The blue-footed booby (Sula nebouxii) is a marine bird in the family Sulidae, which includes ten species of long-winged seabirds. Blue-footed boobies belong to the genus Sula, which comprises six species of boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait. Males display their feet in an elaborate mating ritual by lifting their feet up and down while strutting before the female.

A general view of the residential area is pictured during dusk at Jodhpur in Rajasthan, April 5, 2015. Jodhpur, also known as the blue city in the desert Indian state of Rajasthan, which residents say originally, was used to show where the highest caste of priestly Hindus live, who wanted to set them apart from the rest of the population. Later the rest of the population followed suit. Another reason for the city to be blue is to keep the buildings cool during the summers, local residents said. (Photo by Adnan Abidi/Reuters)

Girls, who are part of Afghan Mobile Mini Circus for Children (MMCC), participate in a juggling competition in Kabul, Afghanistan August 12, 2015. The MMCC, founded by David Mason from Denmark, teaches cooperation and creativity to children scarred by years of war in Afghanistan. Despite the dangers, the project has grown so popular that it now runs centres in ten provinces and has hundreds of regular students. The circus makes visits to internally displaced persons' camps, schools, orphanages, and holds annual festivals. The children are taught the skills of juggling clubs, walking on stilts and acrobatics. (Photo by Ahmad Masood/Reuters)

Blue Marlin is a semi-submersible heavy lift ship from Dockwise Shipping of the Netherlands. Designed to transport very large semi-submersible drilling rigs above the transport ship's deck, it is equipped with 38 cabins to accommodate 60 people, a workout room, sauna and swimming facilities. Blue Marlin and her sister ship MV Black Marlin comprise the Marlin class of heavy lift ship.

Chefchaouen or Chaouen is a city in northwest Morocco. It is the chief town of the province of the same name, and is noted for its buildings in shades of blue.

Aerial Emery trains on the cyr wheel at the Aloft Loft circus training and teaching school which was converted from a church, in Chicago, Illinois, U.S., September 20, 2016. (Photo by Jim Young/Reuters)

Dogs perform during “Stars and starlets”, a new programme, at the National Circus in the Ukrainian capital of Kiev April 30, 2015. (Photo by Gleb Garanich/Reuters)

In this composite image (L-R top row) Dok Haze, Douglas Child as Camp Dracula, Mongolian Laughing Boy, Tony Walls, Asia Sawika as Anastasia, (L-R bottom row) zombie bass guitar player Ozzy Jackson, sword swallower Hannibal Hellmurto, pickled person, Zoe Olivia Ellis and The Sinister Sisters, Steph Bates (L) and Steph Randall (R) pose for a photograph prior to a rehearsal of the Circus of Horrors' latest show The Night of the Zombie at the Wookey Hole Caves Theatre near Wells on October 23, 2014 in Somerset, England. (Photo by Matt Cardy/Getty Images)