Diel timing of nest predation changes across breeding season in a subtropical shorebird

Abstract

Predation is the most common cause of nest failure in birds. While nest predation is relatively well studied in general, our knowledge is unevenly distributed across the globe and taxa, with for example limited information on shorebirds breeding in sub-tropics. Importantly, we know fairly little about the timing of predation within a day and season. Here, we followed 444 nests of red-wattled lapwings (Vanellus indicus), a ground-nesting shorebird, for a sum of 7828 days to estimate a nest predation rate, and continuously monitored 230 of these nests for a sum of 2779 days to reveal how the timing of predation changes over the day and season in a sub-tropical desert. We found that 312 nests (70%) hatched, 76 nests (17%) were predated, 23 (5%) failed for other reasons and 33 (7%) had an unknown fate. Daily predation rate was 0.95% (95%CrI: 0.76% – 1.19%), which for a 30-day long incubation period translates into ~25% (20% – 30%) chance of nest being predated. Such a predation rate is low compared to most other avian species. Predation events (N = 25) were distributed evenly across day and night, with a tendency for increased predation around sunrise. Predation rate and events were distributed evenly also across the season, although night predation was more common later in the season, perhaps because predators reduce their activity during daylight to avoid extreme heat. Indeed, nests were never predated when mid-day ground temperatures exceeded 45°C. Whether the diel activity pattern of resident predators undeniably changes across the breeding season and whether the described predation patterns hold for other populations, species and geographical regions awaits future investigations.

Aggressiveness in a subtropical shorebird's nest defense is adjusted to the predator species and shared by conspecifics

“…Nests were systematically searched for throughout the study area. Incubating adults were readily visible from a distance, and we were, therefore, able to find nearly all active nests (Elhassan et al, 2021; Sládeček et al, 2021). Whenever a nest was found, the GPS position was recorded and the incubation start date was estimated based on an egg flotation test (van Paassen et al, 1984).…”

“…The nests where both parents were ringed with a unique color combination were selected for the experiment. The incubation stages of the treated nests ranged from 1 to 28 days (median = 14 days, mean = 14.3 days, SD= 6.2 days), which is 3%–93% of the total incubation time (30 days; Sládeček et al, 2021). The experiment consisted of three 15‐min trials at each nest with each of the three stuffed models (cat, raven, and moorhen).…”

“…The lagoons also provide suitable habitats for other species, many of which are potential predators of adult lapwings, for example, feral cat, Red Fox ( Vulpes vulpes arabica ), and Desert Monitor ( Varanus griseus ), or potential predators of lapwing nests, for example, Brown‐Necked Raven ( Corvus ruficollis ) and Marsh Harrier ( Circus aeruginosus ). The studied population faces predation pressure spread throughout the day and night (Sládeček et al, 2021).…”

“…In this study, we experimentally investigated the nest defense behavior of subtropical Red‐Wattled Lapwings ( Vanellus indicus aigneri ) in an arid and hot environment in the Arabian desert. Since predator visits to nests are rarely observed in the field (Sládeček et al, 2021), stuffed models were used to ensure standardized conditions similar to previous experimental studies (e.g., Elliot, 1985; Hinde, 1954; Kis et al, 2000). Specifically, we monitored the reactions of breeding adults to stuffed models placed near the nest.…”

Nest reliefs in a cryptically incubating shorebird are quick, but vocal

“…2012, Sládeček et al . 2021). This situation occurs in birds during biparental incubation of eggs when parents coordinate their duties to ensure continuous nest attendance (Clutton‐Brock 1991, Deeming 2002a).…”