I would agree with the heat tape suggestion as more likely to continuously
meet the needs of our hummers (I see them at my feeders as soon as it is
light enough to see and until it is too dark at day's end). Many of the
tapes have a sensor to turn on just above freezing so would only be using
electricity when needed. Also, it seems we have these conditions pretty
infrequently. I would just add some insulation under the heat tape - I"m
sure something that would meet the aesthetic needs of the birds could be
constructed with duct tape or some such. I don't think the handwarmers are
a good option due to the nearly continuous human intervention involved.

I also tend to make the solution stronger during periods of low temperature
(I part sugar - 2 parts water) and it seems to keep it at least slushy into
the 20s F. I appreciate that this could be osmotically dehydrating, but the
birds also have free water always available at my pond/waterfall which is
always flowing a few feet away. My experience, based on the response of
the birds, seems to be they are fine with it - population/use continuous and
increasing...

I also wanted to suggest something we use in bat research which are reusable
hand warmers rather than the disposable ones discussed previously. On cold
nights (when we seem to work...) the bats go into torpor and it can take a
long time to rewarm them. We use these wrapped in a towel in the bottom of
the same cloth bag as the bat.

The warmers are reusable many many times - just boil for about 10 minutes
and the material re-liquefies. When you want to produce heat, you click a
metal disc in the warmer and it crystallizes and gives off heat.

Here is a source: http://www.ghilliesuits.com/re-usableheatpad35x55.aspx
I'm pretty confident I didn't pay $10 each, so look around. Ghillie Suits
are one of the things we (Martyn Stewart, Mark Oberle, Curt Black) talk
about in the nature sound recording workshop which we just scheduled for
next May (info later on http://www.naturesound.org/ ).

The last question about toxicity - I believe the disposable handwarmers use
a finely powdered aluminum which when exposed to oxygen forms aluminum oxide
and some heat...If so - then not too toxic. Always ready to be better
informed if someone has more information on the formulation.

Stay warm out there and enjoy the sun, even if it is only slightly above the
southern horizon. Improvement anticipated soon.

Curt Black
West Seattle


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