After Pennant's death, the French zoologist and naturalist Georges Cuvier wrote of him When the life of a man is entirely devoted to the sciences, it cannot be expected that it will present a variety of incident; it will be found most truly in the analysis of his works. Pennant is cited as an authority by Thomas Bewick throughout his pioneering field guide, A History of British Birds (2 volumes, 1797 and 1804). For example, under The Golden Eagle, Bewick writes that Pennant says there are instances, though rare, of their having bred in Snowdon Hills. Bewick cites him for facts about rare species like The Sclavonian Grebe: This species is not numerous in the British Isles. Pennant says, they inhabit and breed in the fens near Spalding, in Lincolnshire, and that the female makes a nest not unlike that of the Crested Grebe, and lays four or five white eggs. On occasion, Pennant's knowledge could be highly specific: for The Great-Crested Grebe, Bewick records that the nest is made of various kinds of dried fibres, stalks and leaves of water plants, and (Pennant says) of the roots of bugbane, stalks of water-lily, pond-weed and water-violet; when it happens to be blown from among the reeds, it floats about upon the surface of the water.