You'll have most likely driven over the very same limestone, as it was used to make the M6 Preston bypass. Peregrine falcons nest high on the limestone walls, starting their courtship in spring (Image: Surrey Hills Photography)Peregrine falcons nest high on the limestone walls, starting their courtship in spring. Before you've even left the car park for the footpaths, you might catch a glimpse of the peregrine falcons that nest high on the limestone walls, starting their courtship in spring and spending the summer feeding their chicks. It's home to nationally important populations of rare species like the pearl-bordered and small pearl-bordered fritillary, whose caterpillars feed on the violets in the woodlands. Warton Crag is a beautiful spot, and it's an excellent place to venture after the cold, wet winter.