The bulk update request #2803 is pending approval.

create alias black_ears (18557) -> black_ear (66)
create alias blue_ears (11434) -> blue_ear (19)
create alias brown_ears (14799) -> brown_ear (45)
create alias green_ears (3057) -> green_ear (5)
create alias orange_ears (5974) -> orange_ear (19)
create alias pink_ears (6473) -> pink_ear (43)
create alias purple_ears (3989) -> purple_ear (31)
create alias red_ears (3516) -> red_ear (14)
create alias white_ears (13978) -> white_ear (40)
create alias yellow_ears (6597) -> yellow_ear (18)

Reason: Similar to other plural -> singular aliases:
against_walls -> against_wall : alias #35380
air_bubbles -> air_bubble : alias #56146
alchemical_symbols -> alchemical_symbol : alias #31725
alternate_colors -> alternate_color : alias #7381
etc.

Sometimes a character has only one ear visible.

Or for example: character has one pink ear (and 2nd ear of another color),
so wrong to say they have pink_ears (plural).

(existing tag pairs: black_ear and black_ears,
brown_ear and brown_ears,
pink_ear and pink_ears,
purple_ear and purple_ears,
red_ear and red_ears,
tan_ear and tan_ears,
white_ear and white_ears,
yellow_ear and yellow_ears)

(put below in this reply to avoid cluttering up BUR above)

***
First version of script blocked by error message:
"Error: Error: Antecedent name has already been taken (create alias gray_ears -> grey_ear),
Error: Antecedent name has already been taken (create alias beige_ears -> tan_ear)"

so removed some lines from Script:
"alias grey_ears -> grey_ear # duplicate of has blocking transitive relationships, cannot be applied through BUR"
"alias tan_ears -> tan_ear # duplicate of has blocking transitive relationships, cannot be applied through BUR"

2nd version also blocked by same error message,
so removed:
unalias gray_ears -> grey_ears
alias gray_ears -> grey_ear
unalias beige_ears -> tan_ears
alias beige_ears -> tan_ear

***

(I was going to include rainbow_ear* and multicolored_ear* tags in BUR,
but multicolor*/two_tone* issues probably best discussed in topic #24546 OR
similar multicolor*/two_tone*/two-color* forum topic.)

Perhaps these should be reversed. We do tend to prefer singular forms of tags, but there are exceptions, like <color>_eyes and <color>_claws. Ears seems like it would fit as a plural exception (especially since it'd avoid the confusing use of multicolored_ear from each ear being a distinct single color, e.g. a brown left ear and orange right ear).

As Watsit said, things that can pretty much always be expected to come in pairs or groups usually retain the plural form.