BTO: The amazing success of the collared dove

Periods of spring-like warmth have prompted the resident collared doves to initiate their first nesting attempt of the year.

The somewhat repetitive ‘u-ni-ted, u-nit-ed’ call now echoes from just outside the window, the birds having constructed a simple nest of twigs under the eaves.

That the collared doves are here at all is the end of result of an amazing story. The species was first recorded breeding in Britain during the 1950s, the first successful breeding attempt taking place on the North Norfolk coast. More breeding attempts quickly followed and the population expanded, pushing across East Anglia and on into the rest of Britain. This colonisation was part of a much wider expansion in the dove’s breeding range. Before 1930, the collared dove was largely restricted, within Europe, to the Balkans and Turkey. Over the following two decades, the range expanded by more than 1,600km, bringing the first birds to our shores.

It is thought that the sudden expansion in the collared dove’s range was linked to a genetic change influencing the dispersal behaviour of young, recently-fledged birds. However, that the species was able to spread into new areas was almost certainly supported by the food available around farms and domestic dwellings, with spilt cereal grain thought to have been particularly important. Even today you will still see large flocks of collared doves where there is ready access to spilt grain or other food resources.

As data from the British Trust for Ornithology’s Common Birds Census reveal, the increasing abundance of collared dove in the UK was knocked back a bit during the mid-1980s, before increasing again to reach a peak in 2003, since when numbers of declined. The recent period of decline may be linked to the outbreak of trichomonosis – a disease of wild birds caused by a tiny parasite – that began 2005, or it may be a consequence of increasing numbers of woodpigeons. Being larger, the woodpigeon is the dominant species and might displace collared doves from favoured feeding opportunities. More research work is needed to understand the possible roles these different factors may have played.

A collared dove nest is a rather pathetic platform of small sticks, and it is no surprise that many breeding attempts fail because the eggs fall from the nest. However, these persistent birds make a number of nesting attempts each year, resulting in the production of enough fledged young to see the population expand. The pair nesting outside the window may struggle so early in the year but if they can rear their young then the fledglings stand a good chance of surviving. Either way, these birds will certainly be making further nesting attempts as the season progresses and their ‘u-nit-ed’ call is likely to be heard for many more months.