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A Ground-Nesting Galliform's Response to Thermal Heterogeneity: Implications for Ground-Dwelling Birds.

Carroll JM, Davis CA, Elmore RD, Fuhlendorf SD - PLoS ONE (2015)

Bottom Line: We found that thermal space within the study area exhibited differences in Tbb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds.Models of future Tbb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater Tbb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future.These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural Resource Ecology and Management, Oklahoma State University, 008C Ag Hall, Stillwater, Oklahoma, United States of America.

ABSTRACT
The habitat selection choices that individuals make in response to thermal environments influence both survival and reproduction. Importantly, the way that organisms behaviorally respond to thermal environments depends on the availability and juxtaposition of sites affording tolerable or preferred microclimates. Although, ground nesting birds are especially susceptible to heat extremes across many reproductive stages (i.e., breeding, nesting, brood rearing), the mechanistic drivers of nest site selection for these species are not well established from a thermal perspective. Our goal was to assess nest site selection relative to the configuration of the thermal landscape by quantifying thermal environments available to a ground-nesting bird species inhabiting a climatically stressful environment. Using northern bobwhite (Colinus virginanus) as a model species, we measured black bulb temperature (Tbb) and vegetation parameters at 87 nests, 87 paired sites and 205 random landscape sites in Western Oklahoma during spring and summer 2013 and 2014. We found that thermal space within the study area exhibited differences in Tbb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds. Within this thermally heterogeneous landscape, nest sites moderated Tbb by more than 12°C compared to random landscape sites. Furthermore, successful nests remained on average 6°C cooler than unsuccessful nests on days experiencing ambient temperatures ≥ 39°C. Models of future Tbb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater Tbb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future. These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.

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Vegetation characteristics vary among nest and landscape sites.Percent vegetation cover measured at northern bobwhite nest (n = 87) and landscape sites (n = 205) at the Packsaddle WMA, Oklahoma, USA (2013–2014). Asterisks denote significant differences at the p < 0.05 level within cover categories.
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pone.0143676.g005: Vegetation characteristics vary among nest and landscape sites.Percent vegetation cover measured at northern bobwhite nest (n = 87) and landscape sites (n = 205) at the Packsaddle WMA, Oklahoma, USA (2013–2014). Asterisks denote significant differences at the p < 0.05 level within cover categories.

Mentions: The moderated microclimates selected by bobwhites as nest sites also afforded different vegetation structure than those at landscape sites. For example, angle of obstruction (71.61° ± 2.4) was significantly greater at nest sites than at landscape sites (41.45° ± 1.9) (F1, 290 = 80.94, p < 0.0001). Similarly, lateral visual obstruction (6.81dm ± 0.20) at nest sites was also significantly greater than at landscape sites (5.96 dm ± 0.22) (F1, 290 = 5.23, p < 0.05). Moreover, greater percent grass and woody cover and less bare ground cover occurred at nest sites compared to landscape sites (Fig 5), however no differences were found between litter or forb cover. Mean vegetation height (±SE) was similar between successful (0.74 meters ± 0.03) and unsuccessful nests (0.73 meters ± 0.06) and each offered similar lateral visual concealment (F1, 85 = 1.72, p = 0.19) and overhead obstruction (F1,85 = 0.69, p = 0.41). When examining other fine scale vegetation parameters among successful and unsuccessful nests, we found no differences (p > 0.10) in any of the vegetation cover variables that were measured.


A Ground-Nesting Galliform's Response to Thermal Heterogeneity: Implications for Ground-Dwelling Birds.

Carroll JM, Davis CA, Elmore RD, Fuhlendorf SD - PLoS ONE (2015)

Vegetation characteristics vary among nest and landscape sites.Percent vegetation cover measured at northern bobwhite nest (n = 87) and landscape sites (n = 205) at the Packsaddle WMA, Oklahoma, USA (2013–2014). Asterisks denote significant differences at the p < 0.05 level within cover categories.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664423&req=5

pone.0143676.g005: Vegetation characteristics vary among nest and landscape sites.Percent vegetation cover measured at northern bobwhite nest (n = 87) and landscape sites (n = 205) at the Packsaddle WMA, Oklahoma, USA (2013–2014). Asterisks denote significant differences at the p < 0.05 level within cover categories.
Mentions: The moderated microclimates selected by bobwhites as nest sites also afforded different vegetation structure than those at landscape sites. For example, angle of obstruction (71.61° ± 2.4) was significantly greater at nest sites than at landscape sites (41.45° ± 1.9) (F1, 290 = 80.94, p < 0.0001). Similarly, lateral visual obstruction (6.81dm ± 0.20) at nest sites was also significantly greater than at landscape sites (5.96 dm ± 0.22) (F1, 290 = 5.23, p < 0.05). Moreover, greater percent grass and woody cover and less bare ground cover occurred at nest sites compared to landscape sites (Fig 5), however no differences were found between litter or forb cover. Mean vegetation height (±SE) was similar between successful (0.74 meters ± 0.03) and unsuccessful nests (0.73 meters ± 0.06) and each offered similar lateral visual concealment (F1, 85 = 1.72, p = 0.19) and overhead obstruction (F1,85 = 0.69, p = 0.41). When examining other fine scale vegetation parameters among successful and unsuccessful nests, we found no differences (p > 0.10) in any of the vegetation cover variables that were measured.

Bottom Line: We found that thermal space within the study area exhibited differences in Tbb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds.Models of future Tbb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater Tbb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future.These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural Resource Ecology and Management, Oklahoma State University, 008C Ag Hall, Stillwater, Oklahoma, United States of America.

ABSTRACT
The habitat selection choices that individuals make in response to thermal environments influence both survival and reproduction. Importantly, the way that organisms behaviorally respond to thermal environments depends on the availability and juxtaposition of sites affording tolerable or preferred microclimates. Although, ground nesting birds are especially susceptible to heat extremes across many reproductive stages (i.e., breeding, nesting, brood rearing), the mechanistic drivers of nest site selection for these species are not well established from a thermal perspective. Our goal was to assess nest site selection relative to the configuration of the thermal landscape by quantifying thermal environments available to a ground-nesting bird species inhabiting a climatically stressful environment. Using northern bobwhite (Colinus virginanus) as a model species, we measured black bulb temperature (Tbb) and vegetation parameters at 87 nests, 87 paired sites and 205 random landscape sites in Western Oklahoma during spring and summer 2013 and 2014. We found that thermal space within the study area exhibited differences in Tbb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds. Within this thermally heterogeneous landscape, nest sites moderated Tbb by more than 12°C compared to random landscape sites. Furthermore, successful nests remained on average 6°C cooler than unsuccessful nests on days experiencing ambient temperatures ≥ 39°C. Models of future Tbb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater Tbb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future. These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.

Show MeSH
Related in: MedlinePlus