Muheim Rachel, Bäckman Johan, Akesson Susanne
Bird Migration Group, Department of Animal Ecology, Lund University, Ecology Building, Sweden.
J Exp Biol. 2002 Dec;205(Pt 24):3845-56. doi: 10.1242/jeb.205.24.3845.
Magnetic compass orientation in birds has been shown to be light dependent. Results from behavioural studies indicate that magnetoreception capabilities are disrupted under light of peak wavelengths longer than 565 nm, and shifts in orientation have been observed at higher light intensities (43-44x10(15) quanta s(-1) m(-2)). To investigate further the function of the avian magnetic compass with respect to wavelength and intensity of light, we carried out orientation cage experiments with juvenile European robins, caught during their first autumn migration, exposed to light of 560.5 nm (green), 567.5 nm (green-yellow) and 617 nm (red) wavelengths at three different intensities (1 mW m(-2), 5 mW m(-2) and 10 mW m(-2)). We used monochromatic light of a narrow wavelength range (half bandwidth of 9-11 nm, compared with half bandwidths ranging between 30 nm and 70 nm used in other studies) and were thereby able to examine the magnetoreception mechanism in the expected transition zone between oriented and disoriented behaviour around 565 nm in more detail. We show (1) that European robins show seasonally appropriate migratory directions under 560.5 nm light, (2) that they are completely disoriented under 567.5 nm light under a broad range of intensities, (3) that they are able to orient under 617 nm light of lower intensities, although into a direction shifted relative to the expected migratory one, and (4) that magnetoreception is intensity dependent, leading to disorientation under higher intensities. Our results support the hypothesis that birds possess a light-dependent magnetoreception system based on magnetically sensitive, antagonistically interacting spectral mechanisms, with at least one high-sensitive short-wavelength mechanism and one low-sensitive long-wavelength mechanism.
鸟类的磁罗盘定向已被证明依赖于光。行为研究结果表明，在峰值波长大于565 nm的光线下，磁感受能力会受到干扰，并且在较高光强度下（43 - 44×10¹⁵ 量子·秒⁻¹·米⁻²）观察到了定向的变化。为了进一步研究鸟类磁罗盘在光的波长和强度方面的功能，我们对在首次秋季迁徙期间捕获的欧洲知更鸟幼鸟进行了定向笼实验，使其暴露于三种不同强度（1毫瓦·米⁻²、5毫瓦·米⁻² 和10毫瓦·米⁻²）的560.5 nm（绿色）、567.5 nm（绿黄色）和617 nm（红色）波长的光线下。我们使用了窄波长范围的单色光（半带宽为9 - 11 nm，而其他研究中使用的半带宽在30 nm至70 nm之间），从而能够更详细地研究在565 nm左右定向和非定向行为之间的预期过渡区域中的磁感受机制。我们发现：（1）欧洲知更鸟在560.5 nm光线下表现出季节性适宜的迁徙方向；（2）在广泛的强度范围内，它们在567.5 nm光线下完全失去定向能力；（3）它们能够在较低强度的617 nm光线下定向，尽管方向相对于预期的迁徙方向有所偏移；（4）磁感受依赖于强度，在较高强度下会导致失去定向能力。我们的结果支持这样的假设，即鸟类拥有一个基于磁敏感、相互拮抗作用的光谱机制的光依赖磁感受系统，其中至少有一个高灵敏度的短波长机制和一个低灵敏度的长波长机制。
