ᴛᴏ ʙᴜʀʏ ᴏɴᴇ’ꜱ ʜᴇᴀᴅ ɪɴ ᴛʜᴇ ꜱᴀɴᴅ is to refuse to take any notice of a difficulty or problem; to pretend that it does not exist, or think it will go away, or solve itself. The expression is based on the habit of the ostrich which is reputed to bury its head in sand when pursued and in danger, in belief that it cannot be seen.
The ostrich, which is the largest flightless bird of Africa, up to 9ft in height, does not, in fact, do any such thing.
Despite their size, and their weight of around 136kg, ostriches are extremely agile. When they sense the approach of predators they bend their necks parallel to the ground to listen intently and if in danger, they are able to escape running away at speeds of up to 40 mph.
They probably give the impression that they bury their heads when they are seen bending their necks, and listening close to the ground, or when attending the eggs in their nests, which consists of a simple depression scraped in the sand.
P.S – so concerned, though being buried is a better choice at times..