It's not lost. They use the same nests year after year so it makes sense it's back. If it has a mate it's sitting on eggs right now as they lay them in January and takes bout 30-35 days for them to hatch. Both take turns sitting on the eggs. They are very similar looking with only few characteristics telling a female from male. So in reality people may be seeing 2 different birds but think it's the same one. Alone or not, it's not lost and will leave around the same time it did last year. They are very smart birds but are almost to the point of being endangered.