|Abstract or Summary
- The organization of behavioral activities in time is important
to a bird's survival and reproduction. To be successful, either
proximately or ultimately, a bird must apportion its behavior in time
so that it may obtain sufficient energy for maintenance activities and
for such activities as migration and reproduction. The organization
of behavioral activities in time can be expressed as a time budget.
I have described the action patterns and displays of breeding American
Avocets (Recurvirostra americana) and have examined the budgeting
of time among these behaviors and its possible adaptiveness. Particular
consideration is given to patterns of seasonal, diurnal and sexual
The study area was located within an alkaline marsh at Summer
Lake, Oregon. The time budget data were collected by recording at
10 sec. intervals the amount of time spent in 12 categories of behavior. During the 1969 breeding season (April-July) 422 hrs. of data were
taken on 36 individuals.
The breeding season was divided into four stages ; prenesting,
incubation, parental care and post breeding. Seasonally, all maintenance
activities combined took 67% of the avocet's time, and reproductive
activities took 26%. Of all activities, feeding took the largest
portion of time (36%). Feeding, because of its close relationship to
bioenergetics, 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.
I suggest that 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 foraging. There was little seasonal fluctuation
in 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 peaks
of activity, separated by a period of inactivity at midmorning.
This pattern held when all "active" action patterns were combined.
I concluded that 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 night-long fast, while 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. However, males
appeared to be more aggressive while 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 be ecologically similar as well.