It's difficult for me to identify some of the juvenile (immature) herons due to the color changes that occur as it matures. This is particularly true of the Yellow-crowned Night Heron vs the Black-crowned Night Heron.
Brown immature Yellow-crowned Night Heron's appear very similar to Black-crowned Night-Heron. The Yellow-crowned has longer legs and neck and a thicker bill. Its legs project beyond the tail in flight. Juvenile Yellow-crowned has smaller white spots on wing coverts than Black-crowned.