Sparrow vs Starling: What are the differences?

Developers describe Sparrow as "A really fast lightweight queue written in Ruby that speaks memcache". Sparrow keeps messages in memory, but persists them to disk, using Sqlite, when the queue is shutdown. On the other hand, Starling is detailed as "A light weight server for reliable distributed message passing". Starling is a powerful but simple messaging server that enables reliable distributed queuing with an absolutely minimal overhead. It speaks the MemCache protocol for maximum cross-platform compatibility. Any language that speaks MemCache can take advantage of Starling's queue facilities.

Sparrow and Starling can be primarily classified as "Message Queue" tools.

Starling is an open source tool with 468 GitHub stars and 63 GitHub forks. Here's a link to Starling's open source repository on GitHub.