Wild Facts About The Black-Crowned Night Heron

With Family Like This, Who Needs Enemies?

• The behavior of wild animals who inhabit our natural world rarely conforms to human ideas of morality, compassion, and love of family.
• Many species engage in behaviors that humans find off-putting and mean.
  • But judging other creatures by our own standards is foolish and damages our appreciation of the natural world.
• Black-Crowned Night Herons engage in two behaviors that naturally repulse humans; filial cannibalism and sibling aggression.

Filial Cannibalism

• Filial cannibalism involves parent animals eating their own offspring.
  • This behavior can be either direct (the parent actually kills its young) or indirect (the offspring die of other causes and the parent simply eats their body).
  • Filial cannibalism in birds seems to be somewhat rare.
    • But during observations of Black-Crowned Night Herons on Alcatraz Island in San Fransisco Bay, scientists observed four instances of parent birds consuming their dead young (Brussee et al. 2017, https://doi.org/10.1676/16-013.1).

Sibling Aggression

• Sibling aggression in Black-Crowned Night Herons has been observed in nestlings and can involve:
  • Fighting: A series of blows exchanged between chicks in which one chick strikes another forcefully with its beak,
  • Shoving: One chick grasps another’s bill tightly and shoves its head back and forth several times,
  • Head-swallowing: One chick swallows another chick’s head and neck to the point of wing-attachment and holds the victim for a prolonged time.

Head-Swallowing

• During a study completed in Minnesota, researchers observed three fights and two occasions of head-swallowing in a single nest, all of which occurred during feeding.
  • During the first head-swallow, a senior chick swallowed the head of the youngest chick for a total of 2.25 minutes. During this time, the senior chick shook the young chick until it was motionless. Then the senior chick released the young chick, who subsequently recovered.
  • During the second head-swallow, a senior chick swallowed a younger chick’s head for about 3 minutes (Medeiros, Emond, and Ploger 2000, https://doi.org/10.1093/condor/102.2.438