Here’s a story reflecting the theme of Friday the 13th.
As the snowflakes swirl, the winds howl, and the temperature is stuck at levels well below the comfort range of Chimney Swifts and their aerial prey, take a moment to reflect on Rob Stewart’s analysis of loss of Chimney Swift habitat in Manitoba over the last ten years…
Loss of Chimney Swift Habitat in Manitoba, 2007-2016.
Loss of Chimney Swift habitat (chimneys) has been touted as one of the main causes of Chimney Swift population decline. In its tenth year, MCSI is able to retrospectively examine what this habitat loss looks like in Manitoba.
Between the spring of 2007 and fall of 2015, over 9 monitoring seasons, MCSI identified and monitored 178 chimneys considered to be suitable as Chimney Swift habitat. ‘Suitable’ chimneys were of adequate size, not lined with metal, accessible (not capped or screened), and in an area where Chimney Swifts had been observed. Of the 178 chimneys, 29 (16.3%) were no longer available to swifts in May 2016. The most common sources of habitat loss was closing the top of the chimney with a solid cap or wire mesh (20/29= 69%) and chimney removal (8/29=28%). One chimney was lined (1/29 =3%).
These numbers are, however, slightly underestimated due to a recent increase of observer effort. In 2015, the Manitoba Breeding Bird Atlas had been completed and MCSI benefitted greatly from ‘Atlasers’ who joined our ranks of volunteers to help find 26 new sites in 2015. This addition slightly distorts the longer term rates of chimney loss. From 2007 through to spring 2015 there were 152 known sites, of which 26 (17.1%) had been lost.
Winnipeg has the largest number of sites of all municipalities monitored but also the highest rate of loss: 22/109=20.2% (20/99=21.2% before 2015).
These losses refer to both active and potential habitat. MCSI has data to show how important potential habitat is. The large chimney at Assiniboine School, Winnipeg, was open but unoccupied in 2007 and 2008. Between 2009 and 2013, 2 to 8 birds were counted using it. But in 2014 the count was 110 and in 2015 it was 166.
While the inclusion of potential habitat is important, we can calculate loss rates based on active sites only. Loss rates of active chimneys, known to be used by Chimney Swifts in the 9 seasons of observations, is higher than the combined, overall average calculated for both potential and active sites. MCSI has identified 110 active sites, 94 of which were known before the increased monitoring effort in 2015. Of the active sites, 17.3% (19/110 in 2007-2015) to 18.19% (17/94 in 2007-2014) have been lost.
In summary, over the 8 monitoring seasons between early 2007 and the spring of 2015, southern Manitoba, and Winnipeg in particular, lost 17-21% of active or potential Chimney Swift habitat – about 2%/year. If you lived in a 25 X 40 foot bungalow, this 2%/year loss is the same as losing a 1 X 25 foot slice off your home every year. It is not good. And sadly habitat loss is ongoing with closures after the 2015 season.
While MCSI continues to develop artificial structures as replacement habitat, it is important to maintain existing structures for Chimney Swifts to roost and nest in. MCSI depends on your eyes to help our habitat stewardship and outreach programs succeed. Send us news of any known Chimney Swift habitat and alert us if these sites are damaged or facing closure.
— Rob Stewart