Date: 11/13/26 4:06 am From: Stephen T Bird via EBB-Sightings <isseki.ryotoku...> Subject: Re: [EBB-Sightings] Channel Island orange crowned warbler question
Grinnell and Miller 1944 report records of the subspecies ranging from
Eureka! to San Diego. https://digitalcommons.usf.edu/pca/26/ page 394-395
It's only more recently been restricted by coastal development, according
to the NPS, with the island population serving as a reservoir for the
mainland.
It's also been noted that sordida has different diet and nesting practices
than other subspecies, nests in trees compared to their mainland
ground-nesting cousins (when Jays are not present, but will move to nesting
on the ground if a single Jay is heard), and have a much higher 1st year
survival rate (75% vs 46%).
It's extremely likely sordida have a much deeper evolutionary history on
the mainland than the islands. So rather than see this subspecies as "why
are they leaving the islands and heading north?" the better question might
be "why did they leave the mainland to breed on the islands?" And the
answer is "conditions were better for breeding (particularly predation)."
From there they may have differentiated more.
Best
Stephen J
On Thu, Nov 12, 2026, 9:22 PM lavin_fara via EBB-Sightings <pdunten=
<gmail.com...> wrote:
> A quick search of MVZ for OCWA turned up 117 Bay Area records in their
> collection. Here's the part you might not expect. There are no
> *lutescens* from November through February. There are 11 *sordida*,
> between 21 October and 23 February, all from locations near the coast,
> including Palo Alto, Oakland, and Berkeley. There are only two records
> each for *celata* (both in October) and *orestera* (one in September, one
> in February).
>
> Best wishes, Pete
>
>
>
>
