Missing Feathers

Many birds are currently molting their flight feathers (wing and tail feathers). Some have completed their molt while others are still in the process of doing so. I’ve found various wing feathers floating in the Wetlands, on the path around the Explore the Wild/Catch the Wind loop, and at the Bird Feeder Exhibit.

All birds molt. The wear and tear of daily life necessitates the replacement of old, worn feathers. While the contour feathers (the body feathers on the back, head, belly…) are replaced each year at various times of the year, depending upon the species, most flight feather molt occurs during the breeding season, usually while there are still young on the nest. Birds not only have to expend enormous amounts of energy at this time of year dealing with the building of nests and the rearing of young, they must also cope with the energy consumption associated with the growing of new flight feathers. It’s definitely worth the expenditure though – birds can’t fly without feathers!

The wing and tail feathers usually molt sequentially, especially in larger species like hawks, owls, and herons. In the wing, the molt begins with the innermost primary and works its way outward. The secondaries are next, starting with the outermost feather and working in towards the body. The tail feathers are replaced in order from the center outward.

So, if you see a large bird coming into the Wetlands and it appears a bit ragged (missing some feathers in the wing or tail), you’ll know what’s going on. The bird is molting. By the way, only the adults molt their flight feathers at this time of year, so any bird you see that’s missing feathers in its wings or tail will be an adult bird, unless, of course, a young bird has lost a feather due to an encounter with a predator, or has had a heated argument at the bird feeder.

Turkey Vulture nearing completion of its molt

The first image of Turkey Vultures here (TV-1) shows the bird nicely completing its molt. The next to last primary on its left wing is coming in as well as two new secondaries. The tail molt looks to be complete, or nearly so. The bird in the second image (TV-2) apparently hadn’t received the memo about sequential molt and appears to have lost several primaries in each wing at the same time. The tail needs some attention as well. It’s not unusual, however, to see a bird missing so many feathers in its wings or tail as to make you wonder how it can stay aloft!

This turkey vulture apparently hadn't received the memo about sequential molt and appears to ave lost several primaries in each wing at the same time.

July is a month in which some species of bird begin to move south. We may see a few early migrants during the next few weeks. Keep your eyes open!

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