“I noticed that in the vast majority of instances, even when perched on different branches, that the Tiger Shrike (Lanius tigrinus) I posted yesterday favours the left foot, keeping the right tucked away (above).
“I at first though it was the usual cold-morning-tucked-away-foot reason. But I managed to get some limited views of the right foot (above, below) that showed it had large swelling of the phalanges (especially the middle phalange). Even the left foot is not spared and shows early signs of swelling. The literature on causes of such swelling is not well organised and after some reading it could be summarised as:
1. Gout due to uric acid collection with underlying renal failure needs to be considered. The bird was sluggish but did not look unhealthy (uraemic).
2. A common cause, especially in caged birds, is mites of the genus Knemidocoptes which cause scaly legs. The lesions did not look like scales but more as bulbous swellings.
3. It could be due to warts. One known agent is the Fringilla papillomavirus. This is a good possibility as it presents as nodules that may engulf the whole leg while the bird looks healthy.
4. Bumblefoot (ulcerative pododermatitis) is the most confusing term used by many sites to describe this condition. In the strict use of the word it refers to bacterial infection with inflammation. But is loosely used to describe all the above conditions including Vitamin A deficiency as a cause of the swellings. Other terms used include: Scaly Leg Mites, Tassle Foot, Depluming Scabies, Constricted Toe Syndrome.
“Hope the bird makes it as perching appears to have become difficult.”
Sources:
Wikipedia: Bumblefoot (infection) LINK.
Beauty of birds: Bumblefoot LINK.
Beauty of birds: Scaly Leg Mites/Tassle Foot/Depluming Scabies LINK.
British Trust for Ornithology: Growths on legs and feet LINK.
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
30th October 2017
Location: Tambun, Ipoh, Perak, Malaysia
Habitat: Secondary growth near limestone hills
Comments by Dr David Wells:
“Poor bird; if shrikes use their feet in prey capture I guess its survival chances are small. Surprising that foot deformations had advanced so far in an individual only a few months old. Based on lack of dark barring on cap, more or less plain primary coverts, quite a bit of black in the face-mask (behind eye), and blue rather than pinkish bill-base I suggest this is actually a winter-plumage adult.
“Thanks for the extra, high res, picture, but my identification of a (fresh) winter-plumage adult stands. Autumn juveniles have a pink bill with black tip; blueness develops when they mature. They also show black barring on the crown (feather tips that wear off progressively), whereas the adult winter crown is more or less plain from the start. Fresh winter ear-covert feathers are pale-tipped in both, but this bird shows more basal black than usual in juveniles. The discovery that adults alternate plumage-types (often completely but not always – see my Vol 2 for more on that) came from recapture of ringed birds.”
