A study of the amount of some invertebrates that are eaten by wild birds in the Egyptian western desert

Abstract

SUMMARYA study was conducted at two different sites in the Egyptian western desert to investigate the activity of carnivorous birds on some invertebrates. At the first site (sand-dunes in the Gharbaniat area, 52 km west of Alexandria), the most interesting bird found was the great grey shrike Lanius excubitor which seizes its prey and impales it upon spines of Lycium europaeum or on barbed-wire fencing. Studies carried out from January to July 1977 indicated that this bird prefers to feed on certain tenebrionid or scarabaeid beetles as well as some orthopterous insects and small lizards of the area. At the other site (inland depression near Omaycd, 80 km west of Alexandria, and 12 km from the sea) a snail-eating bird, (bifaciated lark) Alaemon alaudipes, was found to be the commonest bird where the non-saline soil of the site is suitable for the desert snail, Eremina desertorum, to breed, so much so that the snails constitute one of the prominent features of the site.The latter bird is more active in the winter than in the summer. From February to the end of June 1979, the estimated snail flesh weight eaten by A. alaudipes birds was about 6·50 kg taken from an area of 2·4 ha. The birds seize a snail, fly upwards to a distance of 6–23 m, select a hard stone, then drop the snail. The snail eventually breaks, and the flesh exposed is readily eaten by the bird. In January 1980, a survey was conducted to investigate the species of birds found in the area that extends between Alexandria and el Alamein. Twenty-six resident, as well as migratory, bird species were observed. The number of species and individual birds in cultivated areas, and sites near the sea shore, were found to be greater than those in natural ecosystems at a distance from the sea.