Date: 7/23/26 2:21 pm From: Samuel Bressler via groups.io <pacificgoldenplover...> Subject: [OrangeCountyBirding] Some California Bird Atlas results for Orange County (as of 7/22/26)
Hi all:
With nesting bird season drawing to a close in the county, I wanted to give a brief summary of the results for the first year of the California Bird Atlas.
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Due to its high population concentrated in a relatively small area, Orange County was one of the most highly atlased counties this past spring:with 86 of 87 blocks centered in the county being atlased at some point. The one exception, San Clemente NE, is located largely within off-limits areas of Rancho Mission Viejo and Mission Viejo. Additionally, lingering trail and road closures from the Airport Fire leave have left many blocks in the Santa Ana Mountains poorly atlased, including those blocks containing Blue Jay Campground and the Holy Jim Trail.
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135 species have been confirmed nesting in the county. The top ten species confirmed across the largest number of blocks (out of 87 total):
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House finch 68
Black phoebe 60
American crow 57
Western bluebird 53
Song sparrow 53
Lesser goldfinch 50
European starling 49
California towhee 49
Bushtit 48
Northern house wren 45
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The following species are likely/known breeders that have NOT been confirmed in the county this year:
Blue-winged teal - I suspect this species is an occasional breeder in coastal wetlands
Mountain quail - Resident in Santa Ana Mountains, but seemingly no coveys observed
Lesser nighthawk - Fairly common breeder, but nocturnal and nests are very difficult to find; may require nocturnal, off-trail surveys
Northern saw-whet owl - historical resident in Bigcone Springs
Violet-green Swallow - Expected in woodlands of the Santa Ana Mountains and higher foothills
Western warbling vireo - Expected to breed in montane riparian woodlands in Santa Ana Mountains/Starr Ranch
Rock wren - Possible/likely breeders in rocky areas of Santa Ana Mountains, as well as lowland dams.
Purple finch - Expected breeder in montane woodlands in Santa Ana Mountains
Red-breasted nuthatch - A pair summering at Clark Regional Park may have bred the last two years, however no confirmation has been obtained.
Black-throated gray warbler - Likely breeder in high elevation montane woodland
Bell’s Sparrow - Extremely local breeder in Santa Ana Mountains (especially in Coal Canyon and along the Main Divide).
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Additionally, the following species were once probable/confirmed breeders in the county but may no longer do so.
Western meadowlark - This formerly common grassland species may be extirpated as a breeder in the county, but could still persist in remnant grasslands.
Swainson’s thrush - Possible breeder in riparian woodland in our foothills, but lack of recent summer records indicate they might be extirpated.
Belted Kingfisher - Formerly bred in steep banks along rivers and lakes; despite a dearth of recent breeding records in the county, every year we get a few summering.
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A number of species recorded or presumed to be breeders during the Orange County Breeding Bird Atlas (compiled based on data collected in the late 1980s by Sylvia Gallagher) are presumed extirpated (e.g.: loggerhead shrike, willow flycatcher, prairie falcon, tricolored blackbird, yellow-headed blackbird, spotted owl, burrowing owl)
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Blocks
The following blocks saw the most diurnal effort hours during the first year of the atlas:
Seal Beach CE (Bolsa Chica Ecological Reserve): 1372
Tustin SW (San Joaquin Wildlife Sanctuary: 467
Newport Beach SW (Santa Ana River Mouth, Fairview Park, Talbert Park): 454
Seal Beach NW (Seal Beach Naval Weapons Station): 180
Orange CE (Irvine Regional Park, Santiago Oaks Regional Park): 170
Seal Beach NE Northside Bolsa Chica, Parkside Ponds, Carr Park): 152
Lake Forest CE (Whiting Ranch Wilderness Park, Agua Chinon): 152
Newport Beach NW (Mile Square Regional Park): 151
San Juan capistrano CW (Laguna Niguel Regional Park, Aliso and Woods Canyon Wilderness Park): 141
Canada Gobernadora NW (Esencia Sports Park, Riley Wilderness Park): 138
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And here are the blocks with most species confirmed:
Seal Beach CE: 74
Tustin SW: 73
Newport Beach SW: 60
La Habra SW (Clark Regional Park, West Coyote Hills): 57
Black Star Canyon SW (Irvine Lake): 56
Orange NE (Upper Santa Ana River, Yorba Regional Park, Pelanconi Park): 53
Orange CE: 48
La Habra SE (Craig Regional Park, Gilman Park): 46
Tustin SE (Quail Hill Preserve, Turtle Rock): 46
Orange CW (Anaheim Coves Park): 45
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Blocks with fewest diurnal effort hours:
San Clemente NE (Rancho Mission Viejo): 0
Alberhill CW (Santa Ana Mountains-Los Pinos Trailhead): 0.18
Santiago Peak CE (Holy Jim Trail): 1.05
Sitton Peak NW (Santa Ana Mountains along Ortega): 1.75
Newport Beach OE S NW (Corner of Newport Beach): 2.08
Canada Gobernadora NE (San Juan Hot Springs): 2.12
Black Star Canyon CE (Black Star Canyon Road, Mariposa Preserve): 2.27
Alberhill SW (Santa Ana Mountains-Blue Jay Campground/Falcon Group Campground): 2.80
Santiago Peak CW (Ramakrishna Monastery, North O’Neill Regional Park): 1
Sitton Peak NW: 2
Alberhill SW: 4
Black Star Canyon CE: 4
Canada Gobernadora NE: 6
Dana Point CW (corner Dana Point Harbor): 6
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Final Notes
Atlasers in future years should especially focus on those blocks with low levels of effort and species confirmation. These blocks can primarily be found in the central and southern Santa Ana Mountains. With most Airport Fire-related closures scheduled to be lifted next year, this should allow us more opportunities to survey in these blocks.
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Expected breeders that have not yet been confirmed consist primarily of montane riparian/coniferous woodland breeders. But a number of species, particularly in foothill.montane chaparral and scrub, have gone underreported. For example, black-chinned sparrow has only been confirmed in three blocks, despite being an expected breeder across much of the Loma Ridge and Santa Ana Mountains. Similarly, only one confirmed record of lazuli bunting (from early July at Irvine Lake) has been recorded, despite this being an expected chaparral breeder in much of the eastern portion of the county. Finally three, black-chinned hummingbird records have been confirmed in the county, a far cry from the 26(!) blocks where they were recorded in the Orange County Breeding Bird Atlas in the 1980s.* Ditto Bullock’s oriole : 9 confirmed blocks this year vs. 50 in the 1980s. Do these represent a true decline or simply lack of observer awareness? Only time and diligent observation will tell!
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To close on a positive note, the least Bells vireo , a species which was coded as only possibly breeding in three blocks (and confirmed in none) in the 1980s atlas, has already been confirmed as a breeder in 13 of the counties atlas blocks, reflecting this species’ dramatic recovery in response to conservation measures implemented in the county and region. I expect that this surprisingly tolerant and adaptable species will be confirmed in riparian woodland in more blocks as the atlas continues.
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I look forward to another productive and exciting atlasing season in 2027. Hopefully we can both tally many of our “missing” species, and survey our undersurveyed blocks.
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*Annoyingly, block size and locations differ slightly between the Orange County Breeding Bird Atlas and the current atlas effort. However, they are close enough that conclusions can easily be drawn.
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*Good birding,*
*Samuel Bressler*
*Brea*
*Regional Coordinator, California Bird Atlas*
