John,

You have asked some very interesting questions about the diet of
over-wintering hummingbirds. This is a topic not often discussed, so is not
widely understood (and I'm not an expert, but I've learned a few things over
the years).

Yes, hummingbirds do need protein in addition to nectar. They cannot put on
body fat unless they consume protein, which is in the form of insects. Most
hummingbirds consume small flying insects, captured in flight. What many
don't realize is that there are insects active in our region (yes, even in
northern Michigan) throughout the winter any time the temperature is above
30-degrees. I have seen swarms of "midges" in Michigan's thumb in January
with temperatures right around 30. If there's a stream nearby, this will be
where the hummingbird goes to find insects as the open water attracts the
insects as well. Virtually every Rufous Hummingbird I've banded (and this
Allen's) have settled in areas with flowing water nearby as well as a good
choice of conifers which they probably prefer to roost in at night. Most
hummingbirds will hold a territory at least 1/4 mile across, perhaps larger.
A few years ago, in December, I caught some insects that were around a home
where a Rufous Hummingbird was being seen and the catch included several
micro-moths (family Microlepidoptera) which were only 2 mm long, and a tiny
sap beetle about 1mm long (I forget the family name just now). Surely, there
are some "bug people" on this list who could add to the potential roster of
small flying insects that are active in cold weather (perhaps gnats, midges,
gall wasps?). But of course when temperatures drop below 30, then these
hummingbirds do become dependent on the homeowners to keep the sugar water
from freezing (a 4:1 water:sugar mix freezes at about 27-degrees farenheit).
Rufous Hummingbirds can (and have) survived more than two weeks straight
consuming only sugar water. Most of the hummingbirds that I band late in the
season have some fat reserves, and I'm sure this gets them through the cold
times when insects cannot be captured. The typical pattern in Rufous
Hummingbirds is to move to a secondary wintering site, sometime around the
winter solstice. This pattern is most pronounced in the deep south, and
along the Gulf Coast, where there are perhaps 3000-4000 overwintering Rufous
Hummingbirds each year, and these movements have been well documented by
banders there. Our northerly birds seem to follow this same pattern, and
many of them have departed during a warm spell and likely survived to move
to another locale to the south, or southwest.

The Rufous Hummingbird is very well adapted to cold temperatures, as it
nests in the northern Rocky Mountains at elevations of 8000 feet and more,
and northward to the Alaska panhandle. These hardy birds arrive in Alaska in
early April and are nesting in the southern parts of their range by early
May, when it is still possible to snow at those elevations. Rufous
Hummingbirds can go into torpor at night to conserve energy when it is cold.
Ruby-throats can do this too, but are not as well adapted as they generally
don't experience the temperature extremes that are often encountered by
Rufous. As the Allen's Hummingbird is a very close relative of the Rufous,
it seems likely that they'd be similarly adapted, but I don't have a lot of
personal experience with the biology of Allen's. In California, the Anna's
Hummingbird is probably every bit as cold-hardy as is Rufous, and there are
records of Anna's from Montana in November and December (and Ohio in
December)! Even desert-dwelling hummingbirds like Costa's and many
Black-chinned must contend with freezing temperatures at night.

So, while such things cannot be guaranteed, and there is variation (this is
nature after all), there is a high probability that most of these birds
linger as long as they need to (I believe they're finishing the first phase
of a molt, but I still need more data), and depart when they're able, or
when their hormones tell them to (does the shortest day of the year have an
effect?). These birds are definitely not "destined to die in Ohio", as I've
described in my blog posting last week. One immature male Rufous Hummingbird
that I banded near Zanesville endured much worse conditions than we have had
so far, and left that home around December 27. The next year, an adult male
Rufous Hummingbird appeared at that same home and when I captured him, I
verified that it was the same bird I'd banded the year before. And again he
lingered into late December, enduring freezing and snow. The year after
that, an adult male was seen briefly at that same yard in October, but he
didn't stay that year.

There are enough records in Ohio (40+) of Rufous Hummingbird, as well as
varying numbers from every eastern state each and every fall to lay to rest
any conception that these are genetically defective birds that are lost or
off course. A small portion of the world population of Rufous Hummingbirds
winters along the U.S. Gulf Coast (my best guess is 3000-4000 as stated
above). Banding studies are beginning to confirm that these birds are rare
but regular transients through the East on their way to their southern
wintering grounds. That they can survive farther north in greater numbers is
surely due to the number of feeders being kept up later, but surely these
birds have been passing through for some time and not stopping? There are
many questions worth studying about this phenomenon, and I hope to
contribute in some small way to that understanding. Given that Allen's
Hummingbird has a much smaller population than Rufous, there are fewer
records of them in the East, but they have been confirmed in places like
Illinois, Tennessee, New Jersey, New York, Massachussetts, and now Ohio.

Allen T. Chartier
amazilia1(at)comcast.net
Inkster, Michigan, USA

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