One of the most difficult birds to photograph in Iceland is the Gyrfalcon. Only 1000 of them exist in Iceland and one needs a permit from the government to photograph them. This is done for protection and minimizing the disturbance during the most vulnerable time of the year.
I use a dome tent when photographing gyrfalcons at a nest. Despite being inside a tent it is evident that the gyrfalcon always knows that I am in the tent. The slightest whisper or a sound makes him aware and even the minimal movement of the lenses make him aware of your presence. It is therefore necessary to have patience to wait for it to calm down and get used to the tent. Preferably start by having the tent few hundred meters away from the tent and then in few days time, move it closer. If the surroundings limit the possibilities to have a tent and it needs to be rather close from the beginning it is a must to remove it if the gyrfalcon does not accept the tents presence in two hours or so.
The tent I have been using is from WildlifeWatchingSupplies in the UK. Rather expensive tents and gear they have, but you get what you pay for.