Hi Betty. He may be stressed for some reason whether it is heat or something else. Does the panting or drooling occur at a specific time such as in the heat of the day or early morning etc. If he pants during the hottest part of the day then it could be heat related. If early morning the drooling could be from eating something toxic etc. Having said this toxic substances or infections can happen at any time. We are just using the time of day as a possible reference to get more information. We would strongly suggest that if the behavior continues or you think something is not right that you get the swan to an avian bird vet with swan or waterfowl experience. Take blood to check for infection and blood chemistry and body temperature. We hope this helps. The Regal Swan