Why must my counts be limited to 20 minutes?

Many people have expressed concern that the 20-minute count session only captures the number of species in their yard during that 20 minutes rather than the total number of species that use their yard throughout the day.

Most bird surveys rely on short duration counts. For example, the protocol for the Breeding Bird Survey relies on count sessions of 3-minute duration. Researchers recognize that some species that use your yard will be missed in a 20-minute count. However, repeated counts from the same location helps researchers overcome the “detecability” problem.

The rate at which observers detect new species quickly reaches a point of diminishing returns.  In other words, at the start of a count session, an observer is likely to detect several new species each minute whereas after some threshold point, it may take an hour or more before a new species is detected.  At the point of diminishing returns, it is more efficient to undertake multiple shorter counts rather than longer counts. Click here to read about how you can make a detectability curve for your yard.

Few participants can spend an entire day counting birds in their yard. For My Yard Coutns, it is very important that all participants count their birds in exactly the same way. Project researchers believe that the 20-minute protocol will allow us to collect quality data from as many participants as possible.

How big is a half-acre?

Participants count birds within an area no larger than 0.5 acres, which is 100 ft. x 217.8 ft. (approximately the length of 2-1/2 city buses by 5-1/2 city buses). The area must either be directly adjacent to a residence or building, or must surround it.

What if my yard is actually bigger than a half-acre?

Select an area that you estimate to be a half-acre and record birds within that limited area. A half-acre is 100 ft. x 217.8 ft. (approximately the length of 2-1/2 city buses by 5-1/2 city buses).

What if my yard is actually smaller than a half-acre?

If your yard is smaller than a half-acre, just specify the size of your count site when you enter data in eBird. To help estimate, remember that one city bus is approximately 40 ft.

I plan to take a two-week vacation from home this summer. Can I still participate?

Don't let vacations stop you from participating. The key is to collect as many checklists as you can in the spring and  summer. You should collect a minimum of 10 checklists, roughly evenly spaced throughout the spring and summer.