Another bird without feathers around its beak - Yellow-rumped Warbler


ireddy@...
 

Hello,
Recently, I mentioned that I found a strange Ruby-crowned kinglet without feathers around its beak. Yesterday, I found another bird (this time a yellow-rumped warbler) with the feathers around its beak gone. It was in Pleasanton, in the canal that borders Val Vista Park. In this case, it seems that the feathers above the beak are growing back but under the beak it is still very much exposed. Could it be a disease or some other causes, like parasites or some type of sticky surface the bird encountered while eating. I hope it is not something in the environment that caused it. Any idea? See my ebird listing for 4 photos. Thank you and have a nice weekend.
https://ebird.org/checklist/S77359110
Isabelle


Bill Bousman
 

Dear Isabelle,

Flowering eucalyptus are a source of nectar for birds (and insects), but our small-billed wintering birds do not appear to do well because they get a gummy deposit on their faces from the flower nectar and eventually the feathers fall off.  Some are able to handle this okay, partly because those feathers are replaced towards spring in the prealternate molt.  Others, perhaps not.  Long billed nectar feeders, like our hummingbirds do not have this problem as they don't get sticky deposits on their feathers, just their bill, and that can be cleaned off (there are many nectar feeders in Australia and they all have long bills).  Other birds, including wintering tanagers, more often prey on the insects attracted to the nectar, and they don't have the same problems.  In my experience this is a common phenomenon, particular for warblers and kinglets, and it becomes progressively worse during the winter season.  It is not a disease as far as I  know, just the result of an individual's feeding preferences.

Bill Bousman
Menlo Park



On 12/12/2020 9:05 AM, ireddy via groups.io wrote:
Hello,
Recently, I mentioned that I found a strange Ruby-crowned kinglet without feathers around its beak. Yesterday, I found another bird (this time a yellow-rumped warbler) with the feathers around its beak gone. It was in Pleasanton, in the canal that borders Val Vista Park. In this case,  it seems that the feathers above the beak are growing back but under the beak it is still very much exposed. Could it be a disease or some other causes, like parasites or some type of sticky surface the bird encountered while eating. I hope it is not something in the environment that caused it. Any idea? See my ebird listing for 4 photos. Thank you and have a nice weekend.
https://ebird.org/checklist/S77359110
Isabelle





ann graham
 

I used to band song birds in Big Sur, and we caught many yellow-rumps (MYWA) during the wintertime that had missing feathers around their beaks, or even gummed up feathers in the same area. It turned out that there was a eucalyptus grove near the banding station, and the warblers could be seen drinking the sap from the tree's flowers. Their bills weren't designed for that and they got sticky residue all around their bill. Hummingbirds did the same thing and didn't have that problem.

Ann Graham 


On Sat, Dec 12, 2020 at 9:30 AM, Bill Bousman
<barlowi@...> wrote:



ireddy@...
 

Thank you Ann for sharing your experience with this. Very helpful. Isabelle


ireddy@...
 

Thank you Bill for your very interesting answer. Isabelle