Orientation of homing pigeons released over the sea

Abstract

The initial orientation of pigeons with various degrees of homing experience was investigated in releases over the sea. The collected data encompasses 22 releases in which a total of 160 pigeons were used and 415 vanishing points recorded. The experiments are grouped into three series: 1. Five groups of young pigeons without homing experience were released over the sea NE, S, and WNW of the loft, situated at S. Piero a Grado near Pisa. Mean directions taken by the birds were between W and NNW (Pigs. 1, 2). In at least four cases the choice seems to be the result of a compromise between a strong directional tendency and a homeward tendency. 2. Young pigeons housed in a loft situated on the coast of the Isle of Capraia and released over the sea at a short distance gave evidence of an orientation influenced by the sight of the island. The pigeons were later divided into two groups and released at 30 km S and 76 km N (Fig. 3); distributions of vanishing points were not significantly different from each other. 3. Two groups of adult pigeons, housed in the loft of S. Piero a Grado and directionally trained on two opposite lines along the coast, were later released from four different points over the sea. All mean directions lead approximately inland and are very close to one another. They do not seem to be affected by the differences in home direction. No deviations between the two groups as predictable on the basis of their training were observed while such deviations are seen to occur in two releases from an overland point (Fig. 6). The orientation over the sea was not guided by direct sensory contact with the land, since birds whose clock had been shifted six hours forward took a course parallel to the coast (Fig. 9). It is tentatively assumed that the birds orientated towards the land by means of a sun-compass mechanism assuming a perpendicular direction to the stretch of the coast with which they had become familiar during their training flights.