Plumbeous and Cassin's vireos in Mono County - eBird, and Merlin

[Chris McCreedy]

Hi,

A situation many of the list subscribers are aware of - Mono County is within the Cassin's Vireo (CAVI) - Plumbeous Vireo (PLVI) contact zone. Several years ago a researcher that was working on them indicated that the eBird maps for the species in Mono seemed to be a bit of a mess, and I agreed. 

I have the filter set at 0 for the two species during the breeding season to encourage observers to track down individuals to confirm the species identification by sight, as too often, observers were hearing "solitary" vireos singing and picking one or another of the two species--sometimes completely arbitrarily, sometimes based on the speed and tone of the songs' deliveries.

Carl has a nice recent checklist here that highlights this issue:

https://ebird.org/checklist/S140400584

Over time the maps have worked themselves out, with visual (and better, photographic) evidence demonstrating how the two species line up across the county in the breeding season. I will generally accept heard-only records from places where one species is overwhelmingly found over the other (e.g., PLVI at Wildrose Canyon), otherwise, I require some notes on the individuals' plumage. 

Reviewers are increasingly confronted with checklists that justify a species ID with something along the lines of "Merlin said so". As pointed out in Carl's checklist and in many recurring examples that pop up in Facebook's eBird discussion group, *Merlin is often correct, and Merlin is often incorrect*. It is a tool designed to help observers narrow down what they may be hearing or seeing, not a final arbiter of what they observed. 

If Merlin is your only justification for a call on a flagged species in eBird, it is not sufficient documentation for the record's approval. There are occasional cases where I've approved records that were documented with Merlin, but this was not because of Merlin, but simply because the species was already known the be present at the location.

Thank you for your documentation of Mono's wonderful birds.

Chris