Local Interest and Allen's Hummingbird S&D
Nothing super exciting for a while now, but a couple more local things of interest. If you don't care about Scaup, skip to the third paragraph. Monday in the Peyton Slough Marsh Complex (McNabney, Waterbird, etc.) diving duck numbers were higher than I ever remember. Seemed to me to indicate a sign of Aythya migration, which I poorly understand. Fide Albert L., this year has been better than most for Aythya sp. Ducks in this area, but 33 Canvasback and 10 Greater (!) Scaup, including a group of 6 Greater Sc. in the dinky, shallow, freshwater pond on Waterbird Way seems to speak to something more.
Today at Bethel Island, Logan K./Jonah B.’s Tufted Duck continued despite a decent period of absence. See Logan’s previous email for access info. Also, there were 3 returning Allen’s Hummingbirds in this very odd and disjunct breeding population.
Since Allen’s Hummingbirds have been back for a couple of weeks now, and with Rufous right around the corner, it’s a good time to remind everyone of Selasphorus distribution in the East Bay. A very important topic, if you care about eBird data quality! There is no easy way to summarize it, but the simplest way to think of it is Allen’s Hummingbird do not regularly occur East of I-680. In the Eastern two-thirds of Contra Costa, and Alameda as far as I know, Allen’s Hummingbird is uncommon to a serious rarity. The single biggest problem spot for this species is Mt. Diablo where Allen’s Hummingbirds are reported on the daily during Spring. Allen’s Hummingbird is a very scarce breeder on Mt. Diablo (I think there were three confirmations on the atlas?), Grinnell had zero, and for what very little it is worth, I haven’t seen one yet either. They’re definitely around (I heard a pair bred at Mitchell last year) but they are very overreported—not one photo exists in eBird of an Allen’s on Diablo! For the 100+ Allen’s reports on Diablo in eBird, you would expect at least one photo! (Rufous, on the other hand, are exceedingly common in the Diablo Range at about the same time 90% of those Allen’s reports come in from Diablo) My house where I can and do photograph Selasphorus tails, in a very wet suburb 1 mile East of 680 last Spring had some 30+ Rufous and by comparison a scant 5 Allen’s; imagine how that changes on dry, chaparral-covered Mt. Diablo. As I’m sure any of the birders who regularly cover the parks immediately E of I-680 can confirm, Rufous Hummingbirds are more common there, too. And of course, once you get to the valley floor away from the anomalous breeding populations on Bradford and Bethel Islands, Allen’s are mostly nonexistent. I’m no expert on this topic, and you really don’t have to be to report Selasphorus accurately. If you are in the vicinity of 680 or further East, female-type and not-optimally seen male hummingbirds should be put down as slashes (Allen’s/Rufous) if not just plain old Rufous unless showing evidence of breeding (Allen's), or with conclusive photos of the spread tail, or displaying, or at a known Allen's breeding location until maybe the latter half of May. Hopefully this doesn’t fall on deaf ears!