20 May 2023. Emily Renzel Wetlands, Palo Alto, CA, USA.

This appears to be an extreme example of the northwestern subspecies "N. a.
hyperboria" with a reddish cocoa color rather than the dark chocolate of
those from eastern North America (N. a. lintnerii) or the almost black of
examples from Eurasia (N. a. antiopa). However the validity of these
subspecies remains uncertain. In England where this species is a migrant,
it is commonly known by the name "Camberwell Beauty."

Reference:

https://leplog.wordpress.com/2014/03/17/mourning-cloak-variation/

Stay well!

--
Joseph Morlan, Pacifica, CA
"It turns out we're very good at not seeing things" - Jack Hitt