Small non-passerine birds of the Lower Tertiary as exploiters of ecological niches now occupied by passerines

Abstract

In spite of the rather inadequate sample of past avian populations provided by the chance preservation of fossil bird bones, the increasing accumulation of such material makes it possible to speculate on the composition of early faunas and to consider the apparent relative dominance of major groups, such as passerines and non-passerines, in earlier geological periods. An examination of the range of species that we now know occurred in the Lower Tertiary of Britain appears to confirm that passerine birds were very scarce and that their great adaptive radiation had not taken place. Their ecological niches were seemingly occupied by small non-passerine land birds, species of this size appearing proportionally more numerous than at the present day.