Temporal and Individual Variation in Offspring Provisioning by Tree Swallows: A New Method of Automated Nest Attendance Monitoring

Alexandra P Rose,Sean Rands

doi:10.1371/journal.pone.0004111

Abstract

Studies of the ecology and evolution of avian nesting behavior have been limited by the difficulty and expense of sampling nest attendance behavior across entire days or throughout a substantial portion of the nestling period. Direct observation of nesting birds using human observers and most automated devices requires sub-sampling of the nestling period, which does not allow for the quantification of the duration of chick-feeding by parents within a day, and may also inadequately capture temporal variation in the rate at which chicks are fed. Here I describe an inexpensive device, the Automated Perch Recorder (APR) system, which collects accurate, long-term data on hourly rates of nest visitation, the duration of a pair's workday, and the total number of visits the pair makes to their nest across the entire period for which it is deployed. I also describe methods for verifying the accuracy of the system in the field, and several examples of how these data can be used to explore the causes of variation in and tradeoffs between the rate at which birds feed their chicks and the total length of time birds spend feeding chicks in a day.

Highlights

Studies of avian nesting behavior have played a central role in the development of several areas of evolution and ecology, including life history evolution [e.g. 1,2], parental investment [e.g. 3], and mating system evolution [e.g. 4]
Automatic Perch Recorders are a powerful tool for exploring many different aspects of nest attendance behavior in a noninvasive way
Automated Perch Recorder (APR) are able to gather a more accurate and detailed picture of nesting behavior because they are always ‘‘on’’, and because they eliminate the possibility of transcription errors

Summary

Introduction

Studies of avian nesting behavior have played a central role in the development of several areas of evolution and ecology, including life history evolution [e.g. 1,2], parental investment [e.g. 3], and mating system evolution [e.g. 4]. Studies rely on lengthy, labor-intensive observation of birds coming and going from their nests in order to explore nest building behavior, the physiology of incubation, chick feeding behavior, sex ratios of parental care, time budgets of breeding birds, and comparative work on parental investment and life histories [e.g. 3,5,6,7]. Because direct observation necessarily sub-samples nesting behavior, it may add considerable amounts of sampling variance to estimates of total time devoted to different behaviors. It potentially limits the ability of researchers to obtain extensive and thorough data on temporal and spatial variability in nesting behaviors. The need to collect extensive individual data in order to quantify variation in nesting behaviors is a critical limitation in many evolutionary and ecological studies

Methods

Results

Conclusion