Management and research applications of long-range surveillance radar data for birds, bats, and flying insects

Abstract

Long-range surveillance radars include weather-surveillance radars, airport-surveillance radars, terminal Doppler weather radars, and private Doppler radars. All of these technologies can be used to study bird, bat, and insect movement patterns. However, with the exception of the weather-surveillance radar system in the United States, access to data from these radars is currently limited. Therefore, we focus this publication on applications of the U.S. weather-surveillance system. The current nationwide system of more than 150 digital Doppler weather surveillance radars, variously known as WSR–88D (Weather Surveillance Radar, 1988 Doppler) or NEXRAD (NEXt generation RADar), is the most well known network of long-range surveillance radars. WSR–88D is also the long-range radar most frequently applied to biological questions. These high-powered and highly sensitive radars repeatedly scan a wide geographic area at multiple elevation angles using a narrow conical beam, providing coarse spatial and temporal resolution. WSR–88D measures three data products that are useful for biological applications: (1) reflectivity, a measure of the amount of energy returned to the radar from targets in the sampled airspace, (2) radial velocity, a measure of mean target velocity toward or away from the radar, and (3) spectral width, a measure of variation in radial velocity. The maximum detection range than 100 km (62 mi). The maximum range increases when these data are used to answer questions about migrating birds at cruising flight altitudes. Data can provide information about bird movement patterns at scales that range from a few kilometers (Diehl and for WSR–88D data typically varies depending on the altitude of birds in the airspace (fig. 1). When these data are used to answer questions related to habitat use (for example, when birds are low to or just taking off from the ground) the maximum detection range is usually less T here is renewed interest in using long-range surveillance radar as a biological research tool due to substantial improvements in the current network of radars within the United States. These improvements include an enhanced capacity to detect biological targets and Doppler capability that enables the measurement of direction and speed of targets. Additionally, the digital nature of the radar data, plus the increasing availability of inexpensive computing power and geographic information systems, enables a broad range of quantitative, spatially explicit biological applications. The purpose of this publication is to provide a summary of long-range surveillance radar technology and applications of these data to questions about movement patterns of birds and other flying wildlife based on publications that provide more detailed information (Buurma, 1995; Gauthreaux and Belser, 2003a, b; Gauthreaux and others, 2003; Diehl and Larkin, 2005; Larkin, 2005). For simplicity we refer primarily to birds in this publication; however, the applications are usually also appropriate for bats and flying insects. The intended audience is potential radar-data end users, including natural-resource management and regulatory agencies, conservation organizations, and industry.