Why are cloudd and bird using so much CPU on my Mac?

What cloudd and bird are

Both are macOS system daemons with Apple manual pages (type man bird or man cloudd in Terminal):

• bird is one of the system daemons backing Documents in the Cloud: the files in iCloud Drive, including Desktop and Documents when you store them there. Apple’s brctl tool, which manages it, calls it the CloudDocs daemon.
• cloudd is the system daemon backing CloudKit. Apple’s developer documentation describes CloudKit as the way apps move data between themselves and iCloud, so you can reach the same data on several devices. So cloudd can be busy for an app syncing its own data, not only for files.

Both pages say they have no configuration options and that users shouldn’t run them manually. They start when there’s something to sync.

The one-minute check

1. Open a Finder window and look at iCloud Drive in the sidebar. Apple says a pie chart next to it shows the overall progress of files moving to and from iCloud Drive, and a storage-full icon means your iCloud storage is full. Hold the pointer over iCloud Drive and click the status icon for details.
2. Click iCloud Drive, choose View, as List, then View, Show View Options, and select iCloud Status. Each item shows its state: Waiting to Upload, a pie chart for a file in transfer, In iCloud for files not downloaded, and no icon once it’s downloaded.
3. In Activity Monitor (Applications, Utilities), click Network and sort by Sent Bytes or Rcvd Bytes. bird or cloudd near the top confirms iCloud is moving data.

Common causes, and what to do

You turned on Desktop & Documents Folders

Apple says that when you turn this on, all the files in your Desktop and Documents folders move to iCloud, and new files there are stored in iCloud automatically. Everything in those folders uploads at once, so the first sync is the big one. Apple says how long it takes to reach your other devices depends on your internet speed.

What to do: let it finish with the Mac awake and online; the pie chart in the sidebar fills as it goes. If another cloud service also syncs those folders, Apple says to turn that feature off first, since the two can interfere.

A new Mac, or Sync this Mac just turned on

Turning on Sync this Mac brings in what’s already in iCloud Drive: Apple says the full contents of iCloud Drive stay on the Mac when space isn’t needed. Apps that sync through CloudKit catch up at the same time.

What to do: the same: awake, online, and plugged in if it’s a laptop. It’s a one-time cost.

Optimize Mac Storage downloading and removing files

With Optimize Mac Storage on, Apple says older documents are stored only in iCloud when space is needed, and the full contents of iCloud Drive stay on the Mac when it isn’t. Files marked In iCloud have to download before you can use them offline (Control-click, Download Now), and the fuller the disk, the more gets moved to iCloud.

What to do: for files you open often, Control-click and choose Keep Downloaded; Apple says those stay on the Mac no matter what. Free some disk space so macOS isn’t constantly making room; see Why is my Mac storage full?

Big files, or files that change all the time

Copying a large folder into iCloud Drive means uploading all of it. Every saved change to a file in iCloud Drive has to be uploaded too, so a folder an app rewrites constantly, like a code project’s build output or a virtual machine disk in Documents, keeps bird busy.

What to do: keep folders like that outside Desktop, Documents and iCloud Drive, for example in your home folder.

Uploads stuck at Waiting to Upload

Apple’s status list explains the usual reasons: Out of Space means iCloud doesn’t have room, and Ineligible means the item couldn’t be stored, usually because it’s over the 50 GB per-item limit. If iCloud is full, Apple says documents stay on the Mac and upload once space is available. Check your plan in System Settings, your name, iCloud.

What not to do

• Don’t force quit bird or cloudd. They’re system daemons; quitting one interrupts the transfer, and the files still need to sync.
• Don’t turn off Desktop & Documents Folders to stop the sync. Apple says your files stay in iCloud Drive and new, empty Desktop and Documents folders are created on the Mac, so your files seem to vanish from where you left them.
• Don’t delete files from iCloud Drive to free Mac space. Deleting there deletes the file on all your devices. Use Remove Download instead, which keeps it in iCloud.

Keep an eye on it from the menu bar

The Finder sidebar shows sync progress when you look. Multimeter keeps the totals in the menu bar all the time:

• Network speed: total upload or download per second across Wi-Fi and Ethernet, one direction per meter. A steady upload that holds for an hour after you turn on Desktop & Documents is the sync at work; when it drops back to near zero, it’s done.
• CPU: total use across all cores, every 3 seconds on power and about every 6 on battery. Yellow above 70%, red above 90% by default.
• Disk space: how full the startup disk is, which decides how often Optimize Mac Storage has to make room.

Multimeter shows totals for the whole Mac, not per process, so it can’t say the traffic is iCloud; Activity Monitor’s Network tab does that. Five live meters use about 3% CPU, and they pause while the displays sleep.