Birds

[MrGee]

Why do nuthatches east mainly when upside down ?

[burnhal]

I presume you mean eat rather than east?
They simply eat wherever they find food- they are pretty omnivourous- eating seeds, insects and nuts and the reason you may have seen them upside down is simply that they can!! Unlike tree-creepers which spiral up a tree trunk then fly to the bottom of the next one, nuthatches can go up or headfirst down a trunk with no problem. I wouldnt say they particularly eat more upside down.