文摘
Interspecific comparative studies in trait responses to nest predation will help uncover potential costs associated with changes in nest predation risk that may constrain the degree of the response. Reptiles build large mounds of sand, soil or compost in which they bury and leave their eggs after laying. As their eggs are not exposed, reptiles consistently lay immaculate white eggs; while some birds that also lay immaculate white eggs place their nests in exposed sites under sunlight. Comparing the spectrum of reptile and bird eggs, especially in the ultraviolet (UV) region, may help us understand the evolution of coloration in bird eggs. We measured white immaculate eggs from four species of turtle and three species of birds by spectrometer, and compared their hue, chroma, UV brightness, and total brightness. Our results indicated that the UV reflectance of bird eggs consistently exhibited peaks and troughs in waveform that obviously differed from that of turtle eggs, which rising gradually from 300 to 400 nm. This finding implies that bird eggs have been released from enclosed nests, like those of reptiles, and have thus evolved an adaptation in UV reflectance as a signal. Furthermore, artificial nest experiments indicated that predation rates of bird eggs were significantly higher than those of turtle eggs, implying that such a signal might exist. Our study provides baseline data and perspective for further research on the evolution of egg coloration between reptiles and birds. Keywords Bird egg Nest predation Turtle egg Ultraviolet spectrum UV reflectance