Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
, 7 Suppl 2 (Suppl 2), S163-77

Directional Orientation of Birds by the Magnetic Field Under Different Light Conditions

Affiliations
Review

Directional Orientation of Birds by the Magnetic Field Under Different Light Conditions

Roswitha Wiltschko et al. J R Soc Interface.

Abstract

This paper reviews the directional orientation of birds with the help of the geomagnetic field under various light conditions. Two fundamentally different types of response can be distinguished. (i) Compass orientation controlled by the inclination compass that allows birds to locate courses of different origin. This is restricted to a narrow functional window around the total intensity of the local geomagnetic field and requires light from the short-wavelength part of the spectrum. The compass is based on radical-pair processes in the right eye; magnetite-based receptors in the beak are not involved. Compass orientation is observed under 'white' and low-level monochromatic light from ultraviolet (UV) to about 565 nm green light. (ii) 'Fixed direction' responses occur under artificial light conditions such as more intense monochromatic light, when 590 nm yellow light is added to short-wavelength light, and in total darkness. The manifestation of these responses depends on the ambient light regime and is 'fixed' in the sense of not showing the normal change between spring and autumn; their biological significance is unclear. In contrast to compass orientation, fixed-direction responses are polar magnetic responses and occur within a wide range of magnetic intensities. They are disrupted by local anaesthesia of the upper beak, which indicates that the respective magnetic information is mediated by iron-based receptors located there. The influence of light conditions on the two types of response suggests complex interactions between magnetoreceptors in the right eye, those in the upper beak and the visual system.

Figures

Figure 1.
Figure 1.
Spectra of the LEDs used in the experiments reported here (figures 2–7). The peak wavelengths are given; the letters indicate the abbreviations used in the figures. Note that the colours are only symbolic.
Figure 2.
Figure 2.
Orientation of European robins during spring migration under monochromatic light of different wavelengths. The light intensity was 7–8 × 1015 quanta s−1 m−2, except for UV light, which was only 0.8 × 1015 quanta s−1 m−2. The triangles at the periphery of the circle give mean headings of individual birds based on three recordings each; the arrows represent the grand mean vectors with the length proportional to the radius of the circle. The two inner circles mark the 5% (dotted) and the 1% significance border of the Rayleigh test (Batschelet 1981); arrows exceeding these circles indicate significant orientation.
Figure 3.
Figure 3.
Orientation by the inclination compass under low-intensity short-wavelength monochromatic light: UV, 373 nm UV; B, 424 nm blue; T, 502 nm turquoise; and G, 565 nm green (figure 1). The light intensities are the same as in figure 2: UV, 0.8 quanta s−1 m−2; blue, turquoise and green, 8 quanta s−1 m−2. In autumn and spring in the local geomagnetic field, the robins prefer their seasonally appropriate southern and northern migratory direction. Inversion of the vertical component of the magnetic field (vi) causes birds to reverse their headings. Treatment with a broadband high-frequency (HF) field including frequencies from 0.1 to 10 MHz at an intensity of 85 nT causes disorientation. Symbols are as in figure 2 (data from Stapput et al. 2005; Thalau et al. 2005; Wiltschko, R. et al. 2005).
Figure 4.
Figure 4.
Orientation of robins in spring under 565 nm green light of increasing intensity. At intensities of 36 × 1015 quanta s−1 m−2 and beyond, the birds no longer prefer their northerly migratory direction, but show a pattern of different responses, including axial preferences. The respective quantal flux is indicated above the diagrams. Symbols are as in figure 2 (data from Wiltschko, R. et al. 2007a).
Figure 5.
Figure 5.
The transient state of axial orientation along the east–west axis in robins is observed at different intensities that increase with increasing wavelengths: UV, 373 nm UV; B, 424 nm blue; T, 502 nm turquoise; and G, 565 nm green. The respective quantal flux is indicated above the diagrams. Symbols are as in figure 2 (data from Wiltschko, R. et al. 2007a).
Figure 6.
Figure 6.
Orientation of robins when 590 nm yellow light is added to 424 nm blue, 502 nm turquoise and 565 nm green light with a quantal flux of about 7 × 1015 quanta s−1 m−2 each, resulting in fixed-direction responses that are different for the different combinations of colours. These responses are not affected by an inversion of the vertical component (vi) of the geomagnetic field, but shift accordingly when the horizontal component is reversed (hr), indicating that they are polar responses to the magnetic field. Symbols are as in figure 2 (data in part from Wiltschko, W. et al. 2004b; Stapput et al. 2005).
Figure 7.
Figure 7.
Effect of high-frequency (HF) fields and of local anaesthesia of the upper beak with the anaesthetic xylocaine in robins on compass orientation under low-intensity green light (a) and the fixed-direction responses observed under bichromatic light combining turquoise and yellow light (b) and in total darkness (c). The HF field disrupts compass orientation and leaves the fixed-direction responses unaffected, whereas anaesthesia of the upper beak (Xy) leaves compass orientation unaffected and disrupts the fixed-direction responses. Symbols are as in figure 2 (data from Thalau et al. 2005; Wiltschko, R. et al. 2007b, 2008; Stapput et al. 2008).
Figure 8.
Figure 8.
Spectral sensitivity curve of the Pekin robin, Leiothrix lutea, a passerine species, determined by conditioning experiments (modified from Maier 1992), with wavelengths used in the conditioning tests marked with dots. The peak sensitivity of the four colour receptors is marked below. The peak intensity of the LEDs used to produce the monochromatic and bichromatic lights is also indicated.
Figure 9.
Figure 9.
Fixed-direction responses observed so far in European robins (triangles) and Australian silvereyes (diamonds). The wavelength and wavelength combinations are indicated.

Similar articles

See all similar articles

Cited by 51 articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback