Compiled seabird densities and distance to fronts in the Southern Ocean
Data files
Mar 12, 2025 version files 1.85 MB
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Antarctic-wide-summer-dens-env-final-021025.xlsx
800.80 KB
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Antarctic-wide-winter-dens-env-final-021025.xlsx
505.04 KB
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Avian_species_codes-021325.xlsx
12.36 KB
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Avian_species_seen_on_summer_cruises-021325.xlsx
11.90 KB
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Avian_species_seen_on_winter_cruises-021325.xlsx
11.13 KB
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Distribution_limits_for_species-front_analyses-022525.docx
24.06 KB
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PALTER-summer-dens-env-final-021025.xlsx
353.55 KB
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README.md
8.74 KB
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SOGLOBEC-winter-dens-env-final-021025.xlsx
120.04 KB
Abstract
We conducted a Southern Ocean seabird data synthesis using previously collected Antarctic-wide cruise data to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer Long Term Ecological Research (LTER) program and the winter Southern Ocean Global Oceans Ecosystems Dynamics (GLOBEC) studies in the eastern Bellingshausen Sea. We combined 9 cruises conducted in areas around the Antarctic continent during the summer (October-March) for an Antarctic-wide summer data set with 2348 transects and 63 species seen at least once. We combined seven cruises conducted in areas around the Antarctic continent during the winter (April-September) for an Antarctic-wide winter data set with 1591 transects and 56 species seen at least once. We used 6 Palmer LTER cruises which, combined, had 1446 transects and 29 species seen at least once. The 4 winter Southern Ocean GLOBEC cruises combined had 652 transects and 16 species seen at least once. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. Using GIS, distances to the different fronts were measured for all transects and water mass determined; these variables were added to the seabird density files for 4 combined density-environmental files (Antarctic-wide-summer, Antarctic-wide-winter, PALTER-summer, SOGLOBEC-winter).
Cruise Data
We combined 9 cruises conducted in areas around the Antarctic continent during the summer (October-March) for an Antarctic-wide summer data set. The cruises were:
Northwind 1976 (Ross Sea)
Burton Island 1977 (Pacific sector of the Southern Ocean)
Northwind 1979 (Ross Sea)
Melville and Westwind 1983 (Weddell-Scotia Confluence)
Glacier 1979 (Ross Sea)
Polar Star 1987 (Bellingshausen Sea)
Polar Duke 1988 (Bellingshausen Sea)
N. B. Palmer 1994 (Amundsen and Bellingshausen Seas)
Aurora Australis 2000 (East Antarctica)
We combined seven cruises conducted in areas around the Antarctic continent during the winter (April-September) for an Antarctic-wide winter data set. These cruises were:
Polar Duke 1985 (Bellingshausen Sea)
Melville and Glacier 1986 (Weddell-Scotia Confluence)
Polar Duke 1987 (Bellingshausen Sea)
Polar Duke 1988 (Bellingshausen Sea)
Aurora Australis 1998 01 (East Antarctica)
Aurora Australis 1998 02 (East Antarctica)
Aurora Australis 1999 (East Antarctica)
The Southern Ocean GLOBEC cruises were:
N. B. Palmer 2001 (A and B), SO GLOBEC (Bellingshausen Sea)
N. B. Palmer 2002 (A and B), SO GLOBEC (Bellingshausen Sea)
The Palmer LTER cruises were:
L.M. Gould, PALTER 1995 (Bellingshausen Sea)
L.M. Gould, PALTER 1996 (Bellingshausen Sea)
L.M. Gould, PALTER 1997 (Bellingshausen Sea)
L.M. Gould, PALTER 1999 (Bellingshausen Sea)
L.M. Gould, PALTER 2003 (Bellingshausen Sea)
L.M. Gould, PALTER 2006 (Bellingshausen Sea)
Description of the data and file structure
FILE: There are 4 Excel data files containing species densities and environmental variables that follow a similar format. The data files are Antarctic-wide-summer-dens-env-final-021025, Antarctic-wide-winter-dens-env-final-021025, SOGLOBEC-winter-dens-env-final-021025, and PALTER-summer-dens-env-final-021025.
The first line of the file is the header followed by lines of data. Each line contains data from a single transect. The general format is as follows:
First column (Summer.Cruise.ID, Winter.Cruise.ID, SOGLOBEC.ID, PALTER.ID) = unique numeric identifier for each transect
CRUISE = Cruise identifier
ID = Transect identifier
BBBB.km2 columns = specific species density (adjusted number/area of transect in km²), where ‘BBBB’ denotes the four-letter species code for the bird being reported (e.g., ALBB.km2). A key to the species codes is in the file Avian species codes-021325.xlsx (e.g., ALBB Black-browed Albatross Thalassarche melanophris). The number of species density columns in each file depends on the number of species seen at least once over the cruises in the file. The Antarctic-wide summer file has 63 species density columns, the Antarctic-wide winter file has 56 species density columns, the PALTER-summer file has 29 species density columns, and the SOGLOBEC-winter has 16 species density columns.
Latitude.decimal.degree = Latitude at the start of the transect in decimal degrees; all latitudes are south latitudes and values are negative.
Longitude.decimal.degree = Longitude at the start of the transect in decimal degrees; west longitude values are negative; east longitude values are positive
Transect.area.km2 = Area of the transect in square kilometers
DICE15 = Distance to the ice edge (km) where the ice edge is defined by 15% ice cover; transects within the ice have negative distances in relation to the ice edge.
DICE50 = Distance to the ice edge (km) where the ice edge is defined by 50% ice cover; transects within the ice have negative distances in relation to the ice edge.
DPOLARF = Distance (km) to the Antarctic Polar Front; transects south (i.e. landward) of the front have negative distances.
DSBACC = Distance (km) to the Southern Boundary of the Antarctic Circumpolar Current; transects south (i.e. landward) of the front have negative distances.
D1000M = Distance (km) to the Shelf Break defined as the single 1000m contour surrounding Antarctica; transects on the Shelf (i.e., landward) have negative distances.
DANT = Distance (km) to the Antarctic Continent
DLAND = Distance (km) to nearest land (i.e., island or continent); frequently the same as DANT
Wmass = coded water mass; SA= subantarctic, LA = low Antarctic, HA = high Antarctic
FILE: Avian species codes-021325.xlsx
Contains information on the 4-letter species codes used in the dens-env files. There are 4 columns, one for each species.
Species.Code = 4-letter species code
Common.Name = common name of species. Multiple common names are separated by a slash.
Scientific.Name = scientific name of species taken from Birds of the World (Billerman et al. 2022)
Mean.weight.g = mean weight of species in grams, primarily obtained from Williams
(1995) and Brooke (2004)
References:
Billerman, S. M., B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg (Editors). 2022. Birds of the World. Cornell Laboratory of Ornithology, Ithaca, NY, USA. https://birdsoftheworld.org/bow/home
Brooke, M., 2004. Albatrosses and Petrels of the World. Oxford University Press, Oxford, UK.
Williams, T.D., 1995. The Penguins. Oxford University Press, Oxford, UK.
FILE: Avian species seen on summer cruises-021325.xlsx
A table showing which species were seen on the individual summer Antarctic-wide and Palmer LTER cruises. Cruises are grouped by Antarctic-wide summer cruises and PALTER-summer cruises. Species seen within a group are indicated with a 1, not seen with a 0. If a species was not seen at all within a group, the cells are blank. Species are represented by species codes; codes are defined in the file Avian species codes-021325.xlsx.
FILE: Avian species seen winter cruises-021325.xlsx
A table showing which species were seen on the individual winter Antarctic-wide and Southern Ocean GLOBEC cruises. Cruises are grouped by Antarctic-wide winter cruises and SOGLOBEC-winter cruises. Species seen within a group are indicated with a 1, not seen with a 0. If a species was not seen at all within a group, the cells are blank. Species are represented by species codes; codes are defined in the file Avian species codes-021325.xlsx.
FILE: Distribution limits for species-front analyses-021825.docx
This is a text file that describes the species distribution limits used for the species-front analyses in Ribic et al. (2011).
Sharing/Access information
Data were derived from the following sources:
- Ainley, D. G., and S. S. Jacobs. 1981. Affinity of seabirds for ocean and ice boundaries in the Antarctic. Deep-Sea Research 28A:1173-1185.
- Ainley, D. G., S.S. Jacobs, C. A. Ribic, and I. Gaffney. 1998. Seabird distribution and oceanic features of the Amundsen and southern Bellingshausen seas. Antarctic Science 10:111-123.
- Ainley, D. G., E. F. O’Connor, and R. J. Boekelheide. 1984. Ecology of seabirds in the Ross Sea, Antarctica. A. O. U. Monograph No. 32. 79 pp.
- Ainley, D. G., C. A. Ribic, and W. R. Fraser. 1994. Ecological structure among migrant and resident seabirds of the Scotia-Weddell Confluence region. Journal of Animal Ecology 63:347-364.
- Chapman, E. W., C. A. Ribic, and W. R. Fraser. 2004. The distribution of seabirds and pinnipeds in Marguerite Bay and their relationship to physical features during austral winter 2001. Deep-Sea Research II 51:2261-2278. https://doi.org/10.1016/j.dsr2.2004.07.005
- Palmer Station Antarctica LTER and W. Fraser. 2020. At-sea seabird censuses. Data on the species encountered (including marine mammals), their abundance, distribution and behavior. Data collected aboard cruises off the coast of the Western Antarctic Peninsula, 1993 - 2018. ver 5. Environmental Data Initiative. knb-lter-pal.100.5 Environmental Data Initiative. [individual sightings by species by cruise]
- Palmer Station Antarctica LTER and W. Fraser. 2020. At-sea seabird censuses. Data on the species encountered (including marine mammals), their abundance, distribution and behavior. Data collected aboard cruises off the coast of the Western Antarctic Peninsula, 1993 - present. ver 5. Environmental Data Initiative. knb-lter-pal.102.5 [ship event log containing information such as cruise, station, latitude, longitude]
- Ribic, C. A., E. W. Chapman, W. R. Fraser, G. L. Lawson, and P. H. Wiebe. 2008. Top predators in relation to bathymetry, ice, and krill during austral winter in Marguerite Bay, Antarctica. Deep-Sea Research II 55:485-499. https://doi.org/10.1016/j.dsr2.2007.11.006
- Woehler, E. J., B. Raymond, and D. J. Watts. 2003. Decadal-scale seabird assemblages in Prydz Bay, East Antarctica. Marine Ecology Progress Series 251:299-310.
The Southern Ocean GLOBEC cruises will be referred to as the Bellingshausen winter cruises and the Palmer LTER cruises as the Bellingshausen summer cruises.
Field and Analysis Methods
All cruises used strip transects to collect data on species occurring along the cruise track. In general, two observers carried out surveys from one side of the ship, usually from the flying bridge. Strip width was 300 m wide. On all cruises, observers noted time of sighting, species identity, whether the bird was stationary (e.g., standing on ice, sitting on water) or flying, and, if flying, direction of the flying bird in relation to the ship. Species sightings were made continuously on all but 3 cruises (winter Aurora Australis cruises) where 10-minute intervals were used. Survey effort was partitioned into 30-minute bins, sequentially, for surveys with continuous counts. All counts were adjusted for bird flux (movement of birds relative to that of the ship) using ship speed, wind speed and direction, and direction of flying birds in relation to the ship following Spear et al. (1992). Species densities by transect were the adjusted number of birds by species/area surveyed (square kilometers). Transect area varied due to differences in transect length, which depends on ship speed (which, in turn, reflects environmental conditions), and transect time interval.
GIS files defining land, the Antarctic coast, and the fronts (southern boundary of the ACC and Antarctic Polar Front) were obtained from the Australian Antarctic Data Centre. The 1000 m isobath was obtained by creating a bathymetric lattice contour GIS file using gridded ETOPO1 data from NOAA’s National Geospatial Data Center, then edited to produce one continuous line defining the position of the shelf break. Using GIS, we measured the following set of environmental variables for every transect:
distance to the ice edge defined by 15% ice cover (km)
distance to the ice edge defined by 50% ice cover (km)
distance to the Antarctic Polar Front (km)
distance to the southern boundary of the Antarctic Circumpolar Current (ACC) (km)
distance to the 1000 m isobath (km) (which represents the Shelf Break Front)
distance to the Antarctic coast (km)
distance to nearest land (nearest mainland or island) (km)
All transects were placed into one of three water masses (Subantarctic, Low Antarctic, High Antarctic). The water masses are separated by the Antarctic Polar Front and the southern boundary of the ACC. The Subantarctic water mass is north of the Antarctic Polar Front, the Low Antarctic water mass is south of the Antarctic Polar Front but north of the southern boundary of the ACC, and the High Antarctic water mass is south of southern boundary of the ACC. Transects with a positive distance to the Antarctic Polar Front (i.e., north of the polar front) were placed in the Subantarctic water mass, transects with a negative distance to the Antarctic Polar Front (i.e., south of the polar front) but a positive distance to the Southern Boundary of the ACC (i.e., north of the southern boundary) were placed in the Low Antarctic water mass, and transects with a negative distance to the southern boundary of the ACC (i.e., south of the southern boundary) were placed in the high Antarctic water mass. See Ribic et al. (2011) for maps of the cruise tracks and fronts by season.
Cruises were divided seasonally between winter (April–September) and summer (October–March). For each season, Antarctic-wide cruises were combined into one data set, resulting in 2348 transects in summer (Antarctic-wide-summer-dens-env-final-021025.xlsx) and 1591 transects in winter (Antarctic-wide-winter-dens-env-final-021025.xlsx). Species listed in the combined data sets are all species seen at least once over all the cruises for the specific season. If a species was not seen on a specific cruise, a zero was entered for the species density value. In the Antarctic-wide-summer file, there are 63 species seen at least once. In the Antarctic-wide-winter file, there are 56 species seen at least once.
Note Ribic et al. (2011) removed 17 transects from Antarctic-wide summer cruises that overlapped the Bellingshausen summer cruise grid, resulting in 2331 transects for analysis in the paper. The removed transects have Summer.Cruise.IDs 2332-2348 in the Antarctic-wide-summer-dens-env-final-021025.xlsx file. No transects in the Antarctic-wide winter cruises overlapped the Bellingshausen winter cruise grid.
While the Bellingshausen summer cruises were analyzed separately, they were combined into a single file for publishing, resulting in a file with 1446 transects (PALTER-summer-dens-env-final-021025.xlsx). While the Bellingshausen winter cruises were analyzed separately, they were combined into a single file for publishing, resulting in a file with 652 transects (SOGLOBEC-winter-dens-env-final-021025.xlsx). Similar to the Antarctic-wide seasonal data files, species listed in the PALTER-summer file are all species seen at least once over the 6 Palmer LTER cruises and species listed in the SOGLOBEC-winter file are all species seen at least once over the 4 Southern Ocean Globec cruises. If a species was not seen on a specific cruise, a zero was entered for the species density value. In the PALTER-summer file, there are 29 species seen at least once. In the SOGLOBEC-winter file, there are 16 species seen at least once.
References:
Ribic, C. A., D. G. Ainley, R. G. Ford, W. R. Fraser, C. T. Tynan, and E. J. Woehler. 2011. Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective. Deep-Sea Research II 58:1695-1709. https://doi.org/10.1016/j.dsr2.2009.09.017
Spear, L. B., N. Nur, and D. G. Ainley. 1992. Estimating absolute densities of flying seabirds using analyses of relative movement. Auk 109:385–389.