One hummingbird species, two maps

Hummingbirds.net Ruby-throated map Mar 2012

The migration map from hummingbirds.net through March 2012.

eBird Ruby-throated map Mar 2012

The same time period on the eBird map.


The best way to follow the spring migration of Ruby-throated Hummingbirds is the map at hummingbirds.net, but if you also follow eBird you might notice that sightings posted there tend to lag a bit behind. This annual discrepancy became a full-blown controversy in 2012, when sightings reported to hummingbirds.net galloped far ahead not only of eBird but of any similar period since 1996, the year hummingbirds.net creator Lanny Chambers began tracking Ruby-throated spring migration.

-w-250The reasons behind the 2012 discrepancy had more to do with different birding styles than with that spring’s odd weather or the birds themselves.  To clear the air and build a bridge between the mainstream birding and hummingbird specialist communities, I wrote an analysis for the May 2014 issue of the American Birding Association‘s Birder’s Guide to Conservation and Community. Whether you’re not yet a member of ABA or missed that issue of the Birder’s Guide, you can read “Parallel Universes” for free right here (page 46).

Thanks to Birder’s Guide editor Michael Retter and all the hardworking folks who make ABA such a great organization, and to Lanny Chambers and his dedicated network of hummingbird watchers.

Are there studies on how red dyes affect hummingbirds?

Feeder solution colored with cherry juice concentrate

Hummingbirds don’t need a colored solution, but natural coloring from fruits and vegetables (in this case, tart cherry juice concentrate) is a far safer alternative to the petroleum-based dyes found in liquid food coloring and commercial “instant nectar” products.

Primum non nocere. [First, do no harm.]
—Thomas Sydenham, “The English Hippocrates” (1624–1689)

A recent visitor to the Field Guide to Hummingbirds Facebook page asked a question that comes up frequently in discussions of the use of petroleum-based food dyes in hummingbird feeder solutions:

Have any scientific studies been conducted to determine the effects of these chemicals on hummingbirds?

Some people are surprised to learn that the answer is an emphatic “NO.” Despite oft-repeated (and oft-debunked) urban legends that the San Diego Zoo, Audubon Society, or some other trustworthy source tested red dye on hummingbirds and found one or more specific effects (liver damage, kidney damage, cancer, tumors, “birth defects,” weakened eggshells, or, in some versions of the story, no harm at all), there is no evidence that any such testing has ever been conducted on hummingbirds by anyone anywhere.

Considering the challenges of such a study, direct testing of dyes on hummingbirds is not likely to happen:

  • Hummingbirds, like most wild birds, are protected by the Migratory Bird Treaty Act and various state laws, and animal research is subject to its own set of federal, state, and institutional regulations, so the first hurdle would be to get all the necessary permits and permissions to capture wild hummingbirds, confine them at a research facility, and perform lethal testing on them.
  • Getting the permits would require the researchers to prove that they could provide proper housing and care for the duration of the study. Hummingbirds are difficult and expensive to house and feed, and it could cost many thousands of dollars to keep dozens of them alive and otherwise healthy for the duration of testing.
  • The size and composition of the study population is very important. If the number of birds is too small, the results may not be clear, or critics may dismiss them as not statistically significant. If only one species is tested, critics may argue that the results may not apply to other hummingbirds. If only males are tested, critics may contend that the dye could affect females differently or not at all and therefore have little effect on populations.
  • To document the effects of dye consumption on the birds, the researchers would have to “sacrifice” and dissect them. It would be difficult to find qualified researchers interested enough in hummingbirds to perform such a study, qualified to undertake or supervise daily care of dozens of captives, and willing to kill them all to get the data. Imagine, too, how the hummingbird-loving public would react to learning that dozens of hummingbirds had been taken from the wild, dosed with dyes, killed, and dissected, even if the results might help to protect the health and safety of millions of other hummingbirds.

“Skeptics” who insist that such studies are required to “prove” that petroleum-based artificial dyes harm hummingbirds are setting the bar far higher than we do for our own health. No one in their right mind would suggest that we evaluate the safety of food additives, drugs, etc. by exposing human subjects to potentially harmful doses. Instead, we rely on the results of testing on lab animals and cell cultures to indicate whether and how various chemicals may affect human health.

Just because artificial dyes have never been tested on hummingbirds doesn’t mean they’ve never been tested. In fact, there are plenty of published studies on the effects of FD&C Red No. 40 and FD&C Red No. 3 to help us make a compelling case against exposing hummingbirds to high doses of these dyes, without taking the life of a single bird.* The real challenges are to increase awareness of this evidence among backyard enthusiasts and persuade manufacturers of commercial “instant nectar” products to use safer alternatives.

Unfortunately, the people who make money selling “instant nectar” products have proven extremely resistant to pressure from both hummingbird experts and the general public, and there are no regulations governing the use of human-approved food additives in foods intended for wild animals. Too many companies put profits ahead of everything, including animals’ lives and federal laws, but persistent, science-based outreach promoting responsible hummingbird feeding will help to shrink the market for artificially dyed “nectar” products and protect the health of the birds we love.



* One “cruelty-free” alternative for directly assessing the effects of dyes on hummingbird health is to look for dye residues and signs of related genetic/cellular/tissue damage in birds that are either found dead or die after being brought to wildlife rehabilitators. These sad cases have provided valuable insights into the diseases and parasites that afflict hummingbirds (see Hummingbird health: pathogens and disease conditions in the family Trochilidae. Loreto A. Godoy, Lisa A. Tell, Holly B. Ernest, J Ornithol (2014) 155:1-12. 
DOI 10.1007/s10336-013-0990-z).