Author: Greg Giusti

Throughout northern coastal California, a great deal of information regarding water quality and fish habitat is being amassed that potentially could change how people view and utilize stream corridors. However, it is widely recognized among the scientific community that stream corridors are an important habitat component for a host of vertebrate and invertebrate species other than fish. Unfortunately, the current fish-centric approach to riparian protection and restoration has often resulted in a narrow discussion of stream corridor management that excludes non-fish species. For example, information detailing the use of oak woodland stream corridors by migratory songbirds in California’s oak woodlands is sorely lacking, limiting the ability of landowners and resource managers to make informed decisions regarding land use practices and policies and their effects on birds. It is important that we consider these other species when managing and restoring riparian areas, as their requirements may be different than those of the fish.

Spring 2012 marks the 20th consecutive year of a bird monitoring study on Parson’s Creek, an ephemeral (seasonal) tributary of the Russian River that traverses the UC Hopland Research and Extension Center (HREC). The goal of this ongoing project is to document resident and migratory bird use of stream corridors in mixed oak woodlands.

                     White-breasted nuthatch. A tree dependent species that forages for food among 
                          the bark, limbs, twigs and leaves of trees. The species is a cavity nester.

Study Site and Sampling Methods

Parson’s Creek, like most creeks in the North Coast, has been subject to many land use impacts over the past 100 years, including livestock grazing, gravel extraction, channelization, and road crossings with associated aggravated erosion. To offset many of these impacts, HREC instituted a series of restoration activities in the early 1990’s to serve as demonstrations to landowners who are interested in stream restoration. Since then, recovery of native vegetation in some sections of Parson’s Creek has been dramatic. In areas that have excluded both sheep and deer, alder and willow have regenerated and are now providing extensive vegetative cover. Other sections were left unprotected and remain denuded, demonstrating how the restored sites used to look. Consequently, vegetative cover is not uniformly distributed throughout the stream reach. Other over-story species that exist across the study area include blue oak, Oregon white oak (also known as Garry oak), and valley oak.

Twelve monitoring points are established along the main creek channel at HREC. Birds are surveyed using a standard sampling protocol commonly referred to as the “point count method”. This method is widely used to survey birds in the field and involves an observer recording birds from a single point for a set length of time.

Each monitoring point is surveyed 3 times a year during the morning. Two 20-minute counts are conducted each spring between mid-May and early June to coincide with the arrival of migratory songbirds. In addition, one 20-minute count is conducted each fall in mid-October, after the departure of neo-tropical migrants to wintering grounds in the tropics. Birds were identified using visual and auditory cues. Only those birds active (perching, foraging, singing, etc.) within the riparian corridor were tallied. Birds flying high above or passing through the stream zone were not counted.

                        Yellow-bellied sapsucker. A relatively uncommon woodpecker of oak woodlands  
                                    is regularly observed in the woody portions of Parson’s Creek.

Findings

Thousands of bird observations have been recorded. The total number of observations per year ranged from a high of 254 (1993) to a low of 173 (1999). The average number of recorded observations over time is 198 detections per year. The unusually high number of recorded observations in 1993 is most likely an aberration of sampling, not a trend in bird presence. Following the first year, the observers became more conservative and standardized in their data collection.

The large number of bird detections yielded an impressive number of species—81 species, representing 24 taxonomic families and 9 orders. Both resident and migratory species were detected in the oak woodland stream corridor. Species most commonly observed and the corresponding number of detections during the study period is provided in Table 1.

Table 1. Most commonly observed species in the Parson's Creek riparian corridor, HREC.

                        Ten Most Commonly           Ten Most Commonly Observed
                        Observed Species              Neo-Tropical Migratory Species

Oak Titmouse (125) Acorn Woodpecker (103) California Towhee (94) Western Scrub-Jay (78) European Starling (66) Black Phoebe (62) House Finch (59) Brewer's Blackbird (54) Nuttall's Woodpecker (52) Anna's Hummingbird (46)

Bullock's Oriole (54) Orange-crowned Warbler (49) Violet-green Swallow (43) Ash-throated Flycatcher (37) Pacific-slope Flycatcher (33) Western Tanager (27) Lazuli Bunting (26) Warbling Vireo (25) Western Kingbird (24) Black-headed Brosbeak (22)

Throughout the study period, an average of 29 species (ranging from 27 to 33) have been detected during the Fall. These species are primarily resident birds that utilize the stream corridor throughout the year. Spring counts averaged 43 species (ranging from 38 to 48). The difference in the average total number of species reflects the seasonal influx of neotropical migratory songbirds that arrive in California’s oak woodlands for the breeding season.

Some species may also be selectively utilizing only portions of the riparian corridor that exhibit special habitat features. For instance, one species in particular, the Black-throated Gray Warbler (Dendroica nigrescens), is consistently found only in those portions of the riparian area where the vegetation canopy is densest. This pattern of occurrence has remained consistent during the entire study period, and suggests that this species may have relatively narrow habitat requirements when compared to other neotropical migrants exploiting the stream corridor.

                      Killdeer are often seen nesting on Parson’s Creek in the areas that are devoid of 
                          vegetation. The bird lays its eggs among the barren rocks. The cryptically 
                             colored eggs are virtually invisible. This is one of the few species that
                                      is not dependent on vegetation in oak woodland settings.

Conclusion

There is very little long-term information detailing the use of oak woodland stream corridors by migratory and resident birds in California’s oak woodlands. Our long-term data set demonstrates that migratory songbirds readily utilize the riparian zone, particularly during the spring breeding season. We also observed that some species are more abundant in sections of the creek where more mature vegetation is present.

We plan to continue to monitor the avian assemblage found within this stream corridor. It is our hope that this project, along with the efforts of others, will generate important, long-term, baseline information that will aid in the sustainable management of California’s riparian hardwood communities.

This webinar will present a series of lectures on the concepts in the ANR publication, “A Planner’s Guide for Oak Woodlands” (UC ANR Publication 3491). The goal will be to create an awareness of the ecological, economic and social values of California’s oak woodlands, and some general planning strategies to ensure long-term conservation of this resource. The selected audience includes city, county, regional and statewide planners, environmental consultants, conservation organizations, land trusts, resource professionals, elected officials, and NGO’s. Complete details on the webinar, including on-line registration instructions, can be found here.

The webinar will be held on March 8, 15, 22 and 29, 2012 from 10 AM to 12 noon, and consists of a series of 2-hour lectures, available on-line through a link to Adobe Connect. This program will be of interest to local planners, professional resource managers and general oak interest groups. The series will be taped and a link to the taped webinar series will be provided for those who are unable to participate on the date and time of the live broadcast. There will also be a weekend field trip to Hopland and/or Sierra Research and Extension Centers at the end of the series.

Participants will register for the webinar and pay a nominal fee ($30) to receive a copy of the publication, ”A Planner’s Guide for Oak Woodlands” and to cover incidental production fees. A social network site will be developed to enhance the sharing of information, and to provide follow-up networking opportunities.

The topics per session include:
March 8-Session 1: Overview of Hardwood Rangeland Resource
March 15-Session 2: Land Management Strategies
March 22-Session 3: Planning Strategies
March 29-Session 4: Sources of Assistance, Developing Plans

Session 5 includes an optional field trip to the Hopland Research and Extension Center on April 21,2012 and to the Sierra Foothill Research and Extension Center on May 5, 2012 from 10 am to 3 pm. The trip will discuss oak planting projects, landscape considerations, mitigation approaches, and addressing ecological functionality through the planning process.

(See: http://ucanr.org/sites/oak_range/Planners_Guidelines_for_Oak_Woodlands/)

The journal California Agriculture offers peer-reviewed research and news in agricultural, natural and human resources. Private land owners are able to share their views on rangeland and forest resources. Two articles in the October-December 2011 issue are of interest to private land owners and those interested in conserving and educating about California’s blue oaks.

The first article, Tree shelters and weed control enhance growth and survival of natural blue oak seedlings, discusses two techniques that can improve the chances for conserving native blue oaks and for managing blue oak sustainability. Here is a preview of the article’s extended abstract:

“Blue oak is regenerating poorly in portions of its range. Techniques to artificially regenerate trees by collecting acorns, growing seedlings in a nursery and then planting them are effective but costly. Improving the growth and survival rate of existing volunteer seedlings in woodlands could be more cost efficient and therefore more widely used. We tested tree shelters and weed control treatments over 3 years at six woodland sites to evaluate whether they helped blue oak seedlings grow into saplings. The tree shelters enhanced height growth, and weed control improved survival”.





The second article, Forest and rangeland owners value land for natural amenities and as financial investment, discusses the recent shift away from “production-oriented ownership” of privately owned land. Here is a snippet of the article’s extended abstract:

“Forty-two percent of California's forests and rangelands are privately owned (34 million acres). These lands provide important ecosystem services such as carbon sequestration, pollination and wildlife habitat, but little is known about the people who own and manage them. We surveyed forest and rangeland owners in California and found that these long-time landowners value their properties for their natural amenities and as a financial investment. Owners of large properties (500 or more acres) were significantly more likely to use their land for income production than owners of smaller properties, and they were also more likely to carry out or be interested in environmental improvements. Many forest and rangeland owners reported they had been previously approached to sell their land for development. Only about one-third had participated in conservation programs; few had conservation easements.”

The survey discussed in the article can ultimately aid in land-owning outreach efforts, and the economic policies, programs and financial incentives for rangeland owners.

To read the full articles and to learn more, CLICK HERE.



References:

Forest and rangeland owners value land for natural amenities and as financial investment
by Shasta Ferranto, Lynn Huntsinger, Christy Getz, Gary Nakamura, William Stewart,
Sabrina Drill, Yana Valachovic, Michael DeLasaux, Maggi Kelly. pp184-191,
doi#10.3733/ca.v065n04p184

Tree shelters and weed control enhance growth and survival of natural blue oak seedlings
by Douglas D. McCreary, William Tietje, Josh Davy, Royce Larsen, Morgan Doran,
Dustin Flavell, Sergio Garcia. pp192-196, doi#10.3733/ca.v065n04p192 -

Four head mature cows have been reported dead in Tulare County foothills from 2500 feet to 1000 foot elevations. All were in the vicinity of Blue Oaks with heavy crop of acorns.

Neil McDougald, Livestock Range Advisor of Madera County indicated that this year is similar to other years he has seen where there have been incidents of acorn toxicity. There is a very large acorn crop, and recent rains has led to some early green-up under Oak Trees which can result in some cows camping and eating an overload of acorns resulting in acorn poisoning.

Most cattle in California spend at least part of the year in areas where oak trees abound. Health problems due to ingestion of oak leaves or acorns are certainly not an everyday problem; however, when problems do occur they can be catastrophic. Several years ago, in a few northern California counties, about 2,700 cattle died due to oak toxicity¹.

Some years have much higher production of oak acorns than others and this year, 2011 in the Foothill Ranges of the Southern Sierras, has been reported as one of the highest production years observed. In addition early rains may increase the risk of acorns by reducing the nutrient value of last year’s forage, as well as causing an early greening of grass under the oaks where acorns are accumulating.

During the week of October 10, 2011 four head mature cows were reported to be found dead in Tulare County foothills from 2500 feet to 1000 foot elevations. All were in the immediate vicinity of Blue Oaks with heavy crop of acorns. These cattle were not available for necropsy and cause of death was not confirmed, however oak acorn toxicity is suspected.

Oak toxicity symptoms usually appear when cattle eat 50% or more of their diet as oak (acorns, leaves, buds). Toxicity can be prevented by supplementing cattle with hay or other supplements when forage conditions are poor and acorns are abundant. A higher risk may occur if early or late snowstorms covers available forage and knocks down oak limbs with large amounts of buds and young leaves or acorns, be sure to start hay supplementation immediately. A delay of only a day or two could result in many deaths.

There are two recommendations to avoid cattle loss due to acorn toxicity. One is to provide supplement to draw cattle away from the acorns, so that their exposure decreases. The other is to remove cattle observed eating acorns from fields with high levels of acorns.

It is recommended that producers work with their local veterinarian and/or diagnostic laboratory, to be certain of the actual cause of death in all livestock losses. There are many other factors that can cause sudden death and although oak toxicity may be likely and immediate actions should be taken to prevent further deaths, a follow up with a veterinarian is often the best course of action to prevent further losses. For a more comprehensive discussion on identification and recommended actions for Oak Toxicity and Acorn Calf syndrome in cattle please refer to the link below.

Dr. John Maas, UC Davis Extension Veterinarian, informative article on oak toxicity (OAK TOXICITY UCD Vet Views California Cattleman, Jan 2001):
http://www.vetmed.ucdavis.edu/vetext/INF-BE_cca/INF-BE_cca01/INF-BE_cca0101.html.


Blue Oak Acorn


Cattle Pasture amongst Blue Oaks