Kate Hudson has paid tribute to her son Ryder on his 16th birthday.

The 'Almost Famous' star admits the first 16 years of her son's life had flown by but she is ''ready'' for whatever comes their way from now on.

Sharing a throwback video of Ryder, she wrote alongside it: ''I didn't realise it would be here so fast! 16 years today. 16. I will savor these next couple years before he flies the nest. People sometimes get sad on days like this. Time creeps up on us and rocks us a bit, reminding us that the years don't wait for us to be ready. Well, RYDER IF YOUR READING! I'M READY!!! I'm excited for your future. An amazing young man you are. I am honored that you chose me to be your mother. And here's the thing...you still have two years under this roof. My roof, my rules ;) Happy Birthday baby @mr.ryderrobinson (sic)''

Meanwhile, Kate previously revealed her son ''doesn't care'' about getting his driver's license, something which surprises her because when she was his age she couldn't wait to have her own car and drive around.

Speaking about her eldest son, Kate - who also has eight-year-old son Bingham with her former fiance Matt Bellamy, and 15-month-old daughter Rani with her partner Danny Fujikawa - said: ''He doesn't care. I don't know what it is about kids right now - they don't really care! I think maybe because of Lyft and Uber. The second I was 15, I was like, 'Give me my permit!' Ryder's kinda like, 'I got basketball practice, I can't really do the permit thing right [now].' But I'm gonna let him do his thing.''

Kate has Ryder with her ex-husband Chris Robinson.