Sand Martins – Ray Colliers Wildlife in the North

sand martinThis is the time of the year when we eagerly anticipate the first summer migrant birds to arrive.  A guide to which comes first , on average, can be found in the annual Highland Bird Report that, as the title suggest,  covers most of the Highlands.     There is a whole page of the first dates of the spring migrants each year.   For me they are always tantalising as my early dates never seem to correspond with those listed!  Looking through the list as far as the small birds are concerned, such as warblers and flycatchers, the first to arrive is invariably the smallest of the swallows and martins.  They are the sand martins who have had a long journey  back from their wintering quarters in  Africa.  For such a small bird the journey itself seems amazing but on  top of that is the fact that in  the process they cross the vast area of the Sahara Desert.      

The sand martins arrive in March, sometimes early in that month, and to us it is a constant wonder that they manage to find any of their food, insects, so early in the year.   However, over water such as lochs, rivers and burns there are enough to sustain  them.  Two favourite place around Inverness are both lochs with one being Loch Flemington, east of Inverness.  There they are often joined, a little later, by swallows and it is a thrill of spring to see these birds hawking low over the water after insects.   The other loch is Loch Dochfour, south west of Inverness.  How different are these two bird’s nest sites with one, the swallow,  favouring ledges in barns and outhouses whilst the sand martin burrows away in sand banks adjoining waterways.

The sand martins are one of the most sociable of birds as they nest in colonies,  sometimes quite large, in  banks on the side of such places as rivers and burns.   They will, however, sometimes nest well away from water although the water must not be far away as that still supplies most of their insects throughout the summer.   If the banks are extensive and ideal, large numbers of sand martins will excavate their nesting burrows.    These holes are between 35-119 cms tunnels with a chamber at the end  that contains a nest of  grass and feathers in which they lay their four or five eggs.   The eggs are incubated by both the males and females for 14-15 days and the chicks are also fed by both sexes. Then the complications may occur as, in good weather, a second brood is reared.    However, if the survival of the first brood is poor, the female may leave the young for the male to feed.  She then may pair up with another male and start another family.

The main problems for sand martins in the Highlands are spates and predators.  Spates are when heavy rain raises water levels that can, and occasionally do, completely flood out the nesting borrows.  Then eggs or chicks can just be drowned and washed away.   Predators are also a major problem and it surprising  how varied these can be.  One unlikely predator is the fox that just digs out the holes and eat the eggs, chicks or any trapped adults.   Weasels and stoats can get into the burrows without digging.  Another very unlikely predator is the great spotted woodpecker that easily digs out the burrows to get the eggs or chicks.  For the sand martin  life in the highlands can be difficult and this is why the colonies are few and far between.   The photograph shows a sand martin on the ground gathering mud for  the nest chamber.

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