Interactive effects between nest microclimate and nest vegetation structure confirm microclimate thresholds for Lesser Prairie-Chicken nest survival

Abstract

The range of Lesser Prairie-Chickens (Tympanuchus pallidicinctus) spans 4 unique ecoregions along 2 distinct environmental gradients. The Sand Shinnery Oak Prairie ecoregion of the Southern High Plains of New Mexico and Texas is environmentally isolated, warmer, and more arid than the Short-Grass, Sand Sagebrush, and Mixed-Grass Prairie ecoregions in Colorado, Kansas, Oklahoma, and the northeast panhandle of Texas. Weather is known to influence Lesser Prairie-Chicken nest survival in the Sand Shinnery Oak Prairie ecoregion; regional variation may also influence nest microclimate and, ultimately, survival during incubation. To address this question, we placed data loggers adjacent to nests during incubation to quantify temperature and humidity distribution functions in 3 ecoregions. We developed a suite of a priori nest survival models that incorporated derived microclimate parameters and visual obstruction as covariates in Program MARK. We monitored 49 nests in Mixed-Grass, 22 nests in Sand Shinnery Oak, and 30 nests in Short-Grass ecoregions from 2010 to 2014. Our findings indicated that (1) the Sand Shinnery Oak Prairie ecoregion was hotter and drier during incubation than the Mixed- and Short-Grass ecoregions; (2) nest microclimate varied among years within ecoregions; (3) visual obstruction was positively associated with nest survival; but (4) daily nest survival probability decreased by 10% every half-hour when temperature was greater than 34°C and vapor pressure deficit was less than −23 mmHg during the day (about 0600–2100 hours). Our major finding confirmed microclimate thresholds for nest survival under natural conditions across the species' distribution, although Lesser Prairie-Chickens are more likely to experience microclimate conditions that result in nest failures in the Sand Shinnery Oak Prairie ecoregion. The species would benefit from identification of thermal landscapes and management actions that promote cooler, more humid nest microclimates.

Interactive effects of severe drought and grazing on the life history cycle of a bioindicator species

“…). The population in our study system not only experiences warmer and drier conditions compared to other populations due to it being the most extreme south and west population, but also the most extreme microclimates, particularly during incubation (Grisham, Godar, & Griffin, ; Grisham, Godar, Boal, et al., ; Grisham, Zavaleta, et al., ). Lesser prairie‐chicken resilience and stability may be increased by efforts to restore marginal croplands back to prairie habitats and to improve habitat quality and connectivity of populations (Ross et al., ), thereby allowing increased immigration and dispersal abilities.…”

“…Within the Southern High Plains, a semiarid subregion at the southwestern extent of the Great Plains, traditional ecological drivers of drought, fire, and grazing have often changed as native prairies have been converted to other land use types (Milchunas, Lauenroth, Chapman, & Kazempour, ; Milchunas, Sala, & Lauenroth, ; Samson & Knopf, , ; Savage, ). Combined, climate change‐driven alterations in temperature and extreme drought occurrence and alterations in other ecological drivers may influence wildlife on the Southern High Plains directly and through changes in vegetation composition and structure (reviewed in Grisham, Godar, Boal, & Haukos, ).…”

Factors influencing nesting ecology of lesser prairie‐chickens

“…Our results are consistent with other findings across the lesser prairie‐chicken range where nest survival was negatively influenced by intensive drought conditions (Lyons et al , Grisham et al ). Nest survival can decrease by 10% for every half hour when temperatures exceed 34°C (Grisham et al ). Additionally, long‐term population trends show a decrease in years following drought and increase following years with normal or above‐average precipitation (Ross et al ).…”

Influence of olfactory and visual cover on nest site selection and nest success for grassland‐nesting birds

“…Although overhead cover could in some cases prevent visual detection of nests by mammalian predators, selection for overhead cover in our study is perhaps more likely to be driven by stressful thermal conditions. Previous studies in the region indicate that increasing overhead cover is associated with cooler microclimates (Carroll et al., ; Hovick et al., ) and that cooler conditions can be selected for and influence nest survival for ground‐nesting birds (Carroll et al., ; Grisham, Godar, Boal, & Haukos, ; Hovick et al., ). Selection for relatively cooler microclimates allows individuals and their nests to avoid lethal summer temperatures, and this strategy of avoiding extreme heat may have been important in our study area as daily temperatures exceeded 30°C on 91 days during the 2015 and 2016 nesting seasons.…”