Predator reduction results in compensatory shifts in losses of avian ground nests

Abstract

Summary1. Nesting birds can be vulnerable to predation. Wildlife managers sometimes manipulate predator communities to enhance avian productivity and abundance. Managers need to know the predation risk from different predator species responsible for nest failures to maximize success. This issue is especially important when considering reductions in only a part of the predator community in complex ecosystems. 2. We conducted a 7-year crossover experiment at four study sites to examine the effect of mesomammalian predator control on nest success of northern bobwhite Colinus virginianus in the southeastern USA. Nests were monitored using 24-h near-infrared video. We hypothesized that nest failures caused by different predator guilds may not be independent and may lead to compensation by other predators as one predator guild was reduced. 3. We compared levels of bobwhite nest predation by mesomammals, snakes and other predators in years with and without mesomammal control. 4. Control of mesomammal predators reduced the levels of mesomammal nest predation, but predation levels by snakes and other predators increased such that total nest mortality was not reduced. Nest mortality among predator groups was best described as compensatory, and total nest mortality differed among sites. 5. Synthesis and applications. Our findings suggest that reductions in predation risk from one predator guild can be compensated by an increased risk from other predators in complex ecosystems. Predator removal within one group may not translate to additive increases in overall nest success, but rather results in shifts in the identity of predators responsible for nest failures. Management efforts focused on manipulating predator communities to enhance avian reproduction are encouraged to examine cause-specific nest fates to determine the effectiveness of predator reduction programmes.

Greater Sage-Grouse (Centrocercus urophasianus) select habitat based on avian predators, landscape composition, and anthropogenic features

“…Similarly, there was a shift in the primary predator of females from coyotes to raptors, despite consistent raptor abundance between years (Orning 2014). Inter-guild compensatory shifts in nest predators was observed in response to predator removal for northern bobwhite Colinus virginianus (Ellis-Felege et al 2012). Such a shift establishes the potential for similar relationships in our system, and suggests a potential indirect effect.…”

“…However, the longevity of predator removal effects to protect bird populations has been questioned (Côté and Sutherland 1997, Smith et al 2010, Ellis-Felege et al 2012. Potential indirect interactions resulting from predator removal have been hypothesized to include apparent competition (Holt 1977), exploitative competition (MacArthur and Levins 1967), and mesopredator release (Mezquida et al 2006).…”

Success and Predation of Bird Nests in Grasslands at Valley Forge National Historical Park

“…I would expect less nest predation by Whitetailed Deer following herd reduction. However, the overall effects of White-tailed predation is compensatory and thus, reduction of one nest predator might allow opportunities for other predators and not affect overall nesting success (Ellis-Felege et al 2012, Ellison et al 2013. A comparison of the nest-predator community before and after reduction of the White-tailed Deer herd would provide insight Forge and potentially give insight on how White-tailed Deer grazing on vegetation In conclusion, nest success for Eastern Meadowlarks, Field Sparrows, and Redin other studies, but continued sampling likely would increase the number of nest--land-nest predators in the Northeast were based on likely predators in the area and species and that cues at the nest cannot be used to accurately identify nest predators Granfors 2000a, Thompson et al 1999).…”

When the hunter becomes the hunted

“…Suppressing the populations of one predator species may cause other predators to increase in number, leaving prey to face unchanged or even heightened predation rates. For example, Ellis-Felege et al have shown in an experimental study that predator control efforts reduce mammalian predation on bobwhite quail nests in the southeastern United States, but these benefits are offset by increased predation from snakes ( 7). Similarly, pronghorn (which are preyed on by coyotes but seldom by wolves) appear to have declined in response to the extirpation of wolves, which caused a dramatic expansion of coyotes across North America ( 8).…”

“…Two keys to this activity are the ability of ESCRT-III family members to form spiraling filaments that can draw membranes toward the fission point (6)(7)(8), and the ability of vacuolar protein sorting 4 (VPS4) to remodel these filaments and thereby provide the power for membrane fission ( 4,5). ESCRT-III subunits also recruit relevant proteins through their exposed terminal tails.…”