21st February 2008 – Bird Identification
Marking birds can take many forms from tiny leg rings to sophisticated miniature transmitters whereby you can follow individual birds by various means. There are other means of marking such as wing tags and these have been extensively used on birds of prey in the re-introduction programmes of the red kites and sea eagle. Tags have large letters or numbers that can be read in the field by using binoculars and telescopes. The movements of many bird in these programmes have been followed and used to work out their whereabouts. Tiny transmitters have been extensively used in the red kite programme but these have also lead to unexpected results. Tracking such individual birds means that if the bird literally stops moving there is something wrong. The high percentage of poisoned and shot red kites, particularly in the north of Scotland, including the Highlands, has been revealed by such transmitter programmes.
As regards small birds the only way in which a bird can be identified is if the bird is caught again or dies and then the age of the bird, its origin and other aspects can be determined. With larger birds such as swans and geese neck rings and leg rings can be so large, still minute for the bird, that the letters or numbers can be read in the field with binoculars and telescopes. In the Highlands this has particularly been the case with whoopers swans that breed in Iceland and come south for the winter. Such flocks, known as herds, frequent the field around the Tain area and people with telescopes often search the birds for the leg and neck rings. The birds seem to use that part of the Highlands but sometimes using it as a stopping point before going on to Ireland. Some of these birds are ringed in Iceland where for a while the adults and juveniles are flightless and are caught up.
One method of identifying individual birds started at Slimbridge in south west England in the 1960s when Peter Scott realised that he could identify individual Berwick’s swans by their yellow markings on the beak. This research and other studies came to the remarkable conclusion that some birds pair for life. At first this was thought to be the case with only the larger, long lived birds but now it is thought that very many birds do, even the small familiar ones in gardens such as blue tits and great tits. In large seabird colonies this may seem even more remarkable that one bird can identify its mate. Perhaps even more so with night birds such as petrels and shearwaters when they come to the colony under the hours of darkness.
What seems even more remarkable is what happens if a bird cannot fly. Sometimes large birds such as geese and swans fly into overhead cables or are hit by shotgun pellets. It sometimes means they cannot fly and therefore cannot join the rest of the birds when they fly north to their breeding grounds. Their mate will often choose to stay with them for the summer. Such was the case with a pair of whooper swans in South Uist a few years ago and a nest was built and the female actually laid eggs. A pair of greylag geese did the same thing at Loch Flemington a few years ago. More recently just after the New Year a mute swan hit overhead cables in Strathnairn. The bird broke its neck and for a few days its mate flew up and down the strath trying to find it.
