当人类向往“甜甜的爱情”时,自然界中也有为找对象而努力打扮自己的鸟儿。
比如,这只留着“杀马特”发型的小鸟也是来找对象的……
这种鸟学名是凤头海雀 (Aethia cristatella),也叫做冠小海雀 (Crested auklet)。
它们日常在白令海和北太平洋的海岸或群岛上潜水捉虾,看它们不太聪明的眼神,再加上头顶特立独行的一撮呆毛,很难不让人想到可达鸭。
Crested auklets have short stubby bodies with relatively long slender wings. Their uniformly slate-gray or black plumage is very dense. These auklets live at sea most of the year, only coming to land to breed. 冠小海雀的身体矮胖,却有着相对细长的翅膀。它们的羽毛非常浓密,呈均匀的灰色或黑色。这些小海雀一年中的大部分时间都生活在海上,只有繁殖期才会到陆地上。
有人说我矮矮胖胖?图源:Phillip Edwards
橘子味的爱情
每年五到八月是冠小海雀求偶的季节,在这时,它们身上会散发出柑橘的 (citrusy)香味。这种香味是与生俱来的。
科学研究发现,冠小海雀会从肩胛骨之间的气味腺羽毛处分泌出一种醛类物质 (aldehyde),而一些与之类似的物质也会用于畅销香水制作。
冠小海雀自带的香水真的能帮它们找到对象吗?有可能。早期研究已经表明,冠羽更大的雄性对雌性有着更强的吸引力——而它们往往也有着更浓烈的柑橘香味。冠小海雀们散发香味的能力与它们的体格密切相关,香味越浓,就越强壮。
Birds with larger crests produced a higher quantity of the citrusy perfume, suggesting that odor is attractive to females. And not only that, more citrusy auklets released corticosterone at a faster rate, suggesting that auklets' capacity to produce perfume is tied to their physical ability—and thus fitness. corticosterone :皮质酮,肾上腺皮质激素之一
其实,冠小海雀的一项“ 求偶仪式”就是互相蹭蹭柑橘香。爱情的味道在它们这里,或许就是橘子味的吧。
海雀贴贴 图源:Lars Petersson
During courtship the male solicits the female by adopting a horizontal posture and giving a soft choking call. She rubs her bill and upper body over his feathers. Then she offers her feathers to the male, and they reciprocate several times, smearing the chemicals over their heads, necks and upper bodies. 在求偶过程中,雄性会横着身体、发出柔和的叫声来吸引雌性。雌性会用嘴和上半身摩擦雄性的羽毛。然后,雌性也会让雄性摩擦自己的羽毛,如此来回几次,使得这些化学物质能够充分涂抹在它们的头部、颈部和上半身上。
冠小海雀对香气的青睐也可能与消灭寄生虫有关。
鸟类的脸部羽毛较短,身体上最容易被虱子、蜱虫等虫子寄生。而鸟类清理身体主要靠嘴,根本啄不到自己的脸和脖子,这时,借助其他鸟的香气就成了最好的解决办法。
聚众吸鸟 图源:Ian L. Jones
爱情就该轰轰烈烈
除了香味,冠小海雀还会用各种各样的叫声进行交际和求偶。它们在陆地上的巢穴往往是最吵闹的地方,众多小鸟们会躲在岩石之间的缝隙里,发出汽车喇叭 (honking)、狗叫 (barking),甚至是吹口哨般的 (whistling)叫声。不得不说表演天赋拉满。
Between 10:00 am and 4:00 pm it's "auklet social hour", says Heather Renner, a biologist with the Alaska Maritime National Wildlife Refuge who's been studying the auklets for more than a decade. "It's just deafening." 来自阿拉斯加国家海洋野生动物保护区的生物学家希瑟·雷纳已研究了十几年小海雀。她介绍说,每天上午十点到下午四点是冠小海雀的“社交时间”,那声音简直震耳欲聋。
研究人员还发现,冠小海雀在求偶时会发出一种特定的复杂叫声,这种叫声被称为“吹喇叭” (trumpet call)。声音频率则很可能与身体状况存在联系。可以说,越吵闹的鸟,越可能更快找到对象。
小海雀的生活烦恼
在保护现状 (conservation status)上,冠小海雀属于无危 (least concern)物种,但这也并不代表它们的生活没有烦恼。
在冠小海雀的栖息地附近,地壳运动往往尤为频繁。特别是位于阿拉斯加的阿留申群岛 (Aleutian Islands),这里有超过三十座火山,而且多数是活火山。
火山爆发后,流动的岩浆造成了更多的石缝,也为鸟儿们提供了更为理想的栖息地。例如,2008年的一次火山爆发造成了数万冠小海雀雏鸟的死亡,但在十年后,科学家们发现这次火山爆发造成的地质改变反而确保了附近冠小海雀的继续繁衍。
In 2008, when Kasatochi Island erupted during breeding season, tens of thousands of unfledged auklet chicks were entombed in the hot ash. But the adults survived, and 10 years after the eruption, the colony is barren rock and as productive as it was before. It was a catastrophe that ultimately assured the colony's survival.
群居的冠小海雀们 图源:Vernon Byrd
不过,近年来的气候变化又成了冠小海雀面临的新威胁。科学家们认为,全球变暖导致了部分海鸟繁殖期提前,而这也有可能进一步影响它们的种群数量。
Surface-feeding seabirds in the north of the Pacific Ocean are moving their breeding season to an earlier timing than the rest of species — about ten days before for over the last thirty-five years — due the ocean's temperature rise and ice melting. 由于海洋温度的上升和冰层融化,在过去的35年里,太平洋北部海面觅食的鸟类的繁殖季节大约提前了10天,比其他鸟类更早进入繁殖期。
以后的冠小海雀们,还能愉快地继续它们橘子味的爱情吗?
编辑:焦洁
实习生:李睿
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