【后海灣一分鐘】八、后海灣的繁殖鷺鳥
鷺鳥一起聚集及築巢繁殖的地方通常稱為鷺鳥林，即鷺鳥的繁殖地。香港約有20個鷺鳥林，分別有五種鷺鳥定期聚集繁殖，包括小白鷺、大白鷺、牛背鷺、夜鷺和池鷺。牠們築巢地點分佈非常局限，都具保育價值，除了小白鷺和大白鷺的繁殖地屬「區域關注」之外，其餘三種都屬「本地關注」。而后海灣濕地正正是這些繁殖鷺鳥的重要覓食地之一。
在「后海灣地區魚塘生態價值研究」（1997）中，尖鼻咀、米埔村及河上鄉鷺鳥林均被選中為研究對象，以了解繁殖鷺鳥的飛行路徑和其降落的地點。結果顯示鷺鳥們主要會飛往潮間帶的泥灘、運作中或降水中的魚塘，而傾向避開露天儲存場（統稱棕地）、住宅區和建築地盤。牠們大多在築巢地點兩公里範圍內活動，有些因應附近地勢亦會飛至遠達四公里的地方。為了保育這些繁殖鷺鳥，我們應妥善保護牠們的繁殖地、覓食地以及飛行路線。
根據2018年的調查，后海灣地區的三大鷺鳥林分別位於米埔村、東成里及米埔隴村[1]。這三個鷺鳥林的鳥巢數量合共佔全港總數的三分之一以上。它們更位於「濕地緩衝區」（WBA）內或剛剛在WBA界線之外，使WBA成為繁殖鷺鳥的飛行走廊/路線，讓牠們能前往位於「濕地保護區」（WCA）內的覓食地和濕地。因此，WBA在后海灣的濕地生態系統中具其生態功能和角色，應得到妥善的保護，以免受到任何發展威脅。
[1] Anon, 2018. Summer 2018 Report: Egretry Counts in Hong Kong with particular reference to the Mai Po Inner Deep Bay Ramsar Site. Report by The Hong Kong Bird Watching Society to the Agriculture, Fisheries and Conservation Department, Hong Kong Special Administrative Region Government.
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【Deep Bay in a Minute】8. Breeding egrets and herons in the Deep Bay area
Herons and egrets nest together in colonies called egretries (which is also known as nesting colonies). In Hong Kong five species breed regularly in some 20 colonies, they are Little Egret, Great Egret, Eastern Cattle Egret, Black-crowned Night Heron, and Chinese Pond Heron. The restrictedness of the nesting sites of these species are of Local Concern, except for Little Egret and Great Egret which are of Regional Concern. Deep Bay wetlands is one of the important foraging grounds to these breeding egrets and herons.
In the “Study on the Ecological Value of Fishponds in the Deep Bay Area (1997)”, Tsim Bei Tsui egretry, Mai Po Village egretry and Ho Sheung Heung egretry were selected to study the flight paths of the breeding birds from the egretry and the corresponding landing location. Results showed the birds mainly fly to the inter-tidal mudflats, operating fishponds and drained fishponds, while they tend to avoid places used for open storage (commonly known as brownfields), residential areas and construction sites. Most birds flew less than 2km from their nests, but some can reach a distance as far as 4km due to the surrounding topography of the egretry. In order to safeguard these breeding egrets and herons, the nesting locations together with feeding grounds and flight paths of the birds should all be protected.
In 2018, the three largest egretries in the Deep Bay area were Mai Po Village egretry, Tung Shing Lane egretry and Mai Po Lung Village[1]. The sum of the nests in these three egretries accounts for over one-third of the total number of nests in Hong Kong. These nest locations are within the Wetland Buffer Area (WBA) or just immediately outside the WBA. Besides, WBA serves as a flight path/corridor such that the breeding egrets and herons can access their foraging grounds and wetlands in the Wetland Conservation Area (WCA). Therefore, WBA has its ecological function and role to play in the Deep Bay wetland ecosystem, and should be adequately protected from development threats.
[1] Anon, 2018. Summer 2018 Report: Egretry Counts in Hong Kong with particular reference to the Mai Po Inner Deep Bay Ramsar Site. Report by The Hong Kong Bird Watching Society to the Agriculture, Fisheries and Conservation Department, Hong Kong Special Administrative Region Government.