The Swallow: In addition to indicating that a sailor had sailed 5000 miles, swallows are also associated with the idea of return. This "return" symbolism is rooted in two ideas. The first was the swallow's famous migration pattern, always returning home to San Juan Capistrano. Second, it was believed that if a sailor dies at sea, birds carry his soul home to heaven.
Tree Swallow - Audubon. The popularity of the bluebird has been a boon to the Tree Swallow, which has taken advantage of bluebird houses over much of North America. In regions with no such ready supply of artificial nest sites, the swallows must compete with other cavity-nesting birds. Unlike other swallows, Tree Swallows eat many berries (especially bayberries), allowing them to survive through wintry spells when other insect-eaters might starve.