This is probably because of NULL values in your database. When you concatenate any string with a NULL value, it will result in NULL. To avoid this, you can use the COALESCE function. The COALESCE function returns the first non-Null value.
So instead of:
SELECT CONCAT(SPNO, ' - ', CommonName) AS BirdName, SPNO FROM aou_list ORDER BY CommonName ASC
Try:
SELECT CONCAT(Coalesce(SPNO,''), ' - ', Coalesce(CommonName,'')) AS BirdName, SPNO FROM aou_list ORDER BY CommonName ASC