In the spring, sand martins are the first of the swallow family to arrive from Africa. A small number nest in the gravel workings at Paxton Pits and you can see them swooping over the reserve, catching flies on the wing, especially over the water. They are similar in shape to house martins, with a notched tail, but have pale underparts with a dark chest bar. They nest in colonies in sandy cliffs and banks, digging tunnels up to 90 cm long. We have just installed some man-made nest sites for them, to replace those that will be lost when the quarry stops working.
April is the month when the tern rafts appear on Heronry North lake. These provide a safe nest site for common terns, which arrive after a journey of up to 6000 miles from southern Africa. It’s crucial not to put the rafts out too early, to stop them being monopolized by black-headed gulls before the terns arrive. Our rafts are now equipped with miniature electric fencing to deter mink and otters! Last year, over twenty terns were seen sitting on nests with at least 17 chicks fledging successfully. You can watch the terns fishing over the pits and rivers throughout the summer, before they make the long journey south in September. You can find out more about common terns here.
If you go for a walk in the damper parts of Paxton Pits in the Spring, you are likely to spot male orange-tips, flying restlessly close to the ground. They seem never to settle, making them frustratingly hard to photograph. You will probably see just as many females, but probably won’t notice them as they lack the orange wing tips, looking very much like a “cabbage white”. Unlike most other early spring butterflies, which overwinter as adults, orange-tips spend the winter in their chrysalis stage.
Next to the “bus-stop” viewing platform by Heronry South lake is a mound of bare, sandy earth. Over the winter, there’s nothing to see there, but in Spring it comes alive … with mining bees. Look closely and you will see lots of small holes. At first, most have tiny piles of sand by them, suggesting that something has dug its way out, as indeed it has. Later, entrance holes appear where bees have excavated burrows in which to lay their eggs. If you stand there for a few minutes, you will see a wide variety of bees of different shapes and sizes using the burrows. The mound supports a whole community of bees: some are true mining bees, others are “furrow bees” and many are parasitic species which lay their eggs in the burrows so that their larvae can feed on those of the miners.