Tree Sparrows Foraging on Elm Seeds for more than a Month

Abstract

In the literature little is mentioned about elm seed as food for Tree sparrows Passer montanus . Deckert (1968) writes: Tree sparrows often stay in the top of the trees searching e .g . elmand alder seeds . Grun (1975) stated that tree sparrows only exceptionally eat seeds of the elm trees Ulmus glabra and Ulmus laevis and rather seldom and mostly only in a numbers of Ulmus minor . We have some large elm trees Ulmus glabra in our garden situated in agricultural surroundings in the south of Jutland, Denmark . In the summer of 1993 the elm trees bore more seeds than ever seen before . From mid-May the nestlings of three pairs of tree sparrows left their nests, and from then on and every day until the first of July we saw the parents with their young, 17 birds altogether, feeding on the elm seeds in our courtyard, which is covered with small stones so that the seeds was easy to find . They were foraging there for six to eight hours every day . It was often possible to observe the tree sparrows so closely that even without binoculars we could see how they bit off the “skin” of the elm seeds all the way around with the cutting edges of their bills, before they ate the little seed in the middle . During the same period, we never saw the tree sparrows feeding on other food items, and never trying to take the seeds which still hung on the trees, as stated by Deckert (1968) . It is mentioned by many authors that the greatest percentage of animal food is consumed from May to July, Deckert (1968), Dementev et al . (1970), Grun (1975), Summers-Smith (1988) . It was obvious to us that the arthropod supply was very poor due to pesticides used for insect control on the corn-fields around us . We also observed a pair of Chaffinch Fringilla coelebs which often joined the tree sparrows in their food searching but never for a long time . We assumed that the chaffinches were also eating elm seeds, because there was obviously no other food in the courtyard at that time, but we never got the opportunity to verify it .