Tuesday 26 March 2013

First Swift Tower in the Netherlands

News of another Swift tower which has been erected in the Netherlands. Thanks to Astrid van den Broek for supplying information about the project, and to Fred van Vliet for permission to use his photographs.

[UPDATE July 2017 by Fred van Vliet 2017-07-15: The Den Helder Swift Tower was erected in July 2012 (see below), and its first full season was 2013. Attraction calls were played throughout the season, as far as we know, but no Swifts occupied any of the nest boxes. 21 of June 2014 5 Swifts hung on and entered different nest boxes and stayed the night. In 2015 and 2016 we only saw Swifts flying around the tower. The first of June 2017 we saw Swifts flying at the entrances. On 8 of July we saw 4 Swifts entering 2 entrance holes and calling from the swift boxes, so we have our first breeding pairs in 2017!]

16 nest-boxes on a 10 metre pole
The Swift tower is located in a city park in Den Helder, it is the first tower to be erected in the Netherlands. The tower contains 16 nest boxes. It is covered by a double, insulated roof to avoid heat problems in the boxes.
Distribution of the 16 nest cavities

The tower is located on top of a 10 metre high pole, which is collapsible: the top part of the pole can be folded down. This enables later adjustments to be made, and checking for occupancy after the breeding season. 

Solar panel for attraction calls
Several speakers, powered by solar panels, have been installed to play Swifts calls.

Local children helping to put up the tower

The tower was put up in July 2012 and attracted attention from swifts this first year. From November, Starlings have been using the boxes, which is a promising sign that when the Swifts return from late April 2013, they will start using the boxes.

The tower was designed by Fred van Vliet and built by the local birders' group (Vogelwerkgroep Den Helder). The tower was financed by the city council of Den Helder and Zeestad, and the association for durable energy, De Eendragt, in Den Helder.

Editorial comment:
Congratulations to all who contributed to this project. About the pole itself, one or two points occur to us. The pole is quite tall and slender, so it would be advisable to keep an eye on it during windy periods to see how stable it is. We note the hooligan barriers around the nearby trees, which  suggests that similar barriers might be needed around the pole. The access holes seem a tad large, certainly large enough for Starlings to gain access. The best advice is that the access hole of a Swift box should be no more than 30mm in height. Width is less critical, 65-75mm being adequate.

Sunday 10 March 2013

The winter movements of a pair of Swifts (part 3)

Contributed by Lyndon Kearsley

Getting into position. A further look at the winter timing of a pair of Belgian swifts in 2012. This is the third instalment of our story about where the Swifts were in December and February.

March is a difficult month for tracking birds using light level dataloggers. From about 15 days either side of the spring equinox on the 20th, the day length is about the same across all latitudes and so no north / south fix is possible. However the timing of local midday is not affected, so longitude (how far east or west) can be calculated. 

In the following map I've plotted the locations during March (shown in closed or open black dots) by using the longitude combined with a fabricated latitude derived by simply dividing the first and last fix before and after the equinox by the number of days. The February and April positions are also included to show how this ties in before and after the equinox

You can see that the female leaves East Africa crossing rapidly to a position which coincides with her December location on the lower Congo River. She remained there at about that longitude for the last two weeks of the month and then departed towards West Africa at the beginning of April.

The male moved very little in this period probably remaining above the lower Congo River wetlands in the Democratic Republic of Congo.

                   Red dots are female positions in February and in April
                   Black dots are female positions in March
                   Blue dots are male positions in February and in April
                   Open dots are male positions in March
                  [Click map to enlarge]
The April tracks show how this story continues and marries up with this theory. The male indeed remains in the lower Congo until about the 20th of April when he too makes his move out to West Africa (Sierra Leone).

The female had already been in West Africa for quite a while by that time having crossed the Gulf of Guinea in early April, and her positions show her to have been first in Ivory coast, then Liberia, Sierra Leone and Guinea. Bear in mind that geolocator fixes are at best approximate and the tracks shown are smoothed 3 day rolling averages. Never the less at this scale one gets a clear idea of the birds timing and strategy.

On 29th and 30th April both birds are shown to be somewhere in Sierra Leone and closer to each other than they have been all winter, nicely placed for the dash back to Belgium.

Recently a  paper discussing a statistical track estimation solution for the latitude problem during both equinoxes was published by Wahlstrom et al (2012). 

Wahlstrom, N., Gustafsson, F., & Akesson, S. (2012, July). A voyage to Africa by Mr Swift. In Information Fusion (FUSION), 2012 15th International Conference on (pp. 808-815). IEEE.

Monday 4 March 2013

Bees in a Swift box

by Dick

Last year, right at the end of July, a swarm of bees occupied the top left box in my 9-box cabinet. The box was one of 5 occupied that year. This pair had failed, but they were still roosting every night, until the day the bees arrived.

The nestbox entrance is at the left end and the Swift nest platform is at the right hand end.

On warmer days recently we have been looking out for bees around the box, but there were none, so we guessed they had not survived the winter. On removing the front of the box I was confronted with a beautiful set of 6 honeycombs, and with many dead bees on the floor of the box.

This is the second time we have had bees occupying a Swift box, the last time was in a church where the bees survived the winter, so were removed to a hive, as the bell-ringers were getting stung!

Friday 1 March 2013

Product Review - Bird Brick Houses Swift box

Written by Dick

We have been sent a sample of a new style of Swift box by Bird Brick Houses Ltd in Sussex. There are two approaches to providing nest boxes for Swifts, either add nest-boxes outside or build them into the fabric of the building. Either way, they need to be an attractive feature or well hidden.  The Bird Brick House product is effectively a bespoke solution that provides a built in nestbox that matches both the existing brickwork and the space available in the wall.

Assembled box
The BBH Swift box comes in 3 sections. The body of the box, occupied by Swifts, is made in 2 halves so that the width can be adjusted to fit the space available in the brickwork and cavity. This can be anything between 100mm, in which Swifts can breed successfully, and 150mm, which gives them plenty of space. The front section holds slices of brick, ~20mm thick, matching the brickwork of the wall.

Removable front
The removable front section is secured with 4 stainless steel bolts so, it is easily removed for clearing out the occasional House Sparrow or Great Tit nest outside the breeding season.

It is easy to incorporate this box in the top courses of brick in a newly built building, but also, it can be retrofitted into an already built wall.  There is no need to cut bricks, so the wall can be restored to its original appearance.

Body of box with front removed
The box material is extruded recycled plastic 3mm thick. The raised central section has a concave indentation and is roughened.

We think this is a well thought out product, providing good accommodation for Swifts which is easy for builders to incorporate.

The price quoted is £75 + vat + p&p.

For further details see:

Example of 4 nest boxes retrofitted into a wall