Swifts diary

The colony of swifts that nests in the Museum tower has been the subject of a research study since May 1947. It is one of the longest continuous studies of a single bird species in the world, and has contributed much to our knowledge of the swift.


2 May 2023

The swifts are early this year. We normally see the swifts arriving between the 5th and 8th May but this year there were two birds sitting in boxes today. This could indicate a good start to the season.


8 May 2023

The weather has not been particularly warm or dry but the swifts seem to have settled in quite quickly. Today there were 8 birds sitting and evidence of a further 8 nests with signs of nest refurbishment, fresh feathers and droppings, nest building and cleaning.


15 May 2023

This was a cold clear day with no rain. There are 22 active nests with 13 eggs visible. Only 2 adults and 1 pair were sitting in the boxes and the tower was unusually quiet. It is possible that the swifts are out feeding somewhere and will return soon.


22 May 2023

Another cool overcast day but much more activity with swifts screaming around the tower and birds in the boxes responding. There were nine adults sitting and another nine pairs in the boxes. Inspection of the boxes revealed at least 23 eggs which, when added to the eggs known to be there last week, gives a total of at least 32 eggs and signs of activity in about 37 of the boxes.

Birds are still arriving and we expect the counts to grow next week. The critical time that determines whether the breeding season will be successful, average, or poor is the weather during the last week of May and the first week of June. We shall see what happens!


31 May 2023

Today was bright but with a bitterly cold east wind, very little swift activity was to be seen around the tower; just an odd lonely swift making a half-hearted call.

Inside the tower it was also very quiet – worryingly so – but nest checks still needed to be carried out. It was pleasing to find out that most of the boxes were occupied. There are 38 boxes either occupied or showing signs of activity. Of these, 28 were occupied by pairs, many with eggs, and another seven boxes had incubating adults sitting on the nest. It was notable that all the boxes on the east side of the tower which were occupied held a pair of birds snuggled tightly together. Lone adults were mainly on the west side.

It was not all good news in the colony, however. Six boxes which had appeared to be active now seem abandoned. These may be inexperienced birds practicing nest construction. One of these nests did have a single egg in it last week — this egg has disappeared. Another nest holds a single cold egg. It may be that the birds will return and complete the clutch, but we shall have to wait until next week and see what happens.



The average numbers of young swifts ringed each year over the last 50 years are:


1963–72: 36.7


1973–82: 70.4


1983–92: 100.0


1993–2002: 99.2


2003–12: 81.1