Methodology:

Nest counts were carried out annually in December or January. All surveys were direct ground counts of nests (and thus incubating birds), carried out by a minimum of two observers and all nests were surveyed at least twice on the same day. Distance from nests was roughly 30 to 40 m, closer if need be. Counts were repeated until values were within 10 percent of each other.

Chick counts were done in mid-March, when they were no longer brooded or guarded by a parent.

Data quality:

All colonies were surveyed at least twice on the same day by a minimum of two observers to maintain consistency. All surveys were repeated until count totals were within 10 percent of each other to ensure accuracy.

Chicks were counted in March, although they do not fledge until late April. This is due to lack of personnel after late March. However, survival from March onwards was over 97 percent, and was thus regarded as a good proxy for breeding success.

Position of nesting groups were recorded with hand-held GPS devices to check for shifts in colony locations.

Colonies surveyed were did not comprise of all giant petrels present on Signy Island, but were part of the subset of individuals annually monitored as part of ongoing British Antarctic Survey research.