Spot pattern of great tits (Parus major) eggs as related to distance from built-up area to nests in a forested patch

Abstract

Great tits (Parus major) lay speckled eggs with reddish spots caused by protoporphyrin pigment. The function of the spot pattern is explained by calcium availability or female stress related health outcomes. This study was explored the relationship between pattern of spots on eggshell and distance factors reflecting habitat environmental properties. Study site was a forested patch surrounded by urbanized areas in Seoul city. Two different distance factors were measured by distance to the habitat edge line (edge distance) and the built-up areas (urban distance). The eggs from the same clutch are not statistically independent, therefore I analysed with linear mixed effects models (LMM) included clutch ID as random effect. As a result, the eggs in nests closer to the built-up areas showed more clustered pattern than those placed farther from the built-up areas. The eggs in nests closer to the habitat edge showed more intense spots than those placed farther from an edge. This study results demonstrated that spot intensity and spot distribution were differently related to the independent factors. On the basis of previous research, spot intensity was more related to edge distance, as related to female health and condition. Spot distribution was more related to urban distance, as related to calcium availability.