Crows stream overhead as they go into or out of a roost; they decorate the trees throughout a wood lot in a night roost site or a late afternoon pre-roost gathering; they pepper the fields as they forage. Are there hundreds? Thousands?? Tens of thousands?? As ecologists study the distribution of crows into roosts in winter, they want to know approximately how many birds are in a given roost. It is a challenge but it is possible to COUNT CROWS to a useful degree of accuracy.
Try these steps:
1. Decide if you are going to be counting flying crows coming into (or out of) a roost or crows sitting in trees of a roost or crows foraging on the ground.
2. Flying Crows: focus on one “flight line” that is moving mostly in one direction. Start to count near the front, as quickly as you can to reach 50 crows; then quickly count another 50. As you reach a “50”, let your eye rest on that group of 50 briefly so that you get a visual picture of what 50 crows looks like. After you are comfortable with the look of a “chunk of 50”, count by 50 crow “chunks” from the front of the line toward the back, keeping a similar perspective on the flying crows. (IF there are relatively few crows, you may be more accurate if you count by tens. IF there are many, many crows, you can increase your chunk size to 100, or even 1000, with a little practice.)
Another way to deal with large numbers of crows flying through your field of view is to count for a minute or fixed number of minutes to get a number per minute, then time the flow of crows past you, as long as the numbers going past seem comparable, and calculate as total minutes with flying crows * number of crows per minute
3. Crows in Trees: one of the easiest ways to count crows in bare trees is to count the number of crows in each of 5-10 average looking trees. Then count the number of tree crowns with crows in them and multiply by your average number per tree.
4. Crows on the Ground: similar to the flying crows, count off in 50-100 bird “groups”, then use your learned view of one grouping to count the groups (i.e. by 50s or 100s).