During the course of four months' work with oil-damaged sea-birds at the Richmond Bird Rescue Centre in California, I made notes which may help to establish meanings for the following names, which are left doubtful in D'Arcy Wentworth Thompson's Glossary of Greek Birds.Θρφξ. Mentioned only in Dionysius, Ixeuticon ii 14, iii 25, where it is coupled with the κόλυμβος as a bird that sleeps upon the water. Κόλυμβος or κολυμβίς is almost certainly the Little Grebe, being described by Alexander of Myndus (ap. Athen, ix 315d) as ‘smallest of all the water birds’, and θρᾷξ should also be a grebe. As the grebes treated at Richmond recovered their health, there was abundant opportunity to observe the bird's preference for sleeping on the water, and it was in fact accepted as a rule that birds should spend two days and nights continuously on the water in an outdoor artificial pool before being released in the sea. These were Western Grebes (Aechmophorus occidentalis), a species unknown in the eastern hemisphere. For θρᾷξ I would suggest the Great Crested Grebe (Podiceps cristatus cristatus), which is certainly known in Thracian waters—‘nowhere so numerous as in the harbour of Istanbul’ in March. But I would suggest that its name (or nickname—οἱ καλουμένοι θρᾷκες: Dionysius loc. cit.) comes rather from its crest, comparable to that of the fox-skin cap and helmet nowadays called Thracian. In a writer of the Roman Imperial period there may also be some reference to ‘Thracian’ gladiators. Western Grebes are very pugnacious birds, until one has gained their confidence, and Great Crested Grebes may share this characteristic.