Common Tern populations have declined greatly over the past few decades mainly due to habitat loss, human and natural factors such as predation and an increase in the ring-billed gull population. Efforts have been made to increase the tern breeding population locally, including building suitable nesting sites away from predators such as mink and raccoons. Dr. John Hartig discusses the matter in his latest instalment of Great Lakes Moment: Detroit River common terns under threat.