The week in wildlife – in pictures

A puffin drops the sand eels it was carrying after being chased by a gull on the Farne Islands off the Northumberland coast. The islands are home to 23 species of seabird, including nearly 40,000 nesting pairs of puffins – an 8% rise from 2008 Photograph: Nigel Roddis/Reuters

Brent geese silhouetted against the sky over Dublin Bay Photograph: Niall Carson/PA

Wildebeest cross the Mara river in the Masai Mara game reserve in Kenya. Only months after their annual migration south to Tanzania's Serengeti national park, thousands of wildebeest have been spotted back in the Masai Mara, a rare occurrence which wildlife officials say may be the result of drought and insufficient pastureland in Tanzania Photograph: Rebecca Blackwell/AP

Snow-covered trees in Krasnaya Polyana, near the Black Sea city of Sochi Photograph: Yuri Kadobnov/AFP/Getty Images

A squirrel clutches a nut in Saski Park in Lublin, Poland Photograph: Wojciech Pacewicz/EPA

A sole tree with red leaves stands out against the blue sky in Rock Creek Park in Washington DC. The park covers an area of about 2.75 square miles and is among the oldest of America's national parks Photograph: Eva Hambach/AFP/Getty Images

A vast flock of geese takes flight over Old Lake in Tata, Hungary. This season about 30,000 geese were observed on the lake, which is one of the largest winter quarters for these migrating birds coming from Scandinavia and Siberia Photograph: Attila Kovacs/EPA

Indian forest guards mounted on domesticated elephants drive away a herd of eight wild elephants which strayed onto farmland on the outskirts of Mysore, in southern Karntaka state Photograph: STR/AFP/Getty Images

Look closely and you can see a turtle swimming at the Riachuelo river Buenos Aires, Argentina. The Matanza-Riachuelo river basin is one of the world's most polluted places, which Green Cross Switzerland and the Blacksmith Institute attribute to industry effluents Photograph: Natacha Pisarenko/AP

American white pelicans take off in Everglades national park. The birds breed in inland regions, and winter along the warm southern coasts of California, the Gulf Coast and Florida Photograph: Andy Newman/AP

Grey seals play underwater by the Farne Islands, whose substantial colony of grey seals arrives each autumn to have their pups Photograph: Nigel Roddis/Reuters

A baby hippo bobs next to its mother, in Kenya's Masai Mara game reserve Photograph: Rebecca Blackwell/AP

A hibiscus flower on an ash-covered plant in Mardingding village, in Sumatra, Indonesia. A volcano on the island continued to emit volcanic ash, throwing an 8,000 metre-high plume into the atmosphere, forcing thousands of residents into temporary shelters Photograph: RONI BINTANG/REUTERS

Two dead pilot whales lie in the water in a remote area of Florida's Everglades national park. They were two of nearly 50 pilot whales that were stranded in shallow water in the area. Four of the whales had to be euthanised, and six others had already died Photograph: Lynne Sladky/AP

A corn bunting perched on a branch. The population of corn buntings has declined greatly in Spain's Soria province, due to intensive agricultural practices harming its food supply Photograph: Jorge Sanz/Corbis

A golden-crowned sifaka lemur leaps from one tree to another in the Marojejy national park in north-east Madagascar Photograph: Wu Xiaoling/Corbis

Mistletoe growing on apple trees in Cotehele, Cornwall – one of the few National Trust locations in the south-west where the festive plant is thriving Photograph: Ben Birchall/PA