1819 | London, England (Part 1)
Common tailorbird (Orthotomus sutorius) nest sewing
Today’s post is the first of two linked pieces (Part 2 is here). You can think of them as the two sides of a postcard: on the front is the image above, a small Asian bird with a remarkable natural talent for stitching. On the back, a short history of failed London museums, collapsing one after another more than two centuries ago.
Or, given our subject today, maybe we should consider them to be two subjects loosely sewn together at their margins. In this case the thin thread that binds them is a simple line accompanying Lot 61 in an 1819 London auction catalogue:
The Tailor Bird, with its curious nest, from the Leverian Museum; the only ornithological specimen from that collection in the sale.
And so, Part 1: the bird and its curious nest.
A well-suited cobbler
The common tailorbird—Orthotomus sutorius—is found across southern and southeastern Asia. It’s a small bird, easily hidden in foliage, with a rusty head, yellow-green back and creamy belly. It also has a remarkably straight and sharp beak, just a little curved at the tip.
The bird’s name-tag identifies its talent. Orthotomus means ‘straight cut’ in Latin, while sutorius means cobbler or shoemaker. Together with its common name, they reference the deft way that females of the species sew together leaves to construct their nests. Here’s one in action (the first two minutes of the film show nest construction, the remainder egg laying and chick rearing):
The nest-building skill of these birds was noted from their earliest scientific naming (as Motacilla sutoria), by Thomas Pennant in the eighteenth century. Writing in his book Indian Zoology, Pennant held deep sympathy for any creature facing the harsh Indian environment—perhaps the reason he never traveled furthest east of his Welsh home than continental Europe. In India, Pennant writes:
you are harassed in one season with a burning heat, or in the other with deluges of rain: you are tormented with clouds of noxious insects: you dread the spring of the Tiger, or the mortal bite of the Naja. The brute creation are more at enmity with one another than in other climates…But the little species we describe, seems to have greater diffidence than any of the others…It picks up a dead leaf, and surprising to relate, sews it to the side of a living one, its slender bill being its needle, and its thread some fine fibres.
On the right below is Pennant’s accompanying illustration, of a tailorbird nest found in a mango tree. The dead brown leaf sewn to the living one is clear in his example. On the left is John Gould’s preparatory sketch for the illustration at the top of this post, female perched alert above her chick, from his magnificent nineteenth century Birds of Asia:
Pennant was correct in saying that the bird stitches leaves together to make an enclosure for its nest. But he wasn’t quite right that a dead leaf is sewn to fresh ones. Instead, sometimes the sewing damage and nest use may kill off a leaf over time, leaving it still attached to the others. The nest age—revealed by well-developed chicks—suggests that’s what’s happened in Pennant’s illustration (and the same process happens in the video above, at around the 5 minute mark).
Unlike Thomas Pennant, Canadian Casey Wood did actually travel southeast Asia before writing about tailorbirds. Wood trained as an ophthalmologist, which led to an interest in animal eyes, and avian eyes in particular (search out his 1917 book The Fundus Oculi of Birds if detailed imagery of the inside of bird eyes takes your fancy). To be fair, Wood was travelling some 150 years after Pennant, following the first World War.
Even though tales of the tailorbird’s talents had become common in the intervening years—Gould’s Birds of Asia notes that it ‘is so well known to every school-boy that a minute account of it is quite unnecessary’—descriptions of its nest were still relatively rare even in the early decades of the twentieth century. The reason lies in the positioning and care taken by the female as she selects and sews the initial leaves, as Wood relates in his 1925 report to the Smithsonian Institution:
The main reason that the nest is difficult to find is that it is built in the midst of thick foliage which is very little disturbed by the operation of nest building. In consequence it is almost impossible to separate, visually, the components of the nest from the surrounding leaves. Moreover—and this is important—the leaves used by the bird are always apposed so that only their upper surfaces are exposed. There is no contrasting of upper and under surfaces to attract the eye.
Wood provided examples of multi-leaf nests, as well as an instance of a single large leaf being sewn to itself to form a funnel. The actual nest that will hold the eggs and hatched chicks is then built up from soft materials inside the shelter. Here are two of Wood’s photographs from Sri Lanka, along with a modern example of a single-leaf tailorbird nest from Karnataka in India:
The material gathered for sewing—one part of the building process that both males and females get involved in—ranges from spider silk to plant fibres of varying fineness, and even human threads. Short fibres might pass through just one hole in each leaf edge, while longer threads are passed back and forth through multiple holes and drawn taut. Sometimes the nest-builder actively winds the loose ends around existing ties to hold them in place. In many cases, though, the frayed end of the fibre acts as a natural rivet or button, prevented from slipping back through the hole by its natural tangles.
Wood investigated an earlier claim that the birds even tied knots as part of this riveting process, finding no evidence to support it. But he did verify that the bird uses the rivet technique not only on the leaf edges, but to anchor the nest lining to the enclosing leaves once the initial stitch-up is complete. The tailorbird takes a piece of the soft lining in her beak, and punches it through the leaf surface from the inside, where it unravels slightly. That anchors the whole nest to the enclosing leaves, and can give the appearance from the outside that the nest is infested with small, white, fluffy bugs.
The rivets are visible in the left-most photo above, from Wood’s 1920s research, as well as in these more recent photos:
Nests are typically only a meter or so off the ground, and once the nesting season is complete and the chicks are grown, the nest decays naturally and rapidly in the tropical environment. While the nests disappear, however, the birds and their genes live on, and molecular analysis of the Cisticolidae family of birds has begun to pick apart the evolution of this behaviour. This work shows that nest sewing potentially evolved several million years ago, in wetter times, and was then gradually lost in those regions that cooled and dried out starting in the mid-Miocene period.
The result is that nest sewing is now found mainly in tropical areas with their large-leaved plants. One outcome of its early origins is that it’s practiced not only by the Orthotomus tailorbirds, but by their relatives in genera such as Artisornis (known as the African tailorbirds) and Prinia (or the ashy wren-warbler, the sister genus of Orthotomus). Casey Wood found that similarities in their construction and their overlapping ranges meant that Prinia nests could be mistaken for those of the tailorbird, despite the ashy warbler’s reddish eggs. Although even more commonly, people confused the leaf balls constructed by red ants as being bird-made nests, presumably with unpleasant results if they tried to collect eggs of any colour from them.
Knitting knowledge
Fortunately, things have changed since 1925. Online photo and video sharing platforms are now powerful tools for comparing and identifying species, for expert and novice alike. Although it may mean that we have less need for John Gould and his team of talented artists to capture our feathered friends, the rate at which we can share our knowledge of the natural world massively improves when we are not tethered to the timelines and strictures of professional journals. And we can now carry a camera and avian database everywhere we go, instead of Gould’s massive multi-volume masterpiece.
If you’re after more images of tailorbirds, or just the birds in your part of the world, I highly recommend visiting a site such as ebird.org, based at the Cornell Lab of Ornithology. There you can search for birds by region, or species, or just play around with their archives of images and sounds. You can also upload your own photos to the site—in my opinion there definitely needs to be more tailorbird nest photos added on there, if you happen to be living in or visiting the right regions to spot them!
And so I’ll leave you with a few more Orthotomus images from that site, taken by citizen scientists in India and Singapore. Perhaps yours will join them soon. And stay tuned for Part 2 of this post, in which we’ll explore some of the lost London museums that brought birds like Orthotomus to wider scientific attention, more than two hundred years ago.
Sources: Pennant, T. (1790) Indian Zoology; https://www.biodiversitylibrary.org/item/257318 || Gould, J. (1873) The Birds of Asia Vol. IV; https://www.biodiversitylibrary.org/item/120503 || Wood, C. (1926) The nest of the Indian tailor bird. Annual Report of the Board of Regents of the Smithsonian Insitution, 1925. Publication 2836. pp. 349–354. Washington. https://archive.org/stream/annualreportofbo1925smit#page/n387/mode/2up || Jerdon, T.C. (1863) The Birds of India Vol. II. Military Orphan Press, Calcutta. || Hutton, T. (1833) On the nest of the Tailor Bird. Journal of the Asiatic Society of Bengal 502-505. https://www.biodiversitylibrary.org/page/37178581. || Nguembock, B. et al. (2007) A phylogeny for the Cisticolidae (Aves: Passeriformes) based on nuclear and mitochondrial DNA sequence data, and a re-interpretation of an unique nest-building specialization. Molecular Phylogenetics and Evolution 42:272–286.
Main image credit: John Gould (1873) The Birds of Asia Vol. IV Plate VII || Video credit: Khame Pensa; https://www.youtube.com/watch?v=GhTselNbMIU || Second image credits: John Gould; Kansas University Libraries John Gould Ornithiological Collection; https://digital.lib.ku.edu/ku-gould/18490 & Pennant (1790) Plate VIII, engraved by Peter Maxell; https://www.biodiversitylibrary.org/item/257318 || Third image credits: Wood (1926, left); & Shreyas Punacha (right; https://ebird.org/species/comtai1 || Fourth image credits: Boon Hong (left; https://www.flickr.com/photos/boon_hong/19194675020/in/photostream ) || Fifth image credits: Aaryan Bhalla, Jeswin Kuriakose & Nicholas Sim (https://ebird.org/species/comtai1)