Arctic Terns in flight. The Arctic Tern has the longest known migration route of any animal - 23,000 miles. Mendenhall Lake, Juneau, Alaska.

All animals featured on Nature In Depth are wild. They have not been baited, captured, or threatened in any way. Additionally, the images have not been digitally altered except to optimize the presentation of what was actually photographed. Please practice respectful techniques when photographing animals and clearly label all composite or digitally altered images as such. Let's keep photography noble!