Tuesday 25 June 2013

Swifts occupy Ibstock swift bricks at Antrim County Library

The Ibstock Swift brick has an internal width of 100mm, leading a number of people to wonder whether it was too narrow for Swifts to successfully breed. This is a heartening story indicating that Swifts may well be able to cope with a space this narrow.

Contributed by Rodney Monteith

[Update: in 2013, 8 of these Ibstock swift bricks were occupied by swifts]

In 2009 a row of 15 Ibstock Swift boxes were included in the construction of a new library in Antrim, Northern Ireland.

15 Ibstock swift bricks installed in a regular array
Click picture to enlarge
Since the library service included these homes for Swifts, I took great interest in the future occupancy of the boxes and watched patiently as each of the boxes was used by House Sparrows, but no interest was shown by Swifts, at least none that was noted.

Then in 2012, with interest in our local Swifts increasing, members of Antrim RSPB put together a call system to speed up the process of colonisation and the impact was almost immediate. The morning after setting up the call system I stopped at the library just after 6.00am and watched as a group of between 3 and 5 Swifts made close flypasts parallel to the boxes and a few days later noted a pair of birds flying into one of the boxes practically beak to tail.

Close-up of 4 of the Ibstock swift bricks
This observation was said at the time to be the first confirmed use of an Ibstock brick and it dispelled all worries that the birds might be unable to turn inside the boxes as both birds did eventually come out again. For the remainder of the summer this pair continued to use the selected box and in addition other Swifts were seen entering neighbouring boxes with one bird regularly favouring a particular box in the middle of the row.

Technical issues meant that the calls were only played for part of the summer and I was asked if it should be set up again this year. Believing that this would be unnecessary as last year’s birds should return unaided we have not played any attraction calls this year.

True to form, last year’s birds have returned to their selected boxes and another pair has also taken up residence. My casual observations have seen birds entering 7 out of the 15 boxes but I think most of these were the same birds that are already nesting and on several occasions Swifts entering boxes were aggressively attacked by the House Sparrows. On one occasion a Swift visited 3 different boxes in quick succession before finally entering its own nest and even the pair that is in its second year was seen entering a neighbouring box before quickly exiting and looping back to its own box. How much of this is just curiosity or confusion from the identical holes is difficult to say. While successful breeding could not be confirmed in 2012 it is almost certain that the pair in the box for a second year will soon be happily feeding chicks!

[Birds successively entering different boxes could well be a result of confusion caused by the regular array of boxes. It is sometimes a good idea to randomly place the boxes or provide other visual clues to differentiate them.  We do not have direct evidence of negative effects of playing calls in an occupied colony, on the contrary it is known to accelerate the growth of an existing colony - Dick]

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