June 6, 2014
Here is another guest student blog post, this one by Dalton Brauer. Thanks for teaching us a bit about hummingbird feeding behavior, Dalton!
Lately, decreases in bird sightings have been blamed on natural catastrophes, human disturbance and climate change, but researchers may have added another possibility to the mix. A greater number of flowers in your neighboring areas will lead to fewer hummingbirds visiting your feeders during that season. On years with low floral abundance, feeders become much more attractive, and these birds will travel a much greater distance to get to your feeder. The hummingbirds, in particular, the Broad-tailed Humminbird, Selasphorus platycercus, the center of David Inouye’s (University of Maryland) research, will not require the food you leave out because the abundance of flowers around their nesting areas is high. Levels of flower abundance changed over time because of more snowfall or harder frosts that pushed blooming further into the season or decreased blooming abilities overall.
Are you finding it hard to spot the Broad-tailed Hummingbird at your feeder this year or is there an overload of hummingbirds coming around? David Inouye looked at how floral resources affected the abundance of Broad-tailed Hummingbirds. Their shiny green bodies and either an iridescent red throat for males or white throat for females can be distinguishing identifiers of these magical birds. They were captured and banded at feeders using nets and cages (because Hummingbirds are so small) at different areas in the Colorado region. Along with banding, researchers listened for the characteristic wing whistle that male hummingbirds make, like the sound of human feet acknowledging their presence, in order to have another count of population size. Flower abundance was tallied by counting the most commonly visited flowers of Broad-tailed Hummingbirds like the glacier lilies and scarlet gilia.
They found that hummingbird population numbers were highest at the beginning and at the end of the season when floral abundance was lowest. Ultimately, this research displays a flaw in doing population studies at feeder sites because bird presence varies with certain environmental conditions. This could be considered when conducting population surveys of any birds, not just the hummingbird. If you’re finding yourself counting large numbers of Broad-tailed Hummingbirds, you might want to take a walk around the neighboring areas and see if there is an abundance of blooming flowers. In the end, even though a feeder gives free, easy food, the birds will resort back to their natural instinct when there is enough food to go around. It’s just like when we drive to a restaurant: we will only drive far for a meal if we can’t get it closer to home!
Inouye, David, Calder, William, and Nickolas Waser. The Effect of Floral Abundance on Feeder Censuses of Hummingbird Populations. The Condor. The Cooper Ornithological Society, 1991: 279-285.