Helen Mark visits Marsden, West Yorkshire, where the whole town is celebrating the annual Cuckoo Day. It's an old Pennine mill town surrounded by wild and beautiful National Trust Moorland and is home to an old legend:

Many years ago the people of Marsden were aware that when the cuckoo arrived, so did the Spring and sunshine. They tried to keep Spring forever, by building a tower around the Cuckoo. Unfortunately, as the last stones were about to be laid, away flew the cuckoo. If only they'd built the tower one layer higher. As the legend says, it "were nobbut just wun course too low".

Now each year the townspeople celebrate the return of the cuckoo with a day-long festival with clog dancing, music, a procession and a famous "cuckoo walk". Marsden Cuckoo Day websites:
Guardian guide to cuckoos
Marsden Cuckoo Day

Helen is asked to be the guest of honour for the day and she opens the proceedings and then explores Marsden Moor itself with David Finnis, National Trust Property Manager for the area. At first glance it may look a bleak and uninviting place, but it houses a wide variety of habitats. The large numbers of birds in the area, including nationally important numbers of golden plover, curlew, dunlin, merlin and twite, make it a Site of Special Scientific Interest. Other summer visitors are the skylark, lapwing, snipe and redshank. There are also large numbers of meadow pipits.
National Trust: Marsden Moor

Helen next meets Tim Melling of the RSPB, who confirms that meadow pippits are the host birds to some cuckoos' eggs, other common hosts in the UK are dunnocks and reed warblers. The common cuckoo, Cuculus canorus, overwinters in Africa and returns to the UK in Spring. Tim explains how the eggs are incubated before they're laid so they hatch before the meadow pippit eggs. The blind cuckoo chick uses its back to slide all the other eggs out of the nest. Tim says that female cuckoos are genetically programmed to produce eggs which mimic just one other bird, and the next generation return to the same area to lay their own eggs. There are two different cuckoo calls: the familiar call of the males, and a wonderful bubbling song of the females.
RSPB: cuckoo info