Several species of seabirds showed alarming declines over the last thirty years. Most pronounced is the Manx Shearwater which declined from some 3000 in 1972 to the verge of extinction in 2004.

Shags have also declined by almost a half in the last 10 years and Razorbills to a quarter of their former numbers. Only the Black-legged Kittiwake has maintained its numbers and even increased over this period. The full report from the Highland Ringing Group can be downloaded from the bottom of this page.

The main cause of the declining seabird populations was believed to be predation by the introduced population of Brown Rats that used to live on the islands. Burrow-nesting seabirds (such as the Manx Shearwater) are particularly vulnerable and were the first to suffer.

To counteract this threat a major programme to eradicate rats from the islands was successfully undertaken, reaching a conclusion in March 2006. Since then, several species of seabirds have started to recover. A Manx Shearwater chick was successfully reared in the main colony in 2006 and calling birds have been recorded each year since then.