Skyrlings are a zerg breed created during after the End War by Abathur as a smaller offshoot of the mutalisk. They were designed as part of Overqueen Zagara's efforts to create adostra, capable of regrowing destroyed worlds, and were designed to carry the adostra from place to place.
Skyrlings possess a form similar to mutalisks, but are much smaller, with a larger grasping claws and wider wings. They were designed to transport the adostra when they were fully grown.
During the One-Day War, skyrlings were used to clear out the smoke from the last adostra nest, allowing the terran and protoss team defending the nest the clean air they needed to care for their wounded.