Gerry Ellis / Hippopotamus (Hippopotamus amphibius) swimming in water lettuce, with Cattle Egret (Bulbulcus ibis) perched on head, Serengeti National Park, Tanzania

Shin Yoshino / African Elephant (Loxodonta africana) along waterhole with wallowing Hippopotamuses (Hippopotamus amphibious) and Cattle Egret (Bubulcus ibis) flock, Ngorongoro Crater, Tanzania

Chase Dekker / African Elephant (Loxodonta africana) herd and Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Chase Dekker / African Elephant (Loxodonta africana) mother and calf and Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Chase Dekker / African Elephant (Loxodonta africana) pair and Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Chase Dekker / African Elephant (Loxodonta africana) females and calf with Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Gary Bell/ Oceanwide / Cattle Egret (Bubulcus ibis) in breeding plumage, Australia

John Shaw / Striated heron (Butorides striata) standing on giant Amazon waterlily leaf (Victoria amazonica). Porto Jofre, Pantanal, Brazil. September.

John Shaw / Cattle egret (Bubulcus ibis) in breeding plumage. Wakodahatchee Wetlands, Florida, USA, March.

Patricio Robles Gil / Indian rhinoceros (Rhinoceros unicornis) mother and calf with Cattle egrets (Bubulcus ibis) Kaziranga National Park, Assam, India.

Patricio Robles Gil / Indian rhinoceros (Rhinoceros unicornis) mother and calf with Cattle egrets (Bubulcus ibis) Kaziranga National Park, Assam, India.

Staffan Widstrand / Wild Wonders of China / Great white egret (Ardea alba), Cattle egret (Bubulcus ibis), Little egret (Egretta garzetta) and Intermediate egret (Ardea intermedia) all together in the Yangtze river at the Hubei Tian'ezhou Mi...