Hummingbirds remember flowers
What scientists who studied the Green-backed Firecrown in Chile learned about the ability of hummingbirds to remember which flowers provide the best nectar — and when.
Published: August 26, 2011
There’s nothing easy about being a hummingbird. Its small size makes it difficult to maintain body heat. And its preferred flight style, hovering, is energetically expensive.
The more efficiently it can locate high-quality nectar the better, but being a productive forager requires knowing a thing or two about flowers — not only where they’re blooming but also which ones are the best nectar sources.
And that’s easier said than done, because flowers are unreliable. Not only does the amount of nectar vary throughout the day, but so does the concentration of that nectar. Can a hummingbird keep track of all this data, and if so, does it then use the information when foraging? Scientists who study the Green-backed Firecrown in Chile say the answer to both questions is yes.
They presented firecrowns with two groups of identical feeders: some that were refilled every 10 minutes and others refilled every 20 minutes. The birds visited the 10-minute feeders at significantly shorter intervals.
Then the researchers offered six firecrowns a choice of feeders refilled every three minutes with low-quality nectar or feeders refilled every six minutes with high-quality nectar. The hummingbirds visited the high-quality feeders more often.
The results showed not only that the birds can recall flowers’ different nectar-renewal rates but also that they adjust the interval between foraging trips to match nectar availability.
But not all of them. Two visited the low-quality feeders. “Some subjects take more time to acquire information about the environment,” explain the authors, “and shorter-interval flowers may be assessed by these subjects as a lower-risk food source than richer flowers that are available at longer time intervals.”