Aeroecology studies how airborne life forms use and interact with the biotic and abiotic components of the atmosphere. The aerosphere is treated as habitat, and how organisms respond to and exploit the dynamic aeroscape affects the ecology, evolution, and conservation of many birds, bats, insects, and plants. Interactions and properties of the aerosphere—the zone closest to Earth's surface—create selective pressures that shape organisms' size, morphology, and behavioral, sensory, metabolic, and respiratory functions. Unlike strictly terrestrial or aquatic organisms, aerial organisms are immediately affected by changing conditions such as wind, air density, oxygen concentration, precipitation, temperature, sunlight, polarized light, moonlight, and geomagnetic and gravitational forces. Traditionally, aeroecology has relied on field methods such as direct observation and detection techniques (e.g., moon-watching, thermal imaging, and bioacoustics). Recently, the field has advanced through remotely sensed data, especially Doppler weather radar (NEXRAD). In March 2012, an international, interdisciplinary Radar Aeroecology Workshop was held at the National Weather Center, University of Oklahoma, Norman, Oklahoma, USA. Experts in ecology and meteorology have discussed how various radar technologies can be applied to aeroecological questions. Aeroecology research groups at the University of Oklahoma and the University of Delaware continue to develop and integrate remotely sensed data to quantify, characterize, and track biological use of the lower aerosphere.

History
Aeroecology is a relatively new field. The concept was introduced by Boston University researcher Thomas Kunz and colleagues in a 2008 paper, "Aeroecology: Probing and Modeling the Aerosphere."

Observational aeroecology
Traditionally, aeroecology relied on ground-based observations of organisms occupying the airspace above, including near-surface foraging behavior and nocturnal passage migrants observed by human observers equipped with optics. The advent and adoption of technologies such as thermographic cameras, marine radar, and NEXRAD for aeroecological studies revolutionized the ability to detect and track sufficiently large animals in the aerosphere.

Radar aeroecology
Studies using weather radar were pioneered by Dr. Sidney A. Gauthreaux during his graduate work at Louisiana State University and later as a professor at Clemson University. His initial work with radar images produced by the WSR-57 network revealed much about the trans-Gulf of Mexico arrivals and departures of Neotropical migratory birds.

Reflectivity: Radar beams reflect off sufficiently dense objects, such as water droplets, airplane fuselages, or flying animals. The reflectance of an object depends on its radar cross-section, which is dictated by the object's size, shape, and material composition. Weather radar reflectivity data represent the summed reflectivity of all objects within the sampled airspace and therefore provide a generalized measure of the amount of rain or, for aeroecological purposes, the abundance of animals in that volume of air. Aeroecologists use the term "bioscatter" to describe radar reflectance from biological objects.

Relative velocity: Weather radars can detect Doppler shifts in returning waveforms. This information is used to estimate a mean relative velocity for all objects within the sampled airspace. Aeroecologists have used this information to distinguish objects drifting with the wind (particulates, e.g., dust, seeds, or pollen) from objects moving slightly faster or at an angle to the wind (e.g., insects), and from objects moving at least 5–6 m/s faster than, or against, the predominant wind direction (e.g., birds and bats). Dual-pol radar: An upgrade of weather radars to allow dual-polarization of the radar beam promises greater characterization and discrimination of airborne targets. For aeroecology, this should improve the ability to distinguish migrating birds from insects, weather, or suspended particulates. Ratios of horizontal to vertical beam reflectivity and Doppler shift hold promise for gauging discrepancies between bird orientation and their realized movement paths, providing a means to assess drift compensation among migratory birds. See also: Natural environment; Nature; Ecology.