The computerised bird monitoring system devised on the basis of MRL-5 meteorological radar enables to perform around-the-clock automated bird monitoring. The paper presents an algorithm for identifying bird signals against a background of other objects. The radar signal reflected from a flying bird changes its location in space. In case the flight direction remains unchanged, the coordinates of the corresponding radio echoes obtained as a result of successive azimuth scans form a straight line. This enables to isolate bird radio echoes from those of motionless or chaotically moving objects, such as ground clutter, clouds, precipitation, atmospheric inhomogeneities, etc. In the proposed algorithm, the coordinates thus obtained are used for estimation of vectors of individual birds and bird groups.In order to identify a bird signal, its fluctuation pattern is analysed. A fluctuation pattern is determined by the frequency of wing-flapping that is characteristic of a certain bird species. The analysis of the spectra of signals obtained in the study indicates that the proposed algorithm enables to isolate bird radio echoes with approximately 85% confidence. The technique implying simultaneous measurements of signal fluctuation pattern and of the effective scattering area (ESA) forms a promising basis for further studies aimed at determining the species of flying birds by means of radar.

Algorithmic System for Identifying Bird Radio-Echo and Plotting Radar Ornithological Charts The territory of Israel is a route for major bird migration from Europe and certain areas in Asia and Africa and back. During the period of intensive migration, the average density of birds may reach over 500 birds per a square kilometre of the air. These figures, alongside with the fact the air over the country is saturated with aircraft, makes it an urgent task to find solutions for prevention of disasters caused by aircraft-bird collisions. In the present paper, a new algorithm is proposed aimed at identifying bird radar echoes against the background of other reflectors. The implementation of the algorithm has made it possible to improve the computerised radar system for bird monitoring developed earlier in Israel on the basis of MRL-5 meteorological radar station. The time needed for echo selection has been significantly reduced, while the trustworthiness of the ornithological data provided by the algorithm has increased. The new algorithm utilizes several echo properties that have been added to the algorithm previously developed by the authors, the most important of them being the pattern of echo movement. These properties in combination with a set of techniques used for their identification enabled to isolate the echo from moving birds against the background of other objects (ground clutter, clouds, atmospheric inhomogeneities, aircraft, etc.) at the accuracy level sufficient for operational purposes. The information on echo movement was used for plotting flight vectors (velocity and direction) of individual birds and bird groups. On the basis of movement pattern, four types of movement were distinguished: straightforward at non-uniform velocity; straightforward at uniform velocity; significant deviation from a straight line, non-uniform velocity and chaotic undirected shifts. The system enables on-line plotting of operational ornithological charts every 15-30 min, including charts that combine meteorological and bird monitoring data, to be provided to air traffic control services. This makes the proposed radar ornithological system an efficient means of maintaining air traffic safety in complicated meteorological and ornithological conditions.

A radar ornithological station has been created based on the meteorological radar MRL-5 and a specially designed algorithm. The system enables to plot radar charts within the radius of 60 km combining meteorological data with vectors of bird field flying at different heights and pass these charts online over to air traffic control operators. The data accumulated in the study made it possible to obtain certain characteristics of seasonal bird migration over central Israel. The system and the results of the study have become an integral part of ensuring air safety for Israeli military aircraft. The paper is an overview and summary of a development of the system, which was described in a few earlier publications.

Dinevich L., Leshem Y., Matsyura A. 2005. Some characteristics of nocturnal bird migration in Israel according to the radars surveillance. Ring 27, 2: 197-213.The present study is aimed at obtaining radar data on nocturnal bird migration over central Israel to be used for improvement of air traffic safety in complicated ornithological settings. The data obtained, together with the radar monitoring procedure previously developed (Dinevich et al. 2004), resulted in establishing a radar network over Israel that forwards information on bird movements to air traffic control stations every 15-30 minutes.The results of radar monitoring of nocturnal bird migration over central Israel are presented (1998Israel are presented ( -2002 enabling to determine a number of characteristics which are of importance for air traffic control, including average and maximum flight altitudes, altitudes of maximum bird density, the dominant directions and velocity of bird flights.The average flight altitude was found to be mainly within the limits of 1800 to 2000 m in autumn and of 2400 to 2900 m in spring. The absolute maximum altitude was estimated at 5700 m in spring and at 5200 m in autumn. Average altitudes of maximum bird density are considerably higher in spring (ca 1500 m) than in autumn (ca 1000 m). The study of flight directions and speed of over of 20 000 bird echoes showed that the dominant direction of migration was 183°in autumn and 6°in spring. Within the altitude band of 0 to 500 m, deviations from the dominant migratory route were observed, being approximately 135°in autumn and 315°in spring, which can be explained by intensive migration of songbirds from the Mediterranean Sea towards winter-quarters in autumn and back in spring. Cases of reverse migration were relatively rare and were not characteristic for the nocturnal bird migration over central Israel. The average speed of bird flights was found to be around 14 m/s in spring and 13 m/s in autumn, the minimum and maximum flight speed being 8 m/s and 18 m/s, respectively.

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