Sacha K. Heath- PhD
- Senior Scientist at San Francisco Estuary Institute
Sacha K. Heath
- PhD
- Senior Scientist at San Francisco Estuary Institute
Applied ecology in the Resilient Landscapes Program at the San Francisco Estuary Institute
About
55
Publications
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654
Citations
Introduction
I conduct ecological research to inform, evaluate, and implement effective biological conservation, focusing on avian ecology in restored, agricultural, and urban landscapes.
Full-text reprint requests can be fulfilled here: https://www.sachaheath.com/publications--cv.html
Current institution
Publications
Publications (55)
Residential yards in the USA have for decades been dominated by manicured lawns, invasive and non-native plants, and pesticide and fertilizer inputs—with demonstrated negative effects on biodiversity. St. Louis Audubon Society’s Bring Conservation Home program (BCH) is a large-scale urban garden initiative which has enrolled over 1,100 volunteer re...
We performed a systematic literature review to summarize what is known by science about the conservation of biodiversity in urban agroecosystems throughout the world. Our initial search among three literature databases captured 9,066 articles, which we screened and reduced to a final set of 431. Our criteria for retaining studies was that they inco...
Urbanization is a leading cause of global biodiversity loss, yet cities can provide resources required by many species throughout the year. In recognition of this, cities around the world are adopting strategies to increase biodiversity. These efforts would benefit from a robust understanding of how natural and enhanced features in urbanized areas...
Avian obligate brood parasitism is a specialised life history strategy that may impact the dispersal of juvenile and adult parasites when compared with non-parasitic (parental) bird species. In contrast to expectations, however, several brood parasites show a territorial spacing system while breeding, including breeding site fidelity within and acr...
Habitat augmentation on farms is predicted to conserve biological diversity and support beneficial animals that reduce crop pests. Effectiveness of local habitat enhancement and subsequent pest reduction services can be mediated by the amount of habitat at larger scales. We tested whether the presence and increase of local and landscape scale bird...
Experimental exclosure of birds and bats constitutes a powerful tool to study the impacts of wildlife on pests and crop yields in agricultural systems. Though widely utilized, exclosure experiments are not standardized across studies. Indeed, key differences surrounding the design, materials, and protocols for implementing field-based exclosure exp...
Considerable funding has been allocated to conservation management of non-crop habitat in agricultural landscapes, particularly field margin habitat such as hedgerows. Evaluation of the biodiversity benefits of non-crop habitat has lagged behind implementation, however, especially in the United States where this habitat has the potential to supply...
Habitat-forming species provide refuges for a variety of associating species; these refuges may mediate interactions between species differently depending on the functional traits of the habitat-forming species. We investigated refuge provisioning by plants with different functional traits for dragonfly and damselfly (Odonata: Anisoptera and Zygopt...
A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The literatures on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and c...
Riparian ecosystems of three major tributaries of Mono Lake, CA, USA have been subjected to decades of cumulative ecological damage caused by water diversions, water impoundments, and livestock grazing. Negotiations leading up to a landmark 1994 legal decision and a 2011 settlement agreement initiated restorative processes on these streams as early...
Background/Question/Methods Conservation biological control focuses on manipulating habitats to favor natural enemy invertebrate communities to maximize pest control services for growers. A growing body of evidence suggests that avian insectivores can also provide important pest control services. Largely untested is the extent to which local habita...
Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for...
Because nest predation strongly limits avian fitness, ornithologists identify nest predators to inform ecological research and conservation. During 2002–2008, we used both video-monitoring of natural nests and direct observations of predation to identify nest predators of open-cup nesting riparian songbirds along tributaries of Mono Lake, Californi...
We compared the red, green, and blue color values from digital photographs of the rictal flanges of nestling Brown-headed Cowbirds (Molothrus ater), a generalist obligate brood parasite, in sympatric Yellow Warbler (Setophaga petechia) and Song Sparrow (Melospiza melodia) nests at Mono Lake, California, USA. We detected significant differences in a...
1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates.
2. This lack of congruence between theory‐based expectation and empirical data may arise when birds already occupy ‘adaptive pea...
Contrary to assumptions of habitat selection theory, field studies frequently detect ‘ecological traps’, where animals prefer habitats conferring lower fitness than available alternatives. Evidence for traps includes cases where birds prefer breeding habitats associated with relatively high nest predation rates despite the importance of nest surviv...
Deciduous riparian ecosystems in the western United States provide habitat for a higher density of breeding birds than reported for any other avian habitat type and provide habitat for more breeding bird species than adjacent uplands. On the east slope of the Sierra Nevada, riparian ecosystems make up <1% of United States Forest Service lands yet e...
Background/Question/Methods
Habitat selection is an ecological trait shaped by natural selection. Animals should select habitats that optimize individual fitness, in which case habitat selection is “adaptive.” However, the adaptive significance of habitat selection may be difficult to document in nature, particularly for populations within which a...
Nestling brown-headed cowbirds Molothrus ater typically hatch earlier and grow faster than young of the many host species of this generalist obligate brood parasite. However, a cowbird chick also benefits from the presence of some host nest mates as the parasite is provisioned disproportionately more with increasing brood size. Since asynchronous h...
Parents influence the phenotype of their offspring by determining the environment in which early development occurs. The many factors that affect growth in avian brood parasites provide an excellent context in which to examine how ecological variables and sex differences influence plasticity of early development. We used a model-selection approach...
Conspecific brood parasitism occurs in many songbird species but has not been reported in Song Sparrows (Melospiza melodia). In three separate study areas where breeding Song Sparrows experience heavy nest predation pressure and Brown-headed Cowbird (Molothrus ater) parasitism, we observed six instances in which newly laid eggs were attributable to...
Conspecific brood parasitism occurs in many songbird species but has not been reported in Song Sparrows (Melospiza melodia). In three separate study areas where breeding Song Sparrows experience heavy nest predation pressure and Brown-headed Cowbird (Molothrus ater) parasitism, we observed six instances in which newly laid eggs were attributable to...
In 2005, nest counts estimated 43,882 adult California Gulls (Larus californicus) were nesting at Mono Lake in late May. This total was the fifth lowest in 23 years of monitoring, and was well below the 1983-2004 average of 48,740 ± 1650. Roughly 75% of the gulls nested on the Negit Islets, 23% on the Paoha Islets, and 1% on Negit Island. Twain Isl...
A strategy for reversing the decline of riparian associated birds in California
In an investigation of the factors leading to geographic structuring among Adélie Penguin (Pygoscelis adeliae) populations, we studied the size and overlap of colony-specific foraging areas within an isolated cluster of colonies. The study area, in the south-western Ross Sea, included one large and three smaller colonies, ranging in size from 3900...
Surveys in the 1990s did not find the Willow Flycatcher along Rush Creek, a
tributary of Mono Lake, Mono County, California. In 2001 and 2002 we located nine Willow
Flycatcher nests along lower Rush Creek, in a riparian corridor currently in its 15th year of
long-term rehabilitation after decades of livestock grazing and water diversion for muni...
We examined bird-habitat relationships within and across a range of aspen habitats in four major watersheds in the eastern Sierra Nevada mountains of California and Nevada to identify habitat features of importance to aspen-breeding birds. Using point counts and vegetation assessments from 462 individual stations between 2001 and 2003 allowed us to...
Compared to other riparian habitat types in the eastern Sierra Nevada, aspen (Populus tremuloides) dominated habitats harbor the most diverse breeding bird communities (Heath and Ballard in press). However, due to inadequate sample sizes, previous investigations were unable to identify specific components within aspen habitats that influenced breed...
We determined several vegetation and environmental features that predicted breeding bird species diversity and focal species occurrence in riparian habitats across three watersheds of the eastern Sierra Nevada bioregion, California. Conducting point counts and associated vegetation assessments at 480 individual riparian points between 1998 and 2000...
In 2002, the Point Reyes Bird Observatory (PRBO) implemented a standardized bird monitoring program in riverine/riparian habitats of the Lower Owens River Project area (LORP). We established 150 new point count stations to supplement the 23 that we had established in 1999, for a total of 173 independent point count stations. 165 of these sites were...
Recent work in riparian habitats of the Eastern Sierra Nevada, California, has documented one of the most abundant populations of Yellow Warblers (Dendroica petechia) in the state, and has determined habitat features associated with the occurrence of this State Species of Special Concern. While these sorts of data are becoming more readily availabl...
A riparian songbird monitoring program was established in the eastern Sierra Nevada/western Great Basin region in 1998, and is expected to continue at least through the year 2000. The program emphasizes coverage of Bureau of Land Management Bishop Field Office and Inyo National Forest managed lands with additional sites located on California Depart...
Questions
Question (1)
In this example, I have created a co-citation reference network that has resulted in 3 coummunities. I would like to link the cited references in those communities (represented by nodes) back to my original list of documents which co-cite these references (i.e., Doc A, Doc B, Doc C, etc. in the attached image). I know how to access the list of references for each community, but not the original citing documents which as far as I can tell is only located in the original M matrix. Any suggestions for how to link the list of cited references, by community, back to those original documents?
