A guide to nestling development and aging in altricial passerines

Nestling growth and development studies have been a topic of interest for a greater part of the last century (Sutton 1935, Walkinshaw 1948) and continue to be of interest today. This is not surprising since studies on nestling growth can provide a wealth of biological information that has larger implications for avian management and conservation. Despite this history of studying nestling development, basic information is still limited or absent for many species. Many questions remain unanswered, and contradictory conclusions are often found in the literature (Starck and Ricklefs 1998a). Therefore, much information on aging and development can still be gained from studying the development patterns of similar species and from comparative studies, across avian orders (Minea et al. 1982, Saunders and Hansen 1989, Carsson and Hörnfeldt 1993). Additionally, nestling growth studies can yield insight into the effects of different nesting strategies on productivity (O’Connor 1978), as well as the impacts of parental effort and environmental variables on fitness (Ross 1980, Ricklefs and Peters 1981, Magrath 1991). Since low reproductive success may play a significant role in the declines of many North American passerines (Sherry and Holmes 1992, Ballard et al. 2003), a better understanding of the factors that influence reproductive success is a vital component of avian conservation (Martin 1992). Data on nestling aging can be used to improve nest survival estimates (Dinsmore 2002, Nur et al. 2004), providing information that can be used to more precisely age nests (Pinkowski 1975, Podlesack and Blem 2002), (Jones and Geupel 2007). Indeed, the relatively short time period young spend developing in the nest is a critical part of a bird’s life cycle and a nestling’s developmental path can affect its survival to independence, its survival as an adult, and its future reproductive success

Autumn and Winter Breeding Records for the American Robin, Turdus migratorius

We report autumn and winter breeding records for the American Robin (Turdus migratorius). We located a nest on the campus of the University of Columbia at Missouri, USA, active 12 to 15 October 1999. This late nesting record prompted us to consult the Cornell Lab of Ornithology’s Nest Record Program and Bird Studies Canada’s Project NestWatch. Of the 11 113 American Robin nest records in Cornell’s database, 15 were active in September and three were active later than September. Of the over 23 000 nest records available from Bird Studies Canada one was active in September and one in October. All four of the latest nests contained nestlings and were active on 3 October 1964 in Massachusetts, 13 October 1932 in Manitoba, 18 November 1964 in West Virginia, and 8 January 1966 in Ohio. Eight of the ten nests monitored until outcome could be determined fledged young successfully

Multiple-Benefit Conservation in Practice: A Framework for Quantifying Multidimensional Effects of Landscape Change in California’s Sacramento–San Joaquin Delta

Conservation efforts and other land-management decisions are often intended to provide multiple benefits, but real or perceived trade-offs between goals can increase conflict and limit the practice of Multiple-Benefit Conservation. To support decision-making, policy, and management in the Sacramento–San Joaquin River Delta of California, where multiple potentially conflicting goals and values have been identified, we developed a flexible framework for quantifying the benefits and trade-offs that result from landscape change, implemented as an open-source R package. Integrating multiple data sets and methods, we developed metrics that represent (1) agricultural livelihoods, (2) water quality, (3) climate-change resilience, and (4) biodiversity support benefits and then projected the net effects on each metric of three alternative Delta landscapes. Each alternative represented changes that could result by 2050 from meeting habitat-restoration targets in the Delta Plan for riparian and non-tidal wetlands, the continued expansion of perennial crops, or a combination of the two. We found that habitat restoration would provide significant biodiversity support benefits and some climate-change resilience and water-quality benefits without significant trade-offs for agricultural livelihoods, while the continued expansion of perennial crops would provide significant benefits to agricultural livelihoods with simultaneous trade-offs to climate-change resilience and a mix of benefits and trade-offs for water-quality metrics. The combined alternative illustrated the interaction between restoration and perennial crop expansion, with still significant but reduced benefits to both agricultural livelihoods and biodiversity support. Our results provide insights into the effects of each of these drivers of landscape change, alone and in combination, with implications for policy and management to support the practice of Multiple-Benefit Conservation in the Sacramento–San Joaquin River Delta. Our framework serves as a foundation for future collaborative development among scientists, managers, policy-makers, and other interested parties to facilitate evaluation of a more comprehensive set of metrics across new alternative landscapes

Establishing the Breeding Provenance of a Temperate-Wintering North American Passerine, the Golden-Crowned Sparrow, Using Light-Level Geolocation

The migratory biology and connectivity of passerines remains poorly known, even for those that move primarily within the temperate zone. We used light-level geolocators to describe the migratory geography of a North American temperate migrant passerine. From February to March of 2010, we attached geolocator tags to 33 Golden-crowned Sparrows (Zonotrichia atricapilla) wintering on the central coast of California, USA, and recovered four tags the following winter (October to December 2010). We used a Bayesian state-space model to estimate the most likely breeding locations. All four birds spent the breeding season on the coast of the Gulf of Alaska. These locations spanned approximately 1200 kilometers, and none of the individuals bred in the same location. Speed of migration was nearly twice as fast during spring than fall. The return rate of birds tagged the previous season (33%) was similar to that of control birds (39%), but comparing return rates was complicated because 7 of 11 returning birds had lost their tags. For birds that we recaptured before spring migration, we found no significant difference in mass change between tagged and control birds. Our results provide insight into the previously-unknown breeding provenance of a wintering population of Golden-crowned Sparrows and provide more evidence of the contributions that light-level geolocation can make to our understanding of the migratory geography of small passerines

Private lands habitat programs benefit California's native birds

To address the loss of wetlands and riparian forests in California, private lands habitat programs are available through U.S. federal and state government agencies to help growers, ranchers and other private landowners create and enhance wildlife habitat. The programs provide financial and technical assistance for implementing conservation practices. To evaluate the benefits of these programs for wildlife, we examined bird use of private wetlands, postharvest flooded croplands and riparian forests enrolled in habitat programs in the Central Valley and North Coast regions of California. We found that private Central Valley wetlands supported 181 bird species during the breeding season. During fall migration, postharvest flooded croplands supported wetland-dependent species and a higher density of shorebirds than did semipermanent wetlands. At the riparian sites, bird species richness increased after restoration. These results demonstrated that the programs provided habitat for the species they were designed to protect; a variety of resident and migratory bird species used the habitats, and many special status species were recorded at the sites

A national-scale assessment of climate change impacts on species: assessing the balance of risks and opportunities for multiple taxa

It is important for conservationists to be able to assess the risks that climate change poses to species, in order to inform decision making. Using standardised and repeatable methods, we present a national-scale assessment of the risks of range loss and opportunities for range expansion, that climate change could pose for over 3,000 plants and animals that occur in England. A basic risk assessment that compared projected future changes in potential range with recently observed changes classified 21% of species as being at high risk and 6% at medium risk of range loss under a B1 climate change scenario. A greater number of species were classified as having a medium (16%) or high (38%) opportunity to potentially expand their distribution. A more comprehensive assessment, incorporating additional ecological information, including potentially confounding and exacerbating factors, was applied to 402 species, of which 35 % were at risk of range loss and 42 % may expand their range extent. This study covers a temperate region with a significant proportion of species at their poleward range limit. The balance of risks and opportunities from climate change may be different elsewhere. The outcome of both risk assessments varied between taxonomic groups, with bryophytes and vascular plants containing the greatest proportion of species at risk from climate change. Upland habitats contained more species at risk than other habitats. Whilst the overall pattern was clear, confidence was generally low for individual assessments, with the exception of well-studied taxa such as birds. In response to climate change, nature conservation needs to plan for changing species distributions and increasing uncertainty of the future

Winter site fidelity and body condition of three riparian songbird species following a fire

The effects of fire on nonbreeding songbird species in riparian habitat have not been studied. We compared body condition, within-year site fidelity, and between-year site fidelity of 3 songbird species (Passerella iliaca, Fox Sparrow; Catharus guttatus, Hermit Thrush; and Regulus calendula, Ruby-crowned Kinglet) at 2 coastal riparian sites. Wildfire, which is rare in this habitat, had occurred at 1 of the sites before data collection. A significantly larger proportion of Passerella iliaca was recaptured in subsequent winters at the unburned site than at the burned site, but little difference was found between sites for Catharus guttatus or Regulus calendula. Body mass of all 3 species declined during winter at the burned site, but differences between sites were not significant. Similarly, body mass indices of new captures were lower at the burned site than the unburned site for all 3 species, but these differences were not significant. The within-year recapture rate for all 3 species combined declined at the burned site over the course of the study, possibly due to changes in vegetation structure caused by the fire. Overall, our data suggest that wintering songbirds were resilient to this disturbance, but that response to the post-fire environment differed among foraging guilds. Well-replicated studies that include pre-burn data are needed to evaluate the effects of this disturbance in riparian systems

Least Bell\u27s Vireo breeding records in the Central Valley following decades of extirpation

The Least Bell\u27s Vireo (Vireo bellii pusillus) was listed as state endangered in 1980 and federally endangered in 1986 in response to a sharp population decline and range reduction. This vireo commonly bred in riparian forests throughout the Central Valley of California, but prior to 2005, no nesting pairs had been confirmed in the region in over 50 years. On 29 June 2005, a Least Bell\u27s Vireo nest was located in a 3-year-old riparian restoration site at the San Joaquin River National Wildlife Refuge in Stanislaus County, California. In 2006, a Least Bell\u27s Vireo pair returned to the refuge to successfully breed, followed by an unsuccessful attempt in 2007 by an unpaired female. These records are approximately 350 km from the nearest known breeding population and appear to be part of a growing number of sightings outside of the species\u27 current southern California breeding range. These nesting attempts lend credence to the idea that extirpated species can recolonize restored habitat by long-distance dispersal