Gary Bell/ Oceanwide / Australian Pelican (Pelecanus conspicillatus) flock, New South Wales, Australia

Alex Mustard / Killer whales (Orcinus orca) at the surface in an Arctic fjord in Spildra, northern Norway, with sea birds. Arctic Ocean

Jack Dykinga / Bald eagle (Haliaeetus leucocephalus) perched as Snow geese (Chen caerulescens) fly by, Bosque del Apache National Wildlife Refuge, New Mexico, USA, January.

Jack Dykinga / Snow goose (Chen caerulescens) landing into a tight packed flock on lake, Bosque del Apache National Wildlife Refuge, New Mexico, USA. January.

Jack Dykinga / Snow goose (Chen caerulescens) landing into flock, Bosque del Apache National Wildlife Refuge, New Mexico, USA, January.

Ernie Janes / Brent geese (Branta bernicla) flying with moon, Titchwell, Norfolk, UK, December

John Chan / California brown pelicans (Pelecanus occidentalis californicus) roosting on a mudflat, with a flock of Elegant terns (Thalasseus elegans) nearby, Southern California, USA May/2019

John Chan / Flock of Western sandpipers (Calidris mauri) taking flight from salt marsh, Southern California, USA.

Francisco Marquez / Greater flamingo (Phoenicopterus ruber) juveniles and a few adults kept temporarily in an enclosure for ringing, Fuente de Piedra lagoon, Malaga, Spain. August.

Francisco Marquez / Greater flamingo (Phoenicopterus ruber) juveniles and a few adults kept temporarily in an enclosure for ringing, Fuente de Piedra lagoon, Malaga, Spain. August.

Francisco Marquez / Volunteers rounding up Greater flamingo (Phoenicopterus ruber) juveniles for ringing, Fuente de Piedra lagoon, Malaga, Spain. August.

Francisco Marquez / Greater flamingo (Phoenicopterus ruber) flock silhouetted in wetland, Fuente de Piedra lagoon, Malaga, Spain. August.

Jack Dykinga / Sandhill cranes (Antigone canadensis) in flight in late evening light, Bosque Del Apache, New Mexico, USA. December

Jack Dykinga / Flocks of Mallard ducks (Anas platyrhynchos) taking off in tree-lined wetlands. Bosque del Apache National Wildlife Refuge, New Mexico, USA.

Jack Dykinga / Yellow-headed blackbirds (Xanthocephalus xanthocephalus) and Redwing blackbirds (Agelaius phoeniceus) roosting. Whitewater Draw Wildlife Area, Arizona, USA, December.

Jack Dykinga / Murmuration of Yellow-headed blackbirds (Xanthocephalus xanthocephalus) and Redwing blackbirds (Agelaius phoeniceus) at sunset, before roosting. Whitewater Draw Wildlife Area, Arizona, USA, December.

SCOTLAND: The Big Picture / Turnstones (Arenaria interpres) and Purple sandpipers (Calidris maritima) over wintering on the beaches of the Orkney Isles, Scotland, UK, April.

Sandesh Kadur / Slow motion clip of Amur falcons (Falco amurensis) congregating at roost site during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.

Sandesh Kadur / Amur falcons (Falco amurensis) congregating during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.

Sandesh Kadur / Amur falcons (Falco amurensis) congregating during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.

Espen Bergersen / Aerial shot of a fishing boat catching Atlantic herring (Clupea harenguis), with Killer whales (Orcinus orca) and Humpback whales (Megaptera novaeangliae) swimming around the boat and large numbers of...

Espen Bergersen / Aerial shot of a fishing boat catching Atlantic herring (Clupea harenguis), with Killer whales (Orcinus orca) and Humpback whales (Megaptera novaeangliae) swimming around the boats and large numbers o...

Espen Bergersen / Aerial shot of Killer whale (Orcinus orca) hunting Atlantic herring (Clupea harengus), Troms, Norway, October.

Espen Bergersen / Aerial shot of a pod of Killer whales (Orcinus orca) carousel feeding, Skjervoy, Troms, Norway, November.

Marie Read / Snow buntings (Plectrophenax nivalis) flock in flight during a snowstorm, New York, USA, January.

Marie Read / Black skimmers (Rynchops niger), three in non-breeding plumage on beach, Fort De Soto Park, St. Petersburg, Florida, USA. January. Digitally altered to remove distractions.

David Pattyn / Magnificent Frigatebirds (Fregata magnificens) trying to steal fish from fishermen coming on land with a fresh catch, Puerto Lopez , Santa Elena Peninsula, Manabi Province, Ecuador, July

Ernie Janes / RF - Mute swans (Cygnus olor) flock of non breeding adults, Fleet lagoon Dorset, England, UK, June. (This image may be licensed either as rights managed or royalty free.)

Markus Varesvuo / White-fronted goose (Anser albifrons) and Taiga bean goose (Anser fabalis rossicus) flocks in flight and on water. Latvia. April.

John Waters / Large murmuration of Common starlings (Sturnus vulgaris) swirling over reedbed roost at sunset, Ham Wall RSPB Reserve, Somerset, England, UK, January.

John Waters / Large flock of Common starlings (Sturnus vulgaris) swirling over reedbed roost at dusk, Ham Wall RSPB Reserve, Somerset, England, UK, November.

John Waters / Large flock of Common starlings (Sturnus vulgaris) swirling over reedbed roost at dusk, Ham Wall RSPB Reserve, Somerset, England, UK, November.

John Chan / Elegant terns (Thalasseus elegans) courting, Southern California, USA, March.

Juan Carlos Munoz / Griffon vulture (Gyps fulvus) landing on coast next to flock. Cantabria, Spain, March.

Paul Souders/ Worldfoto / Lesser Flamingo (Phoenicopterus minor) flock flying, Lake Magadi, Kenya

Paul Souders/ Worldfoto / Lesser Flamingo (Phoenicopterus minor) flock nesting on island, Lake Natron, Tanzania

Paul Souders/ Worldfoto / Lesser Flamingo (Phoenicopterus minor) nesting colony, Lake Natron, Tanzania

Donald M. Jones / Northern Pintail (Anas acuta) males flying with female in spring courtship display, Montana

Pal Hermansen / Avalanche on Gullemot (Uria aalge) nesting cliff on first day birds return to breed. Finnmark, Norway. March.

Tim Fitzharris / Atlantic Sailfish (Istiophorus albicans) and Magnificent Frigatebird (Fregata magnificens) flock hunting Round Sardinella (Sardinella aurita) school, Isla Mujeres, Mexico

Holger Duty/ BIA / Common Crane (Grus grus) flock flying dangerously close to windmill, Mecklenburg-Vorpommern, Germany

David Tipling / Eurasian magpies (Pica pica) gathering prior to going to roost Hortobagy National Park, Hungary January

Nick Garbutt / Red-and-green macaw (Ara chloropterus) flock flying in front of clay lick. Heath River, Tambopata / Bahuaja-Sonene Reserves, Amazonia, Peru / Bolivia border.

Chris Gomersall / Large flock of Red knot (Calidris canutus) moving at high tide roost, in winter plumage, Snettisham RSPB Reserve, Norfolk, England, UK, September.

Jack Dykinga / Sandhill cranes (Grus canadensis) flying in to land at sunset in golden light, Bosque del Apache National Wildlife Refuge, New Mexico, USA, December.

Paul Williams / Budgerigars (Melopsittacus undulatus) flocking to find water, Northern Territory, Australia

John Waters / Slow motion clip of a mixed flock of Teal (Anas crecca) and Wigeon (Anas penelope) landing in a lake, Greylake RSPB Reserve, Somerset Levels, England, UK, February.

Five Films / Large flock of Common starlings (Sturnus vulgaris) flying at dusk, Somerset Levels, England, UK, November.

John Waters / Large mixed flock of Knot (Calidris canutrus), Dunlin (Calidris alpina) and Golden plover (Pluvialis apricaria) in flight at high tide, Steart Marshes WWT Reserve, Somerset, England, UK, December.

Dave Bevan / Murmuration of Common starlings (Sturnus vulgaris) flying above pier, Aberystwyth, Ceredigion, Wales, UK, October.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire Wales, UK, July.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire, Wales, UK, July.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire, Wales, UK, July.

Claudio Contreras / Caribbean Flamingo (Phoenicopterus ruber) breeding colony, Ria Lagartos Biosphere Reserve, Yucatan Peninsula, Mexico, June. Finalist in the Portfolio Category of the Terre Sauvage Nature Images Awards...

Claudio Contreras / Caribbean Flamingo (Phoenicopterus ruber) chick creche in front of attentive adult flamingo group, breeding colony, Ria Lagartos Biosphere Reserve, Yucatan Peninsula, Mexico, June, Finalist in the Por...

Claudio Contreras / Caribbean Flamingo (Phoenicopterus ruber) chick group walking around the breeding colony, Ria Lagartos Biosphere Reserve, Yucatan Peninsula, Mexico, June, Finalist in the Portfolio Category of the Ter...

Claudio Contreras / Aerial view of Caribbean Flamingo (Phoenicopterus ruber) breeding colony, Ria Lagartos Biosphere Reserve, Yucatan Peninsula, Mexico, May, Finalist in the Portfolio Category of the Terre Sauvage Nature...

Terry Whittaker / Slow motion close-up of a large group of Fulmars (Fulmarus glacialis) feeding from a fish processing plant outfall, Grundafjordur, Iceland, March.

John Waters / Mixed flock of Wigeon (Anas penelope) and Northern lapwings (Vanellus vanellus) disturbed by hunting Marsh Harrier (Circus aeruginosus), Greylake RSPB Reserve, Somerset Levels, England, UK, December.

John Waters / Slow motion clip of a flock of Northern lapwings (Vanellus vanellus) flying over a flooded marsh, Catcott Lows Nature Reserve, Somerset Levels, England, UK, December.

Philippe Clement / Flock of Jackdaws (Corvus monedula) congregating at dusk at communal roost, Belgium, December.

Christophe Courteau / Greater flamingoes (Phoenicopterus ruber) and Lesser flamingoes (Phoeniconaias minor), Walvis Bay, Namibia.

Frederique Olivier / Chinstrap penguin (Pygoscelis antarcticus) moving a feather in its nest, Aitcho Island, South Shetland Islands.

Frederique Olivier / Chinstrap penguin (Pygoscelis antarcticus) adding a stick to its nest and fighting with a neighbouring pair, Aitcho Island, South Shetland Islands.

Frederique Olivier / Panning shot of a Chinstrap penguin (Pygoscelis antarcticus) breeding colony, Aitcho Island, South Shetland Islands.

Frederique Olivier / Large flock of Guanay cormorants (Phalacrocorax bougainvilli) flying to feed, Ballestas Islands, Peru.

Frederique Olivier / Large flock of Guanay cormorants (Phalacrocorax bougainvilli) flying to feed, Ballestas Islands, Peru.

Frederique Olivier / Wide angle shot of a large flock of Blue footed boobies (Sula nebouxii) taking off from the sea and diving on a bait ball, Isla Lobos de Terra, Peru.

Frederique Olivier / Wide angle shot of a large flock of Blue footed boobies (Sula nebouxii) taking off from the sea and diving on a bait ball, Isla Lobos de Terra, Peru.

SCOTLAND: The Big Picture / Panning shot of a large flock of Pink-footed geese (Anser brachyrhynchus) taking off from their roosting site, Montrose, Angus, Scotland, UK, November.

Nick Upton / Flock of Jackdaws (Corvus mondedula) taking off from their roost site, Gloucestershire, England, UK, December.

Denis-Huot / Lesser flamingo (Phoeniconaias minor) flock in the mist, Lake Nakuru, Kenya. March.

John & Mary-Lou Aitchison / Flock of Barnacle geese (Branta leucopsis) flying over the sea, Islay, Inner Hebrides, Scotland, UK, November.

Dietmar Nill / Murmuration of Common starlings (Sturnus vulgaris) at dusk, Rome, Italy, December.

Nick Upton / Panning shot of partially flooded pastureland with large flocks of Wigeon (Anas penelope), Lapwings (Vanellus vanellus) and Golden plover (Pluvialis apricaria) in flight, Gloucestershire, England, UK,...

Nick Upton / Panning shot of a flock of Lapwings (Vanellus vanellus) landing on partially flooded pastureland near resting Black-tailed godwits (Limosa limosa) and grazing Wigeon (Anas penelope), Gloucestershire,...

Nick Upton / Flock of Lapwings (Vanellus vanellus) in flight, with Golden plover (Pluvialis apricaria) flying in the background, Gloucestershire, England, UK, January.

Ingo Arndt / Flock of Rooks (Corvus frugilegus) roosting in tree at dusk, Hessen, Germany, Europe

Ingo Arndt / Flock of Bramblings (Fringilla montifringilla) perched together in branches. It's estimated that four million individiuals return to roost during winter in Black Forest, Germany. February.

Ingo Arndt / Flock of Bramblings (Fringilla montifringilla) roosting together in branches. It's estimated that four million individiuals roost in the Black Forest, during winter months, Germany. February.

Ingo Arndt / Flock of Bramblings (Fringilla montifringilla) taking off / landing on branches. It's estimated that four million individiuals roost in the Black Forest, during winter months, Germany. February.

Ingo Arndt / Flock of Brambling (Fringilla montifringilla) perched at roosting tree, overwintering, Steiermark, Austria

Ingo Arndt / Flock of Bramblings (Fringilla montifringilla) in flight, an estimated four million return to roost overwinter in Black Forest, Germany, March.

Ingo Arndt / Common starlings (Sturnus vulgaris) flock flying in formation to confuse hunting Peregrine Falcons (Falco peregrinus), Rome, Italy. January 2009

Ingo Arndt / Large flock of Eastern / Great White Pelican (Pelecanus onocrotalus) preening, Lake Nakuru, Kenya

Ingo Arndt / Flock of Black skimmers (Rynchops nigra) on beach, New Jersey, USA

Ingo Arndt / Large flock of Snow Geese (Chen caerulescens) flying, Bosque del Apache National Wildlife Refuge, New Mexico, USA

Ingo Arndt / Black skimmer (Rynchops nigra) large flock flying, New Jersey, USA

Thomas Marent / Greater Flamingo (Phoenicopterus ruber) flock flying, Los Flamencos Sanctuary, Guajira Peninsula, Colombia

Thomas Krumenacker/ BIA / Common Crane (Grus grus) flock at sunrise, Brandenburg, Germany

Hans Glader/ BIA / White-fronted Goose (Anser albifrons) group flying, North Rhine-Westphalia, Germany

Jack Dykinga / Snow geese (Chen caerulescens) large flock with some landing, Bosque del Apache, New Mexico, USA, December.

Tim Fitzharris / Snow Goose (Chen caerulescens) flock in pond at sunrise, Bosque del Apache National Wildlife Refuge, New Mexico

Yashpal Rathore / Demoiselle crane (Anthropoides virgo) low angle fisheye perspective of feeding cranes. Khichan, Western Rajasthan, India. February, 2015

Yashpal Rathore / Demoiselle crane (Anthropoides virgo) resting on sand dunes during winter migration, Khichan, Western Rajasthan, India. March.

Yashpal Rathore / Demoiselle crane (Anthropoides virgo) low angle view of birds flying and landing near the chugga ghar (bird feeding enclosure ) in Khichan Village, durin their annual migration. Western Rajasthan, Ind...