In the 1970s DDT, a highly effective pesticide then widely in use in the U.S., was believed to be threatening the continuation of a number of bird species. Reports claimed that bald eagles, ospreys, and peregrine falcons exposed to the chemical laid eggs with abnormally thin shells which broke during incubation and resulted in markedly fewer successful hatchings, so new generations were not surviving to replace earlier ones as older birds died off. Because of this looming extinction threat, DDT was subjected to a domestic ban in 1972. Once the pesticide was removed from the environment, the population levels of the endangered birds returned to near their previous levels. (Later studies indicated that factors other than DDT use were likely responsible for most of the decline.)
Half-remembered fragments of the many news stories about the effects of DDT on those threatened raptors may have contributed to a related widespread conviction regarding hummingbirds — that the red dye commonly added to the nectar used in hummingbird feeders works to thin the shells of their eggs, placing them in similar jeopardy:
[Collected via e-mail, 2000]
This morning I got a stern lecture from the checkout lady at the grocery store because I was buying red food coloring to use in a hummingbird feeder. "Don't you know red food coloring weakens their egg shells?" she demanded.
[Collected via e-mail, 2001]
I have heard that the use of red dye in Humming Bird feeders will wipe out the family of the birds using the
feeder in three generations. The dye is surposed to weaken the eggs.
Or the suspicion could have been fueled by a more general wariness attached to red dyes, especially in the wake of the longstanding controversy over Red Dye #3, a colorant the Food and Drug Administration (FDA) banned for a number of uses of in 1990 after it was linked to the development of thyroid tumors in male rats. (Red Dye #2 has been banned by the FDA since 1976.) For whatever reason, many folks have come to suspect the color additive in hummingbird nectar poses a danger to the little creatures, with the "It thins the shells of their eggs" belief heard most often as the specific harm wrought by the coloring. Others reasons claimed for avoiding red dye include a fear the substance will build up in hummingbirds' kidneys or livers, or that new hatchlings whose mothers partook of the sweet will be born blind or deformed.
The red dye traditionally added to attract hummers to nectar dispensers may never have been necessary anyway. While it is true hummingbirds are drawn to red, there is more than one way to entice a bird.
According to an entry found in the Audubon Society's FAQ:
Current thinking is that the red dye may not be good for them, nor is it necessary to attract hummingbirds. The color on your feeder is enough to attract them. You can mix your own nectar using 1/4 cup sugar to every 1 cup of water.
The Audubon Society's page does not detail the harm it fears dye could potentially cause. We're unaware of any definitive study either linking the colorant to a particular illness in hummingbirds or demonstrating it to be harmless. Anecdotal evidence postulates a causal connection with beak and liver tumors.
Rather than take a chance with the little birds' health, many bird fanciers have chosen to omit red dye from the liquid feed they offer their airborne visitors. A mixture of 1 cup of sugar to 4 cups of water makes a perfectly serviceable nectar. (Do not use honey in place of sugar, because it can promote the growth of a fungus that kills hummers.) Dye is unnecessary in the mix because the birds are already attracted to the red coloring of the feeders themselves. But do keep those feeders clean, because the sugar/water mix can ferment fairly quickly in the summer sun, making it bad for the very wildlife it's meant to energize.
The feeding of hummingbirds has attracted a second rumor, one of a more sinister nature:
[Collected via e-mail, 2000]
I heard that a man was recently arrested for cruelty to animals after starving a number of humming birds by putting out feeders with nutra-sweet in them.
We haven't found a news account or other report of any such incident. Moreover, hummingbirds generally draw their sustenance from spiders, flies, gnats, and other insects they eat, not from the sweet nectar they sip. The sugary liquid provides extra energy to the birds, but it's not their primary source of nutrition.
Some bird lovers fear the presence of their nectar dispensers will tempt the little birds to delay migration, causing coddled hummers to become trapped by the sudden onset of cold weather. Yet they need not so fearful, because the hummingbird's instinct to migrate is too strong to be sidetracked. When it's time to go, they know.