[Tweeters] Thoughts on Winter Feeding of Hummingbirds
wallydavis3 at gmail.com
Thu Jan 28 06:46:22 PST 2016
Many years ago as a graduate student in zoology at UC Berkeley, I studied
hummingbird behavior using both wild and captive birds as subjects. Species
I studied included Anna's (Calypte anna), Black-chin (Archilochus
alexandri), Allen's (Selasphorus sasin), and Rufous (Selasphorus rufus).
Most of the time I kept my captive hummingbirds in an 8' x 8' by 8' outdoor
enclosure sheathed in window screen.
Rather than feed simple sugar syrup, I fed a mixture containing sugar,
vitamin drops, protein, and other nutrients. In addition, I maintained a
colony of fruit flies and a couple of times a week would release a large
quantity of them into the hummingbird cages. It was amazing to watch the
action when the fruit flies were released. All of the hummingbirds took to
wing and deftly plucked the fruit flies out of the air or any surface they
happened to land on. The fruit flies didn't stand a chance and were quickly
devoured. Using this approach I kept my captive hummingbirds healthy for
over a year and even fledged and raised two Allen's hummingbirds which I
collected in order to study learned vs. instinctive feeding behavior.
In 1999 I moved to Snohomish, WA where I put up a bird feeder, hung blocks
of suet and, of course, hummingbird feeders. Many Rufous hummingbirds
visited from spring to mid-summer and even nested in the shrubs on my
property, but I didn't see my first Anna's hummingbird until 2011. By 2013
they became year-round residents and were breeding on my property. When the
Anna's showed up I maintained a 4:1 sugar syrup all winter. When
temperatures dropped below the mid 20s I kept the food from freezing with a
ball of small Christmas lights. As a few years passed, I observed that
there were fewer birds in late winter than in early winter. Two possible
reasons for this are that the birds leave and go somewhere else or they do
not survive. Because little natural food is available in the winter, I
believe it is unlikely that the birds leave. It is important to note that,
once you attract hummingbirds for the winter, you must keep it up even if
you are out of town or the birds may starve.
Both of my birding books from the 1960s, Peterson's A Field Guide to Western
Birds (1961) and Robbins, Bruun and Zim's Birds of North America (1966),
placed the north end of the range of the Anna's hummingbird in California.
Since that time they have moved north as residents more than 400 miles.
According to the National Audubon Society, winter feeding and home gardens
have probably supported this movement
While sugar syrup may be fine to attract wild hummingbirds during the
summer, it is not a sufficient diet for captive hummingbirds or, in my
opinion, wild hummingbirds lured by feeding to stay in cold climates north
of their native range. While normal winter mortality will cause loss of
some birds, I believe the winter diet likely contributes to a reduction in
overall fitness. In the near absence of insects and spiders, their primary
source of protein and other nutrients is largely missing. Imagine what it
would do to our health if we consumed mostly sugar water with just an
occasional nutritionally rich food for 3 or 4 months.
In late 2014 I changed my winter feeding program soon after the first frost;
a time when I expect the availability of insects and spiders to be greatly
reduced. At first I tried to replicate the formula I used as a graduate
student but found the ingredients are no longer available. One of the
ingredients I did use was baby formula and, consequently, reviewed the
nutrients in all of the baby formulas I could find. Eventually I selected
Gerber Good Start gentle as my supplement. A key reason for this choice is
that whey protein is the first ingredient. Most baby formulas on the
shelves at my grocery store use soy protein which is of vegetable rather
than animal origin. The formula also contains a good selection of vitamins
and other nutrients.
The recipe on the Gerber can calls for "1 unpacked level scoop (8.9g)" per 2
ounces of water. Given the high quantity of sugar needed to maintain body
temperature, I was concerned that feeding at this rate would provide too
much protein and, consequently, settled on 1 level scoop per 8 ounces of 4:1
sugar syrup. The instructions also say that you can refrigerate for up 24
hours and discard unused formula after 1 hour. While this level of caution
may be reasonable for infants, I have not found it to be necessary for
hummingbird food. I typically mix up 8 ounces at a time then put 2 ounces
in each of two small feeders placed fairly far apart (hummingbirds don't
like to share). The Anna's hummingbirds which are using my feeders consume
this quantity of food in about 3 days. In cold weather there is no sign of
spoilage of the food outside. After a week in the refrigerator it still
tastes and smells as fresh as when it was made up. As the weather warms up
I will probably change the food more often and, when I see insects I will
switch back to just sugar water.
At the end of last winter it appeared to me that there were as many Anna's
hummingbirds as at the beginning. This gives me confidence that there isn't
a downside to adding baby formula; it also gives me one subjective data
point that the formula I use promotes winter survival. Time will tell
whether this pattern continues in the future. At least I can feel confident
that I am providing the hummingbirds with a more nutritious diet then they
would otherwise be able to obtain, and they will hopefully be healthier
coming out of winter.
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