Andy Holden/ Peter Holden: Natural Selection review – artfulness is egg-shaped

Former Newington Library, 155 Walworth Road, London SE17
A father and son ask if birds are born artists in this marvellous Artangel show held together by mud, poetry and natural mysteryThe swallow sculpts its nest out of mud. The horned coot works with pebbles in streams, an avian Andy Goldsworthy. The weaver bird is famous for its elaborate globes and sheaths conjured out of grasses; but the bowerbird surely takes the biscuit, decorating its lavish pavilions with flower petals, shells and shard