Sule Skerry – an overspill gannetry from Sule Stack

Northern Gannets Morus bassanus first bred on Sule Skerry, Orkney, Scotland in
2003. A count made from photographs taken using a drone in July 2018 showed
that the population had increased to 4,515 apparently occupied sites with a mean
annual rate of increase of 19% between 2009 and 2018. As Gannet numbers
increased, they displaced several hundred pairs of Common Guillemots Uria aalge
and about 500 pairs of Atlantic Puffin Fratercula arctica. Ringing of Gannet chicks
showed that some of the increase on Sule Skerry was due to immigration from Sule
Stack 8 km away. Northern Gannets on Sule Stack appear to occupy all suitable
nesting habitat, and the breeding population has been relatively stable at around
4,500 pairs for the last 100 years. The colony on Sule Skerry is now as large as that
on Sule Stack. Given that there appears to be plenty of suitable nesting habitat for
more Gannets on Sule Skerry, it seems likely that the colony will continue to
increase to the detriment of the nationally important population of Atlantic Puffins.