Лучше синица в руках, чем журавль в небе (lúchshe sinítsa v rukákh, chem zhurávl’ v nébe).

Literally: a tomtit in the hands is better than a crane in the sky.

English equivalents:

• a bird in the hand is worth two in the bush;
•  better a dove on the plate than a woodgrouse in the mating place;
•  better an egg today than a hen tomorrow;
• one today is worth two tomorrow;
•  better one small fish than an empty dish;
•  a living dog is better than a dead lion;
• an ounce of (good) fortune is worth a pound of forecast;
• a pound in the purse is worth two in the book;
•  half a loaf is better than no bread;
•  never quit certainty for hope.

P.S. Ivan Tsarevich (Иван-Царевич) & Zhar-Ptitsa (Жар-птица, literally: Heatbird, i.e. Firebird) are Russian folklore creatures – a hero and a magic bird. Thus, of course a tomtit in the hands is better than a crane in the sky but having a Firebird’s feather beats all…