This paper reviews some popular radar techniques involved in ornithological observations. Due to the biological properties of the observable targets, in order to collect correct signatures of the size, ground speed, height and wing beating information, most radar systems originally designed for meteorological detection require various upgrades and modifications, either in the hardware or software design process. Biological targets have relatively smaller Radar Cross Section (RCS) and greater variations in different species. The flying speed could be estimated by a Doppler radar. However, in order to distinguish species from each other, more information such as target altitude, flock patterns, even wing beating frequency have to be obtained from the radar signal processing. The aforementioned considerations and such related issues introduce new aspects and requirements to the radar system design. In the following section, we review various radar considerations in terms of different ornithological signatures. Emphasis is put on the pulse compression and dual polarization imaging techniques from the point of view of recent digital signal processing (DSP) implementation, which may be able to contribute to the advanced radar ornithology system design of the future.