Because it is easier for birds to reach islands than it is for animals that can't fly, bird species diversity on islands is often relatively high. Although the high number is due to migrants, infrequent visitors, and rare species that have arrived on the islands only after being blown off course during spring and summer migrations. Like the island fox, the island scrub-jay has evolved into a unique (endemic) island species. The largest landbird native to the islands is the bald eagle-a species that has recently been reintroduced to the islands.