Swift ringing recoveries and geolocator tracks compared

It is fascinating how 50 years of ringing recoveries had already given us a clue as to where our Swifts spend the winter, but it is also surprising that some important destinations were never detected.

Contributed by Lyndon Kearsley

The BTO recently posted a piece on their Demog Blog about more ringing recovery maps on their Online Ringing Reports. 

When one checks Common Swift, the selection shows totals per country, a general map and a listing of the most interesting movements with full details.

If we look at the country totals for British ringed swifts that have been found abroad and filter this to show either locations due south (France and Iberia) or in Africa, one gets the following:

BTO foreign recoveries of Swifts Apus apus

I put these more or less in a N:S order and split into Europe, N Africa, Central Africa or East and South Africa. There were no recoveries in West Africa at all.

Unfortunately the BTO does not list full details for all recoveries and not for counties with more than a handful of them. The result is a lack of recovery dates for clumps of locations in for instance France, Spain, Morocco, DRC (Congo) and Malawi.

For recoveries where ringing and finding details are listed, I was able to annotate the BTO map as follows:

Foreign locations of birds ringed or recovered in Britain & Ireland

     Purple: ringed in Great Britain & Ireland, recovered here

     Yellow: ringed here, recovered in Great Britain & Ireland

You will note that the finding dates (often many years after initial ringing) are very consistent with the periods that Dick's Landbeach geolocator bird was in that part of Africa. Of note too is that Algerian and Tunisian recoveries are all in May (Spring) and that, although there is a string of recoveries in nearby Malawi, Mozambique only has one recovery where one would expect a great many more. The same goes for West Africa; not one recovery in that part of the continent although we now know that it is so important for a large part of the European population particularly in Spring.

Since all the points on this map are the ringing or finding locations of single individuals recovered over a span of 50 years, it is quite sobering that one tracked swift from Cambridge can join the dots. On the other hand it's just that connection that increases the value of the ringing recoveries. Conversely the ringing recoveries certainly help to confirm the quality of the geolocator results.

What an exciting time we live in. Hopefully we can use this new knowledge to lever a better time for our Swift friends too