Figure 1.
Nest box with Automatic Perch Recorder attached.
The apparatus consists of a dowel-perch attached to a microswitch mounted at the cavity entrance (close-up in panel B), which is in turn connected to an event recording data logger—visible in bottom right of panel A.
Figure 2.
Proportion of all events misclassified using different interval length cutoffs to classify events as “real” or “false”.
All events with intervals less than a given cutoff were classified as false, and those with intervals greater than the cutoff were classified as real. Video recordings were then used to determine what proportion of events were misclassified. When visits with an interval less than or equal to 21 seconds are excluded, the error rate is lowest at 10.2%.
Figure 3.
Automatic Perch Recorders count a “visit” each time parents arrive at their nest.
A) a two and a half day span of time and the cumulative number of feeding visits made to the nest during that time with dashed lines showing the beginning and end of civil twilight; and B) the hourly rate of parental feeding visits to the nest over the same time period.
Figure 4.
The mean daily rate of chick feeding is highly variable across time within and between nests and shows a response to wind speed.
Panels A and B show the rate of chick-feeding (solid line) across time for two different nests, and the moving 5 point average of the chick-feeding rate (dashed line). Panel C shows the chick-feeding anomaly–the difference between a pair's daily chick-feeding rates and the moving 5 point averages–for all pairs across the nesting period, and it demonstrates how daily rates of chick-feeding change synchronously across pairs. Panel D shows the average wind speed for each day of the chick-rearing period. Relative date is the number of days since the hatch date of the first nest in the population.
Table 1.
Variables included in each regression model and their AIC results.
Table 2.
Effects of Present Day and Previous Day Wind Speed on the Chick Feeding Variable.
Figure 5.
Variation in the number of times parents feed chicks per day and the relationships of feeding rate, duration of feeding, and number of times parents feed chicks.
a) Histogram showing variation in the average number of times chicks were fed per day by 17 different pairs of birds. The mean number of times chicks were fed per day by all pairs is 317.4. b) The number of times chicks were fed each day was strongly predicted by the rate at which parents fed chicks. c) The number of times chicks are fed on average is negatively related to the average amount of time pairs spent feeding chicks in a day. d) There is also an inverse relationship between the number of minutes birds spent feeding their chicks and the rate at which they fed them.