Difference between "safe" and "secure"

1. The birds' nests are high up, safe/secure from predators.
2. These elephants are relatively secure/safe from poachers.
3. Make sure you keep these documents safe/secure.
4. Keep your credit cards in a safe/secure place.
5. I always feel safe/secure when I'm around my big dog.

What's the difference between safe and secure in these examples?

Solution 1:

I found this usage note:

Safe and secure, now nearly synonymous, used to be more different; secure was subjective —- man's own sense of the absence of danger —- while safe was objective, the fact of such absence of danger.

I think in your examples, you could pretty much use either word. However, I personally would choose the following, based on the fact that humans didn't do anything to do the securing in Sentences 1, 2, and possibly 5, but they would take steps to make the documents and credit cards safe from loss (secure) in Sentences 3 and 4:

1. The birds' nests are high up, safe from predators.

2. These elephants are relatively safe from poachers.

3. Make sure you keep these documents secure.

4. Keep your credit cards in a secure place.

5. I always feel safe when I'm around my big dog. (If you bought the big dog to make yourself feel secure, then I could also see using secure in this sentence.)