Papagaios, Life & Times on a Speculative Archipelago - Kingrays (Part One)

Taken from ‘Adaptive Radiation and Us: Our Understanding of Evolution in Island Ecosystems’, essay by Leslie Calvert, student at University of Manchester, as part of Master’s module ‘Nature and Artifice: Environmental Sciences since 1800’. Essay written April 2018.

…and so, thanks to favourable winds, the HMS Beagle sailed from Brazil to the Papagaios Archipelago in September 1836, and then onto the Azores before finally returning to England [9]. Darwin wrote little about the wildlife of the Papagaios, being most fascinated with the endemic coastal species and seemingly venturing inland very little during their stay [10][11]. In many ways this was a missed opportunity. True, the coastal marquinhets, petroderm lizards and octopuses are unique, but the birds of the Papagaian interior are a far greater example of adaptive radiation -the evolution of an animal group into a wide variety of types – than even the more famous Galapagos finches…

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The birds of Papagaios are split into two groups, depending on their ancestry. Those descended from an auk-like bird are Marquinhets. The rest are known as Kingrays (pronounced ‘Kin Grays’ in British English, and ‘King Rays’ in American English). The identity of their common ancestor, and indeed the fact they were related at all, took quite some time to understand [16].

As with many words and phrases, the name itself comes from a misunderstanding. Through convergent evolution, many Papagaian birds look similar to those living in mainland Europe and so the early Portuguese settlers named them for the birds they most closely resembled be it finches or oyster catchers, ducks or kingfishers [17]. The more educated settlers named some of the birds from those mentioned in Latin or Greek texts, especially those referenced in the classics but whose identities are no longer known for certain.

When faced with a group of coot-like birds living in the islands rivers and beaches, these scholars called them κιγκράµας (kinkramas), for an unidentified water bird mentioned by Aristotle [14][18]. Beside the Portuguese, there were a number religious exiles from England and the Netherlands who took up work as labourers. In their pidgin Portuguese, ‘kinkramas’ was mangled into a variety of Germanic forms until it settled on ‘Kinge-rais’ as recorded in 1680 [19].

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‘Kingray’ originally only applied to rail like birds [19], or sometimes the wading birds of the beaches and rockpools [20], but in time was expanded to include all birds on the island, aside from the marquinets, said group including burrowing cavadors.

There are today many genera of kingray split across a number of tribes.

Clockwise from top left: fly-catching Trychocapinae; wader of subfamily Gracilirostrum; finch-like Pseudofringillinae; waterborne Eukinkiraminae. Centre: basal kingray.

The oldest group were the Eukinkraminae: duck or rail-like birds living on the islands’ rivers and lakes. Larger and more specialised in lifestyle than the ancestral dipper, this group remains largely conservative in its body plan. Much like the basal kingrays, Eukinkraminae do not have webbed feet and when feeding underwater propel themselves by flapping their short wings[21].

Along the coasts and estuaries of Papagaios, one finds Gracilirostruminae - tall, wading birds that probe the sand with long bills or stalk rockpools on slender legs [20]. Unlike the flightless marquinhets that flee from predators into the sea, members of Gracilirostruminae are clumsy but capable fliers, able to flee to isolated rocks or up onto the cliffs [21].

Further inland, dozens of species have adopted a finch’s form with smaller body sizes and short beaks specialised for tasks including cracking nuts, slicing leaves, probing for insects and nibbling fresh buds. Known as Pseudofringilliinae, they are the extremely colourful, abandoning the duller ancestral colours for bright plumage, especially in males. Fossils from 26 million years ago have melanosomes preserved that indicate that even then garish feather colours were common, even the norm in this group [22][23].

Faster, and most nimble in the air are the fly-catching Trychocapinae. Almost all living kingrays have a tuft of feathers over the beak, suggesting this is an ancestral trait. In some species, this has evolved to be decorative structures such as the giant Rhynchothrixinae, while in others it has become functional. Protruding from the tufts of Trychocapinae are longer, thinner feathers that act as whiskers allowing the birds to sense tiny movements around their beaks as they chase flies and other insects on the wing [24]. Speaking of wings, theirs are short and blunt like all kingrays, but this provides an advantage in being able to weave between trees in pursuit of prey [21].

This account does not even begin to touch on the diversity with in the four most species-rich groups, and has completely ignored the less diverse but no less impressive Rhynchothrixinae. However, these subfamilies…

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…but where to place them, both in relation to each other, and within the broader group that is ‘birds’ was harder to determine. Nevertheless, 19th Century ornithologist were not ones to resist a challenge. After numerous birds were shot and studied in the 1880s, it was deduced that kingrays were all part of a single family of birds, with shared features like backwards facing nostrils, peculiarities of the foot bones, and distinct layers of feathers to provide protection against water [33][34][35]. Even today, the most terrestrial kingrays are fond of bathing in deep puddles and briefly diving into small ponds in the heat of the day.

Birds still exist on the islands that resemble the first kingrays, as known from fossils.

Beyond this, they were placed as members of the Muscicapoidea group [34] which contains thrushes, flycatchers and starlings. They are most closely related to dippers, and the first kingray on the islands likely had many of the traits that dippers themselves possess such as an affinity for water, long legs and low metabolism for their size, and dense feathers with a large preen gland. These features not only helped the ancestral birds survive being blown across the ocean in a storm (the most likely method of their arrival [36]) but also gave them a toolbox full of traits to help them adapt to the many vacant niches on the islands.

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In summary, it is likely that the diversity of the Papagaian birds after 35 million years of evolution made them too distinct for Darwin to even consider their relatedness, let alone base a hypothesis on it. The Galapagos finches by comparison had only 5 million years to evolve and still mostly resembled the ancestral bird. Give them a few million more years and they too might follow the kingrays’ lead and spread across land, sky and water in forms small, and in some cases, very very large…