The week in wildlife

An oak tree in the November fog. Next week is national tree week Photograph: Graham Turner/Guardian

A flock of migratory birds in Hokersar, north of Srinagar, India. More than 600,000 birds flew into the wetlands of the troubled Kashmir region from central Asia and Siberia Photograph: Danish Ismail/Reuters

A deer in a snow-covered forest in Stoetten, Germany Photograph: Karl-josef Hildenbrand/EPA

A tiger in India. Scientists studying sites in the forests of central and north India have found they can estimate tiger numbers as accurately from paw prints and faeces as they can using camera traps. The results have crucial implications for conserving tigers and other endangered species worldwide. This week saw the first international summit on saving the tiger, although a tiger had to be shot dead by police in India after it killed a woman Photograph: Yadvendradev Jhala

A lion cub plays at the zoo in the Bulgarian capital Sofia. Twin lion cubs were born in captivity at the zoo a month ago Photograph: Nikolay Doychinov/AFP/Getty Images

The forest in San Juan Xoconusco, Mexico, part of the wintering grounds of the Monarch butterfly. The Monarch butterfly reserve in the mountains west of Mexico City is a link between developed and developing nations. The butterflies migrate to Mexico from the US and Canada, and the reserve has benefited from international help, like payments to communities to preserve trees and alternative income projects that helped cut the deforestation rate by about 95%. An initiative launched this week allows web users to watch wildlife live from web cams in South American rainforests Photograph: Dario Lopez-Mills/AP

An adult Western gound parrot in Fitzgerald River National Park, Western Australia. A team of researchers have identified a new, critically endangered species of ground parrot. The team used DNA from museum specimens up to 160 years old to reveal that populations of ground parrots in eastern and western Australia are highly distinct from each other and that the western populations should be recognised as a new species, Pezoporus flaviventris Photograph: Brent Barrett/WA Department of Environment and Conservation

Polar bears, above, are likely to lose out to grizzly bears in fierce competition for food as climate change drives the two species closer together into shared habitat, found a study by evolutionary biologists at the University of California, Los Angeles, released this week Photograph: UCLA/Reuters

A male white rhino grazing at the Lewa Wildlife Conservancy where Prince William and his fiancee Kate Middleton were staying while on holiday in Kenya last month Photograph: Simon Maina/AFP/Getty Images

A squirrel climbs a tree at the Yildiz park in Istanbul Photograph: Mustafa Ozer/AFP/Getty Images

A grouse on snow-covered moors at Hutton le Hole in North Yorkshire after snowfalls and blizzards Photograph: John Giles/PA

A herd of bison in the Bitterroot Valley north of Stevensville, Montana, are covered in snow Photograph: Perry Backus/AP

A queen leaf-cutter ant of the species Atta colombica looms over a tiny worker in their fungus garden. A study this week suggests that fungus-cultivating ants may have co-evolved with bacteria whose antibiotic compounds help them protect their crop Photograph: Cameron Currie

A recently discovered species, called a squidworm, found in the Celebes sea in southeast Asia. The ghostly creature was discovered in the deepest reaches of the ocean between Indonesia and the Philippines. The squidworm, Teuthidodrilus samae, up to 9.4cm long, is far more elegant than its name would suggest. Swimming upright, it navigates by moving two body-length rows of thin, paddle-shaped protrusions that cascade like dominoes Photograph: Laurence Madin/AFP/Getty Images

A New study on the southeast Asia Chrysopelea paradisi flying snake was released this week. Meanwhile, the Pentagon wants to study flying snakes for military purposes Photograph: Jake Socha

Stallings flock over the remains of Brighton's West Pier. Such sights make for spectacular photographs Photograph: Linda Nylind/Guardian