We use Baodi S-Band Dual-Polarization Weather Radar data from June 2022 to March 2023 in analyzing the biological activity in the sky over Tianjin Region. The results show that there are obvious seasonal and diurnal variations of biological activities in the sky over Tianjin Region. The migration echoes of migratory birds detected by radar are concentrated from late February to late November, during which wetland bird activity is more obvious in summer, and migratory bird activity is particularly frequent in February and November. The appearence time of bird echo is obviously correlated to sunrise and sunset. The echoes of birds show obvious circular characteristics in the reflectivity products, with the echo inten-sity exceeding 35 dBz. It can be seen from the radial velocity product that the flight speed of birds is about 10-27 m·s-1; and from the product of correlation coefficient (CC) that the overall CC of bird echo is low, mainly distributed in the range of 0.1-0.8. And then from the differential reflectivity （ZDR） products, we can see that the distribution of ZDR is not uniform, up to 3-5 dB as the highest. Compared to single polarization weather radar, S-band dual-polarization weather radar has significant advantages in recognizing biological echoes in the sky.