Date: 3/25/26 4:36 pm From: janet ellis via groups.io <jellis502003...> Subject: Re: [EBB-Sightings] eBird filters, and what to do when something is "rare"
Thank you.
On Wednesday, March 25, 2026, 3:17 PM, Kevin Schwartz via groups.io <kdschwartz...> wrote:
Thank you, Ethan for all you do for eBird! We appreciate you and this was a great write up about why things are getting flagged.
Kevin
| Kevin Schwartz, PhD
Principal Biologist/Wetland and Ecological Restoration Manager
ISA Certified Arborist (#WE-9541A)
ISA Qualified Tree Risk Assessor
CRAM Wetlands Official Practitioner
Olberding Environmental, Inc.
https://olberdingenvironmental.com/
On Wed, Mar 25, 2026, 11:22 AM Ethan Monk via groups.io <z.querula...> wrote:
And for those of you asking "WHY" – why do I have to include a description? We know the spring is early, why can’t you just accept it?
There are, I think, two good answers.
First, the philosophical/doctrinal one. If Species X arrives on the average date of March 15th, and this year the first arrivals are March 7th, even though by March 11th the species may seem “ho-hum” and clearly, they are here, historically the date is still quite significant, even though it may not be significant in the context of this specific season.
If that is not convincing, reason two is that data is always subject to revision. At any time now or in the future, an eBird reviewer can go into the database and update decisions that they think were wrong. We try not to do this frequently, because it is probably a good idea to trust the contemporaneous eBird reviewer, but that does not always happen for a number of reasons. The classic example are Golden-Plovers. In the early days of California birding, most birders thought (what is today known as) American Golden-Plovers were the common species in California, and Pacific Golden-Plovers were the rarest species. It was eventually realized that the exact opposite is the case, Pacifics are the commonest of the two species in California, and American the rarest, and a bunch of old records were revised to account for that mistaken understanding. If you were going back and reevaluating old records of American Golden-Plovers, would you be more likely to throw out records with or without field notes? I know my answer. That is not to say that in the future we will realize the early Western Flycatchers may be another species of Empidonax, for example, but rather a more stringent reviewer may decide to “clean-up” the data, or similar. And the records with no supporting field notes are more likely to be discarded, even if accurate, because… there is nothing there to support them.
Thanks.
Ethan M
On Wed, Mar 25, 2026 at 11:06 AM Ethan Monk <z.querula...> wrote:
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.
Thank you for considering.
Ethan Monk(a Contra Costa County eBird Reviewer)
