Melanin-based colour polymorphism signals aggressive personality in nest and territory defence in the tawny owl (Strix aluco)

Abstract

Nest and territory defence are risky and potentially dangerous behaviours. If the resolution of life history trade-offs differs between individuals, the level of defence may also vary among individuals. Because melanin-based colour traits can be associated with life history strategies, differently coloured individuals may display different nest and territory defence strategies. We investigated this issue in the colour polymorphic tawny owl (Strix aluco) for which plumage varies from dark to light reddish melanic. Accordingly, we found that (1) our presence induced a greater response (flying around) from dark-coloured than light-coloured females and (2) dark reddish males suffered lower nest predation rates than light-coloured males. In experimentally enlarged broods, the probability that females reacted after we played back the hoot calls of a stranger male was higher if these females were lighter reddish; the opposite pattern was found in experimentally reduced broods with dark parents being more reactive than light parents. Finally, darker females alarmed more frequently when paired with a light than with a dark male, suggesting that partners adjust their behaviour to each other. We also tested whether colouration is used as a signal by conspecifics to adjust the level of their defensive behaviour. Accordingly, breeding females responded more vigorously to a dark than a light reddish stuffed tawny owl placed beside their nest. We conclude that melaninbased colouration is a signal of alternative nest and territory defence behaviour that depends on ecological factors.

Sex- and melanic-specific variations in the oxidative status of adult tawny owls in response to manipulated reproductive effort

“…Secondly, tawny owls show continuous variation in melaninbased plumage coloration (from light to dark reddish; for pictures, see Da Silva et al, 2013), the expression of which is strongly genetically controlled and not sensitive, or only weakly so, to environmental conditions (Brommer et al, 2005;Gasparini et al, 2009;Emaresi et al, 2013). Interestingly, differently coloured adult males display alternative trade-off resolution and life histories (Emaresi et al, , 2014.…”

“…Firstly, this monogamous raptor species shows pronounced sexual size dimorphism (females are 20% bigger than males) that is associated with a strong partition of the reproductive roles between sexes. The female parent incubates the clutch for 28 days, and remains close to the nest to brood the hatchlings, distribute food among the progeny and protect the nest against predators (Da Silva et al, 2013), whereas the male parent hunts most prey items delivered to the nest. Offspring leave the nest at 25-30 days of age but are fed and protected by their parents until 90-120 days of age (Sunde, 2008).…”

The effect of skin reflectance on thermal traits in a small heliothermic ectotherm

“…A number of theories have been proposed to explain the evolution of colour pattern variation, with crypsis (Endler, 1984;Stuart-Fox et al, 2004) and communication (Dufva and Allander, 1995;Geen and Johnston, 2014;Joron and Mallet, 1998;Wang and Shaffer, 2008) being the most common. For example, colour can provide critical information used in evaluating the fitness among potential mates (Andersson and Simmons, 2006), it can act as a signal of aggressiveness or toxicity towards competitors and predators (Da Silva et al, 2013;Wang and Shaffer, 2008), and it can serve as camouflage through background matching or disruptive patterning (Endler, 2006;Stuart-Fox et al, 2004).…”

Reproductive effort of both male and female Bar‐throated ApalisApalis thoracicais predicted by ornamentation of self and mate

“…, Da Silva et al . ). Melanin‐based ornamentation may thus serve simultaneously as an intra‐ and inter‐sexual signal and can consequently be expected to influence the optimal allocation of resources of a breeding pair among multiple costly life history traits and be an important predictor of individual fitness of both male and female parents (Anderholm et al .…”