Relationships between some activity variables and census in the Black-headed Gull (Larus ridibundus) in regard to certain meteorological parameters

Abstract

The census, orientation, preening, rest and wing-flapping of a Black-headed guh club were sistematically observed dunng 82.5 hours. Multiple regression analysis was used and possible relations with meteorological parameters were explored. A strong relationship is found between club census and solar elevation. In a year with fine weather and high temperatures, the number of subjects decreases since the gulls return elsewhere for the night, which agrees with the obsemations of Delius (1970, gis reported by Galusha & Amlaner, 1978). A weaker inverse relation was found between club size and wind speed. Orientation is directly related to wind direction (again in agreement with the findings of Bales, 1919 and Austin, 1929, reported in Gochfeld, 1978) aiid solar elevation, and less markedly, to the number of subjects. When the wind blows from the sun position, a direct relation between the orientation of the subjects and the direction of the wind is observed. No environmental influences on the ethological variables of rest, pireening and wing-flapping are found.