Kristen E. Dybala

Climate Models and Ornithology

1Information Center for the Environment, Department of Environmental Science and Policy, University of California, 1 Shields Avenue, Davis, California 95616, USA; 2PRBO Conservation Science, 3820 Cypress Drive #11, Petaluma, California 94954, USA; 3Avian Conservation and Ecology Lab, Department of Wildlife, Fish and Conservation Biology, University of California, 1 Shields Avenue, Davis, California 95616, USA; and 4Climate Change and Impacts Lab, Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA

Projecting demographic responses to climate change: adult and juvenile survival respond differently to direct and indirect effects of weather in a passerine population

Few studies have quantitatively projected changes in demography in response to climate change, yet doing so can provide important insights into the processes that may lead to population declines and changes in species distributions. Using a long-term mark-recapture data set, we examined the influence of multiple direct and indirect effects of weather on adult and juvenile survival for a population of Song Sparrows (Melospiza melodia) in California. We found evidence for a positive, direct effect of winter temperature on adult survival, and a positive, indirect effect of prior rainy season precipitation on juvenile survival, which was consistent with an effect of precipitation on food availability during the breeding season. We used these relationships, and climate projections of significantly warmer and slightly drier winter weather by the year 2100, to project a significant increase in mean adult survival (12-17%) and a slight decrease in mean juvenile survival (4-6%) under the B1 and A2 climate change scenarios. Together with results from previous studies on seasonal fecundity and postfledging survival in this population, we integrated these results in a population model and projected increases in the population growth rate under both climate change scenarios. Our results underscore the importance of considering multiple, direct, and indirect effects of weather throughout the annual cycle, as well as differences in the responses of each life stage to climate change. Projecting demographic responses to climate change can identify not only how populations will be affected by climate change but also indicate the demographic process(es) and specific mechanisms that may be responsible. This information can, in turn, inform climate change adaptation plans, help prioritize future research, and identify where limited conservation resources will be most effectively and efficiently spent.

Dependent vs. independent juvenile survival: contrasting drivers of variation and the buffering effect of parental care

Juvenile survival is often found to be more sensitive than adult survival to variation in environmental conditions, and variation in juvenile survival can have significant impacts on population growth rates and viability. Therefore, understanding the population-level effects of environmental changes requires understanding the effects on juvenile survival. We hypothesized that parental care will buffer the survival of dependent juveniles from variation in environmental conditions, while the survival of independent juveniles will respond more strongly to environmental variation and, in turn, drive the overall variation in annual juvenile survival. We tested this parental-care hypothesis using a 30-year mark-recapture data set to model the survival of juvenile Song Sparrows (Melospiza melodia) during the dependent and independent stages. We examined the effects of weather, density, and cohort mean fledge date and body mass on annual variation in survival during the first 12 weeks after fledging, as well as effects of individual fledge date and body mass on individual variation in survival. The primary driver of annual variation in juvenile survival was precipitation during the previous rainy season, consistent with an effect on food availability, which had a strong positive effect on the survival of independent juveniles, but no effect on dependent juveniles. We also found strong support for effects of body mass and fledge date on individual survival probability, including striking differences in the effect of fledge date by stage. Our results provided evidence that different mechanisms influence juvenile survival during each stage of fledgling development, and that parental care buffers the survival of dependent juveniles from variation in environmental conditions. Consequently, variation in juvenile survival was driven by independent juveniles, not dependent juveniles, and studies focused only on survival during the dependent stage may not be able to detect the major drivers of variation in juvenile survival. We recommend that future efforts to understand or project the population-level effects of environmental change not only examine the effects on juvenile survival, but specifically consider the survival of independent juveniles, as well as how the drivers of variation in juvenile survival may vary by stage.

Forty-Five Years and Counting: Reflections from the Palomarin Field Station on the Contribution of Long-Term Monitoring and Recommendations for the Future

Abstract. Long-term monitoring is essential to understand the effect of environmental change on bird populations. Ornithological field stations that have recorded detailed demographic data on bird populations over decades are well positioned to make important contributions to emerging research questions. On the basis of our experience at PRBO Conservation Sciences Palomarin Field Station and a review of the literature, we assess the ability of field stations to use their long-term data to address current and future issues in conservation and management. We identify barriers to the application of data from field stations as well as some of the unique contributions made by these stations, and we present recommendations regarding the development, maintenance, and enhanced application of long-term data.

Shifting Effects of Ocean Conditions on Survival and Breeding Probability of a Long-Lived Seabird

With a rapidly changing climate, there is an increasing need to predict how species will respond to changes in the physical environment. One approach is to use historic data to estimate the past influence of environmental variation on important demographic parameters and then use these relationships to project the abundance of a population or species under future climate scenarios. However, as novel climate conditions emerge, novel species responses may also appear. In some systems, environmental conditions beyond the range of those observed during the course of most long-term ecological studies are already evident. Yet little attention has been given to how these novel conditions may be influencing previously established environment–species relationships. Here, we model the relationships between ocean conditions and the demography of a long-lived seabird, Brandt’s cormorant (Phalacrocorax penicillatusI), in central California and show that these relationships have changed in recent years. Beginning in 2007/2008, the response of Brandt’s cormorant, an upper trophic level predator, to ocean conditions shifted, resulting in lower than predicted survival and breeding probability. Survival was generally less variable than breeding probability and was initially best predicted by the basin-scale forcing of the El Niño Southern Oscillation rather than local ocean conditions. The shifting response of Brandt’s cormorant to ocean conditions may be just a proximate indication of altered dynamics in the food web and that important forage fish are not responding to the physical ocean environment as expected. These changing relationships have important implications for our ability to project the effects of future climate change for species and communities.

Summer vs. winter: Examining the temporal distribution of avian biodiversity to inform conservation

ABSTRACT Winter habitat quality plays a key role in avian population regulation, and conservation of winter habitat is a priority for waterfowl, shorebirds, and Neotropical migrant landbirds. Yet, there has been little discussion of the importance of conserving temperate wintering habitat for landbirds, including the billions of Neotemperate migratory landbirds that winter in the United States. The value and impact of conservation initiatives in the U.S. could be maximized by accommodating the habitat requirements of bird communities throughout the full annual cycle, particularly in the southern and western U.S. where winter species richness is concentrated. To estimate the degree to which winter bird communities should be a conservation priority, we examined the temporal distribution of avian diversity using riparian habitat in the lower Cosumnes River and lower Putah Creek watersheds in Californias Central Valley. We used hierarchical multispecies occupancy models to estimate seasonal species richness and phylogenetic diversity in each watershed. We found that total species richness was equally as high in winter as in summer, and that phylogenetic diversity was higher in winter, with a considerable proportion of the winter avian diversity attributable to boreal-breeding Neotemperate migrants. Our results provide evidence that maintaining and restoring high-quality riparian habitat for winter bird communities in California is an important conservation opportunity. Broader recognition of the diversity of temperate winter bird communities and additional research into the factors affecting body condition and survival would facilitate effective conservation of high-quality winter habitat, benefiting Neotemperate migrants and year-round residents during a season that can have important impacts on their population dynamics.

New and extralimital records of breeding birds for Putah Creek, California

We report on extralimital and new breeding records from a 16-year study of birds along lower Putah creek, central Valley, california, that began in 1997. surveys for breeding birds have confirmed 74 species nesting on the creek, while nesting of 17 further species remains probable. Among rare or extralimital species, we documented nesting of the hooded Merganser (Lophodytes cucullatus), Selasphorus sp., Pileated Woodpecker (Dryocopus pileatus), Pacific-slope Flycatcher (Empidonax difficilis), Bell’s Vireo (Vireo bellii), Warbling Vireo (V. gilvus), chestnutbacked chickadee (Poecile rufescens), Brown creeper (Certhia americana), Wrentit (Chamaea fasciata), orange-crowned Warbler (Oreothlypis celata), dark-eyed Junco (Junco hyemalis), and Western Tanager (Piranga ludoviciana). The records of nesting of the Brown creeper, chestnut-backed chickadee, and Western Tanager are the first confirmed for those species on the central Valley floor. nine of these species have experienced recent expansions elsewhere in their california ranges, and Bell’s Vireo has begun to reoccupy a few other sites in the central Valley, from which it had been extirpated for decades. We also present evidence for probable breeding by the hairy Woodpecker (Picoides villosus), Western Wood-Pewee (Contopus sordidulus), california Thrasher (Toxostoma redivivum), yellow Warbler (Setophaga petechia), and yellow-breasted chat (Icteria virens). These breeding records attest to the pioneering nature of birds and to the importance of Putah creek in the maintenance of riparian species in the sacramento Valley. The primary interest of most bird inventories is to document the regularly occurring species, as these influential members of local ecosystems play a prominent role in ecogeographical studies. Very often less attention is paid to the scarce, rare, or irregularly occurring species as their role in community ecology seems to be slight or even negligible (Patten and Marantz 1996, Volume 48, number 3, 2017

Population and Habitat Objectives for Avian Conservation in California’s Central Valley Grassland–Oak Savannah Ecosystems

Author(s): DiGaudio, Ryan T.; Dybala, Kristen E.; Seavy, Nathaniel E.; Gardali, Thomas | Abstract: In California’s Central Valley, grassland and oak savannah ecosystems provide multiple economic and social benefits, ecosystem services, and vital bird habitat. There is a growing interest in protecting, restoring, and managing these ecosystems, and the Central Valley Joint Venture (CVJV) provides leadership in the formulation of conservation goals and objectives. We defined a long-term goal of protecting, restoring, and managing Central Valley grassland and oak savannah ecosystems so that they are capable of supporting genetically robust, self-sustaining, and resilient wildlife populations. To measure progress toward this goal, we selected a suite of 12 landbird focal species that primarily breed in grasslands and oak savannahs as indicators of the state of these ecosystems on the Central Valley floor (primary focus area) and in the Central Valley’s surrounding foothills (secondary focus area). Using data on current densities and habitat extent, we estimated that at least three of the focal species populations in the primary focus area and at least two of the focal species populations in the secondary focus area are currently small (l10,000 individuals) and may be vulnerable to extirpation. Furthermore, at least two species appear to have steeply declining population trends. We defined long-term (100-year) population objectives for each focal species that we expect to meet the goal of genetically robust, self-sustaining, and resilient populations. We then estimated corresponding short-term (10-year) habitat objectives of 4,183 ha of additional grassland and 3,433 ha of additional oak savannah that will be required to make progress toward the long-term objectives. We expect that habitat restoration and enhancement efforts aimed at reaching these long-term conservation objectives will result in improvements to the function of Central Valley grassland and oak savannah ecosystems.