Thursday 10 January 2013

The winter movements of a pair of Swifts

It is New Year and our swifts are very very far away. It’s the middle of winter here in the north and of course mid-summer in Southern Africa. Swifts are usually faithful to both nest site and partner, but do they stay together outside the short northern breeding season? Here’s one couple's answer.

Contributed by Lyndon Kearsley

These are maps of one of my geolocator pairs showing movements in December 2011 and January 2012. They nested in a nest box above a busy school playground in Hechtel, Limburg Province, Belgium. The coloured dots are smoothed average 24 hour locations, but remember that swifts keep flying so the accuracy is not great and the light level data weather dependent. Hopefully they are doing well and quite likely in the same regions at the moment. In 2012 they both received new geolocators and with luck we’ll know if they are equally faithful to their preferred wintering grounds come summer.

Click map to enlarge
December 2011
The female is the red track and she spent September, October and November above the Republic of Congo (Congo Brazzaville) and Gabon, leaving there on 6th December to head directly ESE to the lower Zambezi river area in East Africa. This region between Lake Malawi and the Zambezi Delta is an important wetland area with flood plains and coastal mangrove. Two large dam projects higher up-river in Zambia have reduced the impact of the summer rains but it is still a draw for west European Swifts.

The male in blue left west Congo much earlier and was, by this time, already in the south and spent the first half of the month in south east Botswana before heading into South Africa (RSA), close to the Kruger National Park, for Christmas.

As you can see they did not spend their winter together.

Click map to enlarge
January 2012
The lady goes “fly-about”. First up to the SE Tanzanian coast on 5th January where a second Belgian female breeder happened to be wintering, so an interesting area to keep an eye on. Then she flew inland towards the Lower Zambesi National Park in Zambia around 12th January, and finally south towards the Mozambique capital Maputo on 26th January returning to central Mozambique at month’s end.

The male stayed in South Africa (RSA) between Johannesburg and Swaziland in the coastal highlands and remained restricted to a fairly small area in comparison to the female.

In early February they gradually moved north, getting into position for the dash north in early May back to Belgium.

More about that later.

Wednesday 9 January 2013

Swift nest boxing results in Cambs & Suffolk

Written by Dick

As there is not much Swift activity around right now, we thought it might be worth reviewing the results that have been achieved with Swift nest-boxing projects. Most of these have been in Cambridgeshire, with a small number in Suffolk, the county next door.

The table below summarises the results in 2012, though in many of the sites, first occupancy was in a previous year:

Breakdown of Swift nest boxing projects.
The figures are for boxes available before or during 2012.
The large majority of these projects were installed in 2010 or later.

We have explored 2 factors which might influence success rates, first the playing of attraction calls and second whether the project could be regarded as mitigation for nest sites recently lost in the near vicinity.

Although only 13% of boxes are occupied, this figure is influenced by a small number of projects with a large number of boxes, some of which only have a few boxes occupied so far e.g. "The Swifts", Fulbourn (157 boxes, 27 occupied), Edgecombe flats (71 boxes,  2 occupied), St Mary's Church, Ely (96 boxes, 21 occupied plus 11 possibly occupied with some feathers) and the Cambridge Swift Tower (100 boxes, none occupied). Hopefully, over time, these will achieve their full potential. However, 104 new pairs of nesting Swifts is something to be pleased about.

We are encouraged by the number of sites with at least 1 pair of Swifts: 38% of all sites. Of these, those where attraction calls were played, there was a 43% success rate. Those where nest sites had been lost nearby had success in 5 out of 6 projects.  It turns out there were no sites where both factors apply.

If one combines the sites where there was some attracting factor, then 20 out of 41 sites (49%) were successful. The 12 sites with no attracting factor had no success whatsoever.