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Blue House Sparrow
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Note: All images copyright Richard Shears. Source: http://scienceblogs.com/grrlscientist/2009/05/brown_bird_blue_the_follow-up.php

Update - 14 July 2009

A conclusion regarding the cause of this blue colouration has been posted on the blue birds index page.

Overview

blue_house_sparrow_passer_domesticus_01.jpg

In April 2009, Daily Mail journalist Richard Shears published photographs of a blue sparrow which visited his garden in Sydney, Australia.

The image at right shows the blue sparrow in the top right corner, together with normally coloured brown sparrows at bottom left.

Some criticism has argued that the bird is not a sparrow or that the images have been digitally manipulated. Personally the images appear fine - and it is a sparrow.

Causes for blue pigmentation

A quick search for "blue feathers" on the web will quickly present you with numerous articles that explain: birds cannot produce blue pigmentation.

Rather, blue colouration comes from the microstructure of feathers which reflects specific parts of the colour spectrum.

I think for this reason, most theories as to the origin of this colouration in the sparrow have focused on the bird having undergone some sort of genetic mutation which has artificially produced this ability for blue feathers - however the colouration is produced.


blue_house_sparrow_passer_domesticus_02.jpg

Expert opinions

A number of experts have reviewed the photographs. All agree the photos appear genuine. All agree this is a significant find. All agree there is no easy explanation for the colouration.

Ornithologist Mirek Lanparski said "This is amazing. I've never seen anything like it. I thought at first that perhaps someone had dyed it, but looking closely you can see that's not the case, and who would want to catch a sparrow, dye it blue and then let it go again? In any case, those are natural colours and that's very, very peculiar."

New South Wales Field Ornithologists Club official Mr Allan Ible said it was "totally new" to him.

Another member, and former National Parks officer Mr Allan Morris said "This is quite strange. I've seen all kinds of unusual birds, even albino ones, but I've never heard of a blue sparrow."


blue_house_sparrow_passer_domesticus_03.jpg

What are the options?

In various forums including thylacoleo.com, Cryptomundo, the Daily Mail and my earlier announcement at WLMD, several suggestions have been put forward.

Genetic mutation

Genetic mutation is unlikely to be the explanation in my opinion - but for reasons that could not be known in April 2009. Two months later I was contacted by a WLMD reader with information about blue little corellas (Cacatua sanguinea) photographed north of Sydney.

To have two distinct species both exhibit exactly the same genetic mutation for blue colouration - a change which has never before been documented in the avian world - just 2 months apart would go against an incredible sway of odds.

Possible ... but unlikely.

Cross-breeding with a budgerigar

One suggestion was that the sparrow had cross-bred with a budgerigar (colloquially "budgie") - a small native Australian parrot which has become one of the world's most popular household pets. Blue budgie morphs do certainly exist, but in my opinion a cross-breed between a finch (the house sparrow) and a parrot (the budgie) is also incredibly unlikely.

Dye

Another suggestion is that the bird bathed in some liquid which contained a blue dye of some form. This seems a very reasonable prospect, but with news coming 2 months later of similarly blue corellas at a location several tens of kilometres away some questions need to be asked of this theory:

  • Did the sparrow and corella flock at one point travel to the exact same location to be dyed, despite being photographed tens of miles apart?
  • If not, then what could be found so commonl in the environment that two completely different bird species (of very different sizes) were both exposed to it?
  • If the cause is a dye which is commonly found between Sydney and the Central Coast, then are there other blue birds out there waiting to be photographed?

(If Richard Shears is reading this, I would love for you to make contact and provide an indication of the location of the sparrow sighting so it can be compared with the location of the corellas).

Diet

Feeding carrots to yellow canaries turns them blue. The quality of the shrimp that flamingoes eat affects the intensity of their pink colouration.

Could the blue sparrow - and the corellas - be ingesting something which is producing a blue pigment in their feathers?

If so, this would certainly be noteworthy given the fact that prior to this, there is no known bird species in the world which actually produces a blue pigment in its feathers.

In my opinion, this option seems the most feasible because an item perceived as a food source by a sparrow can easily be perceived as a food source by a corella - despite them belonging to different families.

So the questions are:

  • What could they be eating?
  • How is it entering the environment?
  • Have there been significant environmental changes between Sydney and the Central Coast that has exposed some food source causing this pigmentation?

Mineral exposure

One suggestion is that some metals, sulfer and some salts are commonly associated with the colour blue. Could these birds have been exposed to such a source?

Algae

It is well known that polar bears and sloths can turn green when algae inhabits the hollows in the hair of their fur - but could there be a blue algae which affects feathers?

This also seems unlikely, as by nature algae is a plant having clorophyl - which is a green pigment, not blue.

Conclusion

At this stage my opinion is that the colouration is diet related. As a few others have commented - we need to get a feather under the microscope!

The hunt is on, and the challenge is out - serious contenders only please...

If you live in New South Wales, between Wollongong and Newcastle, can you keep your eyes open for unusually blue birds of any species?

Please send all reports to me.

If you can take photographs - all the better. If you manage to obtain a blue feather, then please store it in a clean plastic snap-lock bag, and if possible, don't touch the feather. (Use the plastic bag to pick it up).

With your help we may yet make some fascinating discoveries about blue pigmentation in birds!

(I am also in touch with an ornithologist who is considering this conundrum further and who will discuss the recent corella photographs with members of the Australian Museum.)


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