Robins

[watervole]

Robins are truly gardener's bird.  There's one in our back garden at present who is remarkably tame.   He'll come within a foot of me if I don't move too abruptly.  He's been having a field day today - I've been digging out some old hellibores to makes space for another gooseberry bush this autumn and this, of course, results in lots of freshly dug

Comments

[temeres]

This explains everything, including why it is impossible to tell male and female robins apart. There is actually only one bird per nest, reproducing by some unique variation of parthenogenisis. And if you wonder how the robin manages to impregnate itself, well, the males have always been nicknamed 'cock robin'!

This is the kind of nonsense that gives ornithology a bad name. The truth is far more interesting. The term 'cock robin' is a reference to the fact that although there are indeed male and female robins, only the males are fertile. They reproduce by a process called execral androgenesis, by which the juveniles first appear as tiny buds just inside the cloacal aperture. They then migrate through the male's soft underdown and develop within a brood chamber known as the axillary pouch, where the wing meets the main body.

This is normally carried out in winter, hence the reference in the nursery rhyme to the robin hiding himself in the barn and tucking his head under his wing. Of course, it wasn't until the robin's unique reproductive behaviour was first discovered (by the great Spanish ornithologist Estes Torocaca in the 1930s) that it was realised that what the robin was really doing was feeding his young in the axillary pouch. These days, thanks to global warming, the young may be produced as early as September and androgenetic reproduction may continue into May.

[watervole]

But if this were to be the case, what purpose do the females serve?

The literary reference does credit to your case, but in totality, I find it excrecable.

[temeres]

The very existence of the females was for a long time considered a mystery, perhaps even an evolutionary scandal comparable to the non-existence of males among the bdelloid rotifers. However, it turns out that the females are necessary because they hormonally induce the proper development of the axillary pouch. This was first suggested by some ingenious experiments by B S Monger and confirmed through further research by Maddie Tollup.