Ultraviolet cues affect the foraging behaviour of blue tits

Abstract

The function of avian ultraviolet (UV) vision is only just beginning to be understood. One plausible hypothesis is that UV vision enhances the foraging ability of birds. To test this, we carried out behavioural experiments using wild-caught blue tits foraging for cabbage moth and winter moth caterpillars on natural and arti¢cial backgrounds. The light environment in our experiments was manipulated using either UVblocking or UV-transmitting ¢lters. We found that the blue tits tended to ¢nd the ¢rst prey item (out of four) more quickly when UV cues were present. This suggests that UV vision o¡ers bene¢ts to birds when searching for cryptic prey, despite the prey and backgrounds re£ecting relatively little UV. Although there was no direct e¡ect of UVon the time taken to ¢nd all four prey items in a trial, search performance in the absence of UV wavelengths tended to increase over the course of an experiment. This may re£ect changes in the search tactics of the birds. To our knowledge, these are the ¢rst data to suggest that birds use UVcues to detect cryptic insect prey, and have implications for our understanding of protective coloration.

Trade-off between camouflage and sexual dimorphism revealed by UV digital imaging: the case of Australian Mallee Dragons (Ctenophorus fordi)

“…However, there is also experimental evidence that UV cues are important for foraging and motion detection in birds, which show a preference for UVreflecting targets such as fruits (Church et al, 1998;Siitari et al, 1999;Rubene et al, 2010;Werner et al, 2012). Therefore, for a common prey of birds that are potentially capable of UV vision, it would be advantageous to possess a colour pattern that also provides camouflage in this spectral region, especially in open environments where UV radiation is available (Endler, 1993).…”

The role of a generalized ultraviolet cue for blackbird food selection

“…For example, previous studies investigated the use of UV reflectance for avian detection of mammalian prey [9], insect prey [10], and mature fruit [11]. Beyond the detection and recognition of food items [12,13], UV cues may also provide birds with information regarding the quality of foods [e.g., quality or ripeness of fruit; 1,14].…”

Functional visual sensitivity to ultraviolet wavelengths in the Pileated Woodpecker (Dryocopus pileatus), and its influence on foraging substrate selection

“…As a plumage or integument characteristic, UV reflectance may signal male fitness in terms of resource acquisition or overall health [13] and [14]. Behavioral studies also have demonstrated the potential importance of UV reflectance for foraging activities in frugivores [15] and insectivores [16].…”