Blocking of ultraviolet reflectance on bird eggs reduces nest predation by aerial predators

Abstract

Visual sensitivity in ultraviolet (UV) light is widespread in the animal kingdom and occurs in all major taxonomic groups, including birds, which possess UVsensitive photoreceptors and thus perceive UV light and use it in food selection, mate choice, offspring care and egg discrimination. However, no studies have been conducted to elucidate whether birds (aerial predators) could detect nests by UV light reflectance of eggs. In the present study, we performed artificial tree nest experiments in which pairs of pigeon eggs were treated with either a UV-blocker or a control substance before being exposed to nest predators in a tropical forest. The results showed that nest predation increased with duration of exposure, and that blocking UV reflectance of eggs could significantly reduce nest predation on tree nests. This provides experimental evidence for nest predation risk being linked to UV reflectance, and implies that aerial nest predators may detect nests by UV reflectance of eggs. Die Blockierung ultravioletter Reflexion von Vogeleiern verringert die Nestprädation durch VögelDas Vermögen, ultraviolettes (UV) Licht wahrzunehmen, ist im Tierreich weit verbreitet und tritt in allen großen Taxa, inklusive der Vögel auf. Vögel haben UV-Licht empfindliche Photorezeptoren und nutzen diese Wahrnehmung für die Nahrungs-und Partnersuche, bei der Aufzucht der Jungen und zum Unterscheiden von Eiern. Es gibt jedoch keine Studien, die untersucht haben, ob Vögel, die Nester räubern, die UV-Lichtreflexion von Eiern für das Aufspüren derselben nutzen. Wir haben in unserer Studie ein experimentelles Nestdesign benutzt und paarweise Taubeneier entweder mit UV-Lichtblockern oder einer Kontrollsubstanz behandelt, bevor wir sie im tropischen Regenwald in Baumnestern potentiellen Nestpräda-toren überließen. Die Nestprädation nahm zu, je länger die Eier exponiert waren, und Eier, die mit UV-Lichtblockern behandelt waren, wurden weniger beraubt. Wir konnten daher experimentell nachweisen, dass es eine Verbindung zwischen dem Risiko der Nestprädation und der UVLichtreflexion gibt. Das könnte bedeuten, dass nestraubende Vögel die Nester mittels der UV-Lichtreflexion der Eier aufspüren.

Males in seemingly female‐like plumage do not mimic females: UV reflectance reveals temporal cryptic dimorphism in a manakin species exhibiting delayed plumage maturation

“…According to the cryptic hypothesis, subadult male manakins may exhibit dull olive green plumage to diminish the probability of predation before they reach its reproductive stage (McDonald 1993, Doucet et al 2007b. Meanwhile, the patterns and differences we observed in UV color in the belly and throat, but not in the crown nor in the back of manakins, may allow green individuals to be recognizable by conspecifics at certain wavelengths (< 400 nm) rather than to be perceived from above by UV-sensitive predators (Endler 1980, Cummings et al 2003, Yang et al 2016. Since UV reflectance could be significantly more conspicuous to passerines, rather than to bird raptors, the 'cryptic' coloration of the dorsal parts of white-bearded manikins in green plumage may prevent avian predator detection (Håstad et al 2005), particularly when predators are located above manakins in green plumage, whose dorsal parts (crown and back) reflect less UV than the ventral parts and thus, white-bearded manakins may be less conspicuous aerial bird predators with UV vision.…”

Linkages between stratospheric ozone, UV radiation and climate change and their implications for terrestrial ecosystems

“…For example, UV-reflection of bird eggs attracts aerial predators. 193,194 Conversely, UV-absorbing melanin in egg shells may protect eggs from UV-B radiation directly and reduce their visibility to predators, although the dark pigmented colour may cause overheating in some environments. Across a variety of species, including a palmate newt (Lissotriton helveticus), the expression of SWS1 opsin, a UV-photoreceptor in the eyes of animals, is UV-dependent 195, 196 ; furthermore, plasticity in expression of the photoreceptor depends on the habitat of population origin.…”

Breeding biology and novel reproductive behaviour in the Hainan Partridge (Arborophila ardens)

“…A recent study using infrared camera recording in the same area (Jianfengling) showed that aerial predators were the main cause of ground nest failure, including Greater Necklaced Laughingthrush (Garrulax pectoralis) and Indochinese Green Magpie (Cissa hypoleuca) . This may also imply that Hainan Partridges have evolved such a novel reproductive behaviour under strong selection by aerial and hunting predation pressure in local tropical forests (Liang et al 2013;Wang et al 2016;Yang et al 2016).…”