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ACTIVITY PATTERNS OF GULL CHICKS IN RELATION TO FEEDING BY PARENTS: THEIR POTENTIAL SIGNIFICANCE FOR DENSITY-DEPENDENT MORTALITY GEORGE L. HuNT, JR. , AND STEVEN C. McLooN THIS study compares the activity of Glaucous-winged Gull (Larus glaucescens) chicks after unsuccessful begging for food with their activity after having been fed. We wished to test the hypothesis that differences might exist in the behavior of hungry and well-fed chicks that would result in the hungry chicks wandering from their territories and thus being exposed to more frequent attacks by neighboring adult gulls. If hunger resulted in inappropriate behaviors by chicks, we could then link chick survival with the availability of food to foraging adults. METHODS We studied young Glaucous-winged Gulls from 12 families on Mandarte Island, British Columbia, from 23 June through 12 July 1973. Observations of 1.5 to 3.0 h duration were made from blinds at various times of day between 0600 and 2100 h for 13 periods in June and 16 periods in July. During each period three chicks were watched, each belonging to a different pair of parents. Ages of the chicks ranged from 2 to 32 days over the course of the study. The activity of the chicks and their distance from their nearest parent present on the territory were recorded at 1-min intervals. Five categories of behavior were noted: (1) Resting: The chick was inactive and in some cases may have been hiding. (2) Active I: The chick was less than 4 feet from its parent and was moving about. (3) Active II: The chick was moving about 4 or more feet from its closest parent. (4) Begging: The chick was soliciting food from its parent (see Tinbergen 1960 for a description of begging). (5) Feeding: The chick was obtaining food from its parent. June and July results were similar, and are combined in this presentation. RESULTS Intervals between a chick's feeding and its subsequent initiation of begging were longer during periods in which no parent returned to the territory than when begging followed the return of the parent. When begging was not preceded within an arbitrary 6-min period by the return of a parent, chicks initiated begging an average of 43 ± 24 min after their last feeding (N 61). When a parental return was followed by begging within 6 min, the interval between the previous feeding and that begging was 31 .± 16 min (N = 16). This difference was statistically significant (t = 2.05, P < 0.05). The Auk 92: 523- 527. July 1975

Activity Patterns of Gull Chicks in Relation to Feeding by Parents: Their Potential Significance for Density-Dependent Mortality