What an amazing little creature the swift is; once it has fledged from the nest it spends almost its entire life on the wing only pausing briefly whilst it builds its own nest and then to feed its young. Once breeding is over they often form flying squadrons and race around screaming as they go! We used to see lots of swifts in Hampshire, indeed they nested on the house next door to us in the Test Valley, but here in Dorset we only see the odd one during migration times. It is well documented that their number are declining. They are usually one of the latest arrivals back in the spring and yet are one of the first to leave again in mid-summer once breeding is over.
It seems the first arrivals pass through Dorset from week 16 at the end of April and the bulk move through between then and week 18 in mid-May. Reports continue through the summer months with a sudden peak in week 22 in mid-June but I have no idea why this might be. Reports continue through July and August at a fairly low level as the exodus is spread over a much longer time frame than the spring influx. There are a few reports in September too but the main autumn migration is usually over well before then.
Swifts are reported from numerous sites across the county but it is noticeable that these sites are either in coastal, lake or river settings. This may be because these sites receive more coverage than others but more likely it is because there is an abundance of insect life over expanses of water. The most reports come from Longham Lakes, Radipole Lake, Abbotsbury Swannery and Lodmoor; all four of these sites fit the profile of having large expanses of water.
Keep your eyes upwards in May if you want to add swift to your Dorset list; especially if you are at one of the four sites I have mentioned.