Strut your stuff: pigeon courtship and iridescent feathers

Rock dove (Columba livia) on 16 July 2021 with iridescence

It can be very hard to tell apart male and female domestic pigeons, also called rock doves, Columba livia. There are differences, for example in the size of body, neck, and legs, the shape of nasal knobs, head, forehead, and the degree of iridescence, but there is great deal of overlap in all of these features, so apparently, they cannot be reliably used by humans to determine the sex of pigeons (Nakamura et al., 2006).

Rock dove (Columba livia) – sex unknown – on 31 Mar 2021 with iridescence

However, it is easy to tell which one is the male when it comes to courting. They engage in courtship displays which can include circle walking, bowing, cooing, tail dragging and preening. As everyone knows, the male puffs out his chest and struts about, approaching the female at a rapid walking pace, emitting repetitive cooing noises and bowing and turning as he comes closer. The male usually has the most iridescent feathers.

Rock dove (Columba livia) male on 31 Mar 2121 with iridescence. Photo by Raymond JC Cannon

On 99% of occasions, the courting males simply get ignored by the females, but at some point in the Spring, a female will say yes. But how does she make her choice, I wonder. Has she evaluated all the males in the neighbourhood and come to he own unspoken decision; waiting for Mr Right to show up? And on what does she base her choice? Eventually, she droops her wings and adopts a submissive pose, ducking down indicating her readiness to mate.

Rock dove (Columba livia) male on 31 Mar 2121 with iridescence. Photo by Raymond JC Cannon

Cooing is an important component of dove courtship behaviour, but one aspect that fascinates me is the iridescence of their feathers. I have blogged about the Iridescent feathers of pigeons before, but I think it is worth revisiting, if only to post some more photos of this attractive feature.

Rock dove (Columba livia) male on 31 Mar 2021 with iridescence. Photo by Raymond JC Cannon

The iridescent feathers produce their wonderful green and purple colours by structural colouration, rather than by pigments. These sort of feathers (or scales in butterflies) are generally ‘costly’ to make – physiologically costly that is – in the animal kingdom, so there must be a good reason to have them; to have evolved them. The iridescent feathers on the neck are very different from the other feathers on the body of the bird.

Rock dove (Columba livia) iridescent feathers on neck. Photo by Raymond JC Cannon

The iridescent colours constantly change as the bird moves about in the sunshine; it really is quite magical! And imagine what it looks like to them; with their ultraviolet vision!

Rock dove (Columba livia) iridescent feathers on neck. Photo by Raymond JC Cannon

The conventional explanation, is that structural colours like this tell the birds something about their quality. A showy feature, like the peacock’s tail, which the females use to select the most attractive male. But both sexes have these iridescent feathers, to some extent in pigeons, so what does it tell them about each other?

In conclusion, scientists know a lot about how iridescent colours such as this are generated (produced in nature) but less, I think, about how the organism uses them in their life. That’s harder to understand, but it’s open to everyone to observe. Just watch the birds and see how they behave with their flashy feathers!

Rock dove (Columba livia) on 16 July 2021 with iridescence

Reference

Ghiradella, H. T., & Butler, M. W. (2009). Many variations on a few themes: a broader look at development of iridescent scales (and feathers). Journal of the Royal Society Interface6(suppl_2), S243-S251.

Nakamura, T., Ito, M., Croft, D. B., & Westbrook, R. F. (2006). Domestic pigeons (Columba livia) discriminate between photographs of male and female pigeons. Learning & behavior34(4), 327-339.

Yin, H., Shi, L., Sha, J., Li, Y., Qin, Y., Dong, B., … & Zi, J. (2006). Iridescence in the neck feathers of domestic pigeons. Physical Review E74(5), 051916.

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