In this episode, Iolo investigates the courtship and nesting behaviour of birds, including the amazing courtship display of great crested grebes at a reservoir near Pontypool, the impressive sky dance of hen harriers in the dramatic Cambrian Mountains, how nuthatch use mud like cement to prepare their nest in a woodland near Harlech, and why long-tailed tits near Newtown are exceptional nest builders. On the Lleyn Peninsula near Trefor, he looks at why one colony of shags nest earlier than any others in Wales, and in Pembrokeshire he finds out where house martins nested before they used our buildings. Iolo also looks at the variety of places birds like to nest, from little ringed plovers on shingle banks along the River Tywi to puffins underground on Skomer.