How to Count Birds

Bird Counting Techniques

Shorebird Flock
U.S. Fish and Wildlife Service/Flickr/CC by 2.0

Many citizen science birding projects ask participants to count birds, and many birders enjoy keeping a count of the birds in the field or even just at the feeders. But what good is counting individual birds, and how can you count large, active flocks accurately?

Why Count Birds?

Counting each individual bird you see can be a challenge, but it can also be valuable information for scientific research. As populations of birds change, those fluctuations may indicate shifts in pollution levels, climate change, habitat loss, migration timing, and more. Annual events such as the Christmas Bird Count, Project FeederWatch, the Great Backyard Bird Count, and the Big Garden Birdwatch are different bird census projects, and over several years, they accumulate a massive amount of data about numbers of birds in different locations. That data would be impossible to gather without the help of every participant, however, and the more accurate a count is, the more useful the data will be for conservation projects and research.

Techniques for Counting Birds

There are many ways to count birds depending on the birds present, the size of the flock, and how it is behaving. Easy bird counting techniques include:

  • Individual counts: When just a few, recognizable birds are present, each individual bird can be easily counted without fear of gross miscalculations. This basic one-two-three technique works best when the birds are clearly seen and slow moving so individual birds will not be counted multiple times.
  • Grouping: Counting birds in numeric groups is an easy technique for tallying small or medium-sized flocks. With practice, birders can easily learn to count birds not one by one, but five by five or ten by ten. This allows for a faster count while still keeping the increments small enough for precise numbers.
  • Grids: Also called blocking, this counting technique is most often used with larger, single species flocks where the birds are relatively stationary. The field of view is divided into a grid of even sections, and the birds in one section are counted as close to individually as possible. Multiplying this count by the number of grid sections in the flock can give a reasonable estimate of the total number of birds.
  • Selective counting: When a large flock of birds has some obvious mixed species, it may be possible to selectively count all the birds easily. First, pinpoint the more unusual birds in the flock and count them individually, then use the grid technique on the bulk of the birds. This provides not only a good count of the flock size, but also represents the diversity of the birds present.
  • Proportions: When a mixed flock has too many species or is too active for selective counting, a good estimate can be made by counting proportions of the species present. Similar to the grid technique, only one section of the flock is counted, but each different species is noted individually, and the proportions are used to calculate the total number of birds of each species in the entire flock. This technique is best when a flock is heavily mixed and each species is spread throughout the flock.
  • Timing: When a flock is moving quickly, it can be impossible to create a grid or to count birds individually, since the movement will obscure other birds and make any estimate less accurate. A timing count focuses on a fixed point the flock is passing, and counts the number of birds to pass that point in a certain period of time, such as a few minutes. Then the entire amount of time it takes for the whole flock to pass is noted, and the count is multiplied by the number of increments in that overall time to gauge its full size.
  • Photographs: A digital photograph can be used for an accurate count if the entire flock can be photographed. The photo is then manipulated on a computer or printed out and individual birds are marked off as they are counted. This is a time-consuming method but can be very precise for a reliable count when high levels of accuracy are necessary. A remote camera and a timer to take the photographs can also be used to gather data, and the birds can be counted at a later time.

More Bird Counting Tips

Practice is essential to make the most of your bird counting skills. The more frequently you count birds, the more comfortable you will be with each count you make, knowing the data you collect is accurate and therefore more valuable. There are several ways you be sure your counts are even more accurate and useful, including:

  • Keep a notebook or birding journal handy to write down a record of the birds you count, particularly when counting over a longer period of time. If you have the notes, you will not need to “guesstimate” the birds you thought you’d counted.
  • Account for density when counting flocks, particularly when using grid or timing techniques. Birds are often less dense on the outer edges of the flock, and if your grid sections are not balanced, your count can be significantly off.
  • Work to be as accurate as possible, but when necessary, choose to underestimate rather than overestimate the numbers of birds you see. This will help correct for any inadvertent errors, such as birds that were counted more than once.
  • If you are counting for a specific project, use their guidelines for estimating numbers or how they want birds counted. This will help the project collect data from many sources but still be sure the numbers have been uniformly obtained.

Counting birds can add a new dimension to your birding, and once you start keeping track of the numbers of birds you see, you’ll be amazed at how many birds you find.