How many Red Breasted Nuthatch coins created before 2007 were minted, on average?
CREATE TABLE "canadian_wildlife_series" (
  "year" real,
  "animal" text,
  "artist" text,
  "finish" text,
  "mintage" real,
  "issue_price" text
);
SELECT AVG("mintage") FROM "canadian_wildlife_series" WHERE "animal"='red breasted nuthatch' AND "year"<2007;