"Peanuts" ran for a very long time - 50 years, nearly 18 000 strips..
Some themes and jokes continue across many strips.
One of the birds ("Woodstock") was a long-running character, profiled as being good-hearted.
IIRC the birds were always rather friendly and helpful.
At a guess:
* It's a multi-strip humorous situation
* Across multiple strips, Charlie Brown is making snowmen, and something is affecting the snowmen (maybe other kids destroying them)
* The birds are guarding the snowman as an unrequested service/favour to Snoopy and/or Charlie Brown
Note: even the snowman is a "standard 'Peanuts' snowman",
The black eyes and buttons are traditionally small pieces of coal (probably not now, but Peanuts started in 1950).
Old, long-running comics often assume readers understand the underlying "framing".
If you want to fully understand and enjoy "Peanuts" you'll need to read a lot of them in the correct sequence.
Or read something - there must be a lot of material about "Peanuts".
@Slime_Punk
Purely by coincidence, I saw a reference to a site called "Garfield without Garfield" some time in the last day or two.
Your example probably originated there.