park

Today when I went down to the park for the second time, it was mostly cloudy with some patches of sun.
When I was out on the breakwater, I saw some sea gulls and ducks.
When I was in the park, I heard a crow or raven in the trees somewhere above the trail.
When I was at the battle site bench, it was low tide and I saw some ravens and sea gulls out on the beach. The ravens were closer than the sea gulls were to me and the sea gulls were basically in one small group.
When I was on the side trail near the trail by the river, I saw two male Northern shovelers and some ducks, wigeons, and sea gulls out on the water.
I also saw some crows and one raven on the beach and most of the crows flew off.
Near the beginning of the trail by the river, I saw that there were some bones on the trail, I guessed they were spine bones.
When I was on the trail by the river, I saw a thrush fly up and land on a low tree branch on the river side of the trail I was on.
When I was nearing the foot bridge, I saw that the trail camera was still in the tree.
Why were the bones on the trail?
Why were there two shovelers out on the water?
How did the bones get there?