Unusually coloured birds

Little Corella stained brown.

Overview

Birds of unusual colouration appear regularly in mainstream media and amongst interest groups on social media. This page discusses a few accounts in detail, presents reader-contributed photographs and examples, and offers some explanations for how birds might how unusual colouration.

Causes of unusual colouration in birds

The causes of unusual colouration in birds are varied and include:

• morphs - natural colour variations that may not be common)
• melanism - higher than usual production of dark pigment
• leucism - a lower than usual production of dark pigment (sometimes partial, affecting only parts of the body)
• albinism - a lack of dark pigment, often identifiable by the animal having red pupils in its eyes.
• illness - one often cited example being Psittacine Beak and Feather Disease (PBFD) which can lead to a brown colouration in feathers
• artificial pigments - such as from dyes, which may be used to colour water that has been chemically treated with pesticide, for example
• charcoal - from burnt timber and trees, for example, after bushfire
• fungus - from the body rubbing against fungus that might grow in tree hollows
• wood pulp - especially after wet weather, and especially when a bird such as an Australian parrot is sculpting the interior of a tree hollow
• bio-luminescence - although uncommon, some have speculated that birds may come into contact with bio-luminescent fungus or that the Barn Owl might even exhibit its own bio-luminescence.
• hybrid breeding - when two different species produce young, the young may exhibit colouration that is not an exact match for either of the parent species.
• domestication - when birds are selectively bred over large time scales, the resulting breeds and races may vary enormously from the original species source stock.
• diet - Canaries, in particular, are known for an orange form - rather than the "usual" yellow - that is diet induced.
• misidentification - some have sent through photos of the Blue Bunting, which really is a blue bird, believing it was an unusually coloured sparrow.

Introduction

In April 2009 Richard Shears, a journalist with the Daily Mail (UK) published photographs of a blue House Sparrow (Passer domesticus) which visited his garden in Sydney, Australia. In July a reader of Where Light Meets Dark made contact - quite unaware of the blue sparrow - to enquire about blue Little Corellas (Cacatua sanguinea) photographed by his friend on the Central Coast just north of Sydney, NSW.

Whilst investigating these two incidents, information came to light about a third species of bird seen with blue plumage - the Australian White Ibis (Threskiornis molucca). Finally, in June 2010 another reader sent through photos of another blue sparrow - this time from Canada. In all these cases it seems as if the colouration has been caused by a blue dye. Some explanations for blue-coloured dyes include that it is used with crop spraying insecticides and in shipyards with anti-fouling paint.

From the time of this early investigation, many readers of WLMD have submitted photographs of variously coloured birds. Various birds appear in social media groups and occasionally in mainstream media. I have also found photographs of a Silver Gull with blue staining in my own collection and taken photographs of an Australian Magpie exhibiting leucism.

Critical analyses

Conclusion

In the pages above you'll read of various theories, including genetic mutations, cross-breeding, diet and dye.

Wildlife Management Officer Geoff Ross, with the Parks & Wildlife Group - Department of Environment and Climate Change (PWG/DECC) has this to say about the blue ibis in particular:

"We monitored this bird for a while around Sydney (it hasn't been seen for some time now). In the past we've seen others with dye on the feathers. There are sites in or around Sydney , where somehow these birds come into contact with a dye. Most have been waterbirds, Pelican, Ibis etc. I think the dyes are water soluble because they seem to fade after rain. Usually when the dyed birds show up there's a lot of discussion to find out if anyone is using dye tags, in this case no one knew of any dye tagging programs. Ibis particularly are commonly found at waste centres, tips and other refuse areas and are often exposed to a variety of human refuse. The colouration does not appear to affect their condition, they seem to be able to feed and carry on as usual." (personal communication, 14/7/09)

One more point to note is that although the ibis was commonly seen in large aggregations of ibis, none of the other birds was blue. This tends to favour the theory that the colouration is due to immersion in a dye, rather than ingestion. Likewise the blue sparrow was seen in a normally coloured flock. Although the blue corellas appeared in a flock, the colouration varied significantly from bird to bird and in the case of the last blue corella on that page, appears to have been splattered on the bird.

Regarding the brown corella on the same page, Ross says "I have seen Corella, and Sulphur-crested cockatoos in Sydney suffering from a disease called Psittacine circoviral Disease or "Psittacine Beak & Feather". The brown discolouration on the feathers appears to be a very early symptom of the disease."

Reader contributions - photo gallery

Many readers have sent through sightings and photographs of many bird species in various different colours. Some of these are reproduced here, with permission.