Indicator: Marine Birds

Feb 23, 2017 (Last modified Aug 6, 2020)
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This indicator is a continuous index of highly productive areas for birds that feed exclusively or mainly at sea. It uses seasonal predictions of relative abundance for sixteen species of marine birds. Note: This indicator is at a 200 m resolution, which is coarser than other indicators used in the 2020 Blueprint.

Reason for Selection

Marine birds help identify key areas of ocean productivity and overall ocean health, are regularly monitored, and resonate with a variety of audiences. This indicator complements the marine mammal index by providing finer spatial resolution and stronger connections to forage fish productivity.

Input Data

Blueprint 2.1 ecosystem map (see Appendix A)

– Potential species to include in this indicator began with Tier 1 and Tier 2 priority species in Bird Conservation Region 27 (the Southeastern Coastal Plain) in the Southeast United States Regional Waterbird Conservation Plan. This plan did not include waterfowl species, so additional waterfowl were added from priority species identified by the Northwest Atlantic Birds at Sea Conservation Cooperative. We narrowed down this larger combined list in two ways. First, we removed species from the list that didn’t have spatial models available. Then, we removed species that had models with poor predictive performance and/or large spatial errors. The Marine-Life Data Analysis Team provided input data for this indicator. These relative abundance models cover the entire U.S. Atlantic. They use aggregated survey information and oceanographic variables to predict the relative abundance of marine birds throughout the region. Species with seasonal models used in this indicator are: Audubon’s shearwater (fall, spring, summer), White-winged Scoter (fall, spring, winter), Black Scoter (fall, spring, winter), Horned grebe (winter), Band-rumped storm-petrel (fall), Bermuda petrel (fall), Manx shearwater (fall, spring, summer), Black-capped petrel (spring, summer, winter), Northern gannet (spring, summer, winter), Bonaparte’s gull (spring, winter), Common loon (spring, summer, winter), Red-throated loon (spring, winter), Cory’s shearwater (fall, spring, winter), Royal tern (fall, spring, summer), Great shearwater (fall, spring, summer), Sooty shearwater (fall, spring, summer), and Common tern (fall, spring, summer).

Mapping Steps

1) To identify high quality areas for each species during each season, we used the core-area algorithm in Zonation (edge removal = 0, warp = 1). We included the seasonal relative abundance layer for each species as a separate input and weighted all but one equally. For Bonaparte’s gull in spring, the sole exception, we reduced the weight from 1 to 0.1 to reduce the impact of a spatial artifact related to out-of-sample-area prediction. To account for boundary effects, we ran all the models across the entire U.S. Atlantic.

2) We reprojected the data to Albers Equal area.

3) We filled in the area of missing values near the coast caused by the coarse resolution of the input data, according to the following steps:

– Resampled the marine ecosystem mask to 2,000 meter cells to match the marine bird data

– Expanded the marine ecosystem mask by 3 cells to capture all near-coastal cells

– Used focal statistics (circle with 3 cell radius) to calculate the focal mean of marine bird data

– Where original marine bird data was null, and where it intersects the marine ecosystem, filled in missing values using focal mean

4) We resampled from 2,000 meter pixels to 200 meter pixels using the nearest neighbor method.

5) We changed the values from a floating point raster with a range of 0-1 to an integer raster ranging from 0-100.

6) We clipped the resulting raster to the “Marine” class in the Blueprint 2.1 ecosystem map.

Final indicator values

The final indicator is continuous, with values ranging from:

High: 100 (most important for seasonal abundance of marine bird index species)

Low: 4 (least important for seasonal abundance of marine bird index species)

Known Issues

– Models are likely underpredicting the importance of areas in the eastern part of the marine ecosystem. Survey effort was very low in that area and many input models did not even extend their predictions into the eastern area.

– Does not capture fine resolution patterns nearshore. Model predictions are fairly coarse and do not capture finer variations in relative abundance nearshore and near estuaries.

– Does not connect with equivalent marine bird indicator for the estuarine ecosystem. Many of these marine bird species could also be excellent indicators in the open water portion of the estuarine ecosystem; however, spatial models covering the full area of the estuarine ecosystem are not available at this time.

– While this layer has a 200 m resolution, the source data was coarser than that. We downsampled 2 km pixels to 200 m.

– Please note that this indicator is at a 200 m resolution, which is coarser than other indicators used in the 2020 Blueprint. This is an artifact of the approach used for the marine environment in Blueprint 2020.

Disclaimer: Comparing with Older Indicator Versions

There are numerous problems with using South Atlantic indicators for change analysis. Please consult Blueprint staff if you would like to do this (email

Literature Cited

Curtice, C., Cleary J., Shumchenia E., Halpin P.N. 2016. Marine-life Data and Analysis Team (MDAT) technical report on the methods and development of marine-life data to support regional ocean planning and management. Prepared on behalf of the Marine-life Data and Analysis Team (MDAT). Accessed at:

Hunter, W.C., Golder, W., Melvin, S., Wheeler, J., 2006. Southeast United States Regional Waterbird Conservation Plan. U.S. Fish and Wildlife Service, Atlanta, GA.

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Content date:
2020-08-15 04:00:00 (lastRevision Date), 2020-08-15 04:00:00 (Release Date), 2019-08-15 04:00:00 (Start Date), 2021-08-15 04:00:00 (End Date)
Rua Mordecai(Point of Contact), Amy Keister(Point of Contact), Hilary Morris(Point of Contact), U.S. Fish and Wildlife Service(Point of Contact), Southeast Conservation Adaptation Strategy (SECAS)(Point of Contact), 2020-08-15(lastRevision), 2020-08-15(Release), Indicator: Marine Birds,,
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U.S. Fish and Wildlife Service
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South Atlantic Blueprint

The South Atlantic Conservation Blueprint is a living spatial plan to conserve natural and cultural resources for current and future generations in the face of future change. It spans parts of six states, from Virginia to Florida, including U.S. waters to 200 miles offshore. The Blueprint...