On Tuesday, May 4, 2021 at 12:33:06 PM UTC-6 Dave Leatherman wrote:
Hi All,Wonderful bird, wonderful photos by John Breitsch. Most of the time when we see warblers working cottonwood catkins at this time of year, their target is larvae of a weevil in the genus Dorytomus. John's middle photo shows the warbler tossing down one a larva it has extracted from the flower. The result of feeding by larval Dorytomus weevils is a minor reduction in cottonwood seed (I.e., the fluff we see that could be considered a nuisance in some urban situations). Thus, the weevils are mildly beneficial to humans annoyed with fluff stuck to their screendoors. Add to it the value the larvae have as food for neotropical migrants, and they are distinctly "good". The larvae drop to the ground, pupate in the upper layer of soil and turn into rather non-descript gray adults (photo here taken 10April2010 at Crow Valley many years ago when I was first trying to figure out this warbler attraction to cottonwood catkins thing). The adults emerge in spring, go to the buds, feed a bit by inserting their snouts into buds, lay eggs on the buds, and the resulting larvae feed on cottonwood flower parts until rudely interrupted by a cool warbler.
If you are interested, these weevils are the subject of "The Hungry Bird" article in the April 2011 issue (v45, #2) of "Colorado Birds" archived on the Colorado Field Ornithologists' website.
Needless to say, do not ignore flowering cottonwoods over the next couple weeks when looking for eastern warblers.
Thank you, John, for sharing your photos.
Dave LeathermanFort Collins
From: cob...@googlegroups.com <cob...@googlegroups.com> on behalf of birding...@gmail.com <birding...@gmail.com>
Sent: Tuesday, May 4, 2021 11:02 AM
To: Colorado Birds <cob...@googlegroups.com>
Subject: [cobirds] Blue-winged Warbler - 1st Creek @ GVR, DenverThe bird is still around. This time in the sunlight.
First Creek at Green Valley Ranch - Denver, ColoradoSeen at about 10 am in the cotton woods near the foot bridge (same place as it has been). Good spot by Wolfe R a couple of days ago.
John BreitschDenver, Colorado--
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