John Chan / Downy woodpecker (Picoides pubescens) pecking and probes the cavity it created with its beak, finally retreaving a grub from inside the branch of a eucalyptus tree, Bolsa Chica Ecological Reserve, Sou...

John Chan / Downy woodpecker (Picoides pubescens) pecking on branch as it searches for insects inside, Bolsa Chica Ecological Reserve, Southern California, USA, January.

John Chan / Downy woodpecker (Picoides pubescens) pecking on branch as it searches for insects, Bolsa Chica Ecological Reserve, Southern California, USA, January.

Erlend Haarberg / Spotted redshank (Tringa erythropus), two males fighting in snow. Pasvik, Norway. May.

David Tipling / Black woodpecker (Dryocopus martius) male pecking on snowy tree trunk. Kuusamo, Finland. January.

Nigel Cattlin / Wood pigeon (Columba palumbus) damage to young savoy cabbage (Brassica oleracea) vegetable plants, Berkshire, England, UK, June

Nigel Cattlin / Wood pigeon (Columba palumbus) damage to young savoy cabbage (Brassica oleracea) vegetable plants, Berkshire, England, UK, June

Simon Littlejohn / Bonelli's eagle chicks (Aquila fasciata) in nest pecking each other, aged one week, Andalusia , Spain, May.

Simon Littlejohn / Two Bonelli's eagle (Aquila fasciata) chicks in the nest, pecking each other, Andalusia, Spain, June.

Simon Littlejohn / Griffon vulture (Gyps vulvus) chick pecking parent, trying to get attention, Andalusia, Spain, June.

Doug Perrine / Laysan albatross (Phoebastria immutabilis) attacking unrelated chick to keep it away from its own nesting area. Sand Island, Midway Atoll National Wildlife Refuge, Papahanaumokuakea Marine National Mo...

Doug Wechsler / Eastern tiger swallowtail (Papilio glaucus) and Peck's skipper butterfly (Polites peckius) on swamp milkweed (Asclepias incarnata) French Creek State Park, Pennsylvania, USA. July.

Tui De Roy / Nazca booby (Sula granti) on coast, with Vampire ground finches (Geospiza septentrionalis). These finches peck at birds, feeding on blood when other food sources are scarce, Wolf sland, Galapagos.

John Chan / Great horned owl (Bubo viginianus) pecking its mate, Bolsa Chica Ecological Reserve, Southern California, USA.

Frederique Olivier / Yellow-billed oxpecker (Buphagus africanus) pecking parasites on a Giraffe (Giraffa camelopardalis), Serengeti National Park, Tanzania.

Ismaele Tortella / Cormorant chick (Phalacrocorax carbo) pecking at a Northern gannet (Morus bassanus) in breeding colony, competing for space, northern Norway, July.