This is the 7379th most frequent Russian word.
говорят
"(They) say" or "(People) say."
In this sentence, 'говорят' is used impersonally to mean 'they say', referring to general hearsay or an unspecified group of people conveying information.
Говорят, что завтра будет дождь.
They say that tomorrow it will rain.
Here, 'говорят' is used in a direct context to refer to the teachers specifically, stating their opinion.
Мои учителя говорят, что я хорошо усваиваю материал.
My teachers say that I grasp the material well.
In this example, 'говорят' figuratively describes how birds communicate, attributing 'speaking' as a conceptual metaphor to non-human subjects.