Magnetic Field Orientation of Migratory Savannah Sparrows With Different First Summer Experience

Abstract

Three groups of hand-reared savannah sparrows (Passerculus sandwichensis) were given different exposure to the sky and an ambient magnetic field during their first summer to investigate the possible effect of experience on the magnetic field orientation of their first autumn migration. Whether ever having seen the sky or not, birds raised exposed to local earth's magnetic field showed the same directional orientation during tests in the local earth's magnetic field. Birds with prior experience with the sky were perhaps better oriented. Birds that were raised outdoors in a 90° shifted magnetic field, however, oriented differently during tests in the local earth's magnetic field. Their orientation tended to be orthogonal to the other groups. The data show that first summer experience can influence the magnetic field orientation of migratory savannah sparrows and in a way which suggests the possibility of a calibration process.