Effect of nest age and habitat variables on nest survival in Marsh Harrier (Circus aeruginosus) in a fishpond habitat

Abstract

Background One important anti‐predator strategy adopted by birds involves nest site selection and timing of breeding. Nest-site selection by marsh-nesting birds often involves nest concealment and water depth as key features influencing nest survival. Marsh Harrier (Circus aeruginosus) is an obligate ground nester, which sets it apart from other raptors. The aim of the present study was to identify for the first time possible temporal and habitat factors affecting nest survival in Marsh Harrier. Understanding features which affect nest survival are essential for assessing relevant conservation strategies. Methods To understand the relative contributions of different temporal and habitat variables to brood losses, it is useful to determine the daily survival rate (DSR). We examined 82 Marsh Harrier nests located on fishponds in eastern Poland, where predation is the main cause of nest loss. Six habitat variables were measured for each active nest. DSR was calculated using known-fate models with the RMark package. Results The best-supported model predicted that DSR decreased with nest age and was positively affected by the water depth and the diameter of reed stems, but not by the height or density of vegetation at the nest site. The distances of nests to the fishpond dyke and to open water received no support in the models. The chances of nest survival were lower if a neighbouring nest had been depredated. This result suggests that the Marsh Harrier is more susceptible to mammalian than avian predation and confirms the high level of predator pressure in fishpond habitats.

Variation in growth patterns of Marsh Harrier Circus aeruginosus nestlings: effects of hatching order, nestling subperiod, brood size and weather conditions

“…In other bird species, the rapid growth of wings in later-hatched chicks allows them to leave the nest as soon as possible (Nilsson and Svensson 1996;Mainwaring et al 2010), which increases their chances of survival under high pressure from predators (Remeŝ and Martin 2002;Cheng and Martin 2012). This could also apply to Marsh Harrier, because in our study population, the daily nest survival rate declined with nest age (Zaremba et al 2020). Second, Marsh Harrier is a bird of prey nesting in an aquatic environment, so the ability to fly, as well as wing and feather development, may be crucial for the survival of nestlings during the critical transition when leaving the nest (Simmons and Simmons 2000).…”

Ordinal Date and Tree Diameter Influence Swallow-Tailed Kite (Elanoides forficatus) Nest Survival

“…Nest height can positively (Woolaver et al 2015) or negatively (Chiavacci et al 2014) affect nesting survival for other raptor species. Patch size and other landscape characteristics can be correlated with nest survival for some raptor species (Sadoti 2012, Chiavacci et al 2014) but not for others (Crandall et al 2015, Miller et al 2019, Zaremba et al 2020, Forys et al 2021). Therefore, it is critical to understand how nest site characteristics affect nest survival to implement effective land management strategies and conservation plans (Lantz and Conway 2009) for data deficient species.…”