Can you help House Martins?

The house martin is a familiar summer visitor, more suburban in habits than its country cousin the swallow. Although it once commonly nested on cliff faces, including the chalk cliffs at Hunstanton (where it last bred in 1967), the species has adapted to the opportunities provided by modern housing, choosing to place its characteristic nests under the eaves. However, it appears that the house martin is in trouble, a large-scale decline in abundance prompting researchers to place the species on the amber list of birds of conservation concern. House martin populations at the local level, for example colonies on a particular house or bridge, are known to fluctuate over time and this makes it difficult to untangle any underlying change in abundance that may be masked by such short-term fluctuations. It is clear, however, that even within Norfolk the characteristic large colonies at favoured sites have been lost. Saddlebow Bridge at King’s Lynn used to have a colony numbering 150 active nests but no longer. Nationally, the highest densities tend to occur in villages and small towns across East Anglia, so we should be concerned about the changes seen in Norfolk.

In an attempt to increase our understanding of how house martins are doing, and to add more records to Bird Atlas 2007-11, the British Trust for Ornithology (BTO) has teamed up with BBC Radio 4, to launch a house martin survey. Through the survey, researchers hope to establish where colonies of breeding house martins are to be found and to assess the size and success of individual colonies. If you have a colony nesting on your house, or are aware of one nearby, then visit the British Trust for Ornithology website (www.bto.org) to access the survey.

Despite its familiarity there is still a great deal that we do not know about the house martin. While we know that they tend to arrive here from the middle of May and depart again from September or October we know very little about exactly where they spend the winter. We know that they winter in Africa, south of the Sahara, and some 90 million house martins from Europe cross the Sahara each autumn. However, they are very rarely seen in Africa during the winter months. Unlike swallows and sand martins, they do not gather together in huge winter roosts in reedbeds or other accessible sites and it has been suggested that they actually winter above the thick jungles of central Africa. This, at least, might explain the paucity of sightings and recoveries of ringed birds. We also need to know more about the reasons for the decline seen across Europe. With luck, the new BBC/BTO project will shed some light on this particular mystery.