Intense predation of non-colonial, ground-nesting bird eggs by corvid and mammalian predators

Abstract

Context Loss of eggs to predators is a major cause of reproductive failure among birds. It is especially pronounced among ground-nesting birds because their eggs are accessible to a wide range of predators. Few studies document the main causes of clutch fate of ground-nesting birds. Aims The main objective of the present study was to identify the major egg predator of red-capped plovers (Charadrius ruficapillus). We also investigated the effectiveness of the following two primary strategies available to the plovers to avoid egg predation: (1) the placement of clutches under vegetative cover and (2) avoiding predators by nesting outside the peak season of predator occurrence. Methods Remote-sensing cameras were deployed on plover nests to identify egg predators and nests were monitored over four breeding seasons to document reproductive success and fate. An experiment using false clutches with model eggs investigated the influence of nest cover on the risk of egg predation throughout the year. Line-transect surveys were conducted to estimate the abundance of egg predators in and around the wetlands. Key results The little raven (Corvus mellori) was the major egg predator identified in 78.6% of red-capped plover clutches and in 92.4% of false clutches that were camera-monitored. The hatching success of plover eggs was not influenced by nest cover (P = 0.36), but model egg survival in false clutches improved significantly with the presence of nest cover (P = 0.02). The abundance of little ravens increased during the plover breeding season and was highly negatively correlated with false clutch survival (rpearson = –0.768, P = 0.005). Conclusions Little ravens were the major predator of red-capped plover eggs and their abundance increased significantly during the plover breeding season. Any influence of nest cover on hatching success of eggs may have been masked by the extremely high rate of egg loss associated with the increased little raven abundance during the plover breeding season. Implications The high rate of egg predation is likely to have negative consequences on the local red-capped plover population, suggesting management is warranted. Little raven populations have expanded and, thus, their impact as egg predators needs to be investigated especially on threatened species.

Avian responses to an emergent, wetland weed

“…In particular, corvids are considered a major threat to breeding shorebirds in the study area (Ekanayake et al . ), have resulted in interventionist management to conserve their avian prey (Tan et al . ), and evidently used the perching resources provided by boxthorn (this study).…”

Prédation des nids de deux espèces de bulbuls (Pycnonotidae) dans un écosystème de forêt tropicale humide à Korup, Sud-Ouest Cameroun

“…La perte d'oeufs causée par les prédateurs est particulièrement prononcée chez les oiseaux nichant dans le sous-bois comme les bulbuls parce que leurs oeufs sont accessibles à un large éventail de prédateurs (Ekanayake et al, 2015;Bellamy et al, 2017). L'évaluation de l'influence des types d'habitat et de l'influence du gradient croissant de destruction des forêts sur le taux de prédation des nids a toujours été un travail très compliqué à cause des difficultés à découvrir et à suivre les nids dans les forêts tropicales (Tewksbury et al, 2006;Newmark et Stanley, 2011).…”

Woodland birds and rural towns: artificial clutch survival in fragmented Box-Ironbark forests

“…Generalist predators (mostly birds and small mammals) have often been implicated in high egg depredation rates (Martin & Joron 2003;Wegge et al 2012;Ruffell et al 2014), with generalist avian species such as ravens and crows being common egg predators (Gardner 1998;Marzluff et al 2007;Ekanayake et al 2015). The dominant, most connected landscape feature surrounding woodland habitats can influence egg predator distribution (Debus 2006;Robertson et al 2014) with greater abundance of habitat generalist predators observed in woodland patches close to agricultural lands and irrigated land-use (Robertson et al 2014).…”