The Seasonal Dynamics of Artificial Nest Predation Rates along Edges in a Mosaic Managed Reedbed

Abstract

Boundaries between different habitats can be responsible for changes in species interactions, including modified rates of encounter between predators and prey. Such ‘edge effects’ have been reported in nesting birds, where nest predation rates can be increased at habitat edges. The literature concerning edge effects on nest predation rates reveals a wide variation in results, even within single habitats, suggesting edge effects are not fixed, but dynamic throughout space and time. This study demonstrates the importance of considering dynamic mechanisms underlying edge effects and their relevance when undertaking habitat management. In reedbed habitats, management in the form of mosaic winter reed cutting can create extensive edges which change rapidly with reed regrowth during spring. We investigate the seasonal dynamics of reedbed edges using an artificial nest experiment based on the breeding biology of a reedbed specialist. We first demonstrate that nest predation decreases with increasing distance from the edge of cut reed blocks, suggesting edge effects have a pivotal role in this system. Using repeats throughout the breeding season we then confirm that nest predation rates are temporally dynamic and decline with the regrowth of reed. However, effects of edges on nest predation were consistent throughout the season. These results are of practical importance when considering appropriate habitat management, suggesting that reed cutting may heighten nest predation, especially before new growth matures. They also contribute directly to an overall understanding of the dynamic processes underlying edge effects and their potential role as drivers of time-dependent habitat use.

Dependence of spatial scale in landscape associations with cause‐specific predation of snowy plover nests

“…While we predicted that nest predation by mammalian predators would increase with the density of habitat edges, we detected a positive relationship for all predator species. The influence of habitat edges on nest predation often varies with the predator community (Lahti 2001) and can be a dynamic process through time (Malzer and Helm 2015). Studies of this effect, however, have largely focused on agricultural landscapes with hard edges (Lahti 2001, Batary and Baldi 2004, Stephens et al 2004), while studies from lower‐contrast edges, such as the transition from marsh to playa, are less common (Suvorov et al 2014, Malzer and Helm 2015).…”

“…The influence of habitat edges on nest predation often varies with the predator community (Lahti 2001) and can be a dynamic process through time (Malzer and Helm 2015). Studies of this effect, however, have largely focused on agricultural landscapes with hard edges (Lahti 2001, Batary and Baldi 2004, Stephens et al 2004), while studies from lower‐contrast edges, such as the transition from marsh to playa, are less common (Suvorov et al 2014, Malzer and Helm 2015). In our study, the influence of edge density on coyote nest predation had the highest posterior probability at 5000 m, which could indicate that the actual scale of this effect is larger than what we measured (Jackson and Fahrig 2015).…”

The effects of forest edge and nest height on nest predation in a U.K. deciduous forest fragment

“…Previous studies in Scotland have shown significant seasonality in nest predation rates around spring. Nest predation rates were shown to peak in late April, and then slowly decline until late June (Malzer & Helm, 2015). If this seasonal predation effect is also seen in England, it may help account for the unusually high levels of predation seen in this experiment.…”

“…If this seasonal predation effect is also seen in England, it may help account for the unusually high levels of predation seen in this experiment. However it should be noted that although Malzer & Helm (2015) found an overall effect of season on nest predation, it did not influence the edge effect, which was constant year round.…”

“…There are many potential reasons for this effect. As previously mentioned, it may be due to an annual seasonal effect of spring increasing predation rates nationwide (Malzer & Helm, 2015). The sharp edge of the forest may also play a role.…”