What is normal prey for the gyrfalcon?

The gyrfalcon is known for its preference for larger birds and mammals as prey, and option A provides a list that aligns well with its typical diet. The mention of ptarmigan, pheasant, waterfowl, and grouse reflects the habitats and food sources available to the gyrfalcon, particularly in its arctic and subarctic environments where these birds are abundant.

Ptarmigan are especially notable, as they are a primary food source for gyrfalcons in the tundra regions due to their availability and the falcon's hunting adaptations. Waterfowl and grouse also play an important role in the diet of gyrfalcons, as they are often found in similar hunting grounds where gyrfalcons can effectively employ their hunting skills.

The other options include prey items that either do not accurately fit within the typical diet of gyrfalcons or consist of smaller animals that are not usually targeted by this powerful raptor. This is why option A is the most representative of the normal prey for the gyrfalcon.