Complicated lifestyle of an intriguing bird
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SAND martins have always attracted me, partly because they are one of the first summer migrants to appear and partly because, many years ago, I used to ring hundreds of them.
It was always exciting and rewarding to find birds from abroad that hadf been ringed, and just as moving when a note came through the post telling me of one of "my" birds that had been re-trapped in another country.
The colony I was ringing was at a large sand quarry, and fortunately the owners were very agreeable to leave alone the faces the sand martins used.
Even in those days some people thought it was a good omen to have sand martins breeding in their working sand pits.
I recall once that I had a mist net up to catch the birds and it caught a little owl, although it was never clear whether the bird had gone for the sand martins as food.
There are a number of sand martin colonies with fewer than 100 pairs in the Highlands. These range from Loch Broom down to Loch Arkaig. And apparently there is a large colony of several hundred pairs near Daviot which I must look at to remind me of the old ringing days.
It’s amazing to see how far the small colonies are from water, and I often wonder whether this is their way of avoiding the notorious Highland deluges that can wash colonies out.
If there is torrential rain the rivers and burns can rise in spectacular fashion. Sand martin chicks and eggs can be washed out of the burrows.
I have found two colonies in small quarry faces well away from water.
The last one was not very far from the River Findhorn and I hid not far away with the big lens on the camera. I was using a Canon EOS 600D with a Canon 100-400mm lens and 1.4 extender which seemed to do the trick.
Two birds seemed to be greeting each other at the entrance hole so I wondered if one had just arrived on the scene?
The birds were more than happy to continue with their frenzy of activity, with some still excavating their lengthy holes that can go as deep as 120cms.
At the end of the tunnel is a rounded nest chamber often lined with grass and feathers. The female will lay her four or five eggs and both male and female take it in turns to incubate the eggs for the 15 days to hatching.
Both male and female then continue to feed them. Then things can get complicated if a second brood is undertaken.
If the survival of the first brood is poor, the female may leave the young for the male to feed. She may pair up with a new mate and start a second family.
Males, too, may change mates after the young have become independent.
Even after breeding life seems complicated as the young birds from the first brood may wander off and explore a wide area well away from their breeding sites.
This can include visiting other colonies and joining communal roosts that may contain large numbers of birds. In August, adults and young birds head south-east to make the shortest sea crossing across the Channel.
They fly on to Africa and have to cross the vast expanse of the Sahara Desert. No mean feat when you think that the sand martin is shorter than a great tit!
My books indicate that there are between 20,000 and 60,000 pairs of sand martins in Scotland.
There was a crash in the numbers in 1968-69 which may have been because of problems on their migration rather than in the UK.
Numbers have recovered since then, but for some unknown reason they are now very variable each year, so I wonder what this year will bring.
Interestingly, one of the Scots names for the sand martin is "bitter bank", indicating that it bites at the sand to form its burrow. The Gaelic name is Gobhlan-gainmhich which means "forked one of the sand".
