The Eastern Cattle Egret, 𝘉𝘶𝘣𝘶𝘭𝘤𝘶𝘴 𝘤𝘰𝘳𝘰𝘮𝘢𝘯𝘥𝘶𝘴 (Boddaert., 1783) is a small, terrestrial, and white heron species with a strong and sharp bill like a dagger that belongs to the Ardeidae family. Adult, they grow to around 46 to 56 cm in length with a wingspan of around 90 cm. Despite their relatively modest size, these birds are able to live for 10 years on average. Although they mainly build their nest near water, their primary food source consists of insects including flies and orthopteran insects such as locusts, crickets, and grasshoppers 🦗🍽; and not of fishes contrary to many other heron species that often rely on those.
Eastern Cattle Egrets are mainly found in tropical and subtropical regions, including South and Southeast Asia with a distribution ranging from the Indian subcontinent to southern China, Japan, and the Northern and Eastern part of Australia and New Zealand, with the species colonizing these latter two territories in the first part of the 19th century. In Hong Kong, the Eastern Cattle Egret lives mainly in farmland, wetlands, mudflats, and around fish ponds in a gregarious way, meaning living in flocks. Large numbers of them sometimes appear on freshwater marshes’ banks during their migration period in spring and autumn in search of food and nesting spots.
Do you know birds can change their color❓ During the breeding season from March to August, the plumages of the Eastern Cattle Egrets will change from white to bright orange all over their body including their head, neck, and back while the bills become reddish with a yellow tip, legs become reddish or orange, and the lore becomes purplish. It looks like they are preparing for a show, not for themselves but for their mates 👩❤️👨. The change of the bright color helps the males 🚹 to attract females 🚺 in the breeding season. This breeding performance only happens once every year and after this mating display, the pairs will stay together throughout the breeding season. However, as being serially monogamous, their relationships would not last long. The following year, they will find another partner for the performance - thus breeding pairs mate and divorce each year.
Eastern Cattle Egrets prefer breeding in colonies, usually in trees, swamps, or on islands. During the nesting process, the pair will divide their labor to prepare a cozy nest for their newborn to maximize efficiency. Males 🚹 will search for suitable materials nearby while females 🚺 will use those materials to construct a nice bed with sticks and leaves 🛌. After their young are born, parents will search for food and feed their young by regurgitating partially digested food for easier digestion, which means bringing partially digested food out of the stomach to feed on the babies 🐣.
In Hong Kong, we often see Eastern Cattle Egrets nesting around freshwater banks, farmland, and wetlands as it is easier for them to find materials for building the nests. Moreover, they can live near their neighbors: cattle, and buffaloes 🐮. Sometimes, they will even stand on their back, and that's where its common name ‘Eastern Cattle Egret’ comes from! You may wonder why Eastern Cattle Egrets would tend to feed near bovids, in fact, the mutualistic relationship between the egrets and bovids provides benefits to both partners 🤝. When the bovids move on the mudflats or wetlands, they would disturb the soil and stir up the insects underground, allowing the Eastern Cattle Egrets to have easier access to these insects as a food source, saving more energy compared to feeding alone 🤩.
Additionally, they would even gain protection and enjoy their meal without the threat of being predated or disturbed when riding on the bulky cattle or buffaloes 💯. That's why Eastern Cattle Egrets would prefer staying close to bovids. But what’s the benefit for the mammals then❓ Traveling around muddy areas will attract a number of parasitic arthropods such as ticks and fleas transferring infectious diseases to the bovids. Through their service, the Eastern Cattle Egrets standing on the bovid’s back will pick up the parasites and thus reduce the chance of developing infections. For the Eastern Cattle Egrets, these “parasitic bugs” are, however, more like a bug buffet 🦗🍽🍽👅.
Here at Hong Kong Biodiversity Museum, we have a nice Eastern Cattle Egret specimen welcoming our visitors with its spreading wings 👍🏻.
Text︰Alan Tsoi
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