Although it's a bit alarming to see at first, this cardinal should be just fine. Sometimes cardinals just lose their head feathers all at the same time.

0:00 Whitethroated sparrow
0:27 Northern cardinal
0:50 Northern cardinal
1:08 American goldfinch
1:17 Northern cardinals
1:35 American goldfinches
1:43 House finch
1:52 Northern cardinal
2:10 Northern cardinal, American goldfinch
2:40 Whitethroated sparrow
2:59 Northern cardinal