3955Re: [wsbn] southbound hummingbird migration
- Sep 1, 2009Good work, Larry, and very interesting. It opens to questions of peak
consumption vs. peak attendance. The number of birds per given quantity
of food could be influenced by so many factors. How many birds are
actually in migration, how many resident, how many juvenile, or how many
female vs. males and to what extent are the various groups utilizing
insects? How does the number and arrangement of feeders (not to mention
nearby flowers and insect resources) affect competition and
consumption. Do migrating adults metabolize at a greater rate than the
non migratory birds? It could be for instance that around the August 13
peak, there may have been fewer birds than the previous week.
I've spent much of the summer in the mountains where at peak around the
end of July, we were feeding 12-15 gallons of sugar water daily at our
banding site. Temperatures were unusually cold and I think the
inclement weather held birds where the food was. In three mornings from
July 31-Aug 2, our group banded 1463 hummingbirds.
By August 20, the vast majority of birds were gone, consumption about a
gallon a day, and not a single Rufous or Calliope was seen since. Here
in Palisade on September 1st, we still have a fair number of birds
including several Rufous and Calliope.
If you maintained a constant number of feeders in the same arrangement
year after year, the sugar use data could be very interesting over a
period of years.
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