How do you tell male and female swans apart?

I've noticed that some of the swans in the river outside my flat have less colour on their beaks than the bright orange of the others is that an indicator?
Answers:
Male and female look alike, but if you look carefully, you can tell one from the other:
1- Males are larger than females;
2- The knob at the base of the male's upper bill is larger than the female's knob. By the way, it鈥檚 this knob that distinguishes the mute swan from all others;
3- The neck of a male is thicker than the neck of a female.

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Sexual dimorphism. The male is larger.

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In all bird species the males are more colorful and larger.

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the male weighs more and is just a little bit larger..
Im not sure about the color thing. alot of birds the colorful ones are the males.. sometimes being larger...
the Red Tailed Hawk is one exception... They are identical in their markings... but the female is twice the size as the male.