Biraj Sarkar/ BIA / Ashy-headed Green Pigeon (Treron phayrei) feeding on fruit, Darjeeling, India

Graeme Guy / Pink-necked Green-Pigeon (Treron vernans) male feeding on berries, Kedah, Malaysia

Loic Poidevin / African Green Pigeon (Treron calvus) on a branch, Masai Mara, Kenya. March.

Loic Poidevin / African Green Pigeon (Treron calvus) on a branch, Masai Mara, Kenya. March.

Loic Poidevin / African Green Pigeons (Treron calvus) interacting in a tree, Masai Mara, Kenya. March.

Debapratim Saha/ BIA / Pin-tailed Green-Pigeon (Treron apicauda), West Bengal, India

Cyril Ruoso / African green pigeon (Treron calva) flock flying, Lake Lobak / Lobeke National Park, South East Cameroon, July.

Aflo / White-bellied green pigeons (Treron sieboldii) perched in tree, Takyama, Gifu, Japan.

Dong Lei / Thick-billed green pigeon (Treron curvirostra) group of three drinking from puddle, Xishuangbanna National Nature Reserve, Yunnan Province, China. March.

Dong Lei / Pin-tailed green pigeon (Treron curvirostra) and Thick-billed green pigeon (Treron curvirostra) group foraging in mud. Xishuangbanna National Nature Reserve, Yunnan Province, China. March.

Steve O. Taylor (GHF) / Pink necked green pigeon (Treron vernans) for sale in cages, Singkawang, West Kalimantan, Indonesian Borneo. July 2010.

Pete Oxford / Congo green pigeon (Treron calvus calvus) flock in flight, Lango Bai, Republic of Congo (Congo-Brazzaville), Africa.

Debapratim Saha / Pin-tailed Green-Pigeon (Treron apicauda) pair taking flight, Darjeeling, India

Ashish & Shanthi Chandola / Orange-breasted green pigeon (Treron bicinctus), Yala National Park, Sri Lanka.

Dong Lei / Wedge-tailed Green Pigeon (Treron sphenura) Zhangmu County, Qinghai-Tibet Plateau, Tibet, China, Asia

Ralph Martin / Bruce's Green-Pigeon (Treron waalia), Oman

Ralph Martin / African Green-Pigeon (Treron calvus) flock flying, Okavango Delta, Botswana

Jabruson / Nesting Green Pigeon (Treron calvus) in riverine forest along the Rutshuru river. Rwindi sector of the Virunga National Park, Democratic Republic of Congo.

Jabruson / Flock of Green Pigeons (Treron calvus) taking off after feeding, Rutshuru river. Rwindi sector of the Virunga National Park, Democratic Republic of Congo.

Laurent Geslin / Yellow legged green pigeon {Treron phoenicoptera} Sariska NP, India

Pete Oxford / African Green-Pigeon (Treron calvus) flock flying, Lango Bai, Odzala-Kokoua National Park, Democratic Republic of the Congo

Cyril Ruoso / African Green-Pigeon (Treron calvus) flock flying, Cameroon

Martin Willis / African Green-Pigeon (Treron calvus) sunning itself on a branch, Lake Mburo National Park, Uganda

Loic Poidevin / Yellow legged green pigeon (Treron phoenicoptera) Keoladeo Ghana National Park, Bharatpur, Rajasthan, India, March

Tim Fitzharris / Pink-necked Green-Pigeon (Treron vernans) pair, Jurong Bird Park, Singapore

Sebastian Kennerknecht / Bruce's Green-Pigeon (Treron waalia), Hawf Protected Area, Yemen

Tui De Roy / African Green-Pigeon (Treron calvus), Solio Game Reserve, Kenya

Patricio Robles Gil / Two African green pigeon {Treron calva} feeding in bush, Kruger NP, South Africa

Patricio Robles Gil / African green pigeon {Treron calva} perched in bush, Kruger NP, South Africa

David Tipling / Pompadour green pigeon (Treron pompadora) perched at the top of a tree, Subic, Luzon, Philippines

Tim Laman / Thick-billed green-pigeon (Treron curvirostra) female in fig tree, Subterranean River National Park, Palawan Island, Philippines. October

Tim Laman / Thick-billed green-pigeon (Treron curvirostra) male in fig tree, Subterranean River National Park, Palawan Island, Philippines. October

Hanne & Jens Eriksen / Bruce's green pigeon {Treron waalia} perched in tree, Ayn Razat, Dhofar, Oman

Hanne & Jens Eriksen / Bruce's green pigeon {Treron waalia} perched in tree, Ayn Razat, Dhofar, Oman

Bernard Castelein / Yellow legged green pigeon (Treron phoenicoptera) feeding on berries. Ranthambore NP, Rajasthan, India

Pete Oxford / African green pigeon (Treron calva) in bush. Okavango Delta, Botswana, Southern Africa

Peter Waechtershaeuser/ BIA / Orange-breasted Green-Pigeon (Treron bicincta), Sri Lanka

Graeme Guy/ BIA / Thick-billed Green-Pigeon (Treron curvirostra) male, Penang, Malaysia

Pete Oxford / African Green-Pigeon (Treron calvus) flying near mineral lick, Lango Bai, Odzala-Kokoua National Park, Democratic Republic of the Congo

Pete Oxford / African Green-Pigeon (Treron calvus) flock flying near mineral lick, Lango Bai, Odzala-Kokoua National Park, Democratic Republic of the Congo

Tim Fitzharris / Pink-necked Green-Pigeon (Treron vernans) pair, Jurong Bird Park, Singapore

Suzi Eszterhas / African Green-Pigeon (Treron calvus), Okavango Delta, Botswana

Mike Read / African green pigeon {Treron calva} perched in tree, Kruger National Park, South Africa

Thoswan Devakul / Thick billed green pigeon female (Treron curvirostra) Thailand, Pang Sida NP

Roland Seitre / Wedge-tailed green pigeon (Treron sphenurus) male, perched in tree, Bhutan.

Roland Seitre / Wedge-tailed green pigeon (Treron sphenurus) male, perched in tree, Bhutan.

Roland Seitre / Sumatran green-pigeon (Treron oxyurus) perched on branch, Sumatra, Indonesia. Captive.

Roland Seitre / Pin-tailed green pigeon (Treron apicauda) perched on branch, Assam, India.

Roland Seitre / Three Madagascar green pigeons (Treron australis) perched in tree, Madagascar.

Roland Seitre / Yellow-bellied green pigeon (Treron waalia) perched in tree, Ethiopia.

Roland Seitre / Yellow-legged green pigeon (Treron phoenicopterus) flock in flight, Assam, India.

Roland Seitre / Yellow-legged green pigeon (Treron phoenicopterus) perched on branch, Assam, India.

Roland Seitre / Yellow-legged green pigeon (Treron phoenicopterus) perched on branch, Assam, India.

Roland Seitre / Orange-breasted green pigeon (Treron bicinctus) perched in tree feeding on fruit, Sri Lanka.

Roland Seitre / Orange-breasted green pigeon (Treron bicinctus) perched in tree flapping its wings, Sri Lanka.

Roland Seitre / Little green pigeon (Treron olax) perched in tree, Singapore.

Roland Seitre / Grey-fronted green pigeon (Treron affinis) male, perched in tree, Mudumalai National Park, Tamil Nadu, India.

Roland Seitre / Grey-fronted green pigeon (Treron affinis) male, perched in tree, Mudumalai National Park, Tamil Nadu, India.

Joel Sartore / Photo Ark / Madagascar green pigeon (Treron australis) profile, Riverbanks Zoo. Captive.

Roland Seitre / African Green-Pigeon (Treron calvus), native to Africa

Bruno D'Amicis / Bruce's green pigeon (Treron waalia) perched in Red milkwood (Mimusops kummel) tree. Hamusit, Ethiopia.

Sylvain Cordier / Yellow-footed green pigeon (Treron phoenicoptera) perched on branch. Tadoba Andhari Tiger Reserve / Tadoba National Park, Maharashtra, India.

Debapratim Saha/ BIA / Thick-billed Green-Pigeon (Treron curvirostra) male feeding on fruit, Darjeeling, India