WALKING beside the Ribble last week I found myself amidst a swarm of fast-flying sand martins. I had never seen so many at once so I had a go at videoing them – it’s not brilliant but you can see there are plenty of them. There must have been plenty of insects for them to feast on though I couldn’t see any.
The books say that sand martins (Riparia riparia) are common summer visitors but I don’t think they are as well known as the closely-related house martins (Delichon urbicum). At a glance they look very alike in flight, and they have similar twittering calls, but there are tell-tale differences.
House martins have glossy blue-black upper parts and pure white under parts, with a distinctive white rump.
Sand martins have dark brown upper parts with pale under parts but against the sky it can be hard to tell the colour. However the sand martin has a distinctive dark chest bar, which the house martin lacks, and the sand martin doesn’t have the white rump.
Sand martins spend the winter south of the Sahara and are one of the first spring migrants to appear, arriving mid-March to mid-April.
They nest in colonies, sometimes hundreds of pairs, digging horizontal tunnels in sandy, dry vertical banks which can be found for example in gravel pits, railway cuttings and beside rivers. The tunnels range from a few inches to 3ft long, with a nesting chamber at the end.
This is one of the nesting spots of our sand martins, in the bank of the Ribble at the village of Grindleton. I didn’t think to take my binoculars and could not actually see the nest holes from the opposite bank but I could see the birds disappearing into them.
I presume this nesting technique is a good defence against predators, but it has a major drawback: the river level is subject to rapid and drastic change. I took this picture yesterday when the river was particularly low – we have had next to no rain for at least a month. But when it does rain (and a heavy downpour is forecast for tomorrow) the level will rise by several feet (bear in mind that there are many streams running into the river, multiplying the effect). I spoke to a chap who said it can easily overtop the bank at this point, and often does. In this picture I took a bit further along the bank you can see debris in the trees left by previous floods – I would guess the height above the present level must be at least ten feet, maybe more.
If this happens obviously the nests are destroyed. If it is early enough a second brood may be raised, but the chances are that the year’s breeding will be wiped out.
Some conservation outfits have been trying to help sand martins by providing them with artificial sandbanks. Here is a short film about one in Nottinghamshire.
The sand martins start their return journey to southern Africa for the winter in August, earlier than house martins which often wait until October.
We have had between five and seven mallard drakes taking it easy on our paving next to the stream this week while the females are doing all the hard work looking after the ducklings and trying to protect them from herons and other predators. The white mallard drake has called in a few times this week but he doesn’t stay for long. More exciting is that on Wednesday Alan saw a duck on the Ribble with ten ducklings, three of them yellow instead of the usual tones of brown. Yellow ducklings become white adults, so we think it is likely that these are Whitey’s offspring. Fingers crossed for them, but the odds are not in their favour, first because ducklings as a whole have a poor survival rate and second because yellow ones are much more visible to predators.
This week’s wild ‘flower’ is actually a ‘spadix’. I took this picture of the leaves of lords and ladies, or cuckoo pint (Arum maculatum) in February.
I have noticed the buds, like these, only in the last week.
One thing about them is that there are very few for the number of leaves – only one bud per hundreds of leaves at a guess. These sheaths are technically called ‘spathes’ and they open to reveal a spike, the spadix. This will develop into red berries in the autumn.
I had a lot of trouble getting this picture as 99.9 per cent of the spathes open with their backs to the roads and paths where I walk. As you can see the leaves are now way past their best.
If you look up this plant it is often shown with spotted leaves, but apparently it is very variable.