What are goldfinches doing on tree branches?

At this time of year I often see Goldfinches appearing to feed high on tree branches, often sycamores. It is hard to see what exactly they are doing, but definitely there are no seeds involved, it looks like they are pecking the bark or possibly lichens. I checked and they were not holding seeds under their feet (as they often do) or wiping their bills clean. They appear to peck the surface of the branch. I managed to photograph one that appears to lift and hold a bit of bark with lichen on top (top shot).

I am very curious to know what they are doing. During the breeding season Goldfinches use lichen to camouflage their nests, I only see this behaviour during winter. Has anyone seen this? Please comment! Some more photos of the behaviour follow.

3/12/2017.

25/01/2018

25/01/2018. This individual stayed pecking the end of this branch for quite a while.

16/11/2016

UPDATE 11/1/20
I found out a chorusing Goldfinch flock in a local park today. Several of them were feeding on branches in two lime trees. I managed a couple of videos showing how they target areas at the end of broken branches and deftly peel bark and wood, discarding bits. If they are feeding on the bark or wood itself or on some invertebrates living in it is unclear.

A flock of Goosanders

I went to a local park today for a walk and found a flock of Goosanders in the lake. It is a fishing lake, frequented by anglers in the summer, but it was quiet today, and the Goosanders, had the fish to themselves. Goosanders are hard to count when they are fishing, as they are constantly diving -often one after the other- but I managed to count nine males and six females. I stayed away from the shore, half hidden on a tree trunk, as these ducks are wary of people. Soon after I started watching them, a male caught a large fish, another goosander followed it, interested, but the first one managed to keep it and swallow it.

Drake Goosander with fish.

 The Goosanders kept in a tight flock, when the fishing session was over they spent some time preening and flapping their wings and doing some exaggerated head shaking, which might also be related to courtship as the movement helps show their showy hairdos.

 

 

The fishing lake.

Shaking head looking straight up.

Drake Goosander.

The same drake. The photo shows the neck striations that form a 'bun' at the back of their head. 

Then a female went to the shore for a rest and a preen and one by one, several of the others followed her there, jumping awkwardly onto the edge. Their legs shone bright orange like Mallard's.

A lucky front shot of a male Mute Swan on a local park. He was with his polish variety partner, and ringed and approached me as I walked around the lake.