SAC Bufferlands portion of the Rio Cosumnes CBC on 2 Jan 2020
Surely more info here than many want, but some have found this of interest in the past. Below is a summary of findings I put together for our work group and volunteers on the Bufferlands portion (www.bufferlands.com) of the Rio Cosumnes CBC.
On Thursday, January 2, 2020, seven Bufferlands staff and nine volunteers participated in the 25th annual Rio Cosumnes Christmas Bird Count (CBC). The day started with low fog and 41F, but was mostly sunny for much of the day, with up to 6 mph wind and a high of 60F. For the fourth year in a row we had six teams in the field, allowing very thorough coverage. There was only limited flooding, allowing good access to most of the property. The Bufferlands is at the northwestern portion of the 15-mile diameter CBC circle that includes Stone Lakes National Wildlife Refuge, Cosumnes River Preserve, western Elk Grove, northwestern Galt, and a portion of Merritt Island in Yolo County.
From 7:05 am to 5:34 pm, we recorded 108 species on the Bufferlands, within a historic range of 90 to 120, and counted 103,227 individual birds (90,000 were European Starlings), within a historic range of 7,723 to 811,644 (average 180,580). In 2002 our team began covering Beach Lake Forest, Beach Lake Park, and the ag lands owned by the District on the west side of I-5 in our count area. Since that time we have recorded an average of 111 species, within a range of 104 to 120, and a cumulative total of 161 species over the count’s 25 years. I haven’t received a full summary of what other areas recorded, but the whole circle often produces over 150 species.
An early evening flock of Snow Geese was a good pick up of a species missed by our team over half the time. Two Tundra Swans was another near miss, while we did miss Cackling Geese for the first time since 2005 (prior to which they were considered part of a complex of small Canada Goose subspecies). Overall waterfowl numbers were below average, but highlights included 973 Ring-necked Ducks, a paltry five Canvasbacks (we have recorded thousands), and eight Lesser Scaup was a good local total of a species we miss about half the time; we didn’t find any Redheads. Hooded Mergansers keep increasing, with a new high of 28, while we missed Common Mergansers for only the fifth time; they have declined in recent years on the property, perhaps because of shallower water in Morrison Creek caused by siltation.
Wild Turkeys were first recorded on our portion of the count in 2003, but numbers continue to grow, with a new record of 487 (up from last year’s record of 348). Ring-necked Pheasants remain at low numbers, with only six (the same total as the past two years) after a high of over 400 in 1996, seemingly out of some foggy past, but not that long ago; this species is declining throughout the region. We missed American Bitterns for the sixth time, Green Herons for the ninth time, and Black-crowned Night-Herons also for the ninth time; all three species are getting hard to find on the property in recent years, though only American Bitterns are declining throughout the region.
Overall raptor numbers were about average. A late afternoon pickup of a Prairie Falcon, plus two Peregrine Falcons (for just the fifth time, but all in recent years), two Merlins, and 20 American Kestrels made for a four falcon day (a Merlin was observed diving after sparrows flushed by a Northern Harrier. Despite dozens of dives, neither species appeared to catch anything). Burrowing Owls, at three, were down from last year’s five, but two Burrowing Owls we have regularly seen were not detected on count day. Despite steep declines in Sacramento County and the region, this species is holding on at the Bufferlands—especially in winter. Sandhill Cranes were a surprising miss, though we did see them count week (which includes three days before and three days after count day). We found five Sora and two Virginia Rails, but we missed Common Gallinule for just the fourth time; we no longer expect to find 30 or more gallinules as we did in the first 10 years of the count when the Constructed Wetlands was more fully flooded (Why are they not regular at Fishhead Lake where the habitat seems great for them?).
Shorebird numbers were quite low. We found a single Black-necked Stilt, 57 Least Sandpipers, only two Dunlin, and missed Long-billed Dowitchers. The Western Sandpiper seen count week (12/31) failed to appear on count day. We missed Black-bellied Plover for the ninth year in a row; development of adjacent areas where these birds used to forage likely explains this change, but there have also been regional and global declines of many shorebirds. We found one Long-billed Curlew, but we no longer expect dozens as we did over ten years ago—also likely tied to regional development. We found three Spotted Sandpipers, a regular species at the wastewater treatment plant, but difficult to find in the rest of the count circle. Of the three regular gull species (California, Ring-billed, and Herring gulls), we missed Ring-billed for only the second time (only ten total gulls were recorded on the property on count day).
Two species that have declined since 2005 when West Nile Virus (WNV) arrived in our area, Yellow-billed Magpie (just 20 this year) and Loggerhead Shrike (three), continued at low numbers. We recorded only one Oak Titmouse, another species that appears to be impacted by WNV. By contrast, Common Ravens are increasing: six this year was a new high. Also increasing, 17 Say’s Phoebes were double the historic average, and this is consistent with overall increasing regional abundance of this species—one of the few open country/grassland species that is not declining regionally.
Most teams reported lower than average songbird activity. Sparrow numbers were mostly average our slightly below, but with Savannah Sparrows (229) at their third highest total bucking a general declining trend. We missed Horned Larks, which used to be regular, but are now fairly sporadic on the property (we did have a single calling flyover for count week)—another open country species that is declining.
Also notable was a new high of Anna’s Hummingbirds at 73. A single Hutton’s Vireo, two Pacific Wrens, a White-throated Sparrow, and two Townsend’s Warblers were nice pickups of species that could easily be missed. We had a nice total of Golden-crowned Kinglets (17), but Rock Wren, Brown Creeper, and Varied Thrush failed to show. The large roost in the WTP Clarifiers accounted for most of the individual birds, with 90,000 European Starlings continuing as the most abundant species on the property (87% of individual birds counted). No new species were added to the cumulative species count (161) this time.
It is interesting to note how much year to year variation there has been. Of the 161 species recorded over 25 years of counts, 58 species (38%) have never been missed, with another 29 (18%) missed one to five times (totaling 87 species (54%) that have been missed five times or fewer). By contrast, 18 species (11%) have been recorded only once, with an additional 14 (9%) recorded two to five times (for a total of 32 species (20%) that have been recorded on five or fewer counts). With that amount of variability, it seems remarkable that the number of species found each count has varied rather little (104 to 120) since we began covering the property in pretty much the same way in 2002.
Thanks to everyone who participated in another great count. This 25-year data set reflects the only day each year that we search the whole property for birds. It is a valuable snapshot of our wintering bird population and part of the CBC tradition (https://www.regionalsan.com/general-information/christmas-bird-count). More background on the Rio Cosumnes CBC can be found here (http://www.cvbirds.org/bulletin/downloads/volume-09/); scroll down to the count in the summary articles.
All the best,
Natural Resource Specialist
8521 Laguna Station Rd.
Elk Grove, CA 95758
(916) 876-9700 office
(916) 203-1610 cell