Wednesday, 13 February 2013

New nest boxes at Ely Maltings

UPDATE August 2013. The pair of Swifts in the original 10 boxes returned to breed and 1 additional pair occupied one of the 10 new boxes.

We reported previously on our inspection of the first 10 boxes installed by Bill Murrells at Ely Maltings, Cambridgeshire, where Swifts once bred on top of the wall under the eaves, then nest-boxes were installed as compensation for the loss of nest sites when the building was renovated. Although only one pair of swifts has occupied the nest boxes so far, we have now added 10 more boxes, together with an attraction call player with speakers. The team this time included Bob Tonks, Jake Allsop and Bill Murrells. 

Written by Dick

Ely Maltings. The nest-boxes are out of sight under the eaves. In the foreground is a
Richardson's Goose Branta h. hutchinsii, and 2 members of one of the only two self-sustaining
populations of wild Muscovy Ducks Cairina moschata in the UK. Photo Bob Tonks

Ely Maltings is an attractive Victorian building not far from Ely city centre. It is used for events, such as weddings, concerts and film shows. In the summertime, there is a bar and restaurant, where people can sit out and enjoy the riverside setting. All that is now needed is a vibrant Swift colony, but it is essential that nothing is done to compromise the appearance of the building.

This was certainly achieved with the first 10 boxes which were tucked up well under the eaves and painted black. The entrances were in the bottom of the box, away from the wall, with a vertical 'landing platform' attached adjacent to the entrance. In other projects under eaves we have used a sloping entrance at the front of the box e.g. [1]. [2]. [3]

Successful nest boxes at Rutland Water with entrances
next to and parallel to the wall. Photo Tim Collins
For more pictures see SMSWW photos- requires login
This time we thought we would try something a little different and simpler by placing the entrances next to the wall. Our initial concerns that the swifts may not like an entrance so close to the wall, because of perceived difficulties in manoeuvring when entering and leaving were allayed when we found plenty of examples of successful nest boxes like this. For example Tim Collins project in Rutland (picture left).



Entrances parallel and perpendicular to the wall
We followed Tim's example of not having a back to the boxes and we did away with a roof as well.

There is still a question whether the entrance should be parallel or perpendicular to the wall, there are successful examples of both.

We decided to make 5 of each.

The pictures at left illustrate the simple idea we came up with showing both entrance configurations. [the real boxes were painted black and were not possible to photograph]
Swift's view of entrances

The spaces between the joists varied between 28cm and 34.5cm, so each box had to be tailor-made. The distance from the wall to the front of the boxes was 25cm. The boxes were made of 12mm weather-proof ply.

The boxes were installed by removing the bottom, screwing the sides to the joists, then replacing the bottom.

Two tweeter speakers have been installed ready for playing attraction calls in May (See Cheng Sheng player).


#openeaves

Monday, 11 February 2013

How many Swifts are there in GB and the UK?

The February 2013 issue of British Birds has a paper titled 'Population estimates of Birds in Great Britain and the United Kingdom' by Andy Musgrove et al. This of course includes estimates for the Swift population. As Swift is such a famously difficult species to census, we thought it worthwhile taking a closer look, as well as coming up with our own "fag-packet" estimate to see how it compares.

Written by Dick


The population estimates are produced by the Avian Population Estimates Panel (APEP), composed of representatives from the BTO, GWCT, RSPB, WWT and JNCC. Their estimate of the population of the Common Swift in 2009 is:


GB: 87,000 pairs (63,000 - 111,000)
UK: 87,000 pairs (64,000 - 111,000)
[Note the UK includes the island of Great Britain and Northern Ireland].

The authors believe this to be an underestimate and that the reliability of the result is 'poor'.

The numbers are rounded to 2 digits (so the nearest 1000), implying that there are less than 1000 pairs in Northern Ireland. This seems low, given, for example, the huge numbers of Swifts sometimes seen feeding over Lough Neagh.

The estimate is based on the results of the Breeding Bird Survey (BBS), a survey designed for monitoring population change, rather than absolute population levels. The method calculates the density of birds within a defined distance of a transect, and then extrapolates across the country.

It is not stated whether account has been made for non-breeders and incubating breeders. Swifts do not breed until about 4 years old, implying that roughly 40% must be non breeders. If haIf the breeders are occupied in a nest site, then only ~70% will be at large at any one time for BBS participants to see them.

The final paragraph of the paper invites people to get involved in gathering data and coming up with their own ideas, so here goes!

Fag-packet estimate

Swifts nest in houses, so one might expect the number of pairs in any area to be proportional to the number of houses. In what follows, we do not always know how many houses there are, but we have found figures for the human population, so we have divided this by 2.5 to get the number of houses. From this we calculate the number of pairs per 1000 houses, then we can extrapolate across the UK.

There are a number of published local estimates of the breeding Swift population (see table below). One of the earlier ones was Perrins estimate in 1971 who thought that there were between  20 and 50 times as many breeding Swifts in Oxford as there were in the museum tower, which numbered 40 pairs at the time. So we have taken his lowest number, 800 pairs in 1971. Likewise for Northants we have used a minimum estimate for the population in 1998 by taking the minimum from the 1978 survey times the maximum percentage decline estimated in 1998 (Richardson 1978 and 1998).

Since 1994, Swifts have been declining at a rate of about 3% per annum (BBS).  So, to estimate the population in 2009, we need to make an adjustment to account for the decline since the survey was made. As there are no figures before BBS, we have used the same rate of decline to adjust numbers obtained before 1994 (i.e. Oxford).

The number of households in the UK is ~25 million in 2009. So, the APEP estimate of 87,000 pairs in 2009 translates into 3.5 pairs of Swifts per 1000 houses. In the table below, most surveys come up with a density larger than this:


Analysis of some Swift survey data.
The minimum (Northants) and maximum (Oxford villages) densities translate into overall breeding population estimates between 78,000 and 265,000 pairs. Note though that the Oxford villages sample size is small.

To calculate an estimated mean density across the UK, we can use either a calculated overall mean sample density, or the mean of the sample densities.

Mean sample density - total pairs / total households:
Total estimated pairs in 2009: 6,580
Total Households: 958,252
Average pairs per 1000 households: 6.87
UK population (25,000,000 households): 171,671 pairs

Mean of sample densities
Average of sample densities: 6.28 pairs per 1000 households. 
UK population (25,000,000 households): 156,894 pairs

The first estimate is effectively weighted by sample size and the second is unweighted. The difference is because the largest sample (Cheshire) recorded a relatively high density. 

Based on this latter, lower figure, the estimate for Northern Ireland, with 1.8 million people, would come out at about 4,700 breeding pairs, but we did not use any data from Northern Ireland!

So how many Swifts are there in the UK in total?

Using our lower figure, rounded to 2 figures, of 160,000 as an estimate of UK breeding pairs in 2009, and given that  ~40% are non breeders, then the total number of individual Swifts in the UK during the breeding season in 2009 may have been of the order of 530,000. If each pair of Swifts yields on average 1.5 young, then the number of Swifts leaving the UK in the autumn is 770,000 (minus a small amount of mortality during the breeding season).


Comparison with some other urban species

The paper includes an estimate for House Sparrow of 5,300,000 pairs in the UK, and for Starling the number is 1,900,000 pairs. It is ironic that these two hole-nesting species are red-listed, but Swift, at an official estimate of 87,000, is only amber listed. There must be scope for a huge increase in the Swift population in the UK if we could provide nesting sites for them.

Conclusion

This analysis is a fag packet exercise, and there is scope for more refinement. For example, we could apply the regional BBS changes; we have not accounted for changes in number of households over the years; all of these surveys were in England, and there are not enough of them. Maybe larger samples should be given more weight as should more recent samples. 

With more data from more recent local surveys of this type one could investigate other variances. Wotten et al 2002 showed that houses in rural areas are more likely to hold Swifts than in urban areas; older houses, especially those constructed before 1919 contain more breeding Swifts than houses built since then and there are regional differences in density.

Our result comes within a factor of 2 of the APEP estimate so there could be some mileage in this approach. After all, APEP say that they think that their number is an underestimate, and our estimate is bigger!

Acknowledgements

Thank you to Andy Musgrove and Stuart Newson of the BTO for encouragement to publish this. Thank you to Jake for digging out old papers with much of the data from his Concern for Swifts days and to Chris Mason for providing estimates for 6 Oxford villages.

References

Hornbuckle, J. 1984. Survey of Swifts breeding in the Sheffield areaMagpie 3: 29-33. Sheffield Bird Study Group.

Roberts, Graham C.M. 2001. The 1999-2000 Sussex breeding Swift survey, comparison with the 1968-70 survey and conservation issues The Sussex Bird Report 53

Martin, B. 1998. A survey of summering swifts in Cheshire and Wirral and their conservation status. Cheshire and Wirral Ornithological Society.

Musgrove A., Aebischer N., Eaton M., Hearn R., Newson S., Noble D., Parsons M., Risely K. and Stroud D. 2012.
Population estimates of birds in Great Britain and the United Kingdom. British Birds 106 * February 2013 * 64-100

Perrins, C. 1971Age of first breeding and adult survival rate in the Swift. Bird Study 18: 61-70.

Richardson P. W. 1979. A Survey of Breeding Swifts (Apus apus) in Northamptonshire in 1978. Northants Bird Report 1979

Richardson P. W. 1998. Swifts in Northamptonshire 1998 - a repeat sample survey. In litt.

Wotton S. R., Field R., Langston R. H. W. and Gibbons D. W. 2002. Homes for birds: the use of houses for nesting by birds in the UK. British Birds 95 * November 2002 * 586-592


Saturday, 9 February 2013

New Swift Homes at Greenmount Farm, Antrim

Another excellent example, this time from Antrim, Northern Ireland, of how, with a little ingenuity, an existing colony can be saved when a building is renovated.

Contributed by Rodney Monteith

Just outside the town of Antrim in County Antrim lies Greenmount Campus, part of the College of Agriculture, Food and Rural Enterprise (CAFRE). Within its grounds is a historic farm courtyard dating back to the mid 1800’s that has served both as a working farm building and a training area for the hundreds of agriculture students that have passed through during the past 100 years. Recently some renovation work was carried out to the building and I had the opportunity to examine some Swift nest sites under the slate roof that had been used for many years. 

Square nest site, 200mm x 200m
There has been a great deal of discussion regarding size of entrance hole and nest chamber dimensions so the measurements of the nest spaces are interesting.

Nesting under a slate roof the birds had used an area with a maximum head room of approximately 90mm and this tapered to zero at the front of the chamber due to the slope of the roof. The floor of one square chamber was 200mm x 200mm while the other was a triangle similarly 200mm x 200mm- so half the floor area.

Triangular nest site, 200mm x 200mm
Bearing in mind the slope of the roof the triangular nest site must have been very cramped but was used successfully for many years, and considering the recent discovery of Swifts nesting in House martin nests this obviously wasn’t a problem.

In February 2012 the old roof slates were removed and repairs were made before re-covering.


New nest sites

The timing of the renovation work was coordinated to reach completion before the breeding season and as part of the work the ”fill” on top of the wall was removed. This provided potential nest sites but with no access points for the birds. The original nests were in small sections where the fill was missing but the addition of a fascia board meant the original access points were blocked.

This problem was overcome by partially removing some of the overhanging bricks to provide a series of 30mm x100mm gaps for access to a total of 18 nest areas.


View from the ground showing entrances
Since several pairs of Swifts nest nearby it was not long before the new sites were discovered by prospecting birds, aided by the fact that 3 of the sites were quickly adopted by House Sparrows.


Three of the new sites were visited by Swifts and one that had reared House Sparrows had a pair of Swifts that used it from 24th June until 14th August 2012. Hopefully 2013 will see several of these new nest sites occupied successfully.






Thursday, 7 February 2013

The winter movements of a pair of Swifts (part 2)

This is an update to our story about where the Swifts were in December and January, here.

Contributed by Lyndon Kearsley

It is February 2013 now and some common swifts have been seen in Malta and Israel over the last two weeks and a number of House Martins are in Lisbon (and Malta) along with lots of Swallows. That is normal timing for Southern and Mediterranean Europe, but what are "our" swifts doing. Maybe, they are in habitat like this:

Orange River region in Northern Cape Province / S Namibia in 2011. Photo F. Ambrogio.

Not possessing a crystal ball we can't of course answer that, but here is what the Belgian pair discussed in my last blog entry were doing in February 2012 last year.

February movements (click to enlarge)
The female moved around an area between Lake Malawi and the headwaters of the River Congo in south east Congo Republic (RDC) in February.  This range is about 1000 km in a SE to NW direction. It is very consistent with a second Belgian female who covered a similar range size that month, but a little to the NW in Central Congo.

The male partner which as you remember spent January in a rather small part of South Africa near Johannesburg moved slowly north into southern Zimbabwe and then headed WSW swinging across the south of Botswana in to western Namibia by mid month. It remained thereabouts for 12 days before heading quickly due north into the middle of the Congo Basin. As the crow flies about 4000 km, and always keeping between 1000 and 1500 km south and west of his mate which it neatly bypassed by month end.

Kalahari rain clouds. Photo Oompie
Male track superimposed on SABAP density map
(Click to enlarge)
You'll probably be thinking what on earth made it head over to Namibia? The east coast southern rains form a separate weather system and move due west across the Kalahari through January and February, greening it and triggering insect eruptions, particularly of various termite species. When the track is plotted on the South African Bird Atlas (SABAP) smoothed map of Common Swift observations one sees some correlation, although I have not had access to the dates of the field observations.

Please bear in mind that the geolocator data is only precise to within about 150 km and that Common Swifts are thought to spend the whole of their winter period flying. The dawn and dusk fixes give then only approximate midday and midnight averages. Those plotted here are smoothed averages taking into consideration the movements the day before and day after. The swifts themselves fly a huge multiple of these distances as they dart around going about their business. Since all geolocators are light level archival data-loggers, a constantly flying aerial platform (a swift) is quite ideal, even if not stationary, and the data surprisingly good. The calculated plots when considered on an African scale certainly reveal broad distribution, strategies and timing adequately. 

Tuesday, 5 February 2013

A story about Swifts in Uzbekistan

We know so little about what is being done - if anything - for wildlife in more distant parts of the world. This report from Uzbekistan about attempts to help grounded or injured Swifts is inspirational. We are grateful to Elena and Pavel for sending it to us.

Contributed by Elena Abdullayeva and Pavel Karabayev (edited by Jake)

Elena and Pavel
We are two young people living and working in Tashkent, Uzbekistan. Our first encounter with Swifts was in 2011. We were returning home from work when we came across a grounded bird that we didn't recognize. It was beating its wings helplessly and trying to use its feet to crawl. Like most people, from childhood we had been largely unaware of wildlife, but we couldn't just leave it there. 

So we wrapped the bird in a handkerchief and took it home. Once home, we found out through the internet that our bird was a Swift (Apus apus, the Common Swift, which in Russian is called the "Black Swift").

But together with this information, there was a lot of conflicting advice and recommendations about the care and rehabilitation of grounded birds.

A juvenile that left the nest too early.
However, among a plethora of sites, some professional, some veterinary and some amateur, we found a couple of useful articles, one by a doctor of veterinary medicine, who was the Director of a specialist centre for the rescue of Swifts in Frankfurt-am-Main, Christiane Haupt; and one by a volunteer at the Centre, Hilde Matthes, about the proper care and feeding of rescued birds.

With the help of these professional recommendations, we were able to rear and safely release our grounded Swift. The moment when we saw our little Swift soar into the sky and join flocks of his fellow Swifts changed our lives forever. We had found an activity which has become for us much more than just a hobby.
This juvenile, with a broken bill,
was successfully rehabilitated.
In the following season when the Swifts arrived, we told a great number of our friends and colleagues about our passion, with the result that in 2012 we were able to rehabilitate 24 grounded Swifts.

The care and rearing of Swifts is a very demanding business. Swifts are delicate birds and need careful handling and constant attention. Careless handling, lack of attention to detail, unsuitable diet or insanitary conditions can all have disastrous consequences for the birds. The period was consequently very stressful for us but at the same time very joyful in that there is nothing more beautiful than seeing a bird that was once helpless fly from your hand and soar high into the sky.

We are now getting ready for the coming season when the Swifts arrive, which includes our decision to join the Uzbekistan Society for the Protection of Birds [the Birdlife Partner in Uzbekistan] so as to continue our work on a more serious basis than simply our own enthusiasm.

Of course, our intention in helping Swifts is not purely environmental, but is aimed at promoting a caring and compassionate attitude to all wildlife, so that young people in particular may be not only better informed, but also spiritually enriched.



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Saturday, 2 February 2013

New Swift boxes in Oostvoorne

We saw this heartening story on Norman Deans van Swelm's website, and we thought it worth re-blogging here. A large colony of Swifts in Oostvoorne lost their nests due to roof renovation. However, thanks to an initiative by local citizens, the colony was saved. We also thought that the nest box design was neat and simple, and fitted in well with the houses.

Contributed by Norman Deans van Swelm, adapted by Dick

As in many other places, Swifts, House Sparrows, Starlings, Bats and House Martins all lose out when modern roof renovations conform to government regulations, where, in the Netherlands, all roofs must be delivered "mouse free".

However, as the nests of Swifts are protected by law, the village council provided funds for nest boxes to compensate for the loss of nest-sites.  The nest boxes were designed by Martin van de Reep so that the new entrances could be as close as possible to the old entrances.

Roughly 80% of the 168 boxes installed in 2011 were visited by Swifts that same year. Originally, many of the Swifts entered the roof at the end of the gutter. Others accessed their nests via an entrance next to the rain pipes. It took a while before the birds realised that the former entrance had been blocked by a nest box.

Initially there were quite a few fights between pairs competing for the same nest box.

In 2012, 130 young were ringed.

Also in 2012, House Martins took advantage of the new nest boxes provided. They only needed to use a fraction of the amount of mud that they normally use to reduce the size of the entrance

The previous entrance was behind the pipe. This Swift has successfully found the new entrance.

The new nest boxes do not detract from the appearance of the houses

This is a rather nice outcome

The boxes made were 400mm deep, which is wider than many people's eaves. The material used was Western Red Cedar with stainless steel screws. As these boxes will never be exposed to the sun or rain, then any treated material should last a long time.

Below we have modelled a similar box in Google Sketchup, with indicative minimum dimensions. Ideally, this box needs eaves at least 250mm (~10 inches) wide. We have modified the Oostvoorne design slightly, by extending the front up a small amount, so that it is easier to fit snug under the eaves. If you have more space, then make the box deeper and wider. The whole front can be removed for inspection.

These minimum dimensions are for guidance. One would not want less than 250mm for the depth.
The length could be made longer than 300mm.

Internal structure