Year: 1981
Type: article
Abstract: Changes in frequency and distance of detection during the breeding season (considering both singing-male and all observations) are documented for selected species occupying deciduous forest habitats.Several general patterns are identified in the seasonal profiles of detection and in mean detection distances.The following factors influencing seasonal changes in detection are explored: frequency of song, stage of the breeding cycle, nesting synchrony, breeding season length, flux in community composition, habitat, and weather.The function of song influences persistence of singing throughout the breeding season.Singing frequency and likelihood of escaping detection during counts vary with stage of the breeding cycle; unmated males are most conspicuous.Nesting synchrony depends upon arrival times of males and females and on nesting success.Clumping patterns of count observations are influenced by season length.Seasonal profiles of detection can be used to determine the optimal period to schedule counts for individual species.General application of a series of such profiles depends upon additional research to develop profiles for other species and habitats and to determine the consistency of profiles for individual species.Estimating the size of avian populations is an integral part of many field studies.Usually, the results and conclusions drawn from such studies depend heavily upon the accuracy of the census procedure.Important considerations in developing census methodology are the number and distribution of counts during the study period.Seasonal changes in kinds of cues emitted by birds, emission frequency, and attenuation have been alluded to in the literature, but efforts to quantify these changes and to use this knowledge in designing census schedules are rare.The objectives of my study were to (1) document changes in detection during the breeding season of selected species occupying deciduous forest habitats, (2) develop seasonal profiles of detection and explore factors responsible for seasonal changes, and (3) discuss the general application of such information in planning census schedules.The discussion will focus primarily on passerines and other passerine-like species that breed in North America, although much of the information has broader application.STUDY AREAS AND METHODS Count data used in this report were obtained from two separate studies.Most information came from an investigation of avian communities breeding in habitats adjoining streams in central Iowa (Stauffer and Best 1980).Specific habitats included open-canopy (noncontiguous tree crowns) upland woodland, closedcanopy (contiguous crowns) upland forest, and closedcanopy floodplain forest.The vegetation composition of these habitats is given in Stauffer and Best (1980).(The two upland habitats mentioned here are included in the upland woodland category described by Stauffer and Best.)Each study plot consisted of l-5 transects, marked at 25 m intervals, that paralleled the stream channel; successive transects were 50 m apart.
Author: Best, Louis B.
Language: English
Topic: Avian ecology and behavior
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W7005786534