DOI: 10.5061/dryad.xksn02vsj
title: Compiled seabird densities and distance to fronts in the Southern Ocean

description: 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).
description: The Southern Ocean GLOBEC cruises will be referred to as the
 Bellingshausen winter cruises and the Palmer LTER cruises as the
 Bellingshausen summer cruises. <em>Field and
 Analysis Methods</em> 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)<br>distance to the ice edge defined by
 50% ice cover (km)<br>distance to the Antarctic Polar Front
 (km)<br>distance to the southern boundary of the Antarctic
 Circumpolar Current (ACC) (km)<br>distance to the 1000 m isobath
 (km) (which represents the Shelf Break Front)<br>distance to the
 Antarctic coast (km)<br>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: <br>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.
description: # Compiled seabird densities and distance to fronts in the Southern Ocean
 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](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](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](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.