Salient eyes deter conspecific nest intruders in wild jackdaws ( Corvus monedula )

Abstract

Animals often respond fearfully when encountering eyes or eye-like shapes. Although gaze aversion has been documented in mammals when avoiding group-member conflict, the importance of eye coloration during interactions between conspecifics has yet to be examined in non-primate species. Jackdaws ( Corvus monedula ) have near-white irides, which are conspicuous against their dark feathers and visible when seen from outside the cavities where they nest. Because jackdaws compete for nest sites, their conspicuous eyes may act as a warning signal to indicate that a nest is occupied and deter intrusions by conspecifics. We tested whether jackdaws’ pale irides serve as a deterrent to prospecting conspecifics by comparing prospectors’ behaviour towards nest-boxes displaying images with bright eyes (BEs) only, a jackdaw face with natural BEs, or a jackdaw face with dark eyes. The jackdaw face with BEs was most effective in deterring birds from making contact with nest-boxes, whereas both BE conditions reduced the amount of time jackdaws spent in proximity to the image. We suggest BEs in jackdaws may function to prevent conspecific competitors from approaching occupied nest sites.

New perspectives in gaze sensitivity research

“…In support of the sexual selection hypothesis, it has been proposed that the intensity of iris color in birds may be an honest indicator of metabolic efficiency through the anti-oxidant activities of hemoglobin or pterins present in red-colored irides (McGraw, 2006;Oliphant & Hudon, 1993). To date, the most convincing evidence for a potential function of iris color in non-primates is that conspicuous eyes may be linked to nest guarding in jackdaws, to signal to competitors to keep away from occupied cavities (Davidson, Clayton, & Thornton, 2014). This work represents limited progress, and we urge researchers to explore these potential functions for eye salience and communication.…”

Wide-eyed glare scares raptors: From laboratory evidence to applied management

“…Also, the stimulus was in agreement with Martin’s [ 15 ] suggestion that a deterrent visual image has to be moving and large, especially in relation to raptors’ visual system, specialised for movement detection. On the other hand, jackdaws at least have been repelled from nests through photographs of eyes [ 38 ]. One cannot therefore totally exclude that the stimulus has really been perceived as two big approaching eyes, but why this might scare raptors and corvids as much as other bird species is worth of further experimental investigation.…”

Numbers, distribution and nest site characteristics of Jackdaw Corvus monedula in Slovenia and its conservation status

“…This assumption was used to account for the possibility of individuals prospecting potential nest sites but not actually nesting (cf. Davidson et al 2014). Records of single individuals 126 without observation details that indicated nesting were counted as 0-1 pairs.…”

“…Jackdaw is generally well studied, being a popular model species for numerous ethological studies, focused on research of various aspects of its complex social interactions, learning and instinctive behaviour (e.g. Lorenz 1931, Röel 1978, Schwab et al 2008, Davidson et al 2014, Kubitza et al 2015. Also, many studies of breeding biology, nest site selection, breeding and foraging habitat characteristics and predation were carried out throughout Europe (Antikainen 1980, 1987, Johnsson 1994, Soler & Soler 1993, Biondo 1998, Salvati 2002a, Unger & Peter 2002, Arnold & Griffiths 2003.…”