The N American cowbird originally followed herds of buffalo and later cows, seeking worms and grubs from freshly disturbed soil. Opossums, however, aren't native animals in California. Best evidence shows they were introduced by a farmer in the 1870's who was nostalgic for his home in Missouri. If we decide to purge all non-native animals, we are going to very busy for a very long while. But I agree that it's inappropriate to repost ALL of that discussion in this forum.
Empty wagons make the most noise.