DOI: 10.5285/8902f094-1d1f-4092-9aa5-180a2a8e57ec
title: Breeding success of macaroni penguins at Bird Island, South Georgia, from 1978 to 2025 - VERSION 2.0

description: The breeding success (calculated from nest and chick counts) of macaroni penguins is monitored annually at Bird Island, South Georgia. A transect is used to estimate the incubating nests and chicks hatched in the large colony at Goldcrest Point where counts have been made since 1976. The number of incubating nests and chicks reaching fledging stage in the whole of the smaller colony at Fairy Point are counted and data exist from 1982 onwards.

This dataset is an updated version of Trathan, P., Waluda, C., & Ratcliffe, N. (2021). Breeding success of Macaroni penguins at Bird Island, South Georgia, from 1982 to 2020 (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/1a266e7b-ef8d-4db7-8e7c-155be21d17cd. The update consists of five additional years of data. No changes have been made to the data included in version 1.0 of the dataset.

This work was funded by Natural Environment Research Council (UK) core funding to the British Antarctic Survey.
description: Breeding counts are carried out on the 29 or 30 November in Big Mac (Goldcrest Point) and Little Mac (Fairy Point).

The Big Mac Transects:

Two fixed transects in the Big Mac colony are counted and the numbers used to calculate the estimated number of breeding pairs for the whole colony. The top of transect 1 and the top and bottom of transect 2 are marked with yellow painted rocks. The top of transect 1 is just past the top of the motorway on the Goldcrest Point side. The bottom of transect 2 is on the high point of rocks around the corner from the bottom of the motorway towards the end of Goldcrest Point. The left hand side of the transects are counted in November (left as you look down from the top of transect 1 and up from the bottom of transect 2). 

Two to four people are required to carry out the transect counts. The easiest method is to go to the colony and re-paint the yellow markers before the season really starts. Then counts can be made in each quadrat as marked by paint. If this has not been possible due to ice build up then four people will be needed. They move down the length of the transect stretching the 5m string between them and spray paint rocks at 5m intervals. The other 2 people stretch the 5m string out to the left of each marked rock and walk down the transect, creating 5m squares. The number of incubating penguins in each 5m square is counted by each person and the two numbers are recorded for the square. If there is a large discrepancy between the two counts, the counts are repeated. This is repeated for transect 2 moving up from the bottom of the colony (the 5m squares of transect one are permanently painted in yellow). 

If the transects are painted in advance using the 5m stick and string method and two or three people, then counting can be completed with 2 or 4 people. Two groups of two can start at either end of the transects at the same time and count. 

The transects are repeated on the 30 or 31 December to count the number of chicks hatched in the Big Mac colony. The above protocol is used but the transect is counted on the right of the marked rocks i.e. the opposite side to the breeding count. 

Little Mac colony:

On the same day as the macaroni penguin transect is counted, the number of pairs with eggs are counted in the Little Mac colony at Fairy Point. The count is made three times until the numbers are similar (within around 5%). 

On 16 February, the number of chicks in the Little Mac colony are counted. The count is made 3 times until the numbers are similar (within 5%).

This dataset has been updated to add five additional years of counts. The metadata has been updated accordingly.

All data were collected under permit from the Government of South Georgia and the South Sandwich Islands.

All sampling procedures used were regulated by the British Antarctic Survey Ethical Review Committee in collaboration with Cambridge University and the UK Home Office.