Hummingbird Vocal Learning
Biology 342 Fall 2015
Alex Loukides and Hannah McConnell
Hummingbirds have vocal nuclei, as do other animals that have the vocal learning, like parrots, many songbirds, humans, and seals, although it is believed that each clade developed these brain regions seperately (and there is some evidence that suggests that many of these brain regions developed individually in each species). In hummingbirds, these brain regions are shown to express an immediate early gene, ZENK, a transcriptional regulator that is likely related to the formation of long-term memory on a cellular level, after hearing or vocalizing hummingbird songs. Like other clades' vocal nuclei, the vocal nuclei of hummingbirds appears to be made up of seven regions of the brain, three of which are in the exact same location of the brain as parrots and other songbirds. The other four are in different locations of the telencephalon, but in the same brain subdivision, and have many morphological similarities between the species.
A specialized area of the forebrain and the hummingbird's brain stem together make up the song system of the hummingbird. The song system has two major pathways, the song motor pathway (SMP) and an anterior forebrain pathway (AFP). These pathways derive input from the vocal nucleus of the hummingbird. The SMP appears to be related to the maintenance of crystallized songs, and the AFP is involved with plastic songs and song variability. In both pathways, neurons respond to singing-related activity. This includes both vocalizations that the hummingbird produces, and songs from other birds that it hear, both during the critical period when the birds are juveniles learning to sing, and once they are adults.
Figure 1: The neural pathways of the song system in the brain of a hummingbird.
(Mooney, R. (2009). Neural mechanisms for learned birdsong.
Learning & Memory, 16(11), 655-669.)