What is bird on Mac?

What bird does

bird lives at /System/Library/PrivateFrameworks/iCloudDriveCore.framework/Versions/A/Support/bird and runs as your user. It keeps the files in iCloud Drive in sync with Apple’s servers: uploading what you change, downloading what other devices change, and evicting local copies when Optimize Mac Storage needs space.

On current macOS it works with fileproviderd, the File Provider daemon that also serves Dropbox, OneDrive and Google Drive. Structured app data (Messages, Notes) goes through cloudd instead.

Why it uses CPU

• Desktop & Documents: turning this on moves both folders into iCloud Drive and uploads everything in them.
• Many small files: a code project, a photo export, or an app’s data folder in iCloud Drive. Each file is tracked individually.
• Large files that change: a VM disk or a big database in iCloud Drive re-uploads on every change.
• A stuck item: a file with a name or size iCloud rejects, or one that’s locked, makes bird retry in a loop.
• Low disk space: with Optimize Mac Storage on, bird spends time evicting and re-downloading.

How to make it calm down

See what bird is doing:

brctl status

It lists the items that haven’t finished syncing, per container. A short list that never shrinks points to a stuck item. To watch sync activity live for a minute:

brctl monitor -g -t 60

Then:

1. In Finder, click iCloud Drive in the sidebar. The progress circle at the bottom of the window shows how much is left.
2. Move code projects, VM images and package caches out of iCloud Drive (for example to ~/code).
3. If one item keeps failing, move it out of iCloud Drive, let sync settle, then put it back.
4. Restart the daemons:

killall bird fileproviderd

5. Still stuck: System Settings › [your name] › iCloud › iCloud Drive, turn it off (choose to keep a copy), restart, and turn it back on.

When to worry

Confirm it’s Apple’s:

codesign -dv --verbose=2 /System/Library/PrivateFrameworks/iCloudDriveCore.framework/Versions/A/Support/bird 2>&1 | grep Authority

A file named bird outside that framework is not iCloud. Real bird with high CPU for more than a day or two, and no visible progress in Finder, means a stuck sync. Use brctl status to find the item, and check that your iCloud storage isn’t full.

Seeing it in Stat Space

Stat Space shows disk read and write rates and daily data usage per interface, which tells you whether bird is actually moving data or spinning in place. Its dev space cleanup and large-folder scan help you find what you might move out of iCloud Drive, such as old node_modules folders.