Identifying predators of eggs and chicks of Lapwing Vanellus vanellus and Black‐tailed Godwit Limosa limosa in the Netherlands and the importance of predation on wader reproductive output

Abstract

Farmland bird populations in the Netherlands have shown an accelerating decline in recent years, despite extensive conservation efforts including reserves, agri-environment schemes and protection of nests by volunteers. Although agricultural intensification is the main cause underlying these declines, there is a growing concern that the ongoing decline of grasslandbreeding shorebirds in recent years is caused or aggravated by increasing predation. Although Red Fox Vulpes vulpes and Carrion Crow Corvus corone are often accused of causing widespread breeding losses, and calls for management of these species are made, very few field data are available on the incidence of predation on grassland shorebirds and the relative importance of different predators. To obtain such data, we identified egg predators using temperature loggers and continuous video recordings of 792 clutches, and chick predators by radiotagging 662 chicks of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus . In total, 22 species were identified as predators of eggs or chicks, of which Red Fox, Common Buzzard Buteo buteo , Grey Heron Ardea cinerea and Stoat Mustela erminea were the most frequent. Eggs were taken primarily by mammals and chicks more often by birds. There was great variation in predation levels and species involved in predation of clutches between sites and years, but less in chick predation. Hence, there was no correlation between predation levels on clutches and those on chicks within the same sites. In sites where more then 50% of clutches were lost to predation, however, nocturnal predators took the larger share. As temporal and spatial variation on a small scale significantly influences predation levels, a site-specific approach based on sound knowledge of the local situation will be more effective in reducing predation on farmland birds than general, country-wide measures. Calculations based on our data indicate that eliminating only one loss factor at a time will often not reverse a local population decline, and provide a strong argument for targeting several locally limiting factors simultaneously instead of focusing on mitigation of predation alone.

Just when you thought you knew it all: new evidence for flexible breeding patterns in Continental Black-tailed Godwits

“…One possibility is that the observation of extreme trait values may be more likely when a study is carried out at a large scale. However, Teunissen et al (2008) undertook their study on a truly large scale, comparing godwit reproductive behaviour among 12 agricultural areas spread across The Netherlands, with each averaging 281 ha. In total, they monitored 545 nests and radiotracked more than 130 adults.…”

Wet Grasslands as a Green Infrastructure for Ecological Sustainability: Wader Conservation in Southern Sweden as a Case Study

“…Thus, habitat restoration requires habitat maintenance with a long-term strategy [59]. There are strong arguments for targeting several locally limiting factors for wader populations simultaneously, instead of focusing on mitigation of one factor alone [58,110]. Furthermore, there is increasing evidence that the abundance and breeding success of waders within patches of high quality habitat are not only dependent on processes within their patch, but also on processes and quality of habitat within the surrounding landscape [64].…”

“…Thus, the degradation of wet grasslands has contributed to a sharp decline in waders throughout Europe over the past three to four decades [48,[51][52][53][54]. In particular, several studies show that wader decline is most commonly linked to a decrease in vegetation quantity and quality [52,53,55], and predation [42,[56][57][58][59][60]. Ottvall et al [24] highlight the intrusion of shrubs and trees on wet grasslands as a key factor for the decline of waders.…”

Foraging behaviour of nest predators at open-cup nests of woodland passerines

“…In spite of technical constraints, identification of nest predators became an integral part of avian nesting studies. The available data show that the relative importance of different nest predator species/ classes varies greatly in space and time (Thompson 2007;Teunissen et al 2008;Weidinger 2009). Accordingly, variability in predation rates is often accounted for by variation in species composition of local predators.…”

“…Even a continuous video recording of predatory behaviour has several limitations (Weidinger 2008a(Weidinger , 2009Richardson et al 2009). First of all, an insufficient spatial and temporal replication of field studies, or lack of it, implies repeated sampling of the same or a few individual predators (Sanders and Maloney 2002;Teunissen et al 2008). Apart from being pseudoreplicated, the sample sizes available for different predator and prey species are almost always insufficient for quantitative analyses.…”