The Dangers of
by Sheri Williamson, author of
A Field Guide to Hummingbirds of North
America (Peterson Field Guide Series,
Attracting and Feeding Hummingbirds (T.F.H.
Publications, March 2000)
Originally published in WildBird magazine (2008)
See also: Seeing Red over Dyes, "Perch Hypothermia": Is It A Threat?
and Yellow Feeder Parts and Bees
Decades ago, when hummingbird feeders were made from plain glass vials or bottles, a
little red coloring was often added to the sugar water to attract the birds’ attention. A
tradition was born, and though modern commercial feeders are proven attractive
without additional color in the contents, to many people a hummingbird feeder just
doesn't look right unless it's filled with red liquid.
Hummingbird experts have long discouraged the used of colored feeder solutions as
unnatural and unnecessary, but there was little more than anecdotal evidence to
suggest how synthetic dyes might affect the birds’ health. Now studies on humans, lab
animals, and even cell cultures are providing that evidence without turning the
hummingbirds themselves into “guinea pigs.”
Some of the recent research into dyes and other food additives was spurred by the
concerns of parents who suspected that these chemicals were linked to the increasing
incidence of childhood maladies such as attention-deficit/hyperactivity disorder (ADHD),
asthma, and allergies. One of the prime suspects was FD&C Red No. 40 (allura red),
an azo (coal-tar) dye used in the liquid food coloring found in millions of kitchens as well
as in many prepared foods and beverages. In 2007, British researchers at the
University of Southampton reported that Red No. 40 was among several popular food
colorings that increased hyperactivity and reduced attention span in children when
combined with the common food preservative sodium benzoate. These results
validated previous studies as well as the experiences of many parents and teachers.
Some European manufacturers responded by pledging to eliminate Red No. 40 and
other suspect additives from candy, soft drinks, and similar products.
Though less well publicized than the Southampton study, earlier research also casts
doubt on the safety of Red No. 40. In 2001, researchers in the Department of
Veterinary Medicine at Iwate University in Japan reported that Red No. 40 at doses as
low as 10 milligrams of dye per kilogram of body weight induced DNA damage in the
colons of rats. DNA damage is the first step in transforming a normal cell into a cancer
cell. In a 1983 study, American researchers found that high doses of Red No. 40
resulted in “significantly reduced reproductive success, parental and offspring weight,
brain weight, [and] survival” as well as behavioral abnormalities. Though the U.S. Food
and Drug Administration approved its use over twenty years ago, there is enough
uncertainty about the safety of Red No. 40 that it is banned in Austria, Belgium,
Denmark, France, Germany, Sweden, and Switzerland.
Another food dye under scrutiny is FD&C Red No. 3 (erythrosine), also found in liquid
food coloring and often added to feeder solutions. In 1990, the FDA banned certain
uses of Red No. 3 in response to a study that found that large doses of this dye cause
thyroid tumors in male rats. Subsequent research has identified estrogen-mimicking
effects of the dye on human breast cancer cells and linked high doses to reduced
sperm production and behavioral changes in lab animals. (Neither Red No. 3 nor Red
No. 40 should be confused with the infamous Red No.2, which was banned in the U.S.
What are the implications of this research for hummingbirds and the people who love
and feed them? The most alarming aspect of these studies is that many of the harmful
effects were dose dependent: The larger the dosage of dye, the greater the effect. A
hummingbird the size of a Black-chinned needs to drink about two and a half times its
body weight in 4:1 sugar water to meet its daily energy needs. If that sugar water was
dyed bright red with Red No. 40, the bird would take in ten times the daily dosage of
dye that it took to produce DNA damage in the Japanese study. A hummingbird coping
with cold temperatures or fattening for migration might need to drink twice as much
sugar water per day, thereby doubling its dye intake.
The research into Red No. 40 also solves the mystery of why hummingbirds produce
urine paler in color than the dyed sugar water they drink. Some of the dye is absorbed
and chemically altered by the body, but a 1975 study found that a significant amount
adhered to the intestinal lining of the test subjects. This may explain why the later
Japanese study found the dye’s damage concentrated in the cells of the gut wall.
Not surprisingly, concern over the effects of artificial dyes on human health have
sparked new interest in natural colorants for foods and beverages. Fruit, vegetable, and
flower extracts are seldom as uniform in color or stable under as wide a range of
environmental conditions as their synthetic counterparts, but research is underway to
resolve some of these issues. Until plant-based food dyes become widely available,
dye-free raspberry or other fruit juice makes a safe and simple alternative for coloring
hummingbird feeder solutions.
Feeding Hummingbirds: "Perch Hypothermia"
Yellow Feeder Parts and Bees