Skomer Island lies off the south east coast of Wales and is home to thousands of seabird.
In the early decades of the 20th Century there were 100,000 guillemots on Skomer, but numbers plummeted to just 2000 after the second world war, probably due to oil pollution in the sea.
Now numbers are slowly recovering with the current estimated to be around 25,000; but the increase in storms may be a problem for them in the future.
Professor Tim Birkhead from Sheffield University has led a 42 year study of the birds and reveals some of their secrets.
Produced and presented by Mary Colwell.