It is one of the two largest corvids , alongside the thick-billed raven , and is possibly the heaviest passerine bird ; at maturity , the common raven averages in length and in mass .
It is one of the two largest corvids , alongside the thick-billed raven , and is possibly the heaviest passerine bird ; at maturity , the common raven averages 63 centimetres ( 25 inches ) in length and 1.2 kilograms ( 2.6 pounds ) in mass .