Meeting Abstract
Hummingbirds represent an interesting challenge for sensory processing– they have an extraordinarily small ear (1.3 mm basilar papilla length) and possess only ~1,000 sensory hair cells. As a comparison, the Zebra finch basilar papilla is 1.6 mm and contains ~3,600 hair cells. The specific consequences of hair cell number and basilar papilla length for hearing are not fully known. Some hummingbirds produce auditory signals above the frequency of greatest sensitivity for most birds. Costa’s hummingbird (Calypte costae) vocalizations span 6 to 12 kHz with peak power at 10 kHz and they use these signals in displays, suggesting these sounds are audible. For comparison, most birds hear best from 1 to 5 kHz and have best sensitivity from 2 to 3 kHz. We predict that the Costa’s hummingbird possesses frequency sensitivity that corresponds to the frequency range of their song, and an audiogram (graph of hearing threshold by frequency) that is shifted upward in frequency range when compared with the audiogram of other avian clades. We adapted a go/no-go psychoacoustic paradigm using pure tones and a two up, one down algorithm to measure auditory frequency sensitivity and intensity thresholds in order to assess the auditory abilities of Costa’s Hummingbird. By studying hearing of a small-eared organism behaviorally, we will be able to gain more insight into how ear size and hair cell number might constrain hearing.
