Assessing parental effort in a Neotropical parrot: a comparison of methods

Various behavioural or body condition indices are frequently used to measur e avian parental effort. To determine which of the indices provide meaningf ul short-term assessments of parental effort, we used four of them concurre ntly on breeding green-rumped parrotlets, Forpus passerinus, and then compa red the results with field metabolic rate (FMR) measurements obtained using the doubly labelled water (DLW) technique. Nest provisioning rate correlat ed significantly with FMR among both males and females, while proportion of time away from the nest was correlated with FMR in females but not in male s. Adult mass change during the breeding cycle and feeding latency were bot h unrelated to FMR. Our results suggest researchers should be cautious in a ssuming that any indirect method of quantifying parental effort is reliable for a particular species. We also tested whether the relatively invasive D LW protocol causes potentially confounding changes in study animals' subseq uent behaviour. Paired observations before and after DLW injection showed n o measurable changes in parrotlet nest attendance patterns or nest provisio ning rate. (C) 1999 The Association for the Study of Animal Behaviour.