April is one of the most exciting months of the year, bringing the return of many species from Africa. With March arrivals of the first sand martins and chiffchaffs, the pace of migration increases and, by the end of the month, most summer visitors are here.
The first two weeks should see the first yellow wagtails, willow warblers and nightingales (usually in the first week). The earliest arriving warblers are the easiest to see, as budding leaves have not yet covered the best singing branches.
Later in the month, the first breeding common terns should be back on the islands on Sailing Lake and cuckoos starting their search for nests in which to lay their eggs. But it’s usually the last few days of April before the first reed warblers, lesser whitethroats and common whitethroats are singing. In some years, the first hobby will appear over the pits in the last few days of April - although they do not breed on the reserve, they are regular visitors throughout the summer.
Blackcaps and chiffchaffs, the first of which arrived in March, continue to move north throughout the month, but more pronounced is the wader passage, with redshanks and ringed plovers, plus the occasional dunlin, green sandpiper, snipe and ruff. Breeding in the waterbird colony is already well underway in April – grey heron and cormorant young should be visible from early in the month.
While early spring flowers have already made an appearance during warm days in March, other species bring more than a dash of colour to the reserve. Coltsfoot, sweet violet, primrose and false oxlip are all in flower – look by the path to Kingfisher Hide for these, and also dog’s mercury, with its small white flowers. Where there are bare, mossy areas, it is worth scanning the ground for the several similar-looking white crucifers: whitlow grass has oval seed pods, hairy bitter cress has long pods, while shepherd’s purse has heart-shaped seeds. Blue flowers include the attractive ground ivy and the speedwell species: Persian, germander and thyme-leaved (smaller, pale blue and favouring damper areas).
Blackthorn will continue to blossom during early April, and look out for bullfinches feeding on the buds. Chickweed, red dead nettle, white dead nettle and groundsel usually grow alongside the set-aside field opposite the Kingfisher Hide. Look out, too, for spotted medick – a clover with dark spots on each leaf.
Warm days also bring out grass snakes, the only species of snake at Paxton, either on the water or sunning on grassy or sandy banks. Look out, too, for weasels, badgers, field voles and foxes, all of which have been reported.