Influence of landscape composition on northern bobwhite population response to field border establishment

Abstract

Since the 1960s, habitat loss resulting from cleaner farming, increased urbanization, and maturation of early successional cover has caused range‐wide decline of northern bobwhite (Colinus virginianus). Although field borders increase bobwhite habitat and increase local populations, understanding how the surrounding landscape influences bobwhite response to this management practice is critical to efficient implementation. We determined the relative influence of landscape composition and field border implementation on bobwhite densities and occupancy dynamics around crop fields in North Carolina and South Carolina, USA. We used 10‐minute distance point counts to estimate density, occupancy, colonization, and extinction rates of male bobwhite around 154 agriculture fields, half of which had a fallow field border. We estimated percent of cropland, forest, pasture, early successional, and urban cover within 1‐km radius buffers (314 ha) surrounding all point count locations. We examined the influence of 6 predictor variables (landscape composition metrics and field border presence) on bobwhite density and occupancy dynamics. Bobwhite density increased with the presence of field borders. Conversely, bobwhite density decreased as the percentage of urban, pasture, and forest lands increased. The presence of a field border did not influence occupancy, colonization, or extinction rates. However, as the percentage of cropland increased within the landscape, bobwhite occupancy increased and as the percentage of pasture increased, bobwhite colonization decreased. As the percentage of forest and urban increased and cropland decreased, bobwhite extinction rate increased. Our results indicated that local establishment of field borders does not increase bobwhite occupancy rates, but field borders can increase densities in suitable landscapes where bobwhite are present. Habitat restoration for bobwhite will most effectively increase population densities if focused in landscapes dominated by suitable cover types, where bobwhite occurrence is high. © 2013 The Wildlife Society.

Northern bobwhite breeding season habitat selection in fire‐maintained pine woodland

“…Vegetation that contributes to nest concealment (i.e., shrubs, forbs, grasses) is important for nest‐site selection and subsequent nest success, whereas high forb cover and bare ground are important for brood cover and foraging (Stoddard , Taylor et al , Lusk et al , Richardson ). Thus, an ideal landscape for breeding bobwhite should at least contain the aforementioned vegetation conditions that allow for nesting and brood cover (Riddle et al , Bowling et al ).…”

Population Responses of the Northern Bobwhite (Colinus virginianus) to Land Use Changes in the Agricultural Landscapes of Ohio, USA

“…Because prior studies have documented the positive efects of CRP on bobwhite abundance, density, and occupancy since the program's implementation in 1985 (i.e., Seckinger et al 2006;Riddle et al 2008;Rifel et al 2008;Bowling et al 2014;Conover et al 2014;Evans et al 2014), the recent decline in CRP enrollment is a concern (Stubbs 2014). I found a strong positive correlation between bobwhite abundance and CRP, suggesting its importance in bobwhite conservation.…”

“…Bobwhites have low dispersal rates and require nesting habitat, brood rearing habitat, and wintering habitat in close proximity (Stoddard 1931;Rosene 1969;Schroeder 1985). Small amounts of suitable habitat can cause low dispersal rates due to impermeability of matrix habitat, trapping birds in small habitat islands (Seckinger et al 2006;Riddle et al 2008;Bowling et al 2014). I expected the loss of CRP to increase the rate of population decline (Duren et al 2011;Lohr et al 2011).…”

“…Each unique male bobwhite seen or heard during a 6-min time interval was recorded (Norton et al 1961;Burger et al 2006). The distance to each singing male was estimated up to 500 m on aerial photographs with pre-measured distance rings created in ArcMap 10.1 (Environmental Systems Research Institute, Redlands, CA) to allow estimation of detection probabilities using distance based methods (Burger et al 2006;Rusk et al 2007;Bowling et al 2014). Wind speed, noise level, and cloud cover were estimated for each survey following the Breeding Bird Survey protocol (Sauer et al 2014) and tested as covariates in models of detection probability (Burger et al 2006).…”

“…Map of 4 study sites (Fee, Peach, Thurner, and Wildcat) in Brown and Highland Counties, Ohio, USA monitored from 2009 to 2015 showing where study sites were located within the USA (a), Ohio (b), and Brown and Highland Counties (c) Site level percent habitat change between 2008 and 2014 and estimated annual change in abundance on four study sites in Brown and Highland Counties, Ohio Fee, Thurner, and Wildcat were studied from 2008 to 2014. Peach was studied from 2010 to 2014 ESH early-successional herbaceous, ESW early successional woody I used the Distance package (Miller 2016) in Program R v 3.2.2 (R Core Team 2017) to estimate male bobwhite abundance(Buckland et al 1993;Somershoe et al 2006;Thomas et al 2010;Bowling et al 2014).…”