The area in and around Retford has a varied geology and habitat. There are 30 known Ancient woodlands of more than 2 hectares in Bassetlaw, and the town is surrounded by a rich and diverse ecosystem including rare and endangered animals and birds. A wide range of birds can be spotted - particularly in the Idle Valley Nature Reserve - with Nottinghamshire Wildlife Trust commonly recording sparrowhawk, moorhen, stock dove, woodpigeon, collared dove, swift, green woodpecker, great spotted woodpecker, house martin, pied wagtail, wren, dunnock, robin, blackbird, song thrush, redwing, mistle thrush, blackcap, chiffchaff, goldcrest, long-tailed tit, coal tit, blue tit, great tit, treecreeper, nuthatch, jay, magpie, jackdaw, carrion crow, common starling, house sparrow, chaffinch, greenfinch, goldfinch, bullfinch and siskin.