questionable reports (eBird) of Common Ground Doves and California Gnatcatchers
Justyn Stahl wrote yesterday about the need to set the Common Ground Dove county filters, except in the desert, in eBird to 0 so that all such sightings get reviewed. This species is now very uncommon and very, very, very local in these regions, and it is reliably seen mostly in the Tijuana River Valley, where numbers seem recently down as well. But without a filter set at 0, records of 1 or 2 birds from elsewhere in the coastal-slope lowlands sail right through, with no checking unless the reviewer is willing to check literally every bird on every list. And sure enough, the county eBird reviewers have started to send out queries to observers about their ground dove sightings away from expected areas. And so far the responses have mostly been along the lines of "Oops, I meant Mourning Dove!"
Another species with similar issues, but which one cannot set the filter to 0 without unleashing a torrent records to review, is California Gnatcatcher. While local in distribution, it is obviously far more numerous and widespread here than are the ground doves. But if one looks at the species map in eBird for Cal Gnat, there are pins dropped all over the place where the species does not occur. Some problems are certainly misidentified Blue-gray Gnatcatchers, but another regular issue are mis-plotted lists. One good example is the gnatcatcher situation in the Tijuana River Valley. California Gnatatchers are regular residents in the scrub on the hillside and canyons running up to the border fence along the southern edge of the Valley. They are NOT out in riparian and exotic habitat on the valley floor, except perhaps as a very rare wanderer from appropriate habitat. Also, in contrast, Blue-gray Gnatctachers ARE regular and fairly numerous in these areas. A number of lists from places like "Dairy Mart ponds" or the "Bird & Butterfly Garden" have California Gnatcatcher on them, but with no details. Personally, I've never seen the species at either site. Yes, one bird MIGHT wander there a relatively short ways from the hillside to the south, where they are found, but such an event would be quite rare and should be properly documented AT THE TIME OF THE SIGHTING. Often the problem is a visiting birder lists their eBird site as the "Dairy Mary ponds" but then they actually visit multiple sites in the TRV, including a place several miles away like Goat Canyon where they actually record the CAGN.
This all results in faulty data for declining, threatened, or endangered species for which one desires accurate distribution information. (And of course such errors can also involves ALL species.)
–Paul Lehman, San Diego
Source: SanDiegoRegionBirding Latest Reports