Begging in the absence of parents: a "quick on the trigger" strategy to minimize costly misses

Nestling begging in the absence of parents may reflect "false alarms" due to cognitive constraints or signaling activity toward nest mates (sibling negotiation). According to signal detection theory, cognitive constraints should result in both false alarms (begging in the absence of parents or to inappropriate stimuli) and misses (failure to beg during parental visits). In our study of house sparrows, nestling begging in the absence of parents comprised up to 50% of the begging events at the nest and was more frequent at an early age and among hungrier (lower ranked) nestlings. In contrast, the probability of begging during parental visits was constantly high (80% or more), suggesting that the rate of misses must have been low even at an early age. These results have 2 main implications. First, the observation that begging in the absence of parents decreases with nestling age favors the cognitive constraints hypothesis over functional explanations such as the sibling negotiation hypothesis. Second, the low proportion of "misses" among young nestlings suggests that nestling respond to their cognitive constraints by using low decision criteria (a "quick on the trigger" strategy) that increases the frequency of false alarms but minimizes costly misses. Copyright 2007.