Egg survival is related to the colour matching of eggs to nest background in Black-tailed Gulls

Abstract

A long-standing hypothesis posits that, for species with exposed nests, a close match between the colour of the eggs and that of the nest in which they are laid should enhance egg survival, but this has rarely been tested in a rigorous manner. Here, we demonstrate the effects of egg-nest colour matching on egg survival in Black-tailed Gulls (Larus crassirostris) on Hongdo Island, Korea. We quantified the ground colour of eggshells and that of the nest background using a digital camera and computerized RGB and greyscale colour systems. We show that a close match of eggshell ground colour and nest background colour was associated with increased chances of eggs surviving through to hatching. In particular, there were strong survival advantages for eggs matching the nest colour in sites with poor concealment, whereas there was no effect of eggshell ground colour in nests that were more concealed by vegetation. Our findings support the hypothesis that egg colour functions to make eggs cryptic and that egg colouration may be a significant factor affecting egg loss.

Background matching and camouflage efficiency predict population density in four-eyed turtle ( Sacalia quadriocellata )

“…This is similar to the previous study on Japanese quail, which has been shown to seek out a substrate that best matches their egg coloration as a nest position to provide the most effective camouflage (Lovell et al, 2013). Furthermore, avian egg survival ratio is related to the color matching of eggs to nest background, as in eggs of Black-tailed Gulls (Larus crassirostris) (Lee et al, 2010). The population density (21.5/km) of four-eyed turtles was the highest in midstream of the stream (Xiao, 2014).…”

“…For instance, Japanese quail (Coturnix japonica) females choose a substrate that best matches their egg background coloration in order to provide the most effective camouflage (Lovell et al, 2013). In recent years, some studies have suggested that background matching is associated with reduced risk of predator detection (Lee et al, 2010).…”

“…All the aforementioned advantages of digital photography are important to study background matching, especially when the experiments are conducted in the field. Some recent studies of background matching have adopted digital photography and computer systems to quantify the color of animals (or avian eggs) and their habitat substrate (or avian nest) (Lee et al, 2010;Lovell et al, 2013). However, some authors have suggested that the best method for studying background matching is to test its camouflage efficiency by building a natural predator-prey system (Cuthill et al, 2005).…”

“…Therefore, the four-eyed turtle is thought to be faced with predation pressure of visual predators, especially humans, in Hezonggou stream. Considering that camouflage can reduce predation risk (Cooper and Greenberg, 1992;Lee et al, 2010), we hypothesized that the density difference among stream sections of Hezonggou stream may be correlated to turtle camouflage. Here we conducted comparative studies on background matching among stream sections with different densities in the four-eyed turtle by using digital photography and investigated their camouflage efficiency by considering humans as predators.…”

Dual function of egg-covering in the Kentish plover Charadrius alexandrinus

“…However, during these periods in which the eggs may be uncovered to alleviate overheating, unattended nests may be easier to locate by predators (Keller, 1989;Opermanis, 2004;Prokop & Trnka, 2011), because the eggs are less well camouflaged. As shorebirds suffer high nest predation rates (e.g., Fraga & Amat, 1996;Neuman et al, 2004;Saalfeld et al, 2011), better egg camouflage may be adaptive because this may improve nesting success (Solís & de Lope, 1995;Lee et al, 2010;Colwell et al, 2011).…”