park

Today when I went down to the park, it was raining pretty hard and I wore my rain gear so I stayed dry.
When I was out on the breakwater, I saw one duck, some sea gulls flying around and a kingfisher.
When I was in the park, nearing the battle site bench, I walked out on the beach a little ways to look at some shorebirds, there were three Black bellied plovers, I had seen two yesterday. One of the plovers was walking like it had a hurt leg.
I also saw a bunch of sea gulls and some western or least sandpipers, maybe both.
When I was at the battle site bench, it was low tide, and I saw some sea gulls flying around and a few Savannah sparrows and shorebirds by the seaweed.
When I was on a side trail close to the trail by the river, I saw some shorebirds ducks and two eagles. I saw what looked like the Black bellied plovers fly and land on the beach.
When I was on the trail by the river, I saw one eagle flying and one eagle in a shallow part of the river with some ravens by it. It also flew off.
What scared the plovers?
Why were there two plovers yesterday and three today?
Why was the eagle in the shallow part of the river?