Swifts diary

The colony of swifts that nests in the Museum tower has been the subject of a research study since May 1948. 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.

 

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

Swifts Diary 2021

  • May 5 2021
    After a Bank Holiday weekend of strong north easterly winds accompanied by heavy rain 2 swifts were sighted flying around the Museum’s tower as the sun came out on Tuesday the 5th, exactly on time for their average date for their arrival.  By midday the strengthening sun and light winds saw 5 birds tightly circling the tower and the first couple of tentative screams.
     
  • Monday 17 May 2021
    There were three nests showing signs of occupation. One bird was sitting, but not in the same box as the previous week. The birds have been slow to return this year; a few were screaming desultorily around the tower. There is a huge cold front across northern Spain and southern France which may be holding them up as they follow an isobar north and will not progress beyond where the hatching insects are abundant enough.
     
  • Monday 24 May 2021
    Following another week of wet and windy conditions, the swifts are late in settling down to breed. This week there are 21 nests showing signs of activity. Many of these nests are being renovated by the birds but there are 20 eggs visible spread between nine nests, plus two adults sitting tight in other nests. These presumably have at least one egg and most likely two or three eggs, so we can say between 22 and 26 eggs present.

    The next two weeks are critical to whether or not it will be a good breeding season. Cold, wet weather often causes swifts to either kick eggs out of the nest or just to desert entirely, whereas warm, dry weather encourages more pairs to breed and rear two or three eggs through hatching to fledging. Time will tell.
     

  • Monday 31 May 2021
    The morning was dull, overcast but mild and dry, a dozen or so swifts screaming around the tower was a welcome sight. In the tower, it seems the main body of birds is arriving and getting down to breeding. There are now 37 active nests, 50 adults in the boxes and 24 nests where the adult is sitting tight. Despite this, there are 7 eggs visible and I know from last week that many more are hidden under these sitting birds. Outside the tower a dozen or so birds are still screaming, some will be getting ready to settle, a pair were seen to mate on the wing. By next week the non-breeding young birds should arrive so let us hope that the weather stays warm and dry.
     

  • Monday 7 June 2021
    Finally, we have some warm weather. The cold conditions of this spring have delayed breeding this year and there have already been some losses. One of our nests that contained 3 eggs last week is now empty, abandoned by the parents and 3 other nests had an egg ejected, these are now replaced. This ejection of eggs is related to cold, wet weather and commonly happens most years. Replacing the egg is often successful and they usually hatch normally. Forty nests are now occupied, 41 adults were counted in the colony today with 45 eggs known to be present, a further 12 adults were sitting tight indicating that they probably had at least 2 eggs each. Some boxes were occupied by birds that are yet to lay but at the other extreme we have our first 3 naked, blind chicks which probably hatched today. About a dozen or so birds are making screaming flights around the tower and we still have plenty of vacant nest boxes.
     
  • Monday 21 June 2021
    A cool wet day after a long wet weekend saw lots of birds on the nest today.  There are 40 occupied nest boxes and 21 chicks were observed with others clearly vocalising from under their parents.  The young range from blind and featherless to open-eyed with their feathers already in pin and several nests have 3 chicks each in them. Whilst 45 eggs were counted last week, this week only 19 were visible in nests where the adults were absent, several had once again been ejected and were cold to the touch. These were carefully replaced in the hope that they will develop normally as swift embryos have the remarkable ability to go for several days without incubation.
  • Monday 28 June 2021
    The weather today is overcast and cool following recent rain overnight, a gentle but cold light breeze is blowing. There is evidence of activity in 45 of the boxes and 40 adults could be seen. Roosting birds were occupying 3 of the boxes and 2 others contain a nest with cold eggs so perhaps only 40 boxes are in use for breeding. a count of 75 young were visible as well as at least 5 eggs, several birds were sitting tight so there should be more young to come. The season is late this year, many of the chicks are still naked and blind although some of the early ones are well feathered as can be seen on our webcams.

  • Monday 5 July 2021
    Following a mild week, today was breezy with recent rain overnight. Scattered clouds and mild temperatures have slowed the swift breeding down a little and at least 1 dead youngster was found. Better news was the count of over 70 healthy young and 10 eggs in 40 active nests. Only 23 adults were in the boxes today as many were out feeding and gathering food for the young. Ringing of the young has commenced, 6 were ringed today. Sarah Roberts of the North Wilts Swift Group visited to observe the colony as she is in process of creating a colony in a church steeple so was interested in seeing a successful colony.

  • Monday 12 July 2021
    Recent rain and cool, breezy weather has not been good for the swifts as it has made hunting for insects harder. There is also a report of a sparrowhawk hunting around the tower which may explain the loss of 3 of the previously active nests. The good news is that there are 74 young counted this week, they are in all stages of growth from some that are newly hatched to others that are almost ready to fledge. Two nests contain eggs that are being incubated, these may not survive if they do hatch as the time from hatching to fledging is between 5 to 7 weeks depending on weather conditions and food availability. There are still 37 nests active.

  • Monday 19 July 2021
    It's an official heatwave, temperatures outside on the quad have reached 30 Centigrade. Heat rises and the tower absorbs it so it's like an oven up there. Everything takes longer in the heat and this week is one of the prime ringing weeks. Today I was assisted by a trainee ringer from EGI, teaching takes longer of course and we were both relieved to finish the nestbox round.

    Active nests now number 34, there are 68 young remaining and all eggs are now hatched. At least 7 chicks have fledged but the sparrowhawk has had an effect, we found 3 hungry chicks in one of the west side boxes, these have now been fostered into other broods. In another box, a single very thin chick was also removed and fostered with a brood of 2 of about the same size. Let us hope the sparrowhawk does not take any more adults.

  • Monday 26 July 2021
    The weather continues hot and sunny which seems to suit the swifts. there have been 63 chicks ringed and 23 of these have fledged. Ten more chicks remain to be ringed out of the 50 still in the colony, all are looking well including those which had to be fostered into other nests.

    Twenty-two adults have been identified/ringed, about half of which are new birds, the others being more experienced regular breeding birds. The saga of the sparrowhawk seems to have come to a close (fingers crossed) as no more adults appear to have been lost.

    The Museum foyer camera has been moved onto box W5A containing a single youngster as the chicks from where it was originally installed on box S4B have now fledged.

  • Monday 2 August 2021
    Today was warm and calm but overcast. A small party of swifts was rushing around the tower. Inside the colony it was much quieter than last week. Only 19 nests remain active with chicks, two more chicks are missing, and these two were far too small to fledge so it must be presumed that they either died and were thrown out or perhaps just fell from the box.

    On a happier note there are still 31 young which are growing strongly and many of these will leave this week to join the 39 that are already on their way. This year, 71 young have been ringed and one more is still to be ringed; 17 new adults have been ringed and eight adults reidentified at the nest. One of these adults was ringed as a young chick in the tower so is one of the rare ones that return to the natal colony, usually fewer than 1 in 100 of the young ever return.

  • Monday 9 August 2021
    It's been a wet and windy week. Today it was overcast and humid, the wind was calm and there were no screaming parties of swifts around the tower. Inside the colony was a strange silence; after the hustle, bustle and general noise of breeding swifts it seemed rather strange. Only nine nests remain active with twelve young and one adult in the nesting boxes. So far, 60 young have fledged, 30 adults have been captured and either ringed or identified from a total of 41 successful nests. Soon they will all be on their way to Africa for the winter.

  • Monday 16 August 2021
    It's been a damp week but still mild. No swifts were flying around the tower and it was quiet and still inside. A check of the nesting boxes revealed just five chicks remaining, spread between four boxes. All are at an advanced stage of growth so it will not be long before they too are on the way to Africa.

  • Monday 23 August 2021
    Very quiet in the tower today with just two active nests remaining. The two remaining chicks are now well developed. One was sitting beside the hole looking out of the box so will probably leave soon; the other is about a week younger so the camera has been moved to its box. So far 70 chicks have fledged this year, 13 adults have been ringed and another 13 reidentified which were ringed in previous years.

  • Tuesday 31 August 2021
    The last chick left this morning for the warmer African skies. It has been a good year for the birds with 72 young fledged from 55 nesting attempts. A total of 35 nesting attempts were successful. Five pairs occupied boxes but did not lay eggs, six birds were found in boxes but may have just been roosting, a further six boxes failed at the egg stage, and three failed with young chicks. Unfortunately, a total of nine young died prematurely this year - an unusually high total. Some may have been due to a sparrowhawk taking the adults, others are unaccounted for but we do expect to lose one or two each year.

    On a happier note we were able to foster four young into other nests and all of these did integrate and fledge successfully. Of the adults, 13 were newly ringed and another 13 were re-identified, one of which had been ringed in the same box six years previously as a breeding adult.

    The colony seems to now have a stable population although it is nowhere near full capacity as only 55 out of a potential 147 boxes were used. I conclude that an outside factor such as food availability is limiting the number of breeding pairs. A food bolus was examined in July and consisted of a species of small weevil beetle which has not been seen in a bolus before. I think some investigation into the diet of swifts may be desirable next year.
     

chicksbyyearsmalljpg2019