redundent index?

I just noticed on one of my tables I have the following two indexes:

Indexes: entity_watch_map_pkey primary key btree (entity_id, watch_id),
         ewm_entity_id btree (entity_id),


I can't think of why the second index is there, as ISTM there is no
instance where the first index wouldn't be used in place of the second
one if i were to delete the second one. its a heavily updated table, so
axing the second one would be a bonus for performance, am i missing
something? Thanks in advance, 


Robert Treat
-- 
Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL