Anna's Hummingbird (Calypte anna )
   
 
Narrative and Science Lens
  Image courtesy of Christopher James Clark Audubon shows four males and a nesting female. Note the fanned tail of the upper left male and consider the idea that the two outter feathers are capable of producing a loud chirping sound.

Here's how it works: In its 12-second aerial display, the male climbs 100', takes a J-shaped dive, swooping down and then, while curving upward to form the bottom of the "J", fans its tail for 60 milliseconds, as seen in the photo. At that point, a 50-mph air stream forces the inner vanes of the two outer tail feathers to vibrate like the reed of a woodwind instrument, and the bird quickly “plays” a very loud, “chirp.” For more, see Science, below.
 
 
  Campus Locations
Abundant throughout campus, nesting in virtually any type of tree or tall shrub, even in areas with heavy human activity. Nesting occurs throughout the winter, spring, and summer, peaking in late winter and spring. Concentrations may be present at flowering trees, such as eucalyptus..
  Campus sustainability
  Although these birds are abundant, planning for periods of extreme weather could reduce potential losses. For example, avoid dead-heading: these birds may rely on remnants of pollen or netar from old blossoms, if fresh bloom are unavailable, and provide both drought-resistant late-blooming and early blooming species with trumpet or tubular shaped pink, red, purple, or orange single flowers.
       What you can do
1. Become familiar with these birds and flowers they prefer and see if there are seasonal lapses in blossom availability.
 

Science
            Experimental evidence of tail feather chirping: To verify the tail feather chirping described above, researchers pinpointed the timing and removed or trimmed the outer pair of tail feathers (which regrow) and found that the dives of "trimmed" birds were chirpless. Note: Experiments by Christopher Clark and Teresa Feo included work done in a high-speed wind tunnel at Hopkins Marine Research Station. For more, see the Proc. R. Soc. B report.

Note that sexual selection could be at work: If females prefer males who produce this tail-derived sound, it might have led males to evolve the sound-producing tail feather shape. Males also perform this display to other males and to numerous other species, so it seems to serve as a territorial or resource defense function as well. These birds are well-known for defending unpredictable ephermeral resources.

       Essays from The Birder’s Handbook:
            Nonvocal Sounds; Hummingbirds, Nectar, and Water; Hovering Flight; Hummingbird Foraging Bouts; Coevolution;
          Optimally Foraging Hummers; Range Expansion; Bathing and Dusting; Feeding Birds
       References:
          Ewald and Orians, 1983; Powers, 1987; Stiles, 1972, 1982; Clark and Feo, 2008.
       Videos:
     Become more familiar with hummingbird flight. Stanford mechanical engineering professor David Lentink and his students have been capturing slow-motion video with an eye toward building wing-flapping robots. Lentink has been making his camera and students available to local birders. See  Stanford Students capture the flight of birds on very high-speed video. (See this questionnaire and/or email questions to birderquestionnaire@gmail.com). Lentink says: “We'd like to pair the camera with some bird enthusiasts who might know the natural history of these birds better than us.” He continues, “We want to give people outside of Stanford the magical experience of using this camera and hopefully learn something more about birds in the process.”
  Art
       Photos:
            C (n )
       Drawings and Paintings:
            DW drawing after Audubon
 
  To add reports or images please submit them via the Art at Exits home page