Evidence that plumage bacteria influence feather coloration and body condition of eastern bluebirds<i>Sialia sialis</i>

Gunderson, Alex R.; Forsyth, Mark H.; Swaddle, John P.

doi:10.1111/j.1600-048x.2008.04650.x

Cited by 75 publications

(79 citation statements)

References 58 publications

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“…Shawkey et al (2007) found a positive correlation between the brightness of male eastern bluebirds' (Sialia sialis) structural feather colouration and bacterial loads on their feathers. In contrast, carotenoid-based plumage colouration in house finches (Carpodacus mexicanus) and plumage brightness in female bluebirds were found to be negatively correlated to the densities of feather-degrading bacteria (Shawkey et al 2009;Gunderson et al 2009). Feather colour saturation was also found to be negatively correlated to the number of bacterial species on female great tit feathers (Kilgas et al 2012a).…”

mentioning

confidence: 83%

Do feather-degrading bacteria actually degrade feather colour? No significant effects of plumage microbiome modifications on feather colouration in wild great tits

Jacob

Colmas

Parthuisot

et al. 2014

Naturwissenschaften

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Parasites are known to exert selective pressures on host life history traits since the energy and nutrients needed to mount an immune response are no longer available to invest in other functions. Bird feathers harbour numerous microorganisms, some of which are able to degrade feather keratin (keratinolytic microorganisms) and affect feather integrity and colouration in vitro. Although named "feather-degrading" microorganisms, experimental evidence for their effects on feathers of free-living birds is still lacking. Here, we tested whether (i) keratinolytic microorganisms can degrade feathers in vivo and thus modify the colour of feathers during the nesting period and (ii) whether feather microorganisms have a long-term effect on the investment in colouration of newly moulted feathers. We designed treatments to either favour or inhibit bacterial growth, thus experimentally modifying plumage bacterial communities, in a wild breeding population of great tits (Parus major). Our analyses revealed no significant effects of the treatments on feather colours. Moreover, we found that differences in bacterial exposure during nesting did not significantly affect the colouration of newly moulted feathers. Our results suggest that significant feather degradation obtained during in vitro studies could have led to an overestimation of the potential of keratinolytic microorganisms to shape feather colouration in free-living birds.

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confidence: 83%

Do feather-degrading bacteria actually degrade feather colour? No significant effects of plumage microbiome modifications on feather colouration in wild great tits

Jacob

Colmas

Parthuisot

et al. 2014

Naturwissenschaften

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“…Feather-degrading bacilli occur in the plumage of all avian species sampled to date [4,21]. Furthermore, in the only field study, Gunderson et al [22] showed that feather-degrading bacilli were active in the plumage of eastern bluebirds (Sialia sialis) and altered feather colour, reduced body condition and lowered reproductive success. We assume that feather-degrading bacilli are present in the plumage of parrots and that their presence has potential consequences.…”

Section: Discussionmentioning

confidence: 99%

Colourful parrot feathers resist bacterial degradation

et al. 2010

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The brilliant red, orange and yellow colours of parrot feathers are the product of psittacofulvins, which are synthetic pigments known only from parrots. Recent evidence suggests that some pigments in bird feathers function not just as colour generators, but also preserve plumage integrity by increasing the resistance of feather keratin to bacterial degradation. We exposed a variety of colourful parrot feathers to feather-degrading Bacillus licheniformis and found that feathers with red psittacofulvins degraded at about the same rate as those with melanin and more slowly than white feathers, which lack pigments. Blue feathers, in which colour is based on the microstructural arrangement of keratin, air and melanin granules, and green feathers, which combine structural blue with yellow psittacofulvins, degraded at a rate similar to that of red and black feathers. These differences in resistance to bacterial degradation of differently coloured feathers suggest that colour patterns within the Psittaciformes may have evolved to resist bacterial degradation, in addition to their role in communication and camouflage.

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“…The plumage ecosystem is a nutrient-poor, dry environment, which raises questions about colonization by new microbes as the bird migrates. However, Gunderson et al [10] have shown that featherdegrading bacilli actively degrade feather keratin and change the spectral reflectance of the feathers in Eastern Bluebirds (Sialia sialis) during the breeding season. Taken together, these studies strongly suggest that the microbial community is a dynamic, functioning ecosystem open to the influence of local habitats.…”

Section: Introductionmentioning

confidence: 99%