Date: 3/25/26 11:06 am From: Ethan Monk via groups.io <z.querula...> Subject: [EBB-Sightings] eBird filters, and what to do when something is "rare"
Hi all,
Happy spring. If you use eBird, and would not mind reading for a second, that would be greatly appreciated.
As many people have noticed, it is an early spring, with many birds like Wilson's Warblers and Cassin's Vireos arriving well before they normally do. In Contra Costa County (and in many other counties, it is similar) the eBird filters are set to mark many species "rare" until several days after the all-time, record early spring arrival date. For example, the earliest historical arrivals for Cassin's Vireo in Contra Costa County history are right around March 21st-24th, so they are flagged as rare until March 27th. Early reports are more significant, and so are more deserving of scrutiny, and perhaps are more likely to be wrong (this is especially true in the age of Merlin, which uses some form of probability model when suggesting species identifications). This means that in early springs, like this one, active birders might be flagging the filter a lot, as large waves of spring migrants arriving earlier than typical will often flag as "rare."
So-- I am out eBirding, and I have found a species that flags as rare--what do I do? The "rare" designation is the system's way of telling you that it wants information to substantiate the sighting. How much information is needed is going to depend on the context, for example an aseasonal Western Tanager and a Spotted Redshank will produce the same response from the system ("rare"), but clearly require different levels of documentation. But, if something flags as rare, always always always some helpful information is needed. Writing something like "in pine tree" is only valuable in confirming that it was not a "pocket-click," and thus is not helpful really at all. In springs like this one, when many things are early, the early context can be taken into account, so not much information is needed at all, but again something is needed.
For many spring early arrivals, consider writing ~one sentence describing field marks you observed that led you to the ID. Otherwise, I will send you an email asking for more documentation, and that just creates more work for you and for me :) Even better if you can include something that indicates you understand why a species is rare, but this is not necessary. Going back to the Western Tanager example, say you see an early adult male Western Tanager tomorrow... what would be an ideal description? Well, it is a week or so early, about in line with many other early arriving species this spring. Something like "Early-- red head, bright yellow body, black wings" would probably get the job done. Even better, although absolutely not necessary, if you could write something like "this is an early spring... red head, bright..." That way people looking back on the eBird checklist in future years will have some additional context.
