Birds--General/Fever in Birds.
Can we check and measure the Body Temperature in Birds with a thermometer device?.
I would highly advise against using a thermometer to measure a bird's temperature. It has to be taken via the cloaca and there is too great a risk of rupturing the cloacal sac. Most veterinarians would not even attempt it. Instead, there are other reliable indicators of health that you can use, and don`t carry the risk.
Different species of birds have different body temperature ranges (the normal range is from 104°- 108°F). If you're trying to just get an idea of the bird's temperature, you can hold the bird's beak to your lips, or feel their feet. These are the areas where a bird releases heat from, so cold feet = cold bird. Overheating can be judged by symptoms displayed by the bird, such as breathing with a wide open beak, or holding wings away from the body.