Like this (Very Rough Example - a picture is worth a thousand words). Explanation is after the picture.
This is a map drawn to represent a certain section of canyon. The two thickish curvy lines represent the cliff sides of the canyon. Circles with "X" inside represent other obstacles such as pillars in the canyon.
Each line that has arrows attached to the end represent the direction of a wind current. For example, in this current map, there are 4 lines that are "inside" the canyon, with 3 arrow pointers, and one line that is in the center with only 1 pointer.
The arrow pointers could be what the Avians use to determine wind strength - the more pointers, the higher the wind speed. Eg: each pointer is 25 kph (or any other value you choose). Following this map, the Avian reads: Oh, there are currents going in that direction that go at 75kph. There is also one that goes at 25kph.
But air is 3d. How do we know what level the wind is at? I draw attention to the numbers near each line. Of course, when the Avians do this they'll probably use a different color for the numbers, but the numbers represent a "depth" level. Perhaps 0 being ground level, and every increment of 1 is 50m.
Reading this map, you can see that the currents at the bottom of the canyon (approx 150m down (negative 3)) are at 75 kph, and the currents at 50m above the canyon are only at 25 kph. There is a current to the right of the canyon 200m up that goes at 25 kph.
But what about updrafts? Those are important for lift! Please see the sections on the map labled "UD L:X" where X is a number. It may be hard to see, but I did my best to draw a dotted line area around it. Those areas are "updraft" areas, vertical lift providing areas. UD stands for Updraft, and the Avians could use DD for downdraft (if that exists), etc etc. It's just to denote certain large areas of lift manipulating currents. L:X stands for the amount of lift they'll get. A higher number represents more lift, and lower is less. Note: the numbers I've picked for this map so far are arbitrary and you can use what you want - perhaps the maps can even include a legend and scale on the side that show windspeed/strength.
Of course, when the Avians do this they'll have colors to represent landmasses and ocean, etc, instead of doing it on crappy office lined paper...