Feather-Degrading Bacteria do not Affect Feathers on Captive Birds

Abstract

Attention has recently been focused on microbes that occur in the plumage of wild birds and can degrade feathers under laboratory conditions and in poultry-waste composters. In particular, Bacillus licheniformis, a soil bacterium, was found in the plumage of many birds netted in eastern North America, and poultry feathers were rapidly broken down when incubated in a suspension of this bacterium (Burtt and Ichida 1999). If feather-degrading microbes affect wild birds under normal conditions, they may have played an important role in the evolution of molt, plumage color, and sanitation behavior, such as sunning and preening. We performed the first test on whether a feather-degrading bacterium can degrade feathers of live birds housed outdoors under seminatural conditions. We found no evidence that B. licheniformis degraded wing feathers of Northern Cardinals (Cardinalis cardinalis) when applied twice (with a two-week interval) during the winter, despite the fact that it degraded Northern Cardinal feathers when incubated in our laboratory. In a second experiment, we found no evidence that B. licheniformis degraded feathers of European Starlings (Sturnus vulgaris) when applied twice (with a one-week interval) during the summer, despite the fact that birds were housed in humid conditions that should have favored the growth of B. licheniformis. Las Bacterias que Degradan Plumas no Afectan las Plumas de Aves en Cautiverio

Evidence that plumage bacteria influence feather coloration and body condition of eastern bluebirdsSialia sialis

“…They found no evidence of increased feather damage on inoculated relative to uninoculated birds. However, aspects of their study may have confounded their ability to detect bacterial feather degradation (Cristol et al 2005, Gunderson 2008).…”

“…However, recent studies have attempted to detect bacterial feather degradation on live birds. Cristol et al (2005) inoculated captive birds in an outdoor aviary with the FDB Bacillus licheniformis (OWU 138B), a strain isolated from the plumage of a willow flycatcher Empidonax traillii (Ichida et al 2001). They found no evidence of increased feather damage on inoculated relative to uninoculated birds.…”

Increased plumage darkness of female Shiny Cowbirds Molothrus bonariensis in the subtropics: an adaptation to bacterial degradation?

“…Alternatively, if different feather morphs contain variable amounts of melanins, it might be the sole presence of melanins, but not the concentration, that confers resistance to bacterial degradation. In an experiment in which melanized feathers of two bird species were exposed to bacterial degradation in vivo , there was no damage compared with feathers without bacteria (Cristol et al. 2005).…”

The origin of feather holes: a word of caution

“…Second, little is known about whether FDB disrupt the keratin matrix under natural conditions and about the keratinolytic potential of different bacteria strains (Gunderson ). For instance, FDB had no effect on feather deterioration in vivo, but only in vitro (Cristol et al ). Finally, FDB degrade feathers to dust within one week of in vitro inoculation (Gunderson et al ), hence the small size of feather holes does not correspond to the keratinolytic potential of FDB.…”

“…First, the activity of FDB initiates scratches and fractures of the keratin cortex (Shawkey et al 2007), and both FDB and fungi can digest feather barbules in vitro (Cristol et al 2005, Gunderson 2008, Ruiz-Rodr í guez et al 2009, Lingham-Soliar et al 2010, though not so in vivo (at least the Bacillus licheniformis ; Cristol et al 2005). Unlike in the case of chewing lice, these eff ects are independent of feather tract (body or fl ight feather) or outer structure (plumulaceous or pennaceous).…”