RESUMEN
Common loons (Gavia immer) are diving waterbirds that are particularly challenging to keep in captivity due to their specific behavioral and physiologic needs, special housing requirements, and susceptibility to stress-related disease. We report a novel method for housing and captive rearing common loon chicks that was developed as part of the first-ever loon translocation effort in southeast Massachusetts, from 2015 to 2017. Thirteen loon chicks were reared in aquatic pens in a natural lake environment, utilizing noninvasive feeding and monitoring techniques that avoided human habituation. Chicks were reared in aquatic pens for 16-28 days before being released onto the lake. All chicks remained clinically normal and were monitored on the lake for up to 4 months following release. At least four of the chicks were subsequently confirmed to have survived to adulthood when they returned to the area in breeding plumage two to 3 years following release. Two of these confirmed adults displayed prolonged territorial pair behavior together, and this is an encouraging early sign that captive-reared individuals may form successful breeding pairs in the future. Because most immature loons remain on the ocean until at least 3 years of age, we expect additional captive-reared loons to return to the release area in subsequent years. These husbandry techniques could be applied to other loon and diving bird species that are notoriously difficult to house in captivity. The novel feeding techniques described here could also be adapted for loon chicks being reared in pools or other traditional captive settings.