Inter- and Intra-Specific Diet Overlap during Lean Times between Quelea erythrops and Bill Morphs of Pyrenestes ostrinus

Abstract

Patterns of inter- and intra-specific resource use were examined between bill morphs of the African finch Pyrenestes ostrinus and Quelea erythrops. On my study area in south-central Cameroon diet overlap and breadth were examined after the major dry season when food was most limiting. Overlap values between P. ostrinus and O. erythrops declined with food supply, suggesting that interspecific competition occurred. Changes in the diets of small morphs which had bills more similar in size to Q. erythrops were primarily responsible for this decline. In contrast, diet overlap between morphs increased as food supply declined. Diet breath of small morphs also increased while crop size declined. Diet breadth and crop size in large morphs remained low throughout the study. These results, examined within the context of bill morphology, finch abundance, food supply and crop fullness are consistent with intraspecific competition occurring between morphs. Additionally, small morph and Q. erythrops exploitation of scarce supplies of soft seeds may be responsible for large morphs specializing on hard seeds during the non-breeding season