The mute swan (Cygnus olor) is a large scale species and it is a symbol of royalty and purity.
In the Danube's Delta the well-being of the species is stable. The total population is of around 1000 nesting pairs.
The mute swan has a completely white plumage and a strong, red bill. Young birds, called cygnets, are grey. The black knob atop the bill is more pronounced at male specimens than at female specimens.

It reaches its sexual maturity by the age of 3 years and it has a well-developed territorial sense. During pairing season it fluffs up its feathers and it gracefully courts its partner. The mute swan prefers tall vegetation or reed areas for building its large nest.

Usually, the mute swan eats aquatic or macrophyte vegetation. It will dive as deep as 1 to 1, 20 m, in order to find nourishment.

During flight, the whistling of the wings helps the birds to keep distance between them.
For take-off the swan needs up to 10 m and landing is made with its webbed feet wide open on a 3 to 4 m long landing area.

The whooper swan is more vulnerable during winter and during the molting process. Weak specimens are attacked by foxes and jackals.