[EBB Sightings] Briones Blue Grosbeak

Hi all,
A young male BLue Grosbeak was reported at Briones on
6/16/1985. The recent bird could well be a migrant but
breeding was either confirmed or thought possible at
several sites in the county during the breeding bird
atlas that were away from normal Central Valley
haunts, including on Lawrence Rd near Blackhawk and in
the Nortonville area of Black DIamond Mines Regional
Park. Also, now that I think of it, near Marsh Creek
Res. west of Brentwood. 
Pasted below is text from the almost-finished Contra
Costa County Breeding Bird Atlas.
Good birding,
Steve Glover
Dublin


Blue Grosbeak  (Guiraca caerulea)
Opening comments
The brilliant deep blue plumage and warbling song of
the Blue Grosbeak does much to brighten the weedy
areas of east county during the hot summer at a time
and place where there is often little avian activity.
Males often sing endlessly atop brambles and telephone
wires while their more subdued mate goes about
familial responsibilities below. 
Current status and distribution
Blue Grosbeaks are fairly common summer residents of
far eastern county, where they inhabit willow clumps,
drainage ditches and weedy, bramble-choked fields.
Riparian habitats featuring anything but willows and
blackberry brambles are rare in east county but a few
pairs inhabit narrow strips of oaks and walnuts in the
Brentwood area. Some favored locations where they are
particularly easy to find include Jersey Island, the
north end of Bethel Island, Holland Tract and Orwood
Rd. 
Prior to the atlas project, Blue Grosbeaks were almost
unknown away from traditional breeding areas in the
Delta. Quite a few birds though, were detected during
the atlas project well out of range and possibly
prospecting for potential nest sites. Amongst the
locations was the Nortonville side of Black Diamond
Mines Regional Park, the Concord Naval Weapons
Station, just south of Marsh Creek Res. (a pair), and
near the south end of Lawrence Rd. near Blackhawk.
Prior to the atlas project, the only county records of
true migrants (colonizers?) was one at West Pittsburg
22 May 1979 (AB 9/79) and a young male at Briones
Regional Park 16 June 1985 (AB Wi 85). 
Historical occurrence
Grinnell and Wythe (1927) make no mention of Blue
Grosbeaks from the eastern portions of the Bay region
but Grinnell and Miller (1944) did include eastern
Contra Costa County on their range map, though
apparently based upon assumed range rather than
sightings or specimens. The first known county record,
strongly suggestive of breeding, is now thought to
have been three birds at Bethel Island 6 July 1956
(Quail 8/56). 
	Blue Grosbeaks apparently begin to arrive in Contra
Costa County about 20 April, though the first singing
male detected during the atlas project was 27 April.
The first pair wasn?t recorded until 5 May, though
they doubtless occurred earlier. The lone instance of
an adult carrying nest material was discovered 22 May.
Adults were observed carrying food on five occasions
spanning the narrow window of 25 June to 6 July. A
fledgling was noted 30 June. In years prior to and
after the atlas project, apparent family groups have
been noted on Bethel Island deep into August (pers.
obs.). 
Conservation
	Blue Grosbeak populations in the eastern and
northeastern portions of the county may be reasonably
secure since development of such low-lying areas is
inherently risky. Central Valley birds on slightly
higher ground, however, are highly vulnerable to
recent unrestrained development. 

--- judi sierra  wrote:

> Does anyone know if they've been seen before in
> Briones?
> 
> 
> This morning I found a singing blue grosbeak at the
> top of Briones Crest 
> trail.
> 
> 
> 
> Good birding!
> 
> John Poole
> 
> 
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