Bird Nests and Eggs Reveal More Than Meets the Eye

The nests and eggs of birds have fascinated us for hundreds of years. At its simplest the nest is any structure made by a bird in which eggs are laid and incubated. Yet the truth is more complicated. Nests protect eggs and young from the elements, thwart predators and help maintain the optimal environment. Ultimately, they allow birds to breed successfully in otherwise challenging environments. Below are three rare, iconic, and interesting specimens from the London’s Natural History Museum.

1. Rusty Thicketbird

The bush warbler family are almost all secretive, dull plumaged birds of dense undergrowth which, as far as we know, build deep-cup, sometimes domed, nests. They are difficult to study due to their often impenetrable habitat of dense undergrowth and marshes. This bush warbler, the Rusty Thicketbird, is only found in the lowlands of the island of New Britain, Papua New Guinea and is one of the most poorly known. The collector of this extremely rare nest and two red-speckled eggs provided very limited information about it, simply indicating: ‘this brown, very rare Timaliid, builds a looseleaf nest on the ground.’ In 1880 the German naturalist Theodor Kleinschmidt was the first western scientist to collect specimens for science and his description of its habits remains one of the few published accounts:

‘Lives on the ground and runs with head projecting forwards like a Quail. When in captivity it retired at night into a bundle of grass placed in the corner of its cage on the ground to sleep. Here, suddenly expanding its long dorsal feathers, sinking its rounded wings, and drawing in its head, it looked like a loose round bundle of brown grass-stalks. Food grasshoppers. Iris bright grey, with a light-brown tinge; bill dark horn-colour above, almost black, beneath brighter; legs, feet, and claws dark horn-colour. Native name Talberara. Breeds in November and December and said to lay in a hollow in the ground without any nest.’

The true nature of its nest building was not recognized until this specimen was collected 48 years later.

2. Blue-gray Gnatcatcher

The gnatcatchers are tiny insectivorous birds found in the New World. The Blue-gray Gnatcatcher was memorably described by the pioneering American ornithologist Frank Chapman as ‘a bird of strong character’ and it is the only gnatcatcher found in the colder temperate regions, breeding from Ontario, Canada, south to El Salvador and eastward from California to Maine in the USA. They are one of the earliest breeding insectivorous songbirds with nest building in California beginning in mid-April, and nesting varies by around one month latitudinally. This nest was found in a tree about 40 feet from the ground on a hillside in dense woods. The male and female would have contributed to its building. The high-walled cup is typical of this species and made of tendrils of plant fibres, bark strips and fine grasses held together by spiders’ webs, with the outside carefully camouflaged using crustose lichens and some feathers. Each concentric layer has been built up progressively using ever thinner materials, with the finest and softest comprising the innermost lining. Four bluish-white eggs covered with small spots were laid in the nest. They are regularly parasitized by the Brownheaded Cowbird. As they have no capacity to eject or puncture cowbird eggs this could be contributing to the regional population declines so, for example, in California they have now been lost in some areas and brood-parasitism is the prime suspect.

3. Emperor Penguin

Whilst mistakenly synonymous with the cold, only two species of penguin, the Emperor and the Adélie, are truly Antarctic, with the Endangered Galápagos Penguin, found off the tropical coast of Ecuador, being the most northerly. Some penguins nest in burrows, rock crevices or build nests of stones, but the Emperor has perhaps the most unusual method – the eggs are incubated directly on the feet of the male. The female lays one egg in May to June amid the Antarctic winter, when the average daily temperature in the coldest regions can be around –60 to –65°C (–51 to –54°F). She then carefully transfers her single egg to the male, who balances it on his feet and incubates it for around 62 to 66 days. During this time the males remain on the sea ice, gathered in large huddles in the darkness, waiting patiently for the females to return from feeding at sea. This egg was collected on Captain Robert Falcon Scott’s infamous last expedition to the Antarctic in 1911. It was thought the embryo within the egg would shed light on the evolution of all birds and, whilst this subsequently did not prove to be the case, it remains one of the most iconic, hard won, and extraordinary objects in any museum.

Read more in Smithsonian Handbook of Interesting Bird Nests and Eggs, which is available from Smithsonian Books. Visit Smithsonian Books’ website to learn more about its publications and a full list of titles. 

Excerpt from Smithsonian Handbook of Interesting Bird Nests and Eggs © The Trustees of the Natural History Museum, London 2024