Pliny the Elder [1st century CE] (Natural History, Book 10, 33.66): The tongue-bird [glottis] takes its name from the very long tongue that it puts out of its beak. At the start the charm of traveling lures this bird to sail on eagerly, but in the course of the flight repentance comes to it, no doubt with the fatigue ; but it does not like to return unaccompanied, and it goes on following, though never for more than one day—at the next resting place it deserts. But day after day the company find another one, left behind in a similar manner the year before. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.56): As Pliny says, the glutis has a long tongue, whence the Greek name [glôtta, tongue] was given to it. At the beginning of its journey, it eagerly embarks on its way, flattering itself with the company of the retreating swallows [yrundinibus] and storks, which are at this time escaping winter, but afterwards it is led to regret because of the effort of flight. But because it is reluctant to continue unaccompanied, it follows the birds with such slowness and for so few days that winter arrives before its journey is finished. - [Badke translation/paraphrase]