In other words, we shouldn't be so gullible...
On Monday, February 3, 2020 at 6:07:19 PM UTC-7, David Tønnessen wrote: > > The last several days have seen my eBird rare bird alerts blown up by > reports of "Slaty-backed Gull" with photos of anything from Iceland > Thayer's Gull to the continuing 1st cycle Great Black-backed Gull, or > accompanied by brief description along the lines of "continuing bird." > Prompted by this, I felt the urge to issue a word of caution on hasty gull > identification. > > Right now, there seems to be multiple rare Glaucous-winged Gulls and a > number of confusing gulls of probable Glaucous-winged Gull ancestry at > Warren Lake, Larimer County that are giving even the most experienced > gullers some trouble. The candidate for Slaty-backed Gull that Nick Komar > reported to eBird last week was reviewed by multiple other experienced gull > watchers, and thus far has been deemed inconclusive. I sent the photos to > Alvaro Jaramillo, an established gull identification wiz who has found > multiple Slaty-backed Gulls in California as well as the state's first Kelp > Gull. His response was "It is not a Slaty-backed Gull. Looks better for > Herring, but some odd issues that maybe can be explained away, maybe not. > But it does not look like a Slaty-backed to me." I myself think the bird > looks within variation of some Herring Gull with Glaucous-winged ancestry > mixed in. > > My understanding is that Nick submitted this report in hopes that others > would follow up and try to get better photos of an interesting individual, > not to entice others to flock over with the false hopes of ticking > Slaty-backed Gull off their lifelist. > > Identifying immature Larus gulls is extremely confusing not only because > of physical similarities and variation within individuals of the same > species, but because of the multiple plumages they molt through to reach > adulthood *as well as* the tendency for several species to hybridize with > each other. To complicate things further, recently we've grown to realize > that references to season when describing plumages like "1st winter" and > "2nd summer" is inaccurate because molt timing varies from individual to > individual, thus making assessment even more difficult. I would strongly > encourage the use of "Larus sp" in eBird for any large gulls you aren't > 100% confident on, and for many of the gulls at Warren Lake, > "Herring/Glaucous-winged Gull" seems similarly appropriate. Sometimes eBird > filters, particularly with less experienced or active filter editors, will > have the "sp" and "/" options flagged when they shouldn't be, so don't be > afraid to trip the filter with those taxa. > > > Cordially, > > David Tonnessen > Boulder, CO > > > > -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/a8f3c656-f55e-4824-9f7b-100676c08308%40googlegroups.com.
