What do recoveries really tell us?

A couple of weeks ago I mentioned that we had caught a Brambling at a farm feeding site, which had been ringed originally in Norway. Since then we have had details back from the Norwegian ringing scheme.

The bird was ringed as a male hatched in spring/summer 2020, and ringed on 10th October almost in the southern tip of Norway. We can say that because Brambling don't breed in that area, that this was a bird which had been raised much further north ( and probably east) --and was on it's autumn migration to warmer south western parts.

164 days later on 23 March 2021, Paul caught the bird at the farm feeder. No Bramblings had been seen at the farm all winter so it is safe to assume that our bird had spent the winter further south and was stopping off to feed up on its way back to Norway or wherever it had been raised.

The ringing records will now show a bird recaptured 164 days after original ringing and 845 km from it's original ringing site. Now this is all great information and data that we wouldn't have had were it not for ringing. But it also shows shortcomings--we don't know where the bird originally came from; we don't know where it went between ringing and recapture, and we don't know where it will end up, and we don't know how much distance it covered during it's migratory journey.

So, what's to be done? Well two things really. This example shows the need for continuing to ring birds because although this one bird leaves questions--if we take the total number of Brambling which have been ringed and recaptured we can begin to fill in some of the gaps in our knowledge. Indeed this has been one of the great successes of ringing -- large databanks of bird movements which can be analysed to build up a good picture of migratory movements over the last 100+ years since ringing began.

The second thing calls on developments in new technology. Satellite tracking is developing at pace but as yet the most informative devices are too large ( and costly!) for use with the smaller birds.  However, I'm sure this will change fairly soon and the prospect of attaching these trackers to small birds and following their movements in detail and in real time will be an absolute thrill and a massive game changer--bring it on!!