Christie Brinkley relies on hair extensions to cover her thinning hair.

Now she is 64, the model-and-actress' natural blonde locks have lost a little of their lustre so she has gone ''big on hair extensions'' to give her hair the big bounce she loves.

Speaking to Into the Gloss, she said: ''A lot of women my age complain about hair thinning, and I get that because my hair is thinner than it used to be as well. I'm big on extensions.

''They're so easy to put in - clip in, one two three, just a piece of cake. And I can use one of my extensions to make a ponytail.''

The 'Parks and Recreation' star went on to explain her favorite hairstyles using the pieces including a voluminous ponytail and a ''half-up half down do''.

She explained: ''You know how usually ponytail extensions have one strand that you wrap around to hide the rubber band? I have one that's very good, and I like to use it as a half-up-half-down - it has a pincher in it, and the hair covers the whole pincher. It's very Jean Shrimpton, or you can clip it low and it's easy and chic.

''But my favorite is to take my hair extensions, and instead of spreading them out across the back of my head, I'll clip the middle clip [in the middle of my head], take the side clip and fold it over, and clip it right on top so I have three clips together, and then I pull my hair back around it, and my ponytail will be thick and bouncy. It's so good - it's like night and day. That's a go-to hairdo for me.''