Birds of Indian Subcontinent

The Feeding Ecology of the Bullfinch (Pyrrhula pyrrhula L.) in Southern England

Publication Type:Journal Article
Year of Publication:1967
Authors:Newton, I
Journal:Journal of Animal Ecology
Date Published:1967
ISBN Number:00218790
Keywords:Fringillidae, Pyrrhula, Pyrrhula pyrrhula
Abstract:1. The bullfinch is of ecological interest chiefly because of its numerical importance in many woodland communities, and because it has created a serious problem in parts of southern England by eating the buds of fruit trees. 2. In both woodland (the natural habitat) and open cultivated habitats, bullfinches obtained food from about four-fifths of the woody and half the herbaceous plants, but in neither habitat were these plants exploited in proportion to their availability. The most important foods in woodland are seeds of Ulmus, Mercurialis perennis, Alliaria petiolata, Filipendula ulmaria, Urtica dioica, Rubus fruticosus agg., Betula alba and Fraxinus excelsior and the buds of Crataegus; and in cultivation the seeds of Taraxacum officinale agg., Stellaria media, Ranunculus spp., Sonchus oleraceus and Chenopodium album and buds of fruit trees. 3. The chief factor affecting the proportion of buds in the winter diet, in both woods and cultivation, was the size of the ash crop which acted as a buffer. In years with poor ash crops, the seeds of all the winter food-plants were eaten by the end of December or in January, and from then on buds formed the main food. In years with good ash crops, seed-stocks lasted until the end of the winter and bullfinches did not turn to buds as their staple food until March. 4. The gut-content of some 2000 bullfinches killed on fruit farms indicated that the foods eaten around Oxford were typical of those taken in many other parts of southern England. Seeds from ripe raspberries (if available) are apparently taken in greatest proportion on those farms with fewest weed-seeds and vice-versa, but further study is needed before any action is taken. 5. Adult bullfinches in the breeding season have special pouches under the lower jaw in which food collected for the young is retained; they themselves live almost entirely on seeds at this time but feed their nestlings on a mixture of seeds and small invertebrates (especially caterpillars, snails and spiders), the latter in decreasing proportion as the young grow. Throughout the nestling period, young in open cultivated habitats receive fewer invertebrates than those in woodland. 6. Previous literature on the food is reviewed. Differences in the diet of bullfinches in different areas seem to result mainly from differences in available plant-species: seeds from fleshy fruits, especially Sorbus aucuparia, are always preferred to other foods in autumn, those of Acer, Betula and Fraxinus in winter, buds in spring, and seeds of herbaceous plants (weeds in cultivated areas) in summer. 7. The winter supply of seed is thought to be the chief factor regulating the numbers of bullfinches; disease, parasites and predation are probably of minor importance, and the last acts mainly when food is short. 8. Damage by bullfinches to buds of fruit trees in southern England has increased enormously in the past two decades, because of an increase in the numbers of the species, which will now live and breed in more open (cultivated) habitats than formerly. This expanded habitat tolerance is probably the cause of the increase, and not the result of it, though other factors may have been involved too.
Short Title:Journal of Animal Ecology
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