From backyard surveys to the annual Christmas Bird Count to refugee evaluations, counting birds is an essential tool to accurately understand the numbers of birds in an area. But birds are often active and moving in flocks of all sizes. Different species may be foraging and flying together. How is it possible to accurately count them?
Why Bird Counts Matter
Reasonably accurate bird counts provide invaluable data for conservation efforts. Wildlife officials, ornithologists, and conservation organizations rely on bird population data to determine the size of a species’ population. Bird counts can also measure whether the population is growing or shrinking over time. If a count is taken in late summer or early fall after the breeding season, it can help determine how successful that breeding season has been.
When counts are made during migration periods, comparing data over a few days or weeks can help track when birds are on the move and when migration is at its peak. Bird population numbers can also help evaluate ecosystem health and habitat suitability for different birds, directly helping conservation and preservation efforts. It is essential that bird counts be accurate to be as useful as possible.
Different Ways to Count Birds
There are several ways to count birds effectively. The most useful will depend on the types of birds being counted, the composition and size of flocks, the behavior of the birds being counted, and the skill of the counter. Learning different count techniques can help you prepare to participate in different types of bird surveys.
The simplest method of counting birds is the basic 1-2-3 of individual counting. This highly accurate technique is ideal when birds may be slow-moving or stationary and are unlikely to be counted more than once. This is a good tactic for solitary birds such as raptors or herons. You can also use it for counting small backyard flocks. Take care not to recount individual birds.
As you gain skill with counting birds, it can be easier to count small groups of birds rather than count individuals. You can count larger groups of birds more quickly by twos, threes, fives, or even tens, without a tremendous loss of accuracy. This technique is perfect for small or medium-sized flocks. You can use it when birds are active or moving. It is best for single-species flocks or when different species are easily distinguished and will not be mistaken.
Blocking or Gridding
When large, dense flocks of birds must be counted, a technique called blocking or gridding can be highly effective. This tactic involves mentally dividing a large flock into smaller segments (grids or blocks), and counting just the birds in one section more closely. That number can then be multiplied by the total number of grids in the flock to determine a full count. This counting method is best with single-species flocks when the birds are not moving too much, and when the overall density of birds throughout the flock is relatively uniform. Adjustments may need to be made for uneven flocks or near flock edges.
You can estimating numbers using proportions when several species are flocked together. This involves counting birds by the blocking method, then adjusting the population numbers based on the proportions of birds in each grid. There may be 100 birds per section, for example, with one-quarter being plovers, one-half being gulls, and the remaining one-quarter being sandpipers. If these proportions are relatively consistent throughout a mixed flock, this technique can yield fairly accurate count estimates.
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When birds are in motion, a timed count can be an efficient way to estimate their numbers. To do this, choose a fixed point the birds are passing. Count the birds that pass that point—a specific tree, pole, or building, for example—in a period of time, such as five minutes. Compare that count to the time the flock takes to pass that point—such as 20 minutes—to determine the full flock size. This is a less accurate count method because in-flight flock densities can vary tremendously. It is useful for counting birds in flight, particularly with very large, quickly moving flocks.
A highly accurate way to count birds is with photographs. If you can take a photo of a full flock or count area, you can enlarge it for counting. This can be a painstaking process, but is useful for counting birds in high-stress areas, like rookeries or nesting colonies. Good photography equipment is necessary for the proper resolution and image detail to count the birds well.
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More Tips for Bird Counting
Counting birds can be a fun and easy way to contribute to different citizen science projects. Even novice birders can contribute valuable data to a bird census. Make your count a success with these additional tips:
- Working with a group can ensure more eyes for more accurate counts
- If a specific project has detailed guidelines for how to count birds, be sure to follow those recommendations
- It is better to underestimate numbers than overestimate to account for birds that may have been counted more than once
How many birds will you count today?