Wren hunt for spiders and small insects
Small birds are believed to be suffering because of heavy snow and prolonged deep frosts in the Highlands, RSPB Scotland has said.
The bird charity said few sightings of the wren along with the stonechat and the UK's smallest songbird, goldcrest, have been made since winter started.
Wrens are vulnerable to the cold because of their small size.
They feed on spiders and other insects but a covering of deep snow has made finding prey hard.
RSPB conservation worker Stuart Benn said the robin-sized stonechat and tiny goldcrest have suffered for the same reasons.
The species' small bodies means they lose heat quickly.
According to myth, wren became the king of birds by cheating in a competition to find the bird that could fly the highest.
A wren hid on the back of an eagle and once the raptor tired it flew up into the sky, winning the contest.
Barn owls - which has previously given the RSPB cause for concern - also continue to struggle in the wintry weather, the conservation charity said.
Large numbers of dead owls were recorded by RSPB field workers in the north of Scotland last month.
The charity said it believed severe weather could have led to the birds starving to death.
A dead owl was recently found in Inverness.
Mr Benn said: "We picked up a dead and completely emaciated barn owl a couple of weeks ago from a garden near the Ness Islands.
"Barn owls wouldn't normally come into the town so I think this shows how desperate they must be for food.
"I haven't heard of any since but I suspect this is due to a combination of potential finders not being able to get out and there now probably being very few barn owls still alive that could die - they've taken an absolute hammering this winter."