how do we distinguish between birds and non-bird data such as cloud cover, pollen, and/or insects?
Here are several keys to determining non-bird signals from bird signals. First, if you’re looking at the animated loop, birds are going to enter the radar after sunset, starting nearest the radar station, and growing outward from the center (growing concentric circles). This is because the radar beam is pointing up at an angle toward the sky such that it is closest to the ground at its origin, and highest above the ground at the limit of the beam (farthest away from the origin). Think of an ice-cream cone standing on end, where the bottom of the cone is touching the radar dish, and cone itself extends up into the sky. So, as birds lift off the ground and into the atmosphere after sunset, they are first detected nearest the radar, and subsequently detected further and further away from the radar, as they reach higher and higher altitude. At some point (usually on average around 1500 feet, but depending on the conditions in the atmosphere it may be higher by several thousand feet) they s
