It is highly unlikely that a hawk would kill a 7 lb Yorkshire terrier.
Here is why:
Size Disparity: Hawks, even the largest species, are not typically equipped to take down prey that size. Their talons are designed for smaller creatures like rodents, snakes, and birds.
Defensive Capabilities: A Yorkshire terrier, while small, can be feisty and have a strong bite. They would likely put up a fight, making them an undesirable target for a hawk.
Risk vs. Reward: Hawks are intelligent predators. They would likely assess a Yorkshire terrier as too large and potentially dangerous for the effort involved in hunting it.
However, it is important to note:
Individual Behavior: While rare, there could be a scenario where an unusually large or desperate hawk might attempt to attack a small dog.
Vulnerability: A small dog left unattended in a yard with open access to the sky might be more vulnerable to a hawk attack.
It is best to take precautions to ensure your pet's safety:
Keep your dog on a leash when outside.
Supervise your dog when in the yard.
Be aware of potential predators in your area.
If you have any concerns about your dog's safety, consult a veterinarian or animal behaviorist.