We noticed a number of calls to the headquarters of the BTO recently, asking just that. Well, the simple answer is that many of them are likely to have been held up on their migration north. As feeders on airborne insects, cool wet weather during the peak migration period can severely hamper their progress.
The BirdTrack reporting rate shows that they are currently running around a week later than is the norm but there is still plenty of time for more birds to arrive. With the weather set to get warmer this week, we could see numbers of both species build up.
House martins by Mark Kilner from the Springwatch Flickr group.
Both house martin and swift are amber listed as birds of conservation concern as a result of alarming declines, the reasons behind which are unclear. However, with some amazing advances in technology, we have been able to follow a few swifts to and from Africa on their amazing migrations, and we now know the wintering locations, or at least how much swifts travel during the winter months in Africa. We also hope to soon find out more about house martins.