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.