donderdag 27 november 2014

The variety of birds: a matter of smell?

Sight is an important sense for a bird.
Colour is used as a signal to tell between potential mates or to distinguish their own species.
Mind you, colour is differently perceived by birds than humans because birds can see UV,
we don't!
Next to colour, sight is also used to detect prey (raptors, warblers etc.) or carrion (vultures).

But what about smell? Does a bird use the sense smell as we do?

Well, an Australian study of Crimson rosellas shows this bird can identify their own subspecies based on the odour of another bird's plumage.
Fascinating, I want to know more!

The blue-cheeked Crimson rosellas are beautifully coloured Parrots from eastern and south-eastern Australia and commonly found in gardens and mountain forests where they are sedentary.
The species has 3 subspecies, the Crimson rosella, the yellow rosella (common along Murray river) and the Adelaide rosella (common in Adelaide region).

At the Deakin's Centre for Integrative Ecology (Geelong, Victoria), PhD student Milla Mihailova and her team studied the behaviour of female Crimson rosellas while they were brooding in nest boxes from 2011 to 2013.
It has to be said that the research  was set on testing if female Crimson rosellas could discern the distinctive odour of their own subspecies and whether they could discern between sexes.
After two years it was shown the females preferred going to nest boxes that carried the smell of a male over the smell of another female. This could imply smell could play a role in sexual selection for the Crimson rosella.
Next to this, the females preferred nest boxes that carried the smell of the same subspecies.
This could imply subspecies divergence and maintenance may be explained by smell.
This theory is also in favor of Dr. Bonadonna, a behaviour ecologist working at the National Center of Scientific Research in Montpellier, France.
Before now it was not clear why birds with ~10000 diverse species could have been divided in so many species.
"If birds develop a simple olfactory presence for their own 'group' odours-probably originally shaped by diffrent ecologies and/or environmental conditions, for example foraging-this might isolate groups of phylogenetically-close subjects and lead to speciation".
Dr. Francesco Bonadonna

Rosellas are known for their distinct odour. I kept an Eastern rosella myself 15 years ago and he had a distinct odour which I got accustomed to. When I am in an area with Eastern rosellas I still recognize the smell. When I am in an area with Crimson rosellas they smell differently than the Eastern.
Even years after the birds die they still have the same odour.

Well, the experiment proved Crimson rosella females preferred going to nest boxes that carried the smell of a same subspecies male over the smell of another female.
But this only implies for the Crimson rosella.
What about other birds, for instance other Rosellas?
What about the olfactory system of the Crimson rosella? Where is it and how does it go chemically, physiologycally and neurologically.
And what about the odour itself, what is it chemically and how does it discriminate itself from other Rosella odours?

Just a few questions scientists can be busy with for the coming years.
I just love science, and I love Rosellas.


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