A population of birds lives on a small island. Another population of the same species lives on the mainland. The distance between the island and the mainland is too great for birds to fly back and forth. Recently, a series of
sandbars and tiny islands have formed between the island and the mainland.

The birds can now reach the Island.

Explanation:

The birds can now reach the Island because there is a sandbars and tiny Islands where they can rest for sometime as well as feed on the insects present at that sandbars and tiny Islands. Before these sandbars and tiny islands, the birds can't reach to the mainland due to large distance between Island and mainland so they have no capability to fly such large distance until the tiny Island and sandbars are appeared in the ocean.