Measurements of adult brooding behavior
We videotaped nests for about 6 hours starting at 8:50 and ending at
15:00 to collect information on the rate of parental brooding during the
heating experiment. Video cameras (Sony Corporation, Tokyo, Japan) were
concealed in a corner of the aviary about 3 m away from the nest and
were left unattended. Brooding effort was calculated as percentage of
time spent by at least one of the parents inside the nest box after
excluding the first 10 minutes of recordings to allow adults to resume
their normal activity after the initial disturbance caused by
positioning the camera. Video recordings were made during the
ectothermic phase of growth on day four or five of the nestling stage
because brooding behavior is higher during the early nestling stage and
often ceases as young get older and approach endothermy.