After reading the text, it became clear that during migrations, birds can face the following dangers:

Solution:

Let's analyze the potential dangers listed for migrating birds:

A) birds can forget the way to the wintering grounds

B) being tired, they can fall into the jaws of predators during rest

C) they can lose the metal rings

D) in fog, birds can collide with an obstacle and crash

Based on general knowledge of bird migration:

• A is a possible danger, though 'forgetting' might be anthropomorphic; disorientation is more accurate.
• B is a very real danger; tired birds are vulnerable.
• C is a consequence of migration, but not a danger *to* the bird's survival in the same way as A, B, or D.
• D is a significant danger, especially for large flocks or during adverse weather.

The question asks what dangers *can* await them. Options A, B, and D are all plausible dangers. However, typical questions of this type often focus on direct threats to survival. Let's assume the question refers to immediate threats during the migration itself.

Considering the options for the correct answer:

• 1) AB
• 2) ВГ
• 3) БГ
• 4) AB

Option 1 (AB): 'A' and 'B' are plausible dangers.

Option 2 (ВГ): 'C' is unlikely to be considered a primary danger to the bird itself. 'D' is a danger.

Option 3 (БГ): 'B' and 'D' are both significant dangers during migration.

Option 4 (AB): This seems to be a repeat of option 1.

Given that B and D are direct threats to survival during migration, option 3 (БГ) is the most fitting.

Answer: 3) БГ