As a writer, especially of an autobiography, you have to decide what is important enough to include in your autobiography.
You don’t want to write about every single thing you remember from your childhood. You have to choose the ones that matter the most? Which ones are the most interesting? Which ones do you think would impact the audience most?
With something like ” the ant or the loons,” you have to think, which one will people see less often? People can go to a pond and see a loon. They are interesting birds but maybe not as interesting to some people is getting to see ants fight. Both descriptions are fairly interesting ( long winded) but interesting. And both are interesting creatures but if I were the writer I would have cut back on the loons. But then I would cut back on a lot of things.
I think that you have to be very selective when writing an autobiography.The main reason is that when you’re writing an autobiography you’ve lived life for years, and if you include everything you remember from every year it would be a very long book. Thoreau was only writing on 26 month and it’s a long book.
So, my advice, be selective.