A Natural Hybridization between a Cattle Egret (Bubulcus ibis) and a Little Egret (Egretta garzetta) in Japan

Abstract

In July 2020, an individual considered to be a hybrid between a Cattle Egret (Bubulcus ibis) and a Little Egret (Egretta garzetta) was found in Hashima City, Gifu Prefecture, Japan. The first impression was that the bird was a Little Egret, but detailed observations revealed Cattle Egret characteristics in size and plumage color. The hybrid individual also had partial melanic characteristics. The present study compared the external morphological characteristics of the apparent Cattle Egret and Little Egret hybrid, using observations and measurements obtained from images. The results showed that the tarsus length, the bill length, and the observed ratio of the bill length to the bill depth at the front end of the nostril of the hybrid were intermediate between those of Cattle Egret and Little Egret. There are few accounts of inter-generic hybridization among herons and egrets in nature, with only one report from Japan. This is the first record of hybridization between a Cattle Egret and a Little Egret in nature to our knowledge.