Abstract: Quantization of egg color and intra and interclutch variation plays an important role in understanding the evolution and adaptability of bird egg coloration. Host species utilized by cuckoos have less variation in egg appearance within a clutch and more variation between individuals while species with no history of cuckoo parasitism present opposite properties. In this study, fiber spectrophotometer was used to quantitatively analyze the egg color of a barn swallow (Hirundo rustica) population in Changjiang, Hainan, China. Egg reflectance of ground color in barn swallows was higher than that of the pattern color. The egg pattern reflectance had higher wave crest and lower wave vale, which indicated that egg pattern had bigger color saturation than ground color. Although ground and pattern colors look obviously different by human eyes, avian visual modeling showed that their difference in hue (red, green and bluesensitive cones, RGB) was not statistically significant. However, the chroma, brilliance and ultraviolet (UV) of barn swallow eggs were highly different between ground color and pattern. The intraclutch variation between ground color and pattern was not statistically different. As to the interclutch variation, the hue RGB of pattern was higher than that of the ground color while the UV, chroma and brilliance were not statistically different. To our knowledge, this is the first quantitative study of barn swallow egg coloration.

Key words: oilseed rape, elevated CO₂, ion absorption, transport coefficient.