While it's certainly kind of people to set up hummingbird feeders in their back yards, some scientists are wondering if the practise may be causing more harm than good. In an effort to better understand the issue, researchers recently equipped a group of the birds with tags that were read by devices at urban feeders.
When hummingbirds feed upon flowers in the wild, they tend to do so individually, staying relatively far apart from one another. By contrast, the birds are crowded together at feeders, physically contacting one another and sharing the same nectar. Therefore, it's been suggested that the feeders might raise the risk of disease transmission between birds.
In order to determine just how often the animals visit such feeders – and how long they stay there – a team from the University Of California, Davis captured 230 Anna's and Allen's hummingbirds, and inserted tiny passive integrated transponder (or PIT) tags under their skin. These are the same kind of tags that are used to identify lost dogs and cats.
In the same three California regions in which the birds were captured, the scientists also equipped feeders at seven locations with radio-frequency identification (or RFID) transceivers. When any of the tagged birds subsequently visited any of those feeders, the transceiver would detect the PIT tag, electronically logging which bird was present at the feeder, and for what amount of time. Multiple birds at the same feeder could be tracked simultaneously.
Based on 65,476 feeder visits recorded between September 2016 and March 2018, a number of trends emerged. Among these were the fact that 61 percent of the birds returned to specific feeders at least once, some coming back immediately after their first visit, with others not returning until several months later. Additionally, it was found that females stayed at the feeders longer than males, and that males overlapped their visits with other males more often than with females.
It is now hoped that such data could contribute toward a determination of whether or not the feeders pose a health risk to the birds. If it is determined that they do, hummingbird-lovers could instead plant flowers which the birds are known to feed upon.
"Hummingbird feeders attract birds to gather in areas where they normally wouldn't congregate," says Lisa Tell, a professor at the UC Davis School of Veterinary Medicine, and co-leading author of the study. "This is a human-made issue, so we're looking at how that might change disease transmission and dynamics in populations."
A paper on the research was published this week in the journal PLOS ONE.
Source: University Of California, Davis
