Black Point-Green Point, CA, United States
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De La Hera I.,Netherlands Institute of Ecology | De La Hera I.,University of the Basque Country | DeSante D.F.,Institute for Bird Populations | Mila B.,CSIC - National Museum of Natural Sciences
Auk | Year: 2012

Bird species vary greatly in the duration of their annual complete feather molt. However, such variation is not well documented in birds from many biogeographic areas, which restricts our understanding of the diversification of molt strategies. Recent research has revealed that molt duration can be estimated in passerines from ptilochronology-based measurements of the growth rate of their tail feathers. We used this approach to explore how molt duration varied in 98 Nearctic species that have different migratory strategies and molt patterns. As previously documented for Palearctic species, migration was associated with a shortening of molt duration among species that molted during summer on their breeding range. However, molts of winter-molting migratory species were as long as those of summer-molting sedentary species, which suggests that winter molt also allows Nearctic migrants to avoid the temporal constraints experienced during summer. Our results also suggest that migratory species that undergo a stopover molt within the Mexican monsoon region have the shortest molt duration among all Nearctic passerines. Interestingly, and contrary to expectations from a potential tradeoff between molt duration and feather quality, observed variation in feather growth rate was positively correlated with differences in tail feather mass, which may be caused by differences among groups in the availability of resources for molting. We encourage the use of similar approaches to study the variation in molt duration in other geographic areas where knowledge of the evolution of molt is limited. © 2012 by The American Ornithologists' Union. All rights reserved.


Lee D.E.,Institute for Bird Populations | Lee D.E.,Wild Nature Institute | Bond M.L.,Institute for Bird Populations | Siegel R.B.,Institute for Bird Populations
Condor | Year: 2012

Understanding how habitat disturbances such as forest fire affect local extinction and probability of colonization-the processes that determine site occupancy-is critical for developing forest management appropriate to conserving the California Spotted Owl (Strix occidentalis occidentalis), a subspecies of management concern. We used 11 years of breeding-season survey data from 41 California Spotted Owl sites burned in six forest fires and 145 sites in unburned areas throughout the Sierra Nevada, California, to compare probabilities of local extinction and colonization at burned and unburned sites while accounting for annual and site-specific variation in detectability. We found no significant effects of fre on these probabilities, suggesting that fire, even fire that burns on average 32% of suitable habitat at high severity within a California Spotted Owl site, does not threaten the persistence of the subspecies on the landscape. We used simulations to examine how different allocations of survey effort over 3 years affect estimability and bias of parameters and power to detect differences in colonization and local extinction between groups of sites. Simulations suggest that to determine whether and how habitat disturbance affects California Spotted Owl occupancy within 3 years, managers should strive to annually survey ≥200 affected and ≥200 unaffected historical owl sites throughout the Sierra Nevada 5 times per year. Given the low probability of detection in one year, we recommend more than one year of surveys be used to determine site occupancy before management that could be detrimental to the Spotted Owl is undertaken in potentially occupied habitat. © The Cooper Ornithological Society 2012.


News Article | November 2, 2015
Site: phys.org

In the following years, a trail of dead crows marked the spread of the virus from the East through the Midwest on to the West Coast. It took only four years for the introduced virus to span the continent. But what happened to bird populations in the wake of the virus's advance? Were some species decimated and others left untouched? After the initial die-off were the remaining birds immune, or mown down by successive waves of the disease? Nobody really knew. Now, a study published in the Nov. 2 issue of Proceedings of the National Academy of Sciences provides some answers. The study, a collaboration among scientists at Colorado State University, the University of California at Los Angeles, Washington University in St. Louis and the Institute for Bird Populations (IBP), is the first to fully document the demographic impacts of West Nile virus on North American bird populations. The scientists analyzed 16 years of mark-recapture data collected at more than 500 bird-banding stations operated using the Monitoring Avian Productivity and Survival protocol developed by IBP, a California-based nonprofit that studies declines in bird populations. They discovered large-scale declines in roughly half of the species they studied, a much higher fraction than spot checks like the Christmas bird count had found. "Clearly we didn't see the whole picture," said Joseph A. LaManna, PhD, Tyson postdoctoral researcher in the Department of Biology in Arts & Sciences at Washington University. "It wasn't just the jays that were dying; half the species we studied had significant die-offs." The data also revealed, however, that some species fared much better than others. Roughly half of the afflicted species managed to rebound within a year or two. Ironically, the resilient ones include the crows and other corvids who were so strongly associated with the disease on its arrival. But a second group of birds, including Swainson's thrush, the purple finch and tufted titmouse were not so lucky. Knocked down by the arrival of West Nile virus, they have not rebounded and seem to have suffered long-term population declines. "Many more species of birds than we thought are susceptible to this virus," said T. Luke George, PhD, an ecologist at Colorado State University. "And we also found long-term effects on population growth rates. Prior to this study, we generally thought the West Nile virus had a very short-term effect on bird survival." The scientists aren't sure why some species fare better than others. Was a common evolutionary history predictive? Or similar habitats or diets? "That's really the question our study opens," said Ryan J. Harrigan, a biologist at the University of California, Los Angeles. "In the end, we're not completely sure why some species recovered from this disease and some did not. That would be the next step forward, addressing that question." "The deeper story is that without long-term monitoring and detailed data, we miss patterns like these," LaManna said. "Deaths in one area can be easily masked by immigration from other areas, and we wouldn't really notice unless we happened to be looking at the right type of data. "This year was another big West Nile year," LaManna said. "Most people don't even know that." More information: Persistent impacts of West Nile virus on North American bird populations, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1507747112


Humphrey and Parkes (1959) developed a molt and plumage nomenclature (the "H-P" system) based on the evolution of prebasic molts in birds from ecdysis events in reptiles, followed by later evolution of inserted molts responding to lineage-specific constraints and adaptations in Aves. Pyle (2005) revised H-P molt and plumage terminology of ducks by tracing the evolution of their molts from geese, whereas Hawkins (2011) defended traditional molt and plumage terminologies that defined molts relative to present-day breeding seasonality, ensuing plumage coloration, and other proximal factors. Apart from misinterpreting H-P's evolutionary approach, Hawkins (2011) confused the first-cycle terms of H-P, Howell et al. (2003), and Pyle (2005), and presented no new data or ideas to support traditional molt terminology in ducks. It is unlikely that inserted molts evolved in ancestral taxa based on yet-to-occur adaptations involving plumage color, and it is inconsistent to define homologous molts based on similar ensuing feather coloration while disregarding the substantially different coloration of homologous plumages within many avian lineages. Here the terminology of Pyle (2005) is defended, an alternative interpretation for the initial evolution of two (rather than one) inserted molts in the definitive cycles of female and male ducks is elaborated upon, and the future application of metabolic signatures to trace homologous molts in ducks and other bird lineages is suggested. Prebasic molts in ducks and other birds likely evolved from whole-scale restorative events common to all vertebrates, whereas distinguishable and less-comprehensive endocrinological and metabolic processes may accompany inserted molts.


Saracco J.F.,Institute for Bird Populations | Andrew Royle J.,U.S. Geological Survey | DeSante D.F.,Institute for Bird Populations | Gardner B.,U.S. Geological Survey
Ecology | Year: 2010

The importance of understanding spatial variation in processes driving animal population dynamics is widely recognized. Yet little attention has been paid to spatial modeling of vital rates. Here we describe a hierarchical spatial autoregressive model to provide spatially explicit year-specific estimates of apparent survival (Φ) and residency (π) probabilities from capture-recapture data. We apply the model to data collected on a declining bird species, Wood Thrush (Hylocichla mustelina), as part of a broad-scale bird-banding network, the Monitoring Avian Productivity and Survivorship (MAPS) program. The Wood Thrush analysis showed variability in both Φ and it among years and across space. Spatial heterogeneity in residency probability was particularly striking, suggesting the importance of understanding the role of transients in local populations. We found broad-scale spatial patterning in Wood Thrush Φ and Φ that lend insight into population trends and can direct conservation and research, The spatial model developed here represents a significant advance over approaches to investigating spatial pattern in vital rates that aggregate data at coarse spatial scales and do not explicitly incorporate spatial information in the model. Further development and application of hierarchical capture-recapture models offers the opportunity to more fully investigate spatiotemporal variation in the processes that drive population changes. © 2010 by the Ecological Society of America.


Nelson K.N.,P.O. Box 402 | Pyle P.,Institute for Bird Populations
Western Birds | Year: 2013

There are now numerous records of the Crested Caracara (Caracara cheriway) from California and elsewhere well north of its breeding range, but whether or not they represent wild birds or escapees from zoos or falconers has been debated. Through 2011, the California Bird Records Committee (CBRC) had accepted 49 records that they considered to represent naturally occurring vagrants, but decisions concerning the number of individuals involved in these records were haphazard. Therefore, we assessed the date, location, age, molt status, and appearance of caracaras representing 60 observations specific to date and location in California and propose that these records involve only 11 individuals, recorded between 1 and 34 times throughout the state; a twelfth individual was recorded from December 2011 to April 2012. Our 11-bird scenario was proposed and accepted by the CBRC in January 2012. This synthesis clarifies the species' pattern of occurrence in California: ten of the 11 individuals were first detected in fall or winter, eight individuals were first detected in their first or second years, four of these eight were later detected at appropriate ages elsewhere in California, and six individuals moved north within the state. These patterns are consistent with birds moving north as wild vagrants and so support the CBRC's decision to accept the Crested Caracará as a naturally occurring species. We hope that our analysis will help other records committees evaluate the status of this species in other regions, perhaps revealing a similar pattern of natural vagrancy throughout North America.


Howell S.N.G.,Bolinas | Pyle P.,Institute for Bird Populations
Auk | Year: 2015

Ornithologists have largely embraced the molt terminology of Humphrey and Parkes (1959) as modified by Howell et al. (2003; the H-P-H system). In a recent commentary, Wolfe et al. (2014) summarized the derivation and benefits of HP-H terminology, suggested slight modifications, and promoted analyses on the evolution of molts using H-P-H nomenclature. We appreciate the timeliness of Wolfe et al.'s review and agree with most of their conclusions and modifications. We disagree, however, with Wolfe et al.'s proposal for introducing a new and restricted use of the term "definitive" in H-P-H nomenclature. To avoid confusion, we recommend that definitive plumage and definitive molt cycle continue to be used as defined by Humphrey and Parkes (1959) and Howell et al. (2003), respectively, as terms indicating that plumage appearance and molt cycle have achieved stasis. We also recommend that the term "plumage" can be used more widely than the definition proposed by Humphrey and Parkes (1959), and that the term "juvenal" can henceforth be replaced by "juvenile" in molt and plumage literature. © 2015 American Ornithologists' Union.


Pyle P.,Institute for Bird Populations
Western Birds | Year: 2013

While most basic-plumaged Common Murres (Uria aalge) show white facial plumage and tips to the secondaries, some individuals off central California from September through November have dark faces and secondaries. To investigate the plumage state and age of such birds, I examined specimens and photographs of Common Murres taken off central California and conclude that outgoing and incoming alternate feathers as well as early-replaced and late-replaced dark basic and formative feathers all may contribute to this variation. Hypermelanism may account for a small proportion of cases. The early onset of prebasic molt-before hormone signaling switches from dark feathers typical of the alternate plumage to white feathers typical of the basic plumage-may be responsible for most of the darkest-faced birds in basic plumage. This type of asynchrony of molt and the signal for change in plumage appears to occur more often in second-cycle birds, which initiate the prebasic molt earlier than do older adults, and it may also explain plumages in chicks and juveniles molting during May and June. Common Murres in basic plumage from colonies in central California appear to acquire dark facial feathers more often than birds from more northerly colonies, which could relate to earlier breeding and molt in central California.


I examined over 4500 specimens to investigate the evolutionary significance of molt sequences as related to systematic relationships of falcons and parrots. Nodes of molt among the medial primaries (p4-p6) and at s5 among the secondaries, followed by bidirectional replacement from the node within each tract, was confirmed for most or all taxonomic groupings of both falcons and parrots, with the exception of the Kakapo or Owl Parrot (Strigops habroptila), which appears to replace its remiges in sequences similar to those of most other birds. Initiation of primary molt varies between p4 and p5 in falcons and between p5 and p6 in parrots, including within species, suggesting that the node's position may be fluid within a defined area along the alar tract. The coincidence and consistency of these molt sequences in parrots and falcons but in no other order of birds suggests that molt sequence may be a synapomorphic (shared) character state, supporting recent molecular evidence that the Falconiformes and Psittaciformes are sister taxa. A more ancestral molt sequence in Strigops may suggest that it split from other parrots prior to a Falconiformes-Psittaciformes divergence or it may indicate reversion to a primitive character state in response to the species' unique nocturnal and ground-dwelling habits. The results of this analysis further suggest that synapomorphic wing-molt sequences can be used as an indicator of systematic relationships in birds and that molt sequence is perhaps controlled by a neurological process more fixed than timing, extent, and geographic location of molts. © The Cooper Ornithological Society 2013.


Saracco J.F.,Institute for Bird Populations | Siegel R.B.,Institute for Bird Populations | Wilkerson R.L.,Institute for Bird Populations
Ecosphere | Year: 2011

The Black-backed Woodpecker (Picoides arcticus) has been designated by the USDA Forest Service as a management indicator species for snags in burned conifer forests of the Sierra Nevada of California, USA. However, little is known about the characteristics that affect between-fire and within-fire habitat selection by the species in the region. Here we report on the first broad-scale survey of Black-backed Woodpeckers on wildfire-affected forests of the Sierra Nevada. We implemented a Bayesian hierarchical model to: 1) estimate Black-backed Woodpecker occupancy probability in fire areas burned within a time window of 1-10 years; 2) identify relationships between occupancy probability and habitat covariates (fire age, change in canopy cover pre-to-post fire, and snag basal area), elevation, and latitude; and 3) estimate detection probability and relate it to survey interval length and survey type (passive v. broadcast). We included random fire-area effects in our model of occupancy probability to accommodate clusters of nonindependent points surveyed within the larger set of fire areas. Mean occupancy probability was estimated to be 0.097. Elevation (after controlling for latitude) had the strongest effect on occupancy probability (higher occupancy at higher elevation) followed by latitude (higher occupancy at northerly sites). Fire age was also important; occupancy probability was about 43higher on the youngest compared to oldest fires. Although the direction of regression coefficients were in the expected direction (positive), snag basal area and canopy cover change were of minor importance in affecting occupancy probability. There was some indication, however, that the importance of snag basal area increased with fire age. Weak links between occupancy and canopy cover change suggested the species uses a range of burn severities, and such heterogeneity may promote habitat longevity. Our estimate of overall detection probability (across all survey intervals) was 0.772. We found strong effects of survey interval length (higher for longer interval) and, especially survey type (higher for broadcast survey) on detection probability. Our modeling framework and implementation illustrates the flexibility of the Bayesian hierarchical approach for handling complexities such as estimating derived parameters (and variances) and modeling random effects, and should prove generally useful for occupancy studies. © 2011 Saracco et al.

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