Chapter 1, pt4: Kingfishers

A kingfisher of the species Darwin saw in Cape Verde. Steve Garvie / CC BY-SA 2.0 / Wikimedia Commons

The broad, flat-bottomed valleys, many of which serve during a few days only in the season as watercourses, are clothed with thickets of leafless bushes. Few living creatures inhabit these valleys. The commonest bird is a kingfisher (Dacelo Iagoensis), which tamely sits on the branches of the castor-oil plant, and thence darts on grasshoppers and lizards. It is brightly coloured, but not so beautiful as the European species: in its flight, manners, and place of habitation, which is generally in the driest valley, there is also a wide difference.

As far as I can tell, no one knows why exactly a kingfisher is called a kingfisher. The Online Etymology Dictionary suggests that it originated around the 15th century as king's fisher — "for obscure reasons." The ancient Greeks called them halcyons, after Alcyone, a mythical figure who was transformed into a kingfisher after her lover was lost at sea. They believed that kingfishers built floating nests and laid their eggs at sea, and that Alcyone's father, Aeolus, god of the winds, would calm the seas for a short interval every winter so she could brood her eggs in peace — hence, "halcyon days."

Alcyone mourns her lover, Ceyx, in a marble bas-relief from Lotherton Hall in Leeds, England. Wikipedia

Regardless of the stories behind their names, both the Greeks and the English associated kingfishers, first and foremost, with water. Indeed, the common kingfisher (Alcedo atthis), the predominant species in Europe, feeds almost exclusively on fish and aquatic invertebrates, diving to catch them in streams, ponds, and estuaries. This would have been the bird with which Darwin was familiar. The belted kingfisher (Megaceryle alcyon), the most widespread species in North America, has similar habits.

A common kingfisher (Alcedo atthis). Andreas Trepte / CC BY-SA 2.5 / Wikimedia Commons

However, the kingfishers inhabiting temperate climes, like those of Europe and North America, are in the minority by far. Kingfishers are a largely tropical and subtropical group, achieving their greatest diversity in Australia, though they are believed to have originated in southeast Asia. And plenty of them are entirely terrestrial, with no interest in fishing whatsoever. Like the kingfishers Darwin watched on Santiago, they perch and wait for a likely target, often a large insect or a lizard — though some species hunt mice and even snakes. In fact, this sit-and-wait style of hunting is hypothesized to have been the strategy of the ancestral kingfisher — only later in evolutionary history did these birds adapt their lifestyles to aquatic environments.

A laughing kookaburra (Dacelo novaeguineae) that has captured a snake. Wikimedia Commons

Terrestrial kingfishers, like the ones Darwin watched in Cape Verde, are the norm throughout much of the world. However, to European explorers, they were new and distinctive. The scientific name Darwin gives reflects this: Dacelo Iagoensis.

I'm not sure where exactly that scientific name comes from — who first used it to describe the kingfishers of Santiago — but the meaning of the name is clear. Dacelo is the genus today limited to the kookaburras, a group of terrestrial kingfishers in Australia and New Guinea. Iagoensis refers to the island of Santiago, or St. Iago. Put together, we might call this bird the Santiago kookaburra — except that it isn't.

A grey-headed kingfisher (Halcyon leucocephala) in Rwanda. Azurfrog / CC BY-SA 4.0 / Wikimedia Commons

The only kingfisher known in Cape Verde, and undoubtedly the same species that Darwin observed, is the grey-headed kingfisher (Halcyon leucocephala) — a common terrestrial species throughout much of sub-Saharan Africa. While in the same family as the kookaburras, the grey-headed kingfisher is only distantly related to them. In the evolutionary space between them, species have adapted to new habitats and new feeding strategies many times over. In fact, the closest relatives of the Halcyon genus of kingfishers are the stork-billed kingfishers, Pelargopsis capensis, aquatic kingfishers living in the Indian subcontinent and southeast Asia. Most of the Halcyon kingfishers have largely terrestrial feeding strategies — but some have made their way back to rivers and streams as well.

A stork-billed kingfisher in India. J.M.Garg / CC BY-SA 3.0 / Wikimedia Commons

Darwin was hardly the first biologist, or the last, to be misdirected by kingfisher diversity. One subfamily of kingfishers, the Alcedininae, was divided into genera largely on the basis of feeding habits, with the more aquatic kingfishers, including the common kingfisher of Europe, assigned to Alcedo, while the more terrestrial kingfishers were assigned to the genus Ceyx (the name of Alcyone's mythological lover). Only recently, with the development of a robust molecular phylogeny of kingfishers, has it come to light that these genera are hopelessly intermixed on the evolutionary tree.

An Oriental dwarf kingfisher (Ceyx erithaca) in southern Thailand. Pkhun / CC BY-SA 3.0 / Wikimedia Commons.

Kingfishers are a classic example of the difficulty of using phenotypic characteristics to determine evolutionary relationships within a group of species. To centuries of biologists, the distinction seemed clear: some kingfishers are aquatic, and others are terrestrial. But as it turns out, kingfisher species seem readily able to adapt to their circumstances, and their evolutionary history is marked by constant changes from one lifestyle to another.