Barn owl – Development and food utilization

C. H. Lee

Abstract

Barn owl growth and development was successfully studied in the laboratory. Out of four broods of 7, 6, 5 and 4 eggs, total hatching of all were noted with 3, 5, 5 and 4 reaching full fledged owls. Asynchrony development with intermittent egg laying of 8–22 days between the first and last egg among the broods was noted. Development was sigmoid with a polynomial relationship between age and body weight. The development cycle from egg incubation to full fledged owls ranged from 80 to 92 days. Initial slow growth and low variation in body weight were followed by subsequent large variation in body weight and food/ prey consumption where a meal could sustain the owl for 1–2 days. In the presence of excess preys, chick mortality and cannibalism still occurred among owls. Prey capture was without excessive kill and consumption was efficient without wastage, an indication of effective and efficient food resource utilization. The total number of preys consumed by the broods from egg incubation until dispersal of full fledged owls averaged 553 ± 69 rats. Females had body weight of about 550 g during non-breeding and dispersal phase. The body weight exceeded 600 g during breeding (egg laying and incubation phase). This reflects on the higher energy and nutritional requirements for breeding. This body weight factor is a simple and easy tool for monitoring the activity and phases of the owls in the field, to minimize disturbing their establishment. The study showed that owls have the potential for breeding three broods a year provided there is ample food.

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