Until 2006 the Lundy Cabbage was thought to support two endemic species of beetle. The beetles are now known not to be unique to Lundy, but an endemic weevil, the Lundy cabbage flea beetle, (Psylliodes luridipennis) has been discovered. The island is also home to the purseweb spider (Atypus affinis), the only British member of the bird-eating spider family.

The number of puffins (Fratercula arctica), which may have given the island its name, declined in the late 20th and early 21st centuries, with the 2005 breeding population estimated to be only two or three pairs, as a consequence of depredations by brown and black rats (Rattus rattus) (which have now been eliminated) and possibly also as a result of commercial fishing for sand eels, the puffins' principal prey.

As an isolated island on major migration routes, Lundy has a rich bird life and is a popular site for birding. Large numbers of Black-legged Kittiwake (Rissa tridactyla) nest on the cliffs, as do Razorbill (Alca torda), Guillemot (Uria aalge), Herring Gull (Larus argentatus), Lesser Black-backed Gull (Larus fuscus), Fulmar (Fulmarus glacialis), Shag (Phalacrocorax aristotelis), Oystercatcher (Haematopus ostralegus), Skylark (Alauda arvensis), Meadow pipit (Anthus pratensis), Blackbird (Turdus merula), Robin (Erithacus rubecula) and Linnet (Carduelis cannabina). There are also smaller populations of Peregrine Falcon (Falco peregrinus) and Raven (Corvus corax).

Lundy has attracted many vagrant birds, particular species from North America. The island's bird list totals 317 species. This has included the following species, each of which represents the sole British record: Ancient Murrelet, Eastern Phoebe and Eastern Towhee. Records of Bimaculated Lark, American Robin and Common Yellowthroat were also firsts for Britain (American Robin has also occurred two further times on Lundy). Veerys in 1987 and 1997 were Britain's second and fourth records, a Rüppell's Warbler in 1979 was Britain's second, an Eastern Bonelli's Warbler in 2004 was Britain's fourth, and a Black-faced Bunting in 2001 Britain's third.

Other British Birds rarities that have occurred (single records unless otherwise indicated) are: Little Bittern, Glossy Ibis, Gyrfalcon (3 records), Little and Baillon's crakes, Collared Pratincole, Semipalmated (5 records), Least (2 records), White-rumped and Baird's (2 records) sandpipers, Wilson's Phalarope, Laughing Gull, Bridled Tern, Pallas's Sandgrouse, Great Spotted, Black-billed and Yellow-billed (3 records) cuckoos, European Roller, Olive-backed Pipit, Citrine Wagtail, Alpine Accentor, Thrush Nightingale, Red-flanked Bluetail, Black-eared (2 records) and Desert wheatears, White's, Swainson's (3 records), and Grey-cheeked (2 records) thrushes, Sardinian (2 records), Arctic (3 records), Radde's and Western Bonelli's warblers, Isabelline and Lesser Grey shrikes, Red-eyed Vireo (7 records), Two-barred Crossbill, Yellow-rumped and Blackpoll warblers, Yellow-breasted (2 records) and Black-headed (3 records) buntings, Rose-breasted Grosbeak (2 records), Bobolink and Baltimore Oriole (2 records).