Reactions of passerine birds to aposematic and non-aposematic firebugs (Pyrrhocoris apterus ; Heteroptera)

Abstract

In spite of the existence of many experimental studies on the function of warning coloration in insects, little is known about the universality of reactions of different predators towards a particular warning signal. Reactions of nine passerine bird species, namely Parus major , Parus caeruleus , Aegithalos caudatus , Erithacus rubecula , Turdus merula , Sylvia atricapilla , Fringilla coelebs , Carduelis chloris and Emberiza citrinella , to the firebug Pyrrhocoris apterus wildtype (brachypterous adults) and its artificially obtained (painted) brown non‐aposematic variant were compared. Most insectivorous birds (great tits, blue tits, robins and blackcaps) distinguished between aposematic and non‐aposematic bugs, attacking the former less often. Partly granivorous buntings and finches did not distinguish between them, and attacked both variants equally. As all the birds were caught in the wild, the results can be interpreted in terms of the presence of a higher proportion of experienced individuals among insectivorous than among omnivorous species. Two insectivorous species differed from others. The heaviest blackbird attacked and killed aposematic as well as non‐aposematic firebugs, and, in contrast, the lightest long‐tailed tit avoided both variants. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78, 517–525.

Size-dependent colouration in larvae of Orgyia antiqua (Lepidoptera: Lymantriidae): A trade-off between warning effect and detectability?

“…This leads to the conclusion that detectability might be a more important determinant of survival rate than acceptability, even for a larva whose appearance allows one to expect the opposite. In particular, aposematic larvae are not safe because bird species differ in their ability to discriminate between aposematic and nonaposematic prey (Exnerová et al, 2003), also the threshold signal strength that creates the aversion appears to vary (Exnerová et al, 2006). The birds' willingness to consume aposematic prey also strongly depends on their hunger level as the results of the current and some other studies show (Chai, 1986;Sandre & Mappes, in prep.).…”

“…Quite obviously, detectability is higher if the body is larger, and, somewhat less obviously, there is some evidence that aposematic prey has a steeper size dependent detectability function, as compared to cryptic objects (Mänd et al, 2007;this study). This is biologically relevant because warning colouration rarely offers complete protection to the aposematic prey (Stimson & Berman, 1990;Geffeney et al, 2002;this study), and high detectability may thus be highly detrimental (Exnerová et al, 2003(Exnerová et al, , 2006Endler & Mappes, 2004). Such a trade-off situation may imply that warning colouration is the optimal solution for some intermediate body sizes, while most animals smaller and larger than that are selected to be cryptic, i.e.…”

Not all colors are equal: predation and color polytypism in the aposematic poison frog Oophaga pumilio

“…Endler and Mappes (2004) developed a model that suggested variability in predator communities might allow for decreased levels of conspicuousness in the warning signal, which could permit more variation in color. Additionally, net selection by a group of predators can be less selective than by single predators (Exnerová et al 2003;Lindstedt et al 2011). Whether differences in predator communities contribute to polytypism in O. pumilio, though, remains unknown.…”

Influences of geographic differentiation in the forewing warning signal of the wood tiger moth in Alaska

“…However, warning signals are likely influenced by more than a single predator, which can make a difference in the net selection acting on a warning signal (Lindstedt et al 2011). Furthermore, predators likely differ within and between species in how distasteful they may find various aposematic prey defenses or abilities to detect signals (Thompson 1984a, Endler 1988, Exnerová et al 2003, Endler & Mappes 2004, Mappes et al 2005.…”

“…However, some predators can be unaffected by defenses (Exnerová et al 2003) or be driven by hunger to overcome defenses , Barnett et al 2007) leading aposematic organisms to balance warning signal efficacy with detectability to such predators (Bohlin et al 2008). Therefore, warning signal conspicuousness alone is not always optimized.…”