Spatio-temporal variation in nesting success of colonial waterbirds under the impact of a non-native invasive predator

Abstract

Colonial breeding in birds provides protection from predators and may be particularly important when birds have to cope with an invasive predator. The probability of nest predation in a colony can vary depending on several factors, such as the nest’s location in the colony and the level of aggregation of nests. We studied the nesting success of colonial great crested grebes and monitored the occurrence of the non-native invasive American mink in the colony. From among 92 grebe nests, 54.3% were successful. The daily survival rate (DSR) of grebe nests was positively affected by the increasing distance between the nest and lake shoreline, and negatively affected by the increasing distance between the nest and the five nearest grebe nests. The probability of mink occurrence in the colony increased with consecutive days of the breeding season and decreased with increasing distance from the lake shoreline. The DSR of grebe nests decreased with the increasing probability of mink occurrence along the shoreline distance gradient and the day of the breeding season. The results of the study confirm the impact of the American mink on waterbirds during the breeding season but also indicate that large breeding colonies are partially safe from mink predation, and that nest accessibility and the dilution effect influence the probability of nest survival. Our data suggest that the limited access to safe breeding sites on large lakes that can supply adult grebes and their chicks with food may affect bird productivity and population numbers at the landscape level.Electronic supplementary materialThe online version of this article (10.1007/s00442-018-4270-8) contains supplementary material, which is available to authorized users.

Annual variation in predation risk is related to the direction of selection for brain size in the wild

“…In our study population, relatively large-headed females breed later and have higher nesting success during years of high predation risk, whereas females with small relative head size nest earlier and exhibit higher nesting success in low-predation years with early breeding phenology 20 . This finding is consistent with recent evidence from studies of nest predation in waterfowl suggesting that severe predation pressure is associated with a rapid increase in predator occurrence at the beginning of the breeding season (i.e., the predator occurrence probability curve is concave), whereas a slower increase in the probability of predator occurrence which then accelerates over time (i.e., a convex curvature) is coupled with lower overall losses due to predation 24 . Because predation risks on incubating females and nests are positively correlated 25 , we therefore hypothesised that females with relatively larger brains have relatively higher survival during years with high risk of predation, whereas small-brained females may do better during benign years, assuming that predation then disproportionately affects late-breeding, large-brained individuals.…”

Nesting features and breeding chronology of the crested coot (Fulica cristata) in two North African high altitude wetlands

“…Similar results were reported in the Eurasian coot, which built nests in high-density vegetation habitats to escape predators (Squalli et al, 2020). This strategy is widely reported in bird species (Frederick and Collopy 1989;Schüttler et al 2009), including the Eurasian coot (Del Hoyo et al 1996;Taylor and Van Perlo, 1998) as adaptive behavior to face the predation risk, especially during the incubation where the adults and nestling are in the nests (Brzeziński et al 2018;Engel et al 2020). In parallel, crested coot uses the available vegetation twigs, including Typha and poplars, to build its nests.…”

Mink predation in great crested grebe colonies: random robbery or a well-planned hunt?

“…Such differences were also recorded in the Masurian Lake District; brood losses in colonies were lower than those recorded in grebes breeding solitarily, and an observed switch in behaviour towards colonial nesting probably followed from their higher breeding success in colonies (Brzeziński et al 2012). However, the nesting success of great crested grebes breeding in colonies varies spatiotemporally, and the probability of nest survival in a colony decreases with nest distance to the shoreline and increases with nest aggregation and time of egg laying (Brzeziński et al 2018). Therefore, although colonial breeding is generally an effective defence against predation, and grebe colonies are established in hard-to-reach areas such as vast reedbeds in shallow bays, they are not entirely safe from mink (Brzeziński 2008).…”