In Ohio, there are a surprising number of parks, wildlife areas, trails, and a National Park which are located on a county line. If you carefully keep your bird records by county, it is helpful to know where the county line is located so that the birds will be assigned to the proper county.
In eBird, every complete checklist should be thought of as an attempt to record everything that you can detect from where you are standing or walking. If you are standing along the banks of a river you should certainly scan the river and both of its banks. If you are along a ridgetop, you should be counting birds that you can see in all directions. However, at times there may be a geopolitical border that bisects your walking path or your field of view. Birds never have cared much about geopolitics and in many cases they freely cross borders. What is the best way to do your eBirding in cases like this?
When it comes to the position of the birder and the position of the bird, listing rules can be inconsistent. For example, the preference in Ohio is to only count birds that have demonstrably occurred within the state or county boundaries. However, most yard lists count whatever bird can be seen from your yard. eBird best practices strive to bring more consistency to lists.
Ohio eBird reviewers ask that birders keep precise state and county lists. When you are at a location where you see birds across a state or county line, we ask that you keep two incomplete birding lists, one for each side of the border.
When keeping separate checklists for different sides of a border, please follow these rules:
Continue to follow eBird best practices; submit complete checklists that are short in duration and distance.
When traveling somewhere, begin a new checklist every time you cross a border.
Every bird seen or heard from your location “counts”, regardless of where the bird is.
Plot your location as accurately and precisely as possible.
Any time you see or hear a rare bird across a border, add some notes in the Species Comments about the bird’s location.
Geopolitical units give us a way to organize and summarize eBird observations. Any birds you report on a checklist, regardless of where or how far you travel, will be automatically assigned to a county (where applicable), state/province, and country based on where you plot your list.
In most cases, this also determines the data entry checklist and data quality filter. Your checklist can only use one eBird filter, so there may be mismatches in species data if you include birds from multiple geopolitical areas on the same checklist, especially when those areas have considerably different habitats and birds.
These issues can be avoided by doing all of the following, in addition to the instructions above:
These steps ensure your checklist is assigned to the correct eBird filter and summarized in the appropriate county, state, and country.
From eBird help article Birding Along Borders