Outside the Natural History Museum's bird collection at Tring, a cat basks in the late afternoon sunshine.
Every now and again, a large bell attached to her collar tinkles as she adjusts her position.
The security guard tells me that Pusscat, the museum's resident feline, was fitted with this noisy accessory after apparently supplying the researchers with a few too many new birds.
The ornithology collection here is one of the largest in the world.
There are approximately one million eggs, 700,000 bird skins, 16,000 skeletons and 4,000 nests; not to mention a library packed with books, journals, paintings and notebooks.
Robert Prys-Jones, the head of the bird group, says that despite the vast number of items, nearly every one of them has a story to tell.
BBC News was given an exclusive peek behind the scenes by the ornithologists, and a chance to hear about some of their most prized specimens.
THE WORST JOURNEY
At first glance, the three emperor penguin eggs nestled within one of the many storage cupboards in the archives do not seem out of the ordinary.
But the tale that lies behind their collection is one of extraordinary human endeavour.
On 27 June 1911, zoologist Edward A Wilson, Henry Robertson "Birdie" Bowers and Apsley George Benet Cherry-Garrard set out in the Antarctic winter for a penguin colony at Cape Crozier.
At the time, it was thought that the embryos in the eggs might shed light on the evolutionary link between reptiles and birds.
However, as curator Douglas Russell explains in the video below, their journey was later to be described as the "worst journey in the world".
Birds from the far-flung Galapagos Islands are often hailed as the inspiration behind Charles Darwin's theory of natural selection.
But in fact a markedly less exotic bird - the humble pigeon - was also behind Darwin's big ideas.
Interested in how traits could be enhanced through selective breeding, he began to amass an enormous collection of the birds, begging colleagues from around the world to send him more pigeons to test his hypothesis.
Now specimens from Darwin's personal pigeon collection can be found at Tring. Curator Joanne Cooper explains why she believes these birds are key to Darwin's work.
DEMYSTIFYING THE DODO
Julian Hume says: "I do a lot of my work in Mauritius - but it's not as glamorous at it seems, I spend most of my time in swamps and marshes."
Dr Hume trained as an artist, but is now tasked with the tricky job of trying to recreate what extinct birds would once have looked like just by using skin and skeletons from the long dead creatures.
One such creature he has brought back to life on paper is the one-time Mauritius resident, the iconic Dodo.
In this video, he describes how a pile of bones can help scientists to look into the past.
THE LOST WARBLER
According to Robert Prys-Jones, the two specimens of the Aldabran brush warbler are a symbol of the fragility of life on Earth and the damage that humans can do to it.
This tiny bird was first discovered in Aldabra, an island in the Indian Ocean, in the 1960s - but just 20 years later it was gone.
Dr Prys-Jones was one of the few scientists able to study the bird during the brief period it was known to science.
Here he tells the tale.
The smell as you walk into the area of the collection where seabird skins are stored is unmistakable - oily, petrol-like aromas fill the air.
The smell is not to everyone's taste, says Katrina Cook, but she loves it. A particular favourite in the collection is the Beck's Petrel, (Pseudobulweria becki).
Until recently, this bird was thought to be extinct; but in 2003, Hadoram Shirihai, an ornithologist from Israel confirmed it was alive and well.
In this video, Dr Cook explains why scent is so important for this bird.