Vocal dimorphism in Anna’s Hummingbirds

Sexual dimorphism in vocal signals is found across many bird species. By
evaluating correlations among sex, behaviors, and vocalizations, the
meaning and utility of sound production may be inferred. Anna's
Hummingbirds (Calypte anna) exhibit pronounced sexual dimorphism, with
males being larger and having more vibrant coloration than females, but
vocal dimorphism in the species is less studied. A common vocalization of
Anna's Hummingbirds is the chip note, which is produced by both sexes
in a wide array of contexts. Here, we correlated temporal parameters of
recorded chip notes with individual sex and behavioral contexts gathered
from field observations. The production rate of chip notes differed
significantly between male and female hummingbirds but did not vary much
with behavioral context. Although Anna’s Hummingbirds produce chips across
a broad spectrum of behaviors, dimorphic chip production may be especially
important in territorial behavior.