An assessment of Chough Pyrrhocorax pyrrhocorax diet using multivariate analysis techniques

McCRACKEN D.I., FOSTER G.N., BIGNAU E.M. and BIGNAU S.

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Abstract:

This paper provides the first quantitative information on the diet of the Chough, Pyrrhocorax pyrrhocorax, as assessed by faecal analysis. Fifty taxa (48 invertebrate and 2 plant) were identified in subsamples of Chough faeces collected from under the roosting sites of adults and from chicks in the nest on the island of Islay. Multivariate analyses of the data indicated that the seasonal abundance and availability of prey items was the most important factor influencing Chough diet throughout the year. Soil-dwelling Tipulidae (January to July) and Bibionidae (January to Aprii) larvae, dung-associated insects (during the spring, and late summer and autumn), and surface-active insects (during the summer) were the most abundant invertebrate components of the diet. The invertebrate taxa taken in numbers by the Chough at any particular time of year compared well with those taxa found to be numerous on pasture at that time (McCracken 1990). Cereal grains were the most frequently taken food items during the early winter months, when invertebrate availability was low. The analyses provided an objective grouping of these very heterogeneous data into useful groupings for further study and investigation of the birds behaviour. Implications for the management of Chough areas are suggested, with emphasis on livestock and pasture management and the maintenance of mixed farming including small scale cereal production.