These remarkable nesting locations show how birds can adapt to their environment. Although not all birds nest, they all build or look to find a safe place to lay and hatch their eggs. Until recently it was believed that nest building was an inherent skill, but recent studies suggest that birds can learn to improve.

Man-made birdhouses have existed at least since the 15th-16th century. As agriculture and urbanization altered the environment through deforestation, the number of natural nesting cavities decreased. Birdhouses, or creating nesting spots like those shown here, are a solution and response to this problem.

Which one do you think is the most unusual? Vote, or upload your own photos!