“Cassowaries are large, flightless birds related to emus and (more distantly) to ostriches, rheas, and kiwis”, writes Olivia Judson in the September issue of National Geographic magazine. How large? People-size: Adult males stand well over five foot five and top 110 pounds. Females are even taller, and can weigh more than 160 pounds. Dangerous when roused, they’re shy and peaceable when left alone. But even birds this big and tough are prey to habitat loss. The dense New Guinea and Australia rain forests where they live have dwindled. Today cassowaries might number 1,500 to 2,000. And because they help shape those same forests – by moving seeds from one place to another – “if they vanish”, Judson writes, “the structure of the forest would gradually change” too. (Photo by Christian Ziegler/National Geographic)

This month’s selection of travel imagery mixes quiet moments and superlative views. The overall 2018 prize is a West Greenland trip with Wild Photography Holidays. Here: “This was taken on a safari in Kruger national park, South Africa. The scene was like something straight out of a storybook: a wild baboon, impala and elephant crossing the road together, all lined up neatly in a row”. (Photo by Will Clarke/The Guardian)

“Sokolica”. Sokolica, Poland. (Photo and caption by Marcin Kęsek/National Geographic Traveler Photo Contest)

ATTENTION! All pictures are presented in high resolution. To see Hi-Res images – just TWICE click on any picture. In other words, click small picture – opens the BIG picture. Click BIG picture – opens VERY BIG picture.

“Don't Leave Any Food On Your Plate”. The giraffes at Nairobi's Giraffe Manor are totally at home with humans. They will eat out of your hand, or even off your plate. Photo location: Giraffe Manor, Nairobi, Kenya. (Photo and caption by Gavin Werbeloff/National Geographic Photo Contest)

Penguins majestically march on sand before heading out for a morning swim. Wildlife photographer Wim van den Heever, 45, visited the Falkland Islands this year to shoot pictures and scout the area for future tours. Wim’s breathtaking images show a small group of king penguins before they head out to sea at sunrise. Here: King Penguins marching during sunrise, Falkland Islands. (Photo by Wim van den Heever/Caters News)

These images capture the intricate details of minuscule snowflakes, moments before they melt. The shots were taken by Don Komarechka, 31, who has had a lifelong fascination with all things macro – especially snowflakes. The professional photographer says people often don’t believe that his pictures are real because they’re so perfect. (Photo by Don Komarechka/Caters News Agency)

An anti-Gaddafi fighter tests an anti-aircraft gun southwest of Sirte, Libya one of Muammar Gaddafi's last remaining strongholds, September 16, 2011. A timeline of images dating from 2010 from Sirte, Libya, the home town of deposed Libyan leader Muammar Gaddafi. Libyan forces battling Islamic State in the city of Sirte say they have defeated the militant group after months of street to street fighting backed by U.S. air strikes. Islamic State took control of the city more than a year ago and set up its main base outside Syria and Iraq. (Photo by Goran Tomasevic/Reuters)

Photographer Logan Zillmer took this photo of the harvest moon above a corn field as part of his “Traveler” series on Flickr. (Photo by Logan Zillmer)