Evolution of sex ratios and sexual dimorphism in seabirds

海鸟在世界上所有鸟类中所占的比例不到3%，这证明了以海洋为主的生活所带来的严酷。在远离陆地的地方觅食，并把食物带回哺育雏鸟，这给海鸟带来了一系列特征，这些特征在其他鸟类身上单独出现，但只有在海鸟身上才会出现，这导致了一种“海鸟综合症”的认识：高存活率（寿命长）、低繁殖率、长性成熟期、群体筑巢、一夫一妻制、双亲抚养和性别单一性（雄性和雌性相似）。

Seabirds make up less than three percent of all the bird species in the world, testifying to the rigours imposed by a life predominantly at sea. Feeding far from land and bringing food back to feed the chick imposes on seabirds a suite of characters that occur separately in some other birds but are found together only in seabirds, leading to the recognition of a "seabird syndrome": high survival (long lifespan), low reproductive rate, prolonged period of sexual maturation, colonial nesting, monogamy, biparental care, and sexual monomorphism (males and females similar).