The Black-crowned Night Heron is a medium-sized heron with a truly global presence. In Taiwan, it is one of the most recognizable waterbirds, known for its distinct silhouette and stoic patience.
Adults: Males and females are similar in appearance, both featuring a striking red iris. They have a bluish-black crown and back, while their wing coverts are a pale grayish-brown, and the rest of the body is a soft grayish-white. A key identifying feature is the 2-3 slender white ornamental feathers extending from the back of the head, along with a short white stripe (supercilium) that connects to the forehead.
Juveniles: Younger birds look entirely different. They have yellow or orange-yellow irises and brown bodies covered in white spots, with dense dark-brown longitudinal stripes on their undersides for camouflage.
While migratory in the northernmost parts of their range, they are year-round residents in many areas, including Taiwan. They are highly social and often spend their days perched on tree limbs or concealed within dense foliage. Because they primarily forage at dusk and during the night, they have earned the common nickname "dark-light bird". They are versatile hunters, foraging in water, on mudflats, and occasionally on land.
These birds are highly opportunistic predators, feeding mainly on fish, shrimp, and insects. Most impressively, they are one of only seven heron species known to engage in bait fishing. They will toss buoyant objects—either food or non-food items—into the water to lure fish into striking range. This clever behavior is a rare and remarkable example of tool use in the avian world.
夜鷺是一種體型中等的鷺類，分佈遍及全球。在台灣，它是最容易辨認的水鳥之一，以其獨特的輪廓和沈穩的耐心而聞名。
成鳥：䧳雄同型，虹膜紅色。頭頂及背藍黑、翼覆羽淡灰棕色，其餘部位為灰白色，頭後有 2-3 根細長白色飾羽，白色短眉紋於額前相連。
幼鳥：幼鳥的外型與成鳥截然不同。體上褐色、滿布白色點斑，體下密布暗褐色縱紋，起到偽裝作用。
雖然在其分佈範圍的最北端是候鳥，但在包括台灣在內的許多地區，它們是常年留鳥。它們具有很強的群居性，常常白天棲息在樹枝上或藏身於茂密的樹葉中。由於它們主要在黃昏和夜間覓食，因此也被稱為「暗光鳥」。它們是適應性很強的獵手，會在水中、泥灘上，偶爾也會在陸地上覓食。
它們是機會主義捕食者，主要以魚類、蝦類和昆蟲為食。最令人印象深刻的是，它們是已知僅有的七種會使用餌料捕魚的鷺類之一。它們會將漂浮物——無論是食物還是其他物品——拋入水中，引誘魚類進入攻擊範圍。這種巧妙的行為是鳥類世界中罕見而卓越的工具使用案例。
Photo Date: 2019.06.13 Location: Highland Springs Ranch & Inn, Cherry Valley
Notes 筆記
- The black-crowned night heron or black-capped night heron, commonly shortened to just night heron in Eurasia, is a medium-sized heron found throughout a large part of the world, except in the coldest regions and Australasia.
- Adults have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs.
- The male Black-crowned Night Heron chooses a nest site in a tree or in cattails. They are very noisy birds in their nesting colonies. They nest in groups that often include other species, including herons, egrets, and ibises. They will brood any chick that is placed in its nest. The herons apparently don’t distinguish between their own offspring and nestlings from other parents.
- The breeding habitat is fresh and salt-water wetlands throughout much of the world.
- This heron is migratory in the northernmost part of its range, but otherwise resident (even in the cold Patagonia). The North American population winters in Mexico, the southern United States, Central America, and the West Indies, and the Old World birds winter in tropical Africa and southern Asia.
- They often spend their days perched on tree limbs or concealed among foliage and branches. They forage in the evening and at night, in water, on mudflats, and on land. These birds stand still at the water’s edge and wait to ambush prey, mainly at night or early morning. They primarily eat small fish, crustaceans, frogs, aquatic insects, small mammals, and small birds. They are among the seven heron species observed to engage in bait fishing; luring or distracting fish by tossing edible or inedible buoyant objects into water within their striking range – a rare example of tool use among birds.
- Young Black-crowned Night-Herons leave the nest at the age of 1 month but cannot fly until they are 6 weeks old. They move through the vegetation on foot, joining up in foraging flocks at night.
- 黑頂夜鷺在歐亞大陸通常簡稱為夜鷺，俗稱灰窪子，夜窪子，星雁，暗光鳥仔。夜鷺閩南語稱為“暗光鳥”，客家語稱為“夜鶴”，這個詞也常被代指徹夜未眠的人（同等夜貓子）。除了最冷的地區和大洋洲外，是一種在世界上大部分的地區都可看得到的中型鷺。
- 成年夜鷺有黑色的冠，背部身體其餘部分為白色或灰色，有紅色的眼睛和黃色短腿。
- 雄性夜鷺會在樹上或香蒲上築巢。它們在築巢地非常吵。它們是在集群繁殖，通常與其他物種，如蒼鷺，白鷺和朱鷺一起。它們會孵化在巢中的任何小鷺，蒼鷺並不會區分自己的後代和其他鷺的雛鳥。
- 它們在世界各地的淡水和鹹水濕地繁殖棲息。
- 在北方地區繁殖的夜鷺為候鳥，否則是留鳥（即使在寒冷的巴塔哥尼亞也是如此）。北美的夜鷺去墨西哥，美國南部，中美洲和西印度群島過冬，而舊世界的鳥群則在熱帶非洲和南亞過冬。夜鷺在台灣為常見的留鳥，由於性喜食魚，魚類養殖業者視其為害鳥。曾被誤認為企鵝。在中國大陸全境都能看到它們的身影，在中國東北地區，華北，甘肅，四川，華中，長江流域等省區繁殖，為夏候鳥，在長江以南省份為留鳥。
- 夜鷺白天棲息在樹枝上或藏在枝葉間。 傍晚和晚上在水，泥灘和陸地上覓食。在晚上或清晨，它們會停在水邊，等待伏擊獵物。它們主要吃小魚，甲殼類動物，青蛙，水生昆蟲，小型哺乳動物和小型鳥類。 它們是會用誘餌捕魚的七個鷺類之一，它們將可食或不可食的漂浮物拋入它們可襲擊範圍的水中，來引誘或分散魚的注意力，這是在鳥類裏會使用工具的罕見例子。
- 雛鳥夜鷺在1個月大時離巢，但要等到6周大時才能飛翔。 它們步行穿過植被，在夜間與其它夜鷺一起覓食。
References 參考資料
- Wikipedia: Black-crowned night heron
- All about birds: Black-crowned Night-Heron
- 維基百科: 夜鹭
- 百度百科: 夜鷺 （鷺科夜鷺屬鳥類的一種)
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