Bird nest

I spotted a bird nest today, right beside a trail on my daily jogging route!

From the second photo, you can see it's on open ground and very close to the trail, where runners and bikers pass by, and sometimes even cars (luckily very few). I'm really worried that this nest would be easily destroyed, either by people, or by squirrels! I placed some larger rocks around the nest, hope it will do some protection, or at least let others notice it!

When I was there, the nest owner was around me all the time, singing angrily. I really don't know which kind of bird it is.

So interesting...