18 THE SCIENTIST | the-scientist.com
Notebook SPRING 2022
DAVID RANKIN JUAN LUIS CELIS-DIEZBird Nosed
U
niversity of California, Riverside,
ecologist Erin Wilson-Rankin
didn’t set out to study humming-
birds. A few years ago, she and her then-
postdoc C. Sheena Sidhu were conduct-
ing a field experiment on campus to see
if honey bees avoid feeding on f lowers
with ants on them, something that could
spare them harassment by the aggressive
insects. It turned out that the bees indeed
spent less time on ant-occupied f lowers
(Environ Entomol, 45:420–26, 2016)—
and so, it seemed, did local hummingbirds.
The “charismatic” little birds, as Wil-
son-Rankin describes them, would f ly up
and then quickly move along, opting not
to plunge their long beaks into that f low-er’s nectar. A follow-up study confirmed
the observation: like the honey bees,
hummingbirds avoided f lowers (or feed-
ers) when ants were present (Behav Ecol
Sociobiol, 72:44, 2018).
The researchers knew that the bees
were using smell—the pollinators pre-
ferred feeding on f lowers that didn’t reek
of ant pheromones. But what about the
birds? While the scientific community
has long since discarded the old belief
that most or all birds are anosmic, the
olfactory bulb in most avian species is
small, and hummingbirds have incred-
ibly small brains to begin with. “Con-
ventional wisdom was that if you have a
really small olfactory bulb [a n d ] very few
neurons that are associated with olfac-
tion, you’re not going to have a very goodsense of smell,” Wilson-Rankin says. “Our
first thought wasn’t odor,” she adds—the
group suspected that the birds were using
tactile or even gustatory cues.
To dissect the observation, the team
designed a new study that allowed hum-
mingbirds to choose between a feeder with
plain sugar water and an identical feederSmell in birds is more
common than we thought
before.
—Juan Luis Celis-DiezAVOIDING CONFRONTATION: Hummingbirds
such as this female Calypte costae avoid visiting
flowers when ants are present, researchers report.