Walter Rothschild's unusual birds

Lord Lionel Walter, Second Baron Rothschild (1868-1937) is famous for his passionate interest in ornithology and for having assembled in his museum in Tring, Herts, probably the largest private scientific natural history collection ever amassed, including about 300,000 bird skins and mounts. 

Less well known was his interest in bird hybrids and colour aberrations, as well as the phenomenon of 'sex reversal', for all of which he collected an impressive number of examples. Unfortunately, Rothschild sold almost his entire bird skin collection to the American Museum of Natural History in New York in the early 1930s.

However, he kept back about 3500 skin specimens, as well as all his 2500 or so mounted specimens, the latter mainly being on display in his public museum. 

Rothschild died in 1937, when his vast remaining research collections and his public museum passed to the Natural History Museum as the remarkable Rothschild Bequest. As most of the aberrant-coloured specimens and hybrids in his bird collection were mounted, these are still present in the Museum collection today. In fact, most mounted birds present in the Museum's scientific bird collection are former Rothschild specimens. 

Good examples of both hybridisation and colour aberrations are found among the game birds (Order Galliformes, including grouse, pheasant and partridges). 

Rothschild had many rare hybrid specimens, including not only hybrids between species within the same family, e.g. Black Grouse Tetrao tetrix X Ptarmigan Lagopus muta and Common Pheasant  Phasianus colcichus X domesticated Chicken Gallus gallus, but also between species from different families, e.g. Black Grouse X Common Pheasant and Guinea Fowl Numida melagris X Indian Peafowl Pavo cristatus. 

Although Rothschild keenly acquired hybrid specimens for his collection, he remarkably never published on this subject. 

Visitors to the public displays at the Natural History Museum at Tring see still some of these interesting hybrids and colour aberrations on display, very much as Rothschild left them. Many more are held in the research collections behind-the-scenes, where they are currently the subject of continuing research.

Switching sexes

The phenomenon called ‘sex reversal’, when females birds assume male plumage, is also well-illustrated in game birds.

Normally in female birds only the left ovary, or gonad, fully develops, leaving the tissue of the undeveloped right gonad as a sort of potential testis. If the developed left ovary stops being active or is damaged, e.g. due to age, illness or injury, the right gonad then develops along testis-like lines and produces a male-like hormone, resulting in the bird showing male plumage and even behaviour.