Oriental pied hornbills found to have object permanence levels comparable to apes

A pair of animal behaviorists at the National University of Singapore, has found, via testing, that Oriental pied hornbills have object permanence levels comparable to apes. In their paper published in the journal Biology Letters, Ruitong Yao and Elias Garcia-Pelegrin, describe how they tested object permanence levels in several captive Oriental pied hornbills.