 Female Anna's Hummingbird with a funny looking wing coming into a feeder, Summerhaven, July 20, 2024. Yes, this is a post is about molting! Much of what we observe in the life of birds are their most important everyday duties, such as getting lunch before being lunch, and breeding. However, an essential aspect of every bird's life is molting, replacing all the feathers on the body, which generally occurs on an annual basis, taking time and energy. Molting generally occurs after breeding and before migration, so now, July and August, is the molting season. In August of 2022 I got images of Northern Cardinals and Pyrhuloxia in the middle of their annual molt in the Chiricahua Mountains near Cave Creek Canyon. However, I have never noticed molting in hummingbirds until this past weekend.
Anna's Hummingbirds have 16 flight feathers on each wing, 10 full length primary feathers, which occupy the most distal or end of the wing, and 6 shorter secondary feathers that are shorter and closest to the body. See the diagram below that shows the anatomy of the right wing of typical bird. For each species the primary and secondary flight feathers are numbered from 1 upward beginning where the primaries and secondaries meet. The number of flight feathers will vary by species.   Canon R6 with RF 100-500mm @ 400mm, 1/3200 sec., f/6.3, ISO 3000, EV +0.33. On July 20th I captured a large number of images of hummers in flight by our deck feeders in Summerhaven. As I was going through the deck of photos, tagging "duds" for the trash-basket, I noticed the image above of a female Anna's. The left wing was definitely different. This bird is molting. We can see the wing feathers are being replaced from the junction of the primary and secondary flight feathers going out in both directions, the newest feathers in this photo being the shortest and darkest, which are probably primary flight feathers. I suspect that Primary 1 (P1) is complete and the smallest and darkest feathers are P2, P3, and P4, P4 being the smallest. The secondaries may have been replaced already. We can see molting occurring on the wings, but it is also underway on the body itself, although these changes are more subtle. The pattern of body molting is complex, and varies by species. The science of molting, including classifications and descriptions, is very complicated. For those with interest, I would recommend a subscription to the Cornell Lab Birds of the World, where you will find detail on each species, depending on the amount of research that has been done for that species. Another great reference is the Handbook of Bird Biology (Cornell Lab of Ornithology) 3rd Edition. Warning: this "handbook" is 716 pages and takes two hands to lift . . . . . The next shot, above, shows the symmetrical nature of the molt, with both wings looking the same.  Hummers must fly to eat, so even with the feather loss and replacement, this bird maintains its flight function. Molting is energy intensive and must occur when the bird does not have to consume energy breeding or migrating, and when there is adequate food available. The energy required for molting may explain why hummers spend so much time at nectar feeders this time of year, supplementing what is available from the local flowers and insects.   Above, more views of the Anna's coming in to the feeder. Below, a landing! We can see the flight feathers backlit.  As mentioned earlier, during a molt all the bird's feathers are being replaced. The molting process will make birds look different, perhaps scruffy. For example, below are three images of a male Broad-tailed Hummingbird at our feeders on July 21st. The gorget, the brightly colored area on the throat in the male, looks different.  Canon R6 with RF 100-500mm @ 500mm, 1/50 sec., f/7.1, ISO 200, EV +0.67. A closer look reveals little white "pins" sticking out next to mature contour feathers. These "pins" are most likely the white sheaths that encase the new feather. The new feather opens up much like a blooming flower, shedding the sheath. In the two images below there appears to be new feathers close to the midline with white remnants of the sheaths still present.  
July and August is molting season, so keep your eyes open for birds that "just don't look right." They might be molting! As always, many thanks to Jeff Babson who provided me with his expertise on the molting processes, wings and body, as well as species confirmation. Thanks Jeff! That's all for now! More content in the hopper and coming soon! Happy trails!
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AuthorHenry Johnson, photographer and author of this site. For more detail, see About Categories
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