Use of Remote Sensing Data to Quantify Bird Distributions and Aid in the Environmental Assessment of Energy Development in the Gulf of Mexico Region

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Knowing where migratory birds consistently stop to rest and forage is critical for conservation planning, particularly along the northern and western Gulf where there is increased interest in energy development.

Northern Parula. Photo by Michael Gray

Northern Parula. Photo by Michael Gray

The Science Issue and Relevance:  Millions of landbirds migrate through the Gulf of Mexico region each spring and autumn and they depend on habitats along the way (also known as stopover habitat) to provide the food and cover needed to complete their journey. Knowing where migratory birds consistently stop to rest and forage is critical for conservation planning, particularly along the northern and western Gulf where there is increased interest in energy development. The construction or expansion of energy facilities and related infrastructure like pipelines and roads may alter or remove stopover habitat. Furthermore, multiple studies have documented that nocturnally migrating birds can be attracted to artificial lighting, especially on overcast nights. Artificial lights can disorient migrating birds, causing them to alter their flight behavior which can deplete their energy stores or increase their chances of colliding with man-made structures. With this in mind, the U.S. Fish and Wildlife Service requested bird distribution data that could be used to inform their environmental assessments of energy projects (e.g., liquefied natural gas export terminals, pipelines, and wind turbines) and other development activities (e.g., cell towers and roads).

Stopover distribution of landbirds within 70 km of the Lake Charles, Louisiana radar station

Stopover distribution of landbirds within 70 km of the Lake Charles, Louisiana radar station.

Methodology for Addressing the Issue:  Using weather surveillance radar data, we are identifying stopover habitats within 70 km of radar stations located in Lake Charles, Louisiana and Houston, Texas. We are analyzing data for spring (March 1 – May 31) and fall (August 1 – October 31) migrations in 2013 – 2015 and will select sample dates by screening radar data collected near evening civil twilight at the lowest radar tilt angle. Radar data collected on nights with precipitation, anomalous propagation, and clutter will be eliminated from further analyses. For the remaining data, we will estimate mean target air speed to identify bird-dominated nights (mean target airspeed greater than 5 m/s). Reflectivity data for each bird-dominated night will be interpolated to the sun elevation angle that corresponds to the timing of peak evening exodus (i.e., highest rate of change in reflectivity as birds leave stopover habitat). The data will be combined with an existing 5-year dataset (2008 – 2012), and then a multi-year geometric mean reflectivity will be calculated for spring (7-year mean) and fall (8-year mean). We will measure landscape metrics thought to be important to transient migrant landbirds, calculate statistical models of bird-habitat relations, and predict landbird distributions within 100 km of the Lake Charles, Louisiana radar.

Future Steps:  Future research could include the use of radar data to determine the distribution of waterbird colonies in southwest Louisiana.