Magnetic Remanences in Migratory Birds

Abstract

In connection with indications of the magnetic field detection in migratory birds, the measurements of magnetic remanences were carried out in both the migratory birds (Rustig Bunting and Reed Bunting) and the non-migratory birds (Siberian Meadow Bunting and Tree Sparrow) by means of SQUID magnetometer. Regardless of whether the species was migratory or not, neither heads nor neck musculatures indicated any presence of intrinsic magnetic materials related to the sensory mechanisms. The natural remanence and the induced remanence were of the orders of 10-8-10-7 e.m.u. and of 10-7-10-6 e.m.u. respectively. The magnetic sensor of birds for a compass reception is discussed.

Attempts to condition homing pigeons to magnetic cues in an outdoor flight cage

“…The exact nature and location of magnetic particles (e.g., magnetite) in birds is far from resolved. Walcott, Gould, and Kirschvink (1979) reported 10-6 emu of magnetic materials in the heads of pigeons, and Presti and Pettigrew (1980) reported similar quantities in the neck musculature of pigeons and sparrows; however, J. Crawford (personal communication, June 1985) was unable to locate these particles in pigeons, and Veda et al (1982) were unable to locate magnetic particles in two species of migratory buntings and two nonmigratory passerine species. As is the case for most other animal groups, no causal link has been established between the behavior of birds in magnetic fields and the presence of magnetic materials in their bodies.…”

Orientation and Navigation in Vertebrates

“…Early studies (Presti and Pettigrew 1980;Ueda et al 1982;Beason and Brennan 1986;Edwards et al 1992) on bird natural remanent magnetization (NRM) and isothermal-induced remanent magnetization (IRM), measured on several bird species, showed the presence of magnetite in the bodies of studied birds. In the last study, measurements in the head and neck of 21 species showed that most of the magnetic material in birds is represented by single-domain and pseudo single-domain grains of ferromagnetic nature, although several species might contain superparamagnetite.…”