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3955Re: [wsbn] southbound hummingbird migration

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  • Steve Bouricius
    Sep 1, 2009
      Good 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.


      Steve Bouricius
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