Diurnal Changes in Number of Understory Birds Captured during the Spring Migratory Season

Abstract

Diurnal changes in number within five species of understory birds captured were investigated during three spring migratory seasons (1993-1995) in a low mountain zone in western Hokkaido. Diurnal time periods were divided into three, that is 4:00-9:00 (A), 9:00-14:00 (B) and 14:00-19:00 (C). Four species (Tarsiger cyanurus, Cettia squameiceps, C.diphone and Emberiza spodocephala) showed a significant decrease in number from A to B or C. But one species (Phylloscopus occipitalis) had no significant difference in numbers in each time period.Correlation coefficients were calculated for the relationship between the number of birds of each species captured and time period (A-B, A-C, B-C). Nine statistically significant correlations were shown between specific time periods and species (see Table 3, which also includes regression formulas) As a result, we can estimate not only the number of birds in other time periods by applying data in one time period to these regression lines, but with, even a limited amount of data obtained from captured birds we can also estimate the seasonal changes in number of migartory birds.