[EBB Sightings] Potential breeding warblers in the East Bay (LONG)

Hi all,

A couple of things about Rusty's comments. 

I have often wondered about the possibility of Hermit Warblers nesting in the East Bay. In fact, it seems like every summer Brian Fitch finds a few birds at Vollmer Peak in Tilden Park. They seem to be found in that window where you are never quite sure if they are early post-breeding dispersants or if they might possibly have bred nearby. Unfortunately, Brian doesn't get up there until after the breeding season and I don't think anyone else has really checked it out. We found no signs whatsoever of Hermit Warblers nesting during the atlas project from 1998-2002 but I still consider it a real possibility.

Black-throated Gray Warblers have nested in Contra Costa County. Kevin Hintsa, after several years of trying, finally confirmed the species nesting in Pine Canyon, Mt. Diablo State Park in 1990. We did not achieve any confirmations during the atlas project but did have a few records of apparently territorial males well into June. Shuford, in the Marin Atlas, considered the species to be a common but very local breeder in Marin. I believe the species only nests sporadically in the East Bay.

Rusty's mention of Hermit Thrushes nesting in Contra Costa County brings up an interesting point. I actually found Alameda County's first nest record in 1997 near Redwood Peak. The species had been found literally within yards of Alameda County as early as the 1930 so that particular species has been present in the redwood forest there for at least 75 years. 

However, there are a few species which have colonized the East Bay in the past century which may well have been recolonizing. The Chestnut-backed Chickadee could easily have nested in the 19th Century and earlier in the East Bay. The same could be said for Pygmy Nuthatch and possibly several other species. We will simply never know. 

Also of interest, the Yellow-rumped Warbler has been confirmed nesting twice in Alameda County: In 1941 Milton Seibert found bob-tailed juveniles at Sequoia Park within 1/4 mile of Contra Costa County and in 1994 Bob Richmond confirmed them nesting in knobcone pine forest in southeast Alameda County. 

Note that all of these species have nearby source populations that very likely expand and contract on time scales for which we do not have data. These species may have come and gone numerous times over centuries and millennia.
 
Below, just for the heck of it, is an excerpt from the upcoming Contra Costa County Breeding Bird Atlas.

Historical occurrence
	Grinnell and Wythe (1927) were unaware of any East Bay nesting of the ?Monterey? Hermit Thrush. The first summer records of the Hermit Thrush in the East Bay were in July of 1937 when Leroy Jensen discovered singing birds at the exact site at which nesting currently occurs. Attempts at confirming nesting were unsuccessful in the ensuing few years but finally, on 1 June 1941, Milton Seibert found a nest with three young in a California huckleberry, just inside Contra Costa County (Seibert 1942). The next summer records for the area didn?t follow until 4 July 1956 when three singing males were detected in the same area (AFN 10: no. 5). It would be another 41 years before this area was rechecked with the specific hope of finding this species. On 12 July 1997 an adult was seen feeding a fledgling in Alameda County, just south of the county line with an additional 15+ singing males detected, a few of which were in Contra Costa County (pers. obs.). 

Steve Glover
Dublin, CA
 

--- On Wed, 4/15/09, Rusty Scalf  wrote:

> From: Rusty Scalf 
> Subject: [EBB Sightings] Potential breeding warblers in the East Bay
> To: sightings at diabloaudubon.com
> Date: Wednesday, April 15, 2009, 5:40 PM
> I'd like to add (to the Townsends thread) that Hermit
> Warblers do breed, not far away in the coast ranges. In
> fact, they breed on Mt Tamalpais and in the Santa Cruz Mts.
> I've often wondered about the potential for both Hermit
> and BT Gray Warbler breeding in the East Bay. Neither seems
> far fetched.
> 
> Up through the 19th century, Redwood Reg Park had a
> formidable stand of Redwoods. This was almost entirely wiped
> out in the early 20th century. Steve Glover found nesting
> Hermit Thrushes there a few years back. I wonder if those
> were 'recolonizers' now that the Redwood forest is
> ~100 years old. If Hermit Warblers were there, they could do
> likewise.
> 
>    Rusty Scalf
> 
> 
> 
>       
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