I can tell that the author loves the beach. The author wants to relax in a quiet environment and just escape from the outside world.
I hope this helps you, as I also hope that you add on to this answer as I don't want to do your whole homework.
To write a good thesis statement you have to know what you are looking for. First your question, answer, then your evidence.
Answer:
Even wise people make foolish decisions.
Explanation:
The wisest of people mess up. That's what makes them wise, the times they mess up, they learn from it.
Answer: I thiiiiiinnnk the answer would be the first quote: “They are Nature’s watchmen,— links which connect the days of animated life.”
Explanation: The reason I think this is because we are talking about how he feels about the “natural world.” My guess came from the fact that he views the animals as “Nature’s watchmen,” and feels that they are the “links which connect the days of animated life.”
I deeply apologize if this is incorrect. Good luck!