different sensitivities from that of normal vision). 2. Spectral quality of light: Photoperiodic responses, in particular, have different action spectra from visual receptors in the eyes. In most vertebrates active spectra peak at red wavelenghts. 3. Duration of light pulse: The requirement for the minimal length of time that an animal must be exposed to light during the night to elicit an abnormal photoperiodic response has not been established for most species. However, available evidence indicates that, at least for some (especially insects, and some birds), even a few minutes illumination can be significant if they coincide with the peak of the photosensitive phase of the daily photosensitivity rhythm. 4. Phase realtionship between reflected light and normal daily solar and lunar lighting. 5. Regularity or predictability of light pulses in terms of both the time of day and from day to day: As already mentioned, a single nighttime interruption can have measurable effects, but the significance of the consequences would normally depend on more prolonged interruptions. The data provided in the Boeing Report (especially Table 5) do not detail all of these characteristics of the reflected light, but some may be inferred from the description of phenomena involved in the reflectance. For example, while the description of spectral quality of the reflected light can only be approximated, it may be assumed that it will represent a relatively broad spectrum of wavelengths in the visible range, and hence will contain those wavelengths required to stimulate appropriate photoreceptors. Thus, this aspect of the reflected light is not considered critical for evaluating its effect. However, if the composition of this light should
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