Nest Calling Woodpigeons

Woodpigeon pairs are already formed and nest building is underway. For quite a while I have become accustomed to an unusual song of the Woodpigeon. It starts like it is going to deliver the usual five-syllable song, but instead it stalls and it only delivers two long notes, 'coo, coooo' with the second note dragging on - it reminds me or a revving motorbike. After a minute or so, the two notes are repeated, and it can go on like that for quite a while. I have heard it mostly when the pigeon is concealed from view (inside a cypress) and in one occasion I saw it delivered by a pigeon sitting on its nest. A pair of Woodpigeons have made a nest on a fork in a large weeping willow and the pigeon in the photo was calling in such a way. This call has been named 'the nest calling' and is uttered by the male showing the female a nesting site. According to Murton and Isaakson:

Nest calling is a submissive display, mainly shown by the male and is used to attract the female to the nest or potential nest site. Caressing can occur at the same time as nest calling or away from the nest, and possibly evolved from the food begging movements of the nestling. It usually precedes courtship feeding. On the physical level the display is used to stimulate ovulation in the female, so that when used for long periods in the absence of courtship feeding it appears as a ritualized display.

And according to Cramp:

From early January, and often soon after the pair is definitely formed, the male begins to mark suitable nest sites by Nest Calling. He crouches on the proposed site (which may be a bare fork or branch, or an old nest) and makes short, sharp, downward pecking motions, 

accompanied by the special nest call—a deep, double note, `coo, coo'.

The male may `nest-call' at several sites, and I imagine that the female normally makes the final choice, for the nest is by no means always built on the site where her mate has `nest-called' most persistently. The first nests are seen normally towards the end of March, and the majority start to sit in April.

More information:
Cramp, S.(1958) 'Territorial and other Behaviour of the Woodpigeon', Bird Study, 5: 55-66.here.
Murton, R.K., A. J. Isaacson (1962) The functional basis of some behaviour in the Woodpigeon Columba palumbus. Ibis: 104: 503-521. here.