What is bird on my Mac, and why is it so busy?

Part of macOS · let it sync

bird is the part of macOS that syncs iCloud Drive. It's busy while files upload or download: after you add a lot to iCloud Drive, turn on Desktop & Documents syncing, or set up a new Mac. With Optimize Mac Storage on, it also downloads files when you open them. It works with cloudd, which handles iCloud in general.

Why bird gets busy

bird works hardest when a lot changes in iCloud Drive:

Large uploads: new folders, photos and videos saved into iCloud Drive.
Desktop & Documents syncing, which puts everything in those folders into iCloud.
Folders that never stop changing. Code projects, node_modules, build output and virtual machines inside Desktop or Documents change constantly, so iCloud is always syncing them.

How to check what it's doing

In Finder, iCloud Drive in the sidebar shows a progress circle while it syncs.
In Activity Monitor, bird and cloudd use network and disk while syncing.

What to do

Let it finish with the Mac awake and online.
Keep code projects, virtual machines and other constantly changing folders out of Desktop, Documents and iCloud Drive; a folder like ~/Developer isn't synced.
If syncing seems stuck for days, restart. As a last resort, sign out of iCloud and back in, which re-syncs everything.

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