Hi Norm,
My guess would be midges (family Chironomidae) which can occur anywhere, any time there is open water. It is my understanding their body fluids are spiked with compounds that suppress their freezing point below 32 degrees F. Normal places for open water at this time of year when it has been this cold are near water treatment plants, condensation from places like the Denver Botanic Garden conservatory, springs, etc. That stretch of the Platte River near Commerce City and nearby ditches/streams is probably kept open by effluent from various industrial operations. Say's Phoebes are semi-hardy, as insectivores go, because some of their insect prey is, likewise, semi-hardy. It is also possible that, like many of the larger flycatchers during migration, that they can supplement their diet with tree fruits like Russian-olives, crabapples, etc.
Dave
To: cobirds@googlegroups.com
Subject: [cobirds] Sand Creek Say's Phoebe
From: migrant44@aol.com
Date: Wed, 2 Jan 2013 01:27:13 -0500
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My guess would be midges (family Chironomidae) which can occur anywhere, any time there is open water. It is my understanding their body fluids are spiked with compounds that suppress their freezing point below 32 degrees F. Normal places for open water at this time of year when it has been this cold are near water treatment plants, condensation from places like the Denver Botanic Garden conservatory, springs, etc. That stretch of the Platte River near Commerce City and nearby ditches/streams is probably kept open by effluent from various industrial operations. Say's Phoebes are semi-hardy, as insectivores go, because some of their insect prey is, likewise, semi-hardy. It is also possible that, like many of the larger flycatchers during migration, that they can supplement their diet with tree fruits like Russian-olives, crabapples, etc.
Dave
To: cobirds@googlegroups.com
Subject: [cobirds] Sand Creek Say's Phoebe
From: migrant44@aol.com
Date: Wed, 2 Jan 2013 01:27:13 -0500
I joined Mike Serruto, Nina Routh, Greg Smith and Greg Goodrich for a couple of miles of walking and counting along Sand Creek between Quebec and Havana this morning. We had great numbers of the usual suspects, including lots of beautiful hooded mergs, a nice variety of red-tails including one dark morph and a few other goodies. However, the only bird of real note was a very late (overwintering?) Say's phoebe which was flycatching (or maybe flyhunting- I can't imagine it was catching much, but maybe Dr. Leatherman can comment on that) from perches in an open field along the creek.
Norm Lewis
Lakewood
migrant44@aol.com
migrant44@aol.com
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