Use of Ultraviolet Light as an Aid in Age Classification of Owls

Weidensaul, C. Scott; Colvin, Bruce A.; Brinker, D.J.; Huy, J. Steven

doi:10.1676/09-125.1

Cited by 47 publications

(33 citation statements)

References 16 publications

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“…The presence of porphyrins in feathers was not detected because of the visible colouration that they generate, but due to their fluorescent properties (i.e., they emit long-wavelength light when excited by UV light16), which are also used to detect their production by acne-related bacteria in the human skin19. These fluorescent properties create very conspicuous and intriguing effects20, but the perceptible colour that these pigments generate without artificial UV light excitation has been assumed to be negligible21. However, we have discovered that porphyrins actually create very conspicuous salmon-pink colouration in non-exposed barbs and barbules of contour feathers and down of bustard species, but it has remained unnoticed until now likely because the colour disappears after a few minutes of exposure to sunlight.…”

mentioning

confidence: 99%

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

Galván

Camarero

Mateo

et al. 2016

Sci Rep

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Colours that underlie animal pigmentation can either be permanent or renewable in the short term. Here we describe the discovery of a conspicuous salmon-pink colouration in the base of bustard feathers and down that has never been reported because of its extraordinarily brief expression. HPLC analyses indicated that its constituent pigments are coproporphyrin III and protoporphyrin IX, which are prone to photodegradation. Accordingly, an experimental exposure of feathers of three bustard species to sunlight produced a rapid disappearance of the salmon-pink colouration, together with a marked decrease in reflectance around 670 nm coinciding with the absorption of porphyrin photoproducts. The disappearance of the salmon-pink colouration can occur in a period as short as 12 min, likely making it the most ephemeral colour phenotype in any extant bird. The presence of this colour trait in males performing sexual displays may thus indicate to females a high probability that the males were performing their first displays and would engage in their first copulations in the breeding season. In dominant males, sperm quality decreases over successive copulations, thus porphyrin-based colouration may evolve as a signal of virginity that allows females to maximize their fitness in lek mating systems.

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mentioning

confidence: 99%

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

Galván

Camarero

Mateo

et al. 2016

Sci Rep

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“…Together with their high absolute visual sensitivity (Martin 1977), these elements make it likely that eagle owls have a high capacity to perceive small increments in the red reflectance of feathers due to porphyrin natural fluorescence. Again, the duration of signal expression would be short because the fluorescence of feather porphyrins is also degraded by sunlight exposure and is only observed in recently molted feathers, but eagle owls could exhibit the signal during at least some months after molt (Weidensaul et al 2011). This means that eagle owl fledglings could still signal their porphyrin-based pigmentation after leaving the nest, both during natal dispersal or when they become owners of a territory and show a high signaling activity with other (vocal) traits (Penteriani 2002; see also above).…”

Section: Discussionmentioning

confidence: 99%

“…However, we cannot completely rule out the possibility that a conspicuous coloration is produced in the owls' feathers only during a brief period of time before the pigment photodegrades as in bustards (Galván et al 2016). Furthermore, and despite that the fluorescence of porphyrins in owls' feathers is only perceptible to humans after excitation with artificial UV light (Weidensaul et al 2011), the possibility that owls can actually perceive the fluorescence of porphyrins under natural light should not be discarded either. Porphyrin-based coloration in the feathers of owls is not likely to evolve as an amplifier of reproductive status as in bustards (see above), but it may have a role in sexual selection by acting as an amplifier of breeding site quality if the development of fledglings, including the production of porphyrins, depends on nutritional resources and, thus, on the quality of the breeding site where they are reared (e.g.…”

Section: Figurementioning

confidence: 99%

Feather content of porphyrins in Eurasian eagle owl (Bubo bubo) fledglings depends on body condition and breeding site quality

Galván

Delgado

Camarero

et al. 2018

Integrative Zoology

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Porphyrins are pigments produced in most animal cells during the synthesis of heme, but their importance for external coloration is unclear. Owls (Order Strigiformes) are among the few animals that accumulate porphyrins in the integument, where it could serve as a means of signaling. Here we hypothesized that the porphyrin content of feathers may depend on body condition and breeding site quality in Eurasian eagle owl (Bubo bubo) fledglings and, thus, constitute amplifiers of the quality of the area where they are born. Using high-performance liquid chromatography, we found 2 porphyrins (protoporphyrin IX and coproporphyrin III) in the body feathers of 19 eagle owl fledglings from 7 breeding territories. Coproporphyrin III, but not protoporphyrin IX feather concentration, was positively associated with the body mass of fledglings and with the quality of the breeding sites where they were reared with respect to food quality and availability. As coproporphyrin III is produced under oxidative stress, we suggest that good breeding sites may lead to fledglings in good condition. This, in turn, may make fledglings induce a certain level of free radical and coproporphyrin III production to signal to conspecifics their site-mediated capacity to cope with oxidative stress. This is the first time that porphyrin content in the integument has been found to be related to individual quality, opening a new scenario for studying evolution of animal coloration.

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“…Therefore, we can reasonably assume that our study focused on migrating saw-whet owls. Individuals were aged from molt patterns of primary and secondary flight feathers (Evans and Rosenfield 1987, Pyle 1997, Weidensaul et al 2011, tagged with USGS aluminum leg bands, and released at the capture location. Two age classes were assigned, hatch-year (HY) and after hatch-year (AHY), via visual inspection of primary and secondary feathers.…”

Section: Sample Collection and Age Classificationmentioning

confidence: 99%

“…Feathers of AHY individuals showed obvious variation in color tones: older feathers were dull and faint in comparison to newer feathers. Occasionally an ultraviolet light was used to validate age assignments, because the ultraviolet light allows visualization of fluorescing porphyrin pigments in the heme of new feathers, whereas older generation feathers lack these pigments because porphyrins break down over time when exposed to sunlight (Weidensaul et al 2011). Insulin syringes (0.5 cc, 29 gauge) were used to collect ca 200 μl of whole blood from each owl.…”

Section: Sample Collection and Age Classificationmentioning

confidence: 99%

Haemosporidian prevalence in northern saw‐whet owls Aegolius acadicus is predicted by host age and average annual temperature at breeding grounds

Carlson

Proudfoot

Gentile³

et al. 2018

Journal of Avian Biology

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Understanding factors that determine haemosporidian prevalence is critical in predicting how parasite and avian host populations will respond to environmental change. Here, we used molecular screening of blood samples from migrating northern saw‐whet owls Aegolius acadicus in eastern North America to characterize haemosporidian infections and examine parasite prevalence with respect to abundance of migrants, timing of migration, climatic conditions at the breeding grounds, and avian host age. We identified three haemosporidian genera (Leucocytozoon, Plasmodium, and Haemoproteus) and discovered a new lineage of Leucocytozoon that is thus far specific to the northern saw‐whet owl. We found no significant relationship between parasite prevalence and northern saw‐whet owl abundance or timing of migration. After‐hatch‐year birds were significantly more likely to be parasitized by Leucocytozoon than hatch‐year birds, whereas prevalence of Plasmodium was higher in hatch‐year birds. Of the three climatic variables analyzed at owl breeding grounds (temperature, precipitation, and snowpack days), lower average annual temperatures significantly increased the chance of a bird being parasitized by Leucocytozoon; no significant temperature‐dependent relationship was found for Plasmodium. This study contributes to our general understanding of the relationship between parasite prevalence and host density, host age, resource abundance, and abiotic factors such as temperature and precipitation.

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Use of Ultraviolet Light as an Aid in Age Classification of Owls

Cited by 47 publications

References 16 publications

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

Feather content of porphyrins in Eurasian eagle owl (Bubo bubo) fledglings depends on body condition and breeding site quality

Haemosporidian prevalence in northern saw‐whet owls Aegolius acadicus is predicted by host age and average annual temperature at breeding grounds

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