The week in wildlife

On a warm spring day in Kiev, a sparrow collects a pigeon feather to build its nest in a park in the centre of the Ukrainian capital. Small birds in the UK will be happy spring is finally here: they were hit hard by the cold winter Photograph: Sergei Supinsky/AFP/Getty Images Photograph: Sergei Supinsky/guardian.co.uk A lizard suns itself next to a water-level indicator at the Camatagua water reservoir in Venezuela on 25 March. A drought has lowered water levels in the country's hydroelectric dams to critical levels and triggered a series of electrical outages Photograph: Jorge Silva/Reuters Photograph: Jorge Silva/guardian.co.uk Geese fly through a snowstorm in Carronbridge, central Scotland, after a night of heavy snow on 30 March. Temperatures plunged below freezing as sleet, rain and snow hit all parts of the country Photograph: Andrew Milligan/PA Photograph: Andrew Milligan/guardian.co.uk Scientists have cracked the genetic code of a songbird , the zebra finch, for the first time. They have identified more than 800 genes linked to song-learning, and hope their discovery may shed light on human speech disorders. Baby zebra finches learn to sing in virtually the same way as human babies learn to speak – by copying their elders – which means the tiny bird should serve as a valuable model for understanding human learning and memory Photograph: L. Brian Stauffer/University of Illinois News Bureau/Reuters Photograph: L. Brian Stauffer/University of Illinois News Bureau/guardian.co.uk A volunteer takes a baby cougar for a walk at Machia Park in Villa Tunari, Bolivia. Machia Park provides shelter and care for abused animals through the work of Inti Wara Yassi, a Bolivian conservation NGO run by national and foreign volunteers Photograph: Dado Galdieri/AP Photograph: Dado Galdieri/guardian.co.uk Japanese macaques blasphemously devour cherry blossoms at Tokyo's Ueno zoo on 29 March. Japan's meteorological agency announced that cherry trees bloomed across the Tokyo area six days earlier than previous years Photograph: Yoshikazu Tsuno/AFP/Getty Images Photograph: Yoshikazu Tsuno/guardian.co.uk So the lions' jokes weren't that funny after all: the laugh of the hyena, it turns out, is a way for the animals (such as this spotted hyena in Kenya) to express sex, age, dominance and their individual signature Photograph: Dan Kitwood/Getty Images Photograph: Dan Kitwood/guardian.co.uk The poison-arrow frog, shown here being counted at Sea Life London Aquarium, is at the centre of some apparently shady dealings in Asia . The endangered frog, which produces toxic skin secretions but is popular as a pet because of its exotic appearance, is seemingly being shipped in large numbers from Kazakhstan through Lebanon to Thailand without being reported to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Photograph: David Parry/PA Photograph: David Parry/guardian.co.uk A Beater Harp seal pup tries to suckle in the north gulf of the St Lawrence river on 27 March. Record numbers of young harp seals have died this year – not from Canada's controversial seal hunt, for which only one vessel showed up on the first day according to the International Fund for Animal Welfare and the Canadian government, but as a result of record low ice levels in the gulf Photograph: Stewart Cook/IFAW /Rex Features Photograph: Stewart Cook/IFAW /guardian.co.uk Two toads make their way across a road as a car approaches near the northern German town of Prisdorf on 27 March. Research shows toads are able to detect earthquakes days before they happen Photograph: Philipp Guelland/AFP/Getty Images Photograph: Philipp Guelland/guardian.co.uk A cane toad escapes from a box at the second annual Toad Day Out roundup in Cairns, Australia, on 28 March. Residents across north Queensland dedicated their Saturday night to helping a coordinated effort to reduce the threat of cane toads to the region. The toads were euthanased in freezers and will be used for research and fertiliser, and in some cases to make wallets and golf gloves Photograph: Tracey Nearmy/EPA Photograph: Tracey Nearmy/guardian.co.uk Kirke the wolverine has joined ZSL Whipsnade Zoo in Bedfordshire, as part of Wild Wild Whipsnade, an exhibit featuring animals that used to roam England – moose, lynx, wolverines, bears, wild boar and wolves. The wolverines are being bred at Whipsnade as part of the European endangered species breeding programme Photograph: Geoff Caddick/PA Photograph: Geoff Caddick/guardian.co.uk