生物在億萬年的演化過程中，會演化出某些身體結構和形態，以適應環境和增加生存機會。 鳥類喙部的形狀和大小是最明顯的例子之一，這與其食性有莫大關係。譬如專捕捉魚類為食的雀鳥會演化出有利捕魚的喙部。而即使要獲取同一種食物，不同的鳥類有不同的方法和技巧，故此喙部形態亦不盡相同。下文嘗試以香港不同食性的鳥種去探討鳥喙和食性的關係：

食魚的鳥類

捕魚有不同方法，鷺鳥（鷺鳥科）均有形如匕首的長喙，用以刺穿魚身。鸕鷀（鸕鷀科）的嘴長而端部向下鈎，能鈎緊滑溜的魚身。

例子：蒼鷺（Ardea cinerea）

食較大型脊椎類的鳥類

猛禽（隼形目和鴞形目）捕捉獵物的體型較大，不能整隻吞食，所以嘴粗而鈎，以撕開獵物。

例子：普通鵟（Buteo japonicus）

食泥灘無脊椎動物的鳥類

鷸類（鷸科）多以長喙插入泥下捕捉無脊椎類如蝦、蠕蟲。不一的長度和形狀使各種鷸能捕捉不同深度的獵物，是生態位分化的一例。

例子：白腰杓鷸（Numenius arquata），沙錐（Gallinago sp.)

食水中浮游生物的鳥類

琵嘴鴨嘴扁長，邊緣有梳狀齒突，用以過濾水中浮游生物。

例子：琵嘴鴨（Anas clypeata）

食昆蟲的鳥類

鶯類（鶯科）和鶲類（鶲科）喙部尖幼，適合捕捉細小昆蟲。

例子：長尾縫葉鶯（Orthotomus sutorius）

食花蜜的鳥類

太陽鳥（花蜜鳥科）的嘴幼長而向下彎，方便插進花管內吸食花蜜。

例子：叉尾太陽鳥（Aethopyga christinae）

食種子的鳥類

鵐（鵐科）和文鳥（梅花雀科）的嘴厚而呈錐狀，便於破開種子堅硬的外殼。

例子：白腰文鳥（Lonchura striata）

 

Through billions of years of evolution, organisms would evolve certain body structures and physiques to adapt to the environment, and thus increase their chance of survival. One of the most obvious examples of such evolution is the bills of birds, which vary in shape and size. This has a lot to do with the feeding behaviour of the bird species. For instance, birds that feed on fish will evolve bills that are best for catching fish. However, even if sharing the same food source, different birds have different strategies and methods. This would also result in different bill shapes.  In this article we shall look at the relationship between bird bills and bird feeding behaviours, through observing birds in Hong Kong with different food sources.

Birds that feed on fish

Fishing comes in many different ways.  Herons (family Ardeidae) have long dagger-like bills, which they use to pierce fish. Cormorants (family Phalacrocoracidae) have long bills, which are hooked downwards at the end. This allows them to hook onto slippery fish bodies.

Example: Grey Heron (Ardea cinerea)

Birds that feed on relatively larger vertebrates

Birds of prey (orders Falconiformes and Strigiformes) hunt prey that are often too large to be devoured whole. Hence, they have developed thick curved bills to tear their prey into smaller pieces.

Example: Eastern Buzzard (Buteo japonicus)

Birds that feed on mud flat invertebrates

Sandpipers (family Scolopacidae) usually probe muddy shores with their long bills to look for invertebrates like shrimps and slugs. Different bill lengths and shapes allow different sandpipers to hunt prey at different water depths. This is an example of niche differentiation.

Examples: Eurasian Curlew (Numenius arquata), Snipe (Gallinago sp.)

Birds that feed on plankton

Northern Shovellers have wide flat bills with comb-like structures on the edge. This feature enables them to skim plankton from the water.

Example: Northern Shoveller (Anas clypeata)

Birds that feed on insects

Warblers (family Sylviidae) and Old World flycatchers (family Muscicapidae) possess thin and pointed bills. Such bills are very suitable to catch small insects.

Example: Common tailorbird (Orthotomus sutorius)

Birds that feed on nectar

The bills of sunbirds (family Nectariniidae) are long, thin and curved downwards. This allows the bird to insert its bill into flowers and drink the nectar inside.

Example: Fork-tailed sunbird (Aethopyga christinae)

Birds that feed on seeds

Buntings or American sparrows (family Emberizidae) and Java Sparrows (family Estrildidae) have thick and conical bills, which are used to crack the hard outer shells to reach the seeds.

Example: White-rumped Munia (Lonchura striata)