10 most difficult or­ni­tol­o­gy riddles

Owl's eye colour depends on the time of day in which they hunt. The ones that hunt during daylight have yellow eyes. The ones that hunt at night but also at the evenings and mornings have orange eyes. Black eyes are typical to owls that hunt only at night.

The Philippine eagle also known as the monkey-eating eagle is endemic to the Philippines and can be found on four major islands: eastern Luzon, Samar, Leyte, and Mindanao. The largest numbers of eagles reside on Mindanao, with between 82 and 233 breeding pairs.

The nest of the long-tailed tit is constructed from four materials - lichen, feathers, spider egg cocoons and moss, with over 6,000 pieces used for a typical nest.

Found in open woods, parks, hedges and cultivated land, the mistle thrush feeds on a wide variety of invertebrates, seeds and berries. Its preferred fruits including those of the mistletoe, holly and yew. Mistletoe is favoured where it is available, and this is reflected in the thrush's English and scientific names.

The Indian darter or oriental darter is like all other anhingas, a cormorant-like species that has a very long neck. The structure of the neck is as in other species of darter with strongly developed muscles about a kink in the neck at the 8th and 9th vertebrae that allows it to be flexed and darted forward with rapid force to stab fish underwater. The fibrous representative of Donitz's bridge is seen attached to the ninth cervical vertebra.

A synanthrope is a member of a species of wild animals and plants of various kinds that live near, and benefit from, an association with humans and the somewhat artificial habitats that humans create around them.

Nightjar, is a crepuscular and nocturnal bird that breeds across most of Europe and temperate Asia. It does not build a nest, and its two grey and brown blotched eggs are laid directly on the ground.

The American woodcock is the only species of woodcock inhabiting North America. During migration, their flight speeds have been clocked at 26 to 45 kilometers per hour. However, the slowest flight speed ever recorded for a bird, 8 kilometers per hour, was also recorded for this species.

Hyacinthine macaw, is a parrot native to central and eastern South America. With a length of about 100 cm it is longer than any other species of parrot. It is the largest macaw and the largest flying parrot species, though the flightless kakapo of New Zealand can outweigh it at up to 3.5 kg.

As the name suggests, bee-eaters predominantly eat insects, especially bees, wasps, and hornets. They catch insects in flight, in sorties from an open perch. Before eating a bee, the European bee-eater removes the sting by repeatedly hitting the insect on a hard surface.