Orientation Preferences in Birds

Orientation Preferences in Birds

Alvin Sherman Library 4009

Most bird species have a dark dorsum and lighter ventrum. A possible explanation for such a color pattern could be countershading, which makes a bird less conspicuous to predators. The level of conspicuousness depends on the orientation of the bird with respect to the sun. In order for the bird to successfully camouflage itself, it must face its dorsum towards the sun when the sun is at low elevation. The purpose of this study was to investigate whether countershaded and non-countershaded birds do in fact orient with respect to the sun. A goniometer was used to measure angles of perches with respect to the sun. G statistics were used to determine the goodness-of-fit of the sample to the null hypothesis of random orientation. Several birds were found to hold an orientation preference while others were not. Orientation preferences varied. Many of the species that did hold an orientation preference tended to face the sun. However, a few were found to either face sideways or away from the sun. The data indicate that color pattern and perch orientation are related.