This dataset contains information on the breeding outcome, breeding site occupancy, and breeding site quality for a sample of common guillemots breeding on the Isle of May, Scotland. Data is available for all attributes from 1981-2018. These data are part of the Isle of May long-term study to assess population trends of seabirds under environmental change (IMLOTS https://www.ceh.ac.uk/our-science/projects/isle-may-long-term-study). Full details about this dataset can be found at https://doi.org/10.5285/33b42f0a-12a5-47fe-aaaf-25f4ee5e13a5

Several populations of Northern (Macronectes halli) and Southern Giant Petrel (Macronectes giganteus) at South Georgia have been monitored since 2014. Three colonies of Northern Giant Petrel are monitored at Greene Peninsula, Discovery Point and Maiviken, and two of Southern Giant Petrel at Greene Peninsula and Harpon Bay. Summary data on breeding numbers and productivity for each season and colony are available, based on data from individual nests.

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 work was funded by Natural Environment Research Council (UK) core funding to the British Antarctic Survey.

The breeding success (calculated from nest and chick counts) of Gentoo penguins is monitored annually at Bird Island, South Georgia. The number of incubating nests and chicks reaching fledging stage are counted in several Gentoo penguin colonies. Data exist from 1982 onwards. This work was funded by Natural Environment Research Council (UK) core funding to the British Antarctic Survey.

The breeding success (calculated from nest and chick counts) of Gentoo penguins is monitored annually at Maiviken, South Georgia. The number of incubating nests and chicks reaching fledging stage are counted. Data exist from 2010 onwards. This work was funded by Natural Environment Research Council (UK) core funding to the British Antarctic Survey.

100 nests in designated Adelie and Chinstrap penguin colonies are marked and then regularly monitored. Data are collected on when eggs are laid in each nest, when they hatch, when eggs or chicks are lost, and when chicks become unguarded. Data exist from 1996 onwards. For Adelie penguins, 100 nests in a colony designated A41 was monitored between 1996 and 2002, from 2003 onwards 100 nests in a colony designated A39 were monitored. For Chinstrap penguins, 100 nests in a colony designated A69 were monitored between 1996 and 2015, from 2016 onwards, 100 nests in a colony designated C66 were monitored. No data were collected in the 1997-98, 1999-2000 and 2010-2011 seasons. To calculate the annual hatching date a binomial model was fitted using the proportion of nests containing one or more chicks as the response variable and the date in days after 1 Oct as the explanatory variable. This model was fitted for each species and year separately. The dose.p function in the MASS package in R was used to derive the day when 50% of nests contained one or more chicks to produce the mean hatching date for each species-year combination. Mean laying dates were back-calculated from the mean hatching dates by subtracting the average incubation periods for each species (35 days for Adelies and 36.4 days for chinstraps, which are relatively constant between years). This has been calculated for data from 1996 to 2016.

100 nests in designated Adelie and Chinstrap penguin colonies are marked and then regularly monitored. Data are collected on when eggs are laid in each nest, when they hatch, when eggs or chicks are lost, and when chicks become unguarded. Data exist from 1996 onwards. For Adelie penguins, 100 nests in a colony designated A41 was monitored between 1996 and 2002, from 2003 onwards 100 nests in a colony designated A39 were monitored. For Chinstrap penguins, 100 nests in a colony designated A69 were monitored between 1996 and 2015, from 2016 onwards, 100 nests in a colony designated C66 were monitored. No data were collected in the 1997-98, 1999-2000 and 2010-2011 seasons. To calculate the annual hatching date a binomial model was fitted using the proportion of nests containing one or more chicks as the response variable and the date in days after 1 Oct as the explanatory variable. This model was fitted for each species and year separately. The dose.p function in the MASS package in R was used to derive the day when 50% of nests contained one or more chicks to produce the mean hatching date for each species-year combination. Mean laying dates were back-calculated from the mean hatching dates by subtracting the average incubation periods for each species (35 days for Adelies and 36.4 days for chinstraps, which are relatively constant between years). This has been calculated for data from 1996 to 2016.

This dataset contains information on the occupancy of breeding sites in the non-breeding season, breeding timing and success, and breeding site quality for a sample of common guillemots breeding on the Isle of May, Scotland. Data is available for all attributes for the non-breeding season of 2017/18, 2018/19 and 2019/20. These data are part of the Isle of May long-term study to assess population trends of seabirds under environmental change (IMLOTS). Full details about this dataset can be found at https://doi.org/10.5285/40d28d0b-f93d-4c6c-90ef-97a26a510f81

Brown Skuas (Stercorarius [antarcticus] lonnbergi) on Bird Island have been monitored in a standardised study area since 2011. Data on ringed birds, nest locations, number and size of eggs, number and mass of chicks as well as non-breeders resightings and productivity data are recorded.

Monitoring of Black-browed Albatrosses (Thalassarche melanophris) and Grey-headed Albatrosses (Thalassarche chrysostoma) in various colonies on Bird Island began in 1976. Data are available for the number of nests for each colony per year. More detailed information is available for selected colonies including the number of eggs laid and chicks hatched and fledged from 1989 onwards. An estimation of the total number of pairs on the island each year using a correction factor, and annual breeding success is also available.