Re: [CALBIRDS] [EBB-Sightings] Sandwich Tern (6/16/2019) - photos

Bob Toleno

As one of the observers who saw a medium-sized dark-billed tern with a
yellowish bill tip yesterday at Hayward Regional Shoreline, i want to lay
out the timeline and my own analysis of the situation as i see it. On 6/15
at 2:40pm, Bob Richmond found, and then later both he and John Luther
observed what they described as an adult Sandwich Tern in the main tern
nesting pond at Hayward Regional Shoreline. Their observations are recorded
in the eBird checklists below:

I can't comment on their sightings other than to note that they were likely
significantly closer than we were for the majority of their observation
time than i and the other observers the next day were. (They are both
permitted to be inside an area where the general public is not allowed.)
Also, i don't know of any photographs that either of them acquired on 6/15.

The next morning (6/16), Jerry Ting, Juli Chamberlin, Bob Dunn, Joel Herr,
and myself spent several hours scoping the tern nesting pond from the Least
Tern sign, the closest publicly accessible spot to view this pond. Jerry
had arrived the earliest, and had already observed a few Elegant Terns
along with one dark-billed tern with a yellowish tip that he obtained a
distant, blurry flight shot of. All of those terns had settled on the far
side of the NE island in the tern pond by the time the rest of us had
arrived. This island is roughly 300-350 meters from where we were standing.
Knowing the bird in question was likely on the back side of that island, we
kept a close watch there.

While we waited, an Elegant Tern or two would occasionally pop up from the
back side of the NE island, then settle back down, sometimes in view,
sometimes out of view. About 70-80 minutes after Juli and i arrived, a
medium-sized black-billed tern with a yellowish tip to the bill flew out
from the back side of that island and landed on the front side, where it
spent the next 15-20 minutes preening and getting us all very excited.
Through our 85mm Swarovski ATX scope with 50x magnification and a 1.7x
magnification extender, we could tell that the bill tip was distinctly
yellowish, with the yellow restricted to approximately the last one inch of
the bill. One oddity was that there seemed to be some pale coloration at
the base of the bill, visible with scope magnification cranked up to the
max (~85x). We knew that some juvenile Sandwich Terns show pale coloration
beyond the tip, but in other respects the bird appeared to be an adult (and
had been described as an adult bird by the two observers from 6/15). The
forehead showed some white, which seemed to indicate it was starting to
transition from alternate to basic plumage, though the black covered the
crown and extended down to the nape. Wing color appeared very pale gray
with darker gray wingtips, and legs were pure black. Crest did not appear
quite as long and shaggy as Elegant Terns.

After approximately 15-20 minutes of preening on the front of that island,
the bird in question flew. It circled around the back of the tern pond then
turned and headed roughly in our direction toward the bay. While flying
past us at a distance of no more than 20-40 meters, Jerry Ting managed to
get a couple of flight shots of the bird, which can be seen in his eBird
checklist here:

Those shots clearly show fairly extensive orange coloration at the base of
both the upper and lower mandible. They also show the yellow coloration at
the tip seeming to blend somewhat with the black coloration and extend
further down the bill instead of ending in a crisp demarcation that would
normally be expected on Sandwich Tern. The structure of the bill also seems
longer and "droopy" at the tip, exactly like the structure of an Elegant
Tern bill. None of this was evident from our distant scope views, but i'm
confident that the bird in the flight shots is the same one we observed
preening on the front of the island. When i shared this photo with Alvaro
Jaramillo, his opinion was that the photographed bird is an aberrant
dark-billed but otherwise pure Elegant Tern, not a hybrid. Other expert
opinions may differ, but it seems clear that either way, the bird we
observed on 6/16 was not a pure Sandwich Tern.

This leaves open the question about the bird observed on 6/15. I see just
two possibilities:
1) There were two medium-sized terns that both have mostly black bills with
a yellow tip, both present in the same area at roughly the same time,
associating loosely with a small flock of Elegant Terns, one of which was
seen by on 6/15 but (probably) not photographed, and one of which was seen
and/or photographed on 6/16 by myself and others, *yet at no time did any
observers see these two dark-billed terns with yellowish bill tips together*
2) There was just one tern with a yellow-tipped black-ish bill, and the
bird seen on 6/15 is the same tern that Jerry photographed on 6/16.

Given the relative rarity of dark-billed Elegant Terns in general, and the
extreme rarity of Sandwich Terns in California, it seems to me unlikely
that one of each would show up at the same time in the same place, but
never be observed together. In the absence of any other photographic
evidence or further sightings of the putative second bird, i think the most
parsimonious explanation is possibility #2 above. I was not present on
6/15, and the observers on that date were very likely much closer to the
bird than we were, so it is entirely possible that the "two-bird theory" is
true. I'll let the observers from 6/15 make their own case for their
sighting. I've edited my own eBird report to dark-billed Elegant Tern for
the bird i observed on 6/16.

Bob Toleno

On Sun, Jun 16, 2019 at 10:27 PM Todd Easterla <teasterla@...>

Surprised no one, other than John Sterling who is out of the country has
commented whether the TERN seen and photographed today by a small group of
birders was or is a hybrid, or not....? Fritz Steurer and my self did not
actually see the bird, but were shown images of the bird and it seemed to
clearly show a small amount of orange on the bill, about Midway down the
bill mostly on the lower mandible, which would clearly put this bird on the
hybrid side.

Maybe, it was just an artifact of light but in the photo on the back of
the photographers camera it sure seemed to be orange in color, with a
yellow tipped mostly black bill.

Maybe this group and the photographer will post something about it at a
later date ( hopefully sooner than later) so others that don't want to
chase a possible hybrid, will not.


Todd Easterla
El Dorado Hills, Ca.

Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: John Sterling <jsterling@...>
Date: 6/16/19 8:37 PM (GMT-08:00)
To: jtnikon@...
Subject: Re: [EBB-Sightings] Sandwich Tern (6/16/2019) - photos

I received a text message from an expert who I totally trust who saw the
bird and determined that it was a hybrid. I’ll let him comment but just
wanted to get the word out. Several records in recent years in California
have proven to be hybrids. I’m in China so I haven’t seen the bird.
John Sterling
530 908-3836
26 Palm Ave
Woodland, CA 95695

On Jun 17, 2019, at 10:26 AM, Jerry Ting via Groups.Io <jtnikon=> wrote:

As Bob Toleno stated in his previous posts, the Sandwich Tern reported
by Bob Richmond and John Luther continued to be seen in the tern colony
pond in Hayward Marsh that can be seen (using a scope) from the Least Tern
sign and spent most of the time preening on the south side of the island
(37.630029, -122.144366) on northeast of the Least Tern island. I have
included 2 distant shots of the bird in my eBird report in which you can
see the yellowish tip on the dark bill and dark legs.

Happy Birding,
Jerry Ting

Join to automatically receive all group messages.