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Fire Size and Wildlife Response
Fire frequencies < 3 years are necessary to sustain habitat for bobwhites and other declining species in upland pine ecosystems. Fire extent (the size of individual fires), along with fire frequency and season, is an important parameter necessary to defining natural or managed fire regimes.
The Game Bird Program is interested in how bobwhite and other species are influenced by fire extent. On private lands, burn extents are often relatively small (<200 acres) as compared to public lands where fuel reduction and wildfire prevention are often the primary goal of fire programs (versus wildlife management). To meet burn acreage goals, fire managers often depend on large burn extents (>1000 acres). We hypothesize that the combination of low fire return intervals (>2 years) and large burn extents may be a major reason for decline of bobwhites and other species on public lands in the Southeastern U.S. Further, we are concerned that when habitats are recovered using large extent fires that bobwhite may not respond.
Once the scale of management surpasses the behavioral adaptations and physiological ability of a species to respond to change their populations could be negatively impacted. This is likely the case with bobwhite where our studies indicate that survival rates decline as scale increases. As bobwhite populations are highly sensitive to survival rates of adults, larger extent fires result a loss of habitat and possibly even direct mortality. In areas where recovery of bobwhite is a priority, reducing burn extent should be considered.
Cotton Rats and Fire Extent
Cotton rats are an important prey species that influence bobwhite demographics by possibly buffering bobwhites from predators. Therefore, we have investigated how burn extent may influence cotton rats. As with most species, burning reduces their habitat temporarily. However, juveniles produced in adjacent habitats quickly repopulate burned areas after the vegetation recovers – but only if refuge areas are nearby. As the summer progresses rats in the burned areas reproduce adding to the overall population. Radio-tagged rats respond to burns by emigrating to adjacent habitat patches. They seek refuge in odd habitats provided along roads, ditches, ponds, before returning to burned habitats following recovery of vegetation or setting up a new home range.
We have both radio-tagged and banded thousands of rats to estimate their habitat use, their monthly survival, and their abundance. Cotton rats, like bobwhites, have low survival rates. As such without immigration and successful recruitment the rat numbers in an area can quickly be reduced. This has implications for other prey species, such as quail, as rats make up a large proportion of the diet of many species, including snakes, bobcats, and coyotes. Much more research is needed to understand how extent of fire influences the prey community.
Bachman’s Sparrow Effects of Fire
We also have begun studies on how burn extent affects Bachman’s sparrow behaviors. Interestingly Bachman’s share very similar habitat needs as bobwhite and frequency of burning influences their habitats in very similar ways. Both select for areas that were recently burned and begin to avoid areas after 2 or 3 years post fire. The difference is Bachman’s are much longer lived than bobwhites and also obviously more mobile than bobwhites. Understanding how species with different life histories respond to fire events provides a broader picture of how burn scale influences wildlife. Each species would likely have a different threshold of fire size beyond which their populations are likely to be negatively influenced.
To begin to address these questions, UGA graduate student Sarah Brown has radio-tagged over 30 Bachman’s sparrows over the past 2 years on the Munson Sand Hill Unit of the Apalachicola NF, one of our UERP areas. The goal of her research was to understand movements of Bachman’s in relation to relatively large fires > 400 acres. Results show that individual Bachman’s respond quite differently following a relatively large extent fire. Some and set up new home ranges on the edge of the burns whereas others apparently leave the study area as they cannot be found (4700 acres). Without radio-tracking technology, it would have been unlikely to be able to follow the movements of these birds as some move several miles. Surprisingly, some Bachman’s show large movements even without fire suggesting they are quite adept at dealing with larger burns that other species. Bachman’s response to fire may be much more dynamic than bobwhites and additional research is needed on how it may influence individual fitness.
Take home message from our research is that fire extent will affect different species in different ways and that the issue is quite complex. That said, we know that fire frequency is the most important variable in sustaining habitat for bobwhites and other species adapted to these habitats. We recommend burning at any season to maintain high fire frequency. Species with low survival rates, limited dispersal ability, that depend on high recruitment to sustain populations, are likely to be negatively affected as scale is increased.