eBird rarity - what are the criteria?

[Mike Bickerdike]

Very helpful, thank you Peter.

BUT the problem is that Bushy Park, like Motutapu Island and doubtless many other small reserves, falls within a much larger Bird New Zealand region (e.g., 88-ha Bushy Park within 2+ million ha Manawatū-Whanganui region). The filters are set at a regional level. It would be a mind-numbing task to set filters individually for every little reserve or patch of bush or wetland within these regions, so for reintroduced species or others that occur in only a few well-known sites, they will always be flagged (and those birders looking for rarities, alerted). Flagging these sightings is important because one big question is to what extent, if any, these reintroductions can serve as nuclei from which a species can spread out and begin colonising surrounding areas. If we did not flag them, we might miss the opportunity to assess, as a first cut, the validity of sightings outside the areas to which the species have been reintroduced (and perhaps the chance to alert others to what might be happening).

This is an especially useful point, and explains some of the discrepancies and strange triggers for some rarities I've observed - that makes a lot of sense now.

[Raewyn]

This has been very useful for me to learn more about what eBird can do and how it works. Having just uploaded my list from our recent trip to Spirits Bay, I came across something that has always puzzled me and hasn't been mentioned here. That is, the list of "not reported" birds often includes reasonably common birds, including those that I have previously reported at the specific place. Is that a problem or just something to live with?

[Brendan T]

Hi Raewyn, the thread's been growing so it's perfectly understandable that Nick's really helpful reply may have been overlooked, but I'll copy the relevant part where he addressed that for you here:

"If you are asking why the species has a red dot against in in the mobile app, that is based on sightings in previous years (data held in a mainframe somewhere-so the phone has to talk with the mainframe and the mainframe with the phone) within the same 3 day window within a square area. The size of the area is dependent on the number of lists that have been submitted in that time window. So for poorly birded areas this might be say 180 x 180 km, and for well birded areas less than 10 x 10 km. The most frequently reported species get no dot, those less frequently reported a yellowy half dot, and those with very few/no records a red dot. True rarities should get an R in an orange square. Issues can arise when you have no connection with a cell tower (and there are a few other anomalies that occasionally occur)."

Here is the same information, worded differently, directly from one of eBird's explanatory pages:

"Red dot: Unreported. Species not previously recorded on any checklist in that grid square and time period*

* The "time period" is the past 10 years of data for the 3-week period centered on the current week. The "grid square" is the fixed 20x20km square in which the checklist occurs, unless fewer than 25 complete checklists have been submitted from that square in the last 3 weeks, in which case a 60km grid is used, then 100km, and then the regional level."

Edited to add: To directly answer your question, it's probably because the species, while common, has happened to not be reported in that particular area around that particular time before.

[Raewyn]

Thank you Brendan. I missed that because of the mention of dots in the mobile app etc. I never use that, rather do my uploads retrospectively on the desktop computer. For local birdwatching it's the same or next day. For trips to Spirits Bay it's often weeks later - like this time.

I now understand that it's not just "never reported" but really means "has not previously been reported in that particular 3-weeks of the year". Makes perfect sense now.

[Nick Allen]

Here's an example of rare birds not having UBRs submitted to make them official. So far only 1 accepted UBR for Chatham Taiko away from the Chathams and no UBRs fully accepted for Pycroft's Petrel south of the Bay of Plenty. Lots of birders names...

https://ebird.org/checklist/S27821912

[Mike Bickerdike]

On this topic, I've noticed I'm getting alerts for small numbers of feral (rock) pigeons in Auckland. Given these are extremely common, I wonder if the filters need tweaking for this species, so they come off the eBird alert list. e.g.: https://ebird.org/checklist/S229051448

[Brendan T]

My understanding is that is a reporting issue rather than a filter issue, as Rock Pigeon should be reported as Rock Pigeon (Feral).

There's a great eBird article here, explaining it: https://ebird.org/news/rock-pigeon/

A relevant summary from the above page, emphasis added:

Again, in the Americas and other areas where they are all introduced, “Rock Pigeon” is not the correct option to eBird your Rock Pigeon sightings. In the below areas birds are all from domestic stock and hence are all “Rock Pigeon (Feral Pigeon),” regardless of the plumage:

North America
South America
Asia, anywhere north and east of a line from India to Kazakhstan
Australia and New Zealand
Most Pacific, Atlantic, and Indian Ocean islands
most countries in northern Europe (see European range of wild type Rock Pigeon above)

None of which helps us stop getting those false alerts, of course! But can be handy to know why it's happening.