What type is required to capture the RETURNING from an Update?

Within 8.4, If I have an update like the following :

EXECUTE $c$
UPDATE field_seasons dr
SET season_id = ds.season_id, field_id = ds.field_id
FROM data_set ds
WHERE ds.data_set_id = dr.data_set_id
AND ds.season_id = _season_id
RETURNING field_seasons_id
$c$
INTO _id_array;

in a pgsql FUNCTION... What is the type on the variable that can accept
the list of id's?

integer[] doesn't work. It gives back "22P02 array value must start
with "{" or dimension information."

Roxanne