Ecological Aspects of the Time Budget of the American Avocet

Publisher Website
Google Scholar
Abstract
During the 1969 breeding season (April-July) 422 h of time-budget data were collected on 36 American avocets (Recurvirostra americana) in an alkaline marsh at Summer Lake, Oregon [USA]. Time-budget data were collected by recording at 10 s intervals the time spent in 12 categories of behavior through 4 stages of the breeding cycle: prenesting, incubation, parental care and postbreeding. Data were also recorded for six 2 h periods from 0600-1800. Seasonally, all maintenance activities combined took 76% of the avocet''s time, and reproductive activities took 26%. Of all activities, feeding took the largest portion of time (36%). Because of its close relationship to bioenergetics, feeding is probably one of the most important aspects of the time budget. Through the breeding season energy requirements change, and this is reflected in a seasonal flux in time spent feeding. Seasonal variation in temperature, activity levels, prey abundance, and such energetically expensive processes as egg production, molting and premigratory fat deposition may determine the amount of time spent in resting, preening or in aggressive activities. Incubation and caring for the young required similar amounts of time. Diurnally, several categories of behavior, such as feeding, preening and nest-building, exhibited morning and afternoon activity peaks, separated by a period of inactivity at midmorning. This pattern held when all active action patterns were combined. Foraging patterns largely dictate the form of the diurnal activity pattern. The morning feeding peak may be related to a need to feed after the nightlong fast; the afternoon peak is perhaps associated with optimum environmental conditions for feeding, such as maximum insect availability. Avocet males and females exhibited few significant differences in either the seasonal or diurnal time budgets. Males appeared to be more aggressive; females spent more time incubating. The general similarities of morphology, behavior and temporal organization of behavior indicate that the sexes have similar roles in the social system and may also be ecologically similar.