title: Functional visual sensitivity to ultraviolet wavelengths in the Pileated Woodpecker (Dryocopus pileatus), and its influence on foraging substrate selection.
abstract: Most diurnal birds are presumed visually sensitive to near ultraviolet (UV) wavelengths, however, controlled behavioral studies investigating UV sensitivity remain few. Although woodpeckers are important as primary cavity excavators and nuisance animals, published work on their visual systems is limited. We developed a novel foraging-based behavioral assay designed to test UV sensitivity in the Pileated Woodpecker (Dryocopus pileatus). We acclimated 21 wild-caught woodpeckers to foraging for frozen mealworms within 1.2m sections of peeled cedar (Thuja spp.) poles. We then tested the functional significance of UV cues by placing frozen mealworms behind UV-reflective covers, UV-absorptive covers, or decayed red pine substrates within the same 1.2m poles in independent experiments. Behavioral responses were greater toward both UV-reflective and UV-absorptive substrates in three experiments. Study subjects therefore reliably differentiated and attended to two distinct UV conditions of a foraging substrate. Cue-naïve subjects showed a preference for UV-absorptive substrates, suggesting that woodpeckers may be pre-disposed to foraging from such substrates. Behavioral responses were greater toward decayed pine substrates (UV-reflective) than sound pine substrates suggesting that decayed pine can be a useful foraging cue. The finding that cue-naïve subjects selected UV-absorbing foraging substrates has implications for ecological interactions of woodpeckers with fungi. Woodpeckers transport fungal spores, and communication methods analogous to those of plant-pollinator mutualisms (i.e. UV-absorbing patterns) may have evolved to support woodpecker-fungus mutualisms.
authors.affiliation: Missouri Cooperative Fish and Wildlife Research Unit, 302 ABNR, University of Missouri, Columbia, MO 65211, USA; Department of Fisheries and Wildlife Sciences, 302 ABNR, University of Missouri, Columbia, MO 65211, USA. Electronic address: sean.t.odaniels@aphis.usda.gov.
authors.forename: Sean T
authors.initials: ST
authors.lastname: O'Daniels
authors.affiliation: Department of Fisheries and Wildlife Sciences, 302 ABNR, University of Missouri, Columbia, MO 65211, USA; The Institute for Bird Populations, 11435 CA-1 Suite 23, Point Reyes Station, CA 94956.
authors.forename: Dylan C
authors.initials: DC
authors.lastname: Kesler
authors.affiliation: Division of Plant Sciences, 110 Waters Hall, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Jeanne D
authors.initials: JD
authors.lastname: Mihail
authors.affiliation: U.S. Geological Survey, Missouri Cooperative Fish and Wildlife Research Unit, 302 ABNR, University of Missouri, Columbia, MO, 65211, USA; Department of Fisheries and Wildlife Sciences, 302 ABNR, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Elisabeth B
authors.initials: EB
authors.lastname: Webb
authors.affiliation: USDA/APHIS/Wildlife Services, National Wildlife Research Center, 4101, Laporte Ave, Ft. Collins, CO 80521, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Werner
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D003463:Cues; D005247:Feeding Behavior / Q000502:physiology*; D005518:Food Preferences / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology*; D014466:Ultraviolet Rays; D014796:Visual Perception / Q000502:physiology* / Q000528:radiation effects
keywords: Dryocopus pileatus; Feeding cue; Foraging behavior; Fungi; Mutualisms; Wildlife damage control