Date: 4/14/17 12:18 pm From: Christopher Hill <Chill...> Subject: Re: eBird reporting
I deleted the specific checklist Kent was responding to, but I will agree with him. When looking for areas of Loggerhead Shrike concentrations in South Carolina, I have been a bit frustrated by ebird lists that had high numbers, but then turned out to be from a 200 mile drive that started or ended in another state! The dot on the map had basically no relationship to the birds counted. That’s an extreme example, but what Kent says is true. Outliers like that get incorporated into maps and other data processing and distort the picture.
It's a long page so I'll quote just the relevant section:
Traveling counts have proven to be the most effective type of observation for modeling bird populations at large scales. By doing these counts birders often detect a good proportion of the birds in a given habitat. It is critical, however, that your traveling counts not be too long. Our analysts are able to effectively use traveling counts that are ≤5 miles. Most birding that is conducted on foot easily falls within this window, but traveling counts by car can often be longer. Please consider breaking up your long traveling counts into shorter distance ones. It's best if these shorter counts are in a relatively consistent habitat, or does not pass through habitats that are too different. For example, a logical point to break a longer route into segments would be a transition between forest and farmland, as the birds found in these two habitat types are vastly different. Doing so would make information associated with each location — such as vegetation information from satellite images — more informative. Plot your location at the center of the area traveled, not at the start point or end point.