebrush and sand shinnery oak areas, with food habitats from mixed grass communities less well-documented. Insects are a key component of the diet when available, and are especially important for broods. Martin et al. (1951:97) reported oaks as a primary food in fall, winter and spring, with grain crops, especially wheat and sorghum used in fall and winter, with sumac in winter, and gromwell in spring and summer. They reported insects as a key summer food with grasshoppers the largest component followed by “beetles, bugs, and caterpillars”. As summarized (USFWS 2012a), vegetation provides the bulk of the diet of adults through fall, winter and early spring. Green vegetation becomes important in spring, with seeds, mast, and leafy vegetation being selected throughout this time. In sand shinnery oak, acorns are an important food item when available, but their availability varies considerably from year to year (Smith 1979). Thus, selected vegetation to be eaten by LPC is diverse.
Water has not been considered a direct requirement of LPC (Davison 1935, Elmore et al. 2009, USFWS 2012a), although they will use surface water when it is available. Supplemental water sources were noted as being more available today than historically because of water developments for livestock. Supplemental water was suggested as a benefit during periods of drought (Crawford 1974), but no data to support its importance are available. Generally, water developments in most parts of the range are not considered to be a habitat improvement practice for LPC. However, Haukos (USGS, personal communication) noted that with the drawdown of the Ogallala aquifer in the sand hills of the Southern Great Plains many springs and seeps appear to have dried up. Loss of these water sources could reduce LPC habitat in these dry landscapes so that water improvements may be desired in these areas. Boal and Pirius (2012) reported that 99.9% of the locations for 23 birds they monitored in west Texas were within 2 mi (3.2 km) of a water source, raising the question of the importance of water for LPC in this part of its range.
Home ranges of LPC have been reported in various studies, and have been summarized by the USFWS (2012a). Home ranges vary by sex, age, season, and weather patterns. LPC are not territorial, so home ranges of individuals overlap. Taylor and Guthery (1980c) reported home ranges of 19 telemetered birds in western Texas as ranging from 86 acres (35 ha) for one immature female in February to 4804 acres (1,944 ha) for three immature males in December. The overall average monthly home range for the 19 birds was 988 acres (400 ha). Riley et al. 1994 conducted telemetry studies in New Mexico and found that 51 females averaged home range sizes of 571 acres (231 ha) during pre-nesting and 227 acres (92 ha) while nesting. Females with broods had home ranges that averaged 294 acres (119 ha) while females without broods averaged 180 acres (73 ha) in the post-nesting timeframe. Toole (2005) studied LPC in Texas and found that home ranges for 24 birds distributed across two study areas for two years ranged from 286 acres (116 ha) to 729 acres (295 ha) during the breeding season while home ranges for seven birds across the two study areas during one fall ranged from 422 acres (171 ha) to 647 acres (262 ha). Toole (2005) found no significant differences in home ranges between sexes or ages of the birds he monitored. Giesen (1998) reported that home ranges for males in
Colorado were 512 acres (207 ha), while females were 1,473 acres (596 ha). Jamison (2000) reported home ranges of males in Kansas to range from 30 acres (12 ha) to 346 acres (140 ha) in the spring, 190 acres (77 ha) to 356 acres (144 ha) in the summer, and 566 acres (229 ha) to 1,010 acres (409 ha) in the fall. Taylor and Guthery (1980a) reported winter home ranges in Texas to range from 86 acres (35 ha) to 1,223 acres (495 ha). Boal and Pirius (2012) monitored home ranges of 23 LPC in west Texas and reported that female prairie chickens had slightly larger home ranges, averaging 1,244 acres (504 ha), compared to 1,209 acres (489 ha) for males, with this difference not significant. Kukal (2010) reported home range sizes for 11 male LPC in the northeastern Panhandle of Texas in the fall and winter of 2008-2009 as 1,657 acres (671 ha) in fall and 1,271 acres (515 ha) in winter. He reported home ranges for 18 male LPC in the fall and winter of 2009-2010 as 1,483 acres (600 ha) and 1,189 acres (481 ha) respectively. Kukal (2010) reported home ranges of 3 females for the fall of 2008 as 791 acres (320 ha), and reported three females having fall and winter home ranges in 2009-2010 of 1,880 acres (791 ha) and 697 acres (282 ha).
Home ranges have been noted to increase in size during droughts (Copelin 1963, Ahlborn 1980, Merchant 1982). Merchant (1982) found the average home range size of 7 female LPC was 430 acres (174 ha) during a year of normal precipitation, but was 1,146 acres (464 ha) for eight females in a drought year, a 267% increase. Home ranges have generally not been compared to measures of habitat quality, although an assumption that could be applied to the Merchant (1982) study is that habitat quality was reduced during drought years resulting in the larger home range sizes. Thus, in general, nearly all home ranges of LPC have been found to be less than 2,000 acres (809 ha) in size at all times of the year.
MINIMUM SIZES OF HABITAT BLOCKS
To ensure a sustainable population, Applegate and Riley (1998) recommended clusters of 6-10 or more leks, each with a minimum of six males, separated from one another by a distance of 1.2 mi (1.9 km) or less. A number of studies have reported distances between leks of 1 mi (1.6 km) or less (Crawford 1974, Crawford and Bolen 1976a, Taylor 1979, Locke 1992, Jamison et al. 2002a). If each lek in the cluster were surrounded by a two mi radius area (3.2 km) (i.e., the minimum breeding season patch size around a lek), the entire cluster of leks and core habitat complex might occupy up to 32 sq. mi (83 sq. km) (~21,000 acres) (8,500 ha), with a wider perimeter of habitat for autumn and winter foraging and escape cover. This is consistent with the 25,000-acre (10,118 ha) estimate of Bidwell et al. (2003) for a lek complex.
Taylor and Guthery (1980c) recommended LPC be managed in units of at least 16,000 acres (6475 ha) in size. Bidwell et al. (2003) suggested that the collective home range of all birds attending a particular lek site averages approximately 19 sq. mi (49 sq. km) (>12,000 acres) (4,856 ha), indicating large areas are needed to ensure long-term persistence of LPC populations (Elmore et al. 2009). Although the minimum habitat patch size to support LPC is not clear, several studies have speculated that habitat mosaics containing patches ranging from 1,200 acres (486 ha) to 25,000 acres (10,118 ha) of contiguous native rangelands may be necessary to sustain LPC populations (Davison 1940, Copelin 1963, Crawford and Bolen 1976a, Taylor and Guthery 1980b, Wildlife Management Institute 1999, Woodward et al. 2001, Bidwell et al. 2003). Crawford and Bolen (1976a) reported that areas should be greater than 63% high quality habitat to provide favorable habitat conditions. A LPC conservation plan in Oklahoma (Haufler et al. 2012) used recommendations developed by a science team that reviewed the available information on sizes of habitat blocks and set an objective for core LPC conservation areas to average 50,000 acres (20,236 ha) in size with at least 70% of the area in good to high quality habitat.
LPC do not defend territories other than the small area of a lek defended by a male during the breeding season. Therefore, determination of home range sizes does not provide a basis for density estimates as it can for other species. Density estimates are best derived from surveys of bird numbers occurring at leks, and extrapolating this to population sizes over the surveyed area. Texas estimated a mean density of 5.63 LPC/sq. mi (14.6 LPC/sq. km) (range 2.18-8.64 (5.6-22.4)) (Davis et al. 2008). New Mexico used an estimate of 4.85 birds/sq. mi birds/sq. km) (Davis et al. 2008). Kansas estimated densities of LPC in much of its range at 10 breeding birds/sq. mi (25.9 birds/sq. km) (Davis et al. 2008). In development of the Oklahoma LPC conservation plan, an estimate of 5 birds/ sq. mi was used in setting habitat goals (Haufler et al. 2012). Olawsky and Smith (1991), using transect sampling, reported summer densities of 52-67 birds/sq. mi, and 88-137 birds /sq. mi in winter in their study areas in Texas and New Mexico. Davison (1935) estimated a spring population of 850 birds on a 10,000 acre ranch in sand shinnery oak in northwestern Oklahoma in 1935, a density of approximately 55 birds/sq. mi, and reported an average density of males of 24/sq. mi for 7 years of monitoring in the 1930’s, a decade with reported reduced numbers of LPC due to drought conditions (Davison 1940). These higher densities of birds may have been influenced by declining amounts of available habitat.
Displacement of birds due to development may have concentrated LPC within the remaining habitat, which increased density until population equilibrium, similar to what was recorded in the sandsage ecoregion when conversion of sandsage habitat to center pivot irrigation appeared to inflate population counts from 1968 to 1983.
Movements of LPC may be expressed as normal daily movements or occasionally as dispersal movements. Campbell (1972) observed that males moved several miles from their leks to feed in grain fields in the winter. Taylor and Guthery (1980c) recorded a daily movement of over 2.4 mi (3.9km) in one day, with one juvenile male moving 7.7 mi (12.4km) in 4 days, a move that they attributed to dispersal. A banded juvenile male LPC moved an average of 5.3 mi (8.5km) [range 0.2- 12.6 mi (0.3-20.3km)] from the lek they were captured on to where they were collected by hunters (Campbell 1972). Riley et al. (1994) reported that 3 females with broods moved an average of 910 ft. (277m) per day. Kukal (2010) reported on fall and winter movements of 15 male LPC monitored in the northeastern Panhandle of Texas in 2008-2009 and found minimum average daily movements of 2,015 ft. (614 m) in fall and 1,588 ft. (484 m) in winter. Male LPC monitored in 2009-2010 (n=18) had minimum average daily movements of 2,067 ft. (630 m) in fall and 1,581 ft. (482 m) in winter.
Davis et al. (2008) provided a good description of the relationship of fire to LPC: “Fire was a naturally occurring form of disturbance on the pre-Columbian Great Plains and was ignited not only by lightning, but for at least 12,000 years, by aboriginal Americans. The impact of fire was a major force in shaping the structure of the vegetation community (e.g., Knopf and Samson 1997). The long history of large ungulate herbivores on the Great Plains is also well accepted (Milchunas et al. 1988). Large ungulates are attracted to recently-burned areas by the new growth that is typically more palatable and of greater nutritional quality than vegetation in unburned areas. In turn, recently burned, and consequently, heavily-grazed areas supported more forbs and were less likely to burn in subsequent years due to a reduction in grass litter. The effect of this historical pattern, known as the fire-grazing interaction, created a mosaic of patches
(burned/unburned, heavily grazed/lightly grazed, dominated by forbs/dominated by grasses) that shifted spatially over time (Vinton et al. 1997, Hartnett et al. 1996, Fuhlendorf and Engle 2001). LPC tend to nest in areas with greater heights and density of grasses and shrubs (e.g. Riley et al. 1992, Pitman et al. 2005, Lyons et al. 2011) and then move their just-hatched chicks to areas with less grass, more forbs, and greater insect availability (e.g. Bidwell et al. 2003, Jamison et al. 2002b, Hagen et al. 2005, Bell et al. 2010). This shifting mosaic of historical habitat satisfied this critical reproductive need. Average intervals of fire return to any given area varied and were generally more frequent in eastern sections of the Great Plains where litter accumulation rates were greater. Within the range of the LPC, fire return intervals varied from an average of 5 years in eastern sections of the range to 10-20 years in the more-arid, western-most parts of the species’ range (Hahn 2003).
Thus, having a mix of nesting habitat from April 15-June 15 and brood rearing habitat from June 15-August 15 are considered the most critical time components of LPC habitat. These should be in relatively close proximity and fairly well interspersed to maximize habitat quality. The movement and home range information reported in above sections supports the need for these two habitat requirements to be in relatively close proximity to provide optimum habitat conditions. As previously discussed, Hagen et al. (in review) suggested a 2/3 to 1/3 mix of nesting to brood habitat to optimize LPC habitat. Brood habitat can be created by fire, or by other disturbances including grazing, herbicide application, or mechanical treatments. However, for a site to maintain its dynamics where it will return rapidly from a brood condition to an optimum nesting condition, as occurred with historical fire regimes, it needs to support appropriate shrub/grass/forb communities. Disturbances that create brood habitat but do not sustain the compositions to allow the transition of brood habitat to nesting habitat make development of the mix of good nesting and brood habitat difficult.