A hand-coloured engraving by John James Audubon, 'Plate 173 Barn Swallow' depicts a pair of barn swallows perched on their nest, showcasing the artist's meticulous attention to detail and scientific accuracy.

John James Audubon (1785-1851) was an American ornithologist, naturalist, and painter, notable for his extensive studies documenting all types of American birds and for his detailed illustrations that depicted the birds in their natural habitats. His major work, *The Birds of America*, is a collection of 435 life-size prints, made from hand-engraved plates, and is considered one of the greatest achievements in ornithological illustration. Audubon combined his skills as an artist and a naturalist to create scientifically accurate and aesthetically pleasing images. His work had a significant impact on the field of ornithology and continues to be admired for its artistic merit. Plate 173, titled 'Barn Swallow', features a pair of barn swallows perched on their nest. The birds are rendered with careful attention to detail, showing their distinctive forked tails, iridescent blue-black upperparts, and reddish-brown throats. The nest, constructed on a wooden beam, is depicted with its intricate structure of mud and straw. The composition is simple, with the birds and nest set against a plain background, allowing the viewer to focus on the natural beauty and characteristics of the swallows.