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Nesting ecology and reproductive success of Lesser Prairie-Chickens in shinnery oak-dominated rangelands.

Article Excerpt
Lesser Prairie-Chickens (Tympanuchus pallidicinctus) occupy mid-grass rangelands characterized by shinnery oak (Quercus havardii), sand sagebrush (Artemisia filifolia), and mixed-grass communities in five states within the southern Great Plains. This species has experienced significant declines throughout its range since the 19th century (Taylor and Guthery 1980). Lesser Prairie-Chickens occupy six of 12 counties believed to comprise their historical distribution in New Mexico and have been extirpated from nearly 56% of their historical range (Bailey and Williams 2000).

Nesting and brood survival have been identified as the two most critical factors associated with prairie grouse demography and population size (Bergerud 1988, Peterson and Silvy 1996, Wisdom and Mills 1997). Understanding the nesting and brood ecology of Lesser Prairie-Chickens is critical for managing habitats and maintaining viable populations of this species. The general habitat requirements of Lesser Prairie-Chickens are well documented (Hagen 2005), but few data are available on their habitat use in shinnery oak-dominated landscapes. Information on the influence of shinnery oak cover on nest success and brood survival is lacking.

Bailey et al. (2000) suggested a lack of quality nesting habitat (tall, relatively dense residual cover from the previous growing season) may be limiting Lesser Prairie-Chicken numbers, and could be responsible for the historical and recent decline of the species in New Mexico. Studies in New Mexico have described vegetation associated with nest sites in short- and mid-grass prairies co-dominated with shinnery oak, but habitat characteristics influencing habitat use, nesting, and brood success have not been previously identified for Lesser Prairie-Chickens occupying shinnery oak-dominated rangelands. Shinnery oak density might affect the level of use by Lesser Prairie-Chickens (Cannon and Knopf 1981), but the threshold of shinnery oak cover at which use by Lesser Prairie-Chickens is reduced or ceases has not been assessed. More information is needed to describe the optimal shinnery oak density in habitats used by Lesser Prairie-Chickens and its effects on demography. The objectives of this study were to: (1) evaluate nesting habitat within the core of Lesser Prairie-Chicken range in east-central New Mexico, and (2) assess whether vegetative structure is related to nest success.

METHODS

Study Area.--The Milnesand Prairie Preserve (33[degrees] 69' N, 103[degrees] 38' W) encompasses 75 [km.sup.2] of private rangelands in Roosevelt County, New Mexico. The primary land use is livestock production and the dominant vegetation is shinnery oak. Other common woody vegetation includes sand sagebrush, honey mesquite (Prosopsis glandulosa), cholla (Opuntia spp.), broom snakeweed (Gutierrezia sarothrae), and yucca (Yucca spp.). Common grasses include sand bluestem (Andropogon hallii), little bluestem (Schizachyrium scoparium), dropseeds (Sporabolus spp.), grama (Bouteloua spp.), three-awn (Aristida spp.), and buffalograss (Buchloe dactyloides).

Capture and Handling.--Female Lesser Prairie-Chickens were trapped during March-April, 2004 and 2005 on lek sites with rocket nets and/or walk-in funnel traps (Haukos et al. 1990, Schroeder and Braun 1991). Females were fitted with a 10-g necklace configuration radio collar (Telemetry Solutions, Concord, CA, USA) and a serially numbered aluminum leg band. Females were classified as yearlings (first breeding year) or adults (after first breeding year) through examination of outer primaries (Copelin 1963, Campbell 1972).

Females were monitored once per week with a hand-held 3-element, Yagi antenna and portable receiver throughout the breeding season to ascertain habitats used for nesting. The female was approached until observed on the nest when monitoring indicated a nest had been initiated. Subsequently, nesting females were monitored remotely (>25 m) to avoid disturbance.

Nests were examined to ascertain fate once monitoring revealed a female had moved from the nest and incubation had likely ceased. Nests were classified as successful if [greater than or equal to] 1 egg hatched. Depredated nests were distinguished from successful nests by the presence of a firmly attached shell membrane in broken eggs (Wallestad and Pyrah 1974). Unsuccessful females were monitored to identify renesting activities. Broods were monitored three times per...

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