Christmas Bird Count Research Articles

From passion to science

We began our ornithological careers out of passion, for watching birds, for identifying them, for sharing our excitement and knowledge with our friends. At some point our desire to know and understand birds led us into science. We joined Christmas Bird Counts and wondered why the species and numbers varied annually. We wondered what characterized good sparrow habitat. We found that special patch and saw more sparrows than any other participant. Then, we discovered that people wrote about and published their observations of birds. We read some of those papers, at first the short ones, those that focused on natural history, on what we could observe. Then we tried to imitate the authors, by watching birds, asking questions and collecting data. We were unaware that the child hobbyist had become the adolescent scientist. I joined the Wilson Ornithological Society and began to prepare my observations for publication. One day I screwed up my courage and submitted a short paper on Tree Swallows (Tachycineta bicolor). It was rejected. But by then I was an undergraduate. I had just received a small research grant. The die was cast. Graduate school followed. I wrote more short papers. Some were published. I synthesized some of these into longer papers with substantive conclusions that were cited by real ornithologists. Imperceptibly, I became a scientist. I began to formulate hypotheses, deduce predictions, collect data, and create new explanations about the evolution of avian color, an aspect of birds that had fascinated me almost since I became aware of birds and painted a papier-mâché duck brilliant white with scarlet feet and bill, and large, blue eyes.This observation-based entry into a scientific career is very different from a course-based entry in which the future scientist learns a paradigm, is excited and decides to devote her or his career to that scientific discipline. The importance of one’s introduction to science is explored with respect to different disciplines and the way different scientists think about science. Finally, the importance of the observation-based entry into science is explored with respect to the Wilson Ornithological Society, The Wilson Journal of Ornithology, ornithology, and the field sciences generally.

73rd Annual Saskatchewan Christmas Bird Count - 2014

73rd Annual Saskatchewan Christmas Bird Count - 2014

Ongoing changes in the avifauna of La Selva Biological Station, Costa Rica: Twenty-three years of Christmas Bird Counts

Tropical forest fragmentation influences community composition via differential species-level effects. Avian responses to fragmentation at La Selva Biological Station are, in part, responsible for the particular concern over the fate of understory insectivorous species. However, since the 1990s, much previously deforested land within and surrounding La Selva has reverted to forest, providing an opportunity to test hypotheses explaining ongoing avifaunal change. Analyses of 23years (1989–2011) of Christmas Bird Counts reveal that 63 of 202 species have increased whereas 44 are declining, with declines occurring more rapidly than increases. Habitat association was an important predictor of population trends, as understory birds continue to decline whereas forest generalists increased. Our results differ from previous work in the tropics by revealing that, at La Selva, insectivores are not currently suffering greater declines than birds of other dietary guilds. Instead, body size was more strongly associated with population change than was diet, with smaller birds having more negative population trends than larger birds. These results suggest that we must consider additional hypotheses that may explain ongoing population declines of tropical birds. In particular, the associations between population trends and body size implicate physiological mechanisms influencing population change, which may result from direct or indirect consequences of changing climates.

Range expansion and population dynamics of an invasive species: the Eurasian Collared-Dove (Streptopelia decaocto).

Invasive species offer ecologists the opportunity to study the factors governing species distributions and population growth. The Eurasian Collared-Dove (Streptopelia decaocto) serves as a model organism for invasive spread because of the wealth of abundance records and the recent development of the invasion. We tested whether a set of environmental variables were related to the carrying capacities and growth rates of individual populations by modeling the growth trajectories of individual populations of the Collared-Dove using Breeding Bird Survey (BBS) and Christmas Bird Count (CBC) data. Depending on the fit of our growth models, carrying capacity and growth rate parameters were extracted and modeled using historical, geographical, land cover and climatic predictors. Model averaging and individual variable importance weights were used to assess the strength of these predictors. The specific variables with the greatest support in our models differed between data sets, which may be the result of temporal and spatial differences between the BBS and CBC. However, our results indicate that both carrying capacity and population growth rates are related to developed land cover and temperature, while growth rates may also be influenced by dispersal patterns along the invasion front. Model averaged multivariate models explained 35–48% and 41–46% of the variation in carrying capacities and population growth rates, respectively. Our results suggest that widespread species invasions can be evaluated within a predictable population ecology framework. Land cover and climate both have important effects on population growth rates and carrying capacities of Collared-Dove populations. Efforts to model aspects of population growth of this invasive species were more successful than attempts to model static abundance patterns, pointing to a potentially fruitful avenue for the development of improved invasive distribution models.

Bird mortality from the Deepwater Horizon oil spill. II. Carcass sampling and exposure probability in the coastal Gulf of Mexico

Two separate approaches, a carcass sampling model and an exposure probability model, provided estimates of bird mortalities of 600 000 and 800 000, respectively, from the 2010 Deepwater Horizon MC 252 oil spill in coastal waters of the Gulf of Mexico. Monte Carlo simula- tion of parameter uncertainty led to respective 95% uncertainty intervals of 320 000 to 1200 000 and 160 000 to 1900 000. Carcass sampling relied on expansion factors multiplied by counts of bird carcasses retrieved in shoreline surveys, whereas exposure probability estimated bird deaths as a product of estimated coastal bird density, average oil slick size, slick duration, and proportionate mortality due to oiling. The low proportion of small-sized carcasses recovered, compared with considerably higher proportions of small live birds in coastal Gulf habitats, indicate an especially low probability of recovery for small birds after oil spills at sea. Most mortality affected 4 species: laughing gull Leucophaeus atricilla (32% of the northern Gulf of Mexico population killed), royal tern Thalasseus maximus (15%), northern gannet Morus bassanus (8%) and brown pelican Pele- canus occidentalis (12%). Declines in laughing gulls were confirmed by ~60% reductions in National Audubon Society Christmas Bird Count data for 2010−2013 along the Gulf coast. Popu- lation-level effects in apex predators of this magnitude likely had effects on prey populations that warrant careful assessment.

The Countercultural Potential of Citizen Science

What is the countercultural potential of citizen science? As a participant in the wider citizen science movement, I can attest that contemporary citizen science initiatives rarely characterise themselves as countercultural. Rather, the goal of most citizen science projects is to be seen as producing orthodox scientific knowledge: the ethos is respectability rather than rebellion (NERC). I will suggest instead that there are resonances with the counterculture that emerged in the 1960s, most visibly through an emphasis on participatory experimentation and the principles of environmental sustainability and social justice. This will be illustrated by example, through two citizen science projects that have a commitment to combining social values with scientific practice. I will then describe the explicitly countercultural organisation, Science for the People, which arose from within the scientific community itself, out of opposition to the Vietnam War. Methodological and conceptual weaknesses in the authoritative model of science are explored, suggesting that there is an opportunity for citizen science to become anti-hegemonic by challenging the hegemony of science itself. This reformulation will be expressed through Deleuze and Guattari's notion of nomadic science, the means through which citizen science could become countercultural.

Assessing predictions of population viability analysis: Peregrine Falcon populations in California.

Population viability analysis (PVA) has been an important tool for evaluating species extinction risk and alternative management strategies, but there is little information on how well PVA predicts population trajectories following changes in management actions. We tested previously published predictions from a stage-structured PVA of Peregrine Falcons (Falco peregrinus) in California, USA (Wootton and Bell 1992), against population trajectories following the 1992 termination of statewide, active management (population supplementation of captive-reared young). In the absence of extensive post-management monitoring, we developed surrogate estimates of breeding population size by calibrating several citizen science data sets (Christmas Bird Count, CBC; and North American Breeding Bird Survey, BBS) to intensive population surveys taken primarily during the active management period. CBC abundance data standardized by observer effort exhibited a strong relationship to intensive survey data (r2 = 0.971), indicated significantly reduced annual population growth rates after management was terminated (λ = 0.023 ± 0.013 SE) than when supplementation occurred (λ = 0.089 ± 0.023 SE), and demonstrated an increasing population as predicted by the PVA. The population trajectory fell within the 95% CI of stochastic simulations of the model either with or without density dependence and assuming either measurement error or process error, but models with process error were most strongly supported by the data. These results indicate that PVA can quantitatively anticipate population trajectories following changes in management, highlight the importance of post-management monitoring of species of concern, and illustrate the benefits of using management changes as large-scale experiments to more rigorously test PVA.

Range expansion and the breakdown of Bergmann's Rule in Red-Bellied Woodpeckers (Melanerpes carolinus)

Abstract Previous studies of northward expansion of breeding ranges of North American bird species have focused on correlated changes in climate and land-use, but very few studies have examined patterns of morphological change within the context of range expansion. We used data from museum specimens to examine geographic and temporal variation in body size of the Red-bellied Woodpecker (Melanerpes carolinus), a species undergoing dramatic range expansion. We plotted georeferenced occurrence data from Christmas Bird Counts (winter distributions going back to the year 1900), USGS Breeding Bird Surveys (summer distributions since 1966), and the holdings of twenty-six natural history museums (year-round distributions since 1867) to document the historic range of M. carolinus in decade increments. Christmas Bird Counts, but not museum specimens, indicate a trend of slow northward expansion beginning as early as the 1910s, and all data sets show rapid expansion to the north and west since the 1950s (average of ...

Assessing the status and conservation priorities of the short‐eared owl in North America

AbstractThe North American Breeding Bird Survey, Christmas Bird Count, and regional and national conservation assessments provide convincing evidence that the short‐eared owl (Asio flammeus) is experiencing a range‐wide, long‐term decline in abundance in North America. However, the species has received little conservation or research attention. The short‐eared owl is vulnerable to decline because it relies heavily on large, intact grasslands and a specialized diet of unpredictable small mammal prey. The species' nomadic movements compound these vulnerabilities by making a decline difficult to detect with current monitoring programs while obfuscating stewardship responsibilities for managers. The primary threat to the species is loss, fragmentation, and degradation of large tracts of native grasslands and wetlands. We propose the following conservation priorities to better understand and begin addressing the short‐eared owl's decline: 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re‐evaluate NatureServe's short‐eared owl national conservation classifications; 5) develop management plans and tools; and 6) classify raptors, including short‐eared owls, as migratory birds in Canada. We contend that the short‐eared owl's need for habitat conservation at large spatial scales, status as a predator, and high reproductive potential that affords the species capacity to recover, make it an effective and useful candidate as an umbrella species for grassland conservation. © 2014 The Wildlife Society.

72nd Annual Saskatchewan Christmas Bird Count - 2013

72nd Annual Saskatchewan Christmas Bird Count - 2013

Exotic birds show lags in population growth

AbstractAimA key aspect of the ecology and management of biological invasions is the prevalence and duration of lag phases in population growth. Here, we explore the occurrence of lag phases in exotic bird populations using theAudubonChristmasBirdCount database.LocationHawaiianIsland archipelago.MethodsWe expand on the use of piecewise model fitting techniques to detect lags in exotic bird populations onHawaii. We searched for explanations as to the occurrence of these lags using five possible mechanisms (body size, niche breadth, propagule pressure, length of record and lag phase growth rate).ResultsWe found evidence of lag phases for 14 of 17 species we evaluated (range: 10–38 years, mean using observed data = 16 ± 12), and we discovered very rapid growth to maximum abundance following the end of the lag phase (mean using observed data = 8 ± 6 years). We found no evidence for any association between the possible mechanisms influencing the occurrence and duration of the lag phases.Main conclusionsOur results are the first to rigorously quantify lags in exotic animal populations; most existing evidence comes from plants. We show that lags are as common in birds as in plants, although we provide preliminary evidence that the duration of lags in birds is shorter than in plants. We highlight the need for continued efforts to elucidate lag phase occurrence and duration in biological invasions, and we demonstrate the expanded utility of piecewise model fitting approaches to quantify these lags using count data.

Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends

Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975–2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs) were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus) and Golden Eagles (Aquila chrysaetos) showed the fastest rate of change, with 8.41 km yr−1 and 7.74 km yr−1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally change as species experience changes in distribution in response to climate change.

Capsule Commentary on Ranard et al., Crowdsourcing—Harnessing the Masses to Advance Health and Medicine, a Systematic Review

While crowdsourcing is a research method that is over two centuries old, it has not been traditionally used in medical research. Crowdsourcing turns to the public for help. Current examples include the Audubon Society’s Christmas Bird Count, the Galaxy Zoo project,1 in which the public helps classify galaxies, and a whale call classification project.2 Crowdsourcing uses the power of many, employing the collective wisdom and resources of the crowd to solve problems. Ranard et al.’s systematic review on crowdsourcing found surprisingly few studies.3 Among the 21 they identified, there were four distinct categories of research: problem solving, data processing, surveillance/monitoring, and surveying. Examples of projects using crowdsourcing include predicting protein folding structures (problem solving), classifying polyps on computed tomography (CT) colonography images (data processing) and tracking influenza outbreaks (surveillance) in near real time. The authors found five benefits of crowdsourcing, including quality, cost, volume, speed, and developing novel science. For example, many eyes reviewing colonography results found more polyps, thus improving quality. Costs are minimal, just those to set up the web portal. Crowdsourcing has the potential to reach hundreds of thousands of participants, generating a large volume response. Problems that might take one person months to decipher can be solved quickly. For example, protein folding problems were sometimes solved in minutes once released to the crowd. Additionally, the unique perspectives of the diverse participants may suggest novel new approaches to the task. Some important problems with using crowdsourcing for medical research include lack of information about the crowd (demographics) and a need for consistent reporting of the experimental setup. There are limitations on the type of research that could be conducted; research that requires informed consent would be impractical, for example. There are also significant ethical issues; what is it reasonable to expose the crowd to? Predicting potential harm for participants may be difficult when little is known about who they are. With the advent of the internet, crowdsourcing has more potential than ever before; it presents an easy and efficient way to engage the public in research and health surveillance. Like any research methodology, crowdsourcing needs to start with the right question for the approach; however, it could be another viable tool for researchers to use when designing projects.

The role of citizen science in monitoring biodiversity in Ireland

Citizen science is proving to be an effective tool in tracking the rapid pace at which our environment is changing over large geographic areas. It is becoming increasingly popular, in places such as North America and some European countries, to engage members of the general public and school pupils in the collection of scientific data to support long-term environmental monitoring. Participants in such schemes are generally volunteers and are referred to as citizen scientists. The Christmas bird count in the US is one of the worlds longest running citizen science projects whereby volunteers have been collecting data on birds on a specific day since 1900. Similar volunteer networks in Ireland have been in existence since the 1960s and were established to monitor the number and diversity of birds throughout the country. More recently, initiatives such as Greenwave (2006) and Nature Watch (2009) invite school children and members of the general public respectively, to record phenology data from a range of common species of plant, insect and bird. In addition, the Irish butterfly and bumblebee monitoring schemes engage volunteers to record data on sightings of these species. The primary purpose of all of these networks is to collect data by which to monitor changes in wildlife development and diversity, and in the case of Greenwave to involve children in hands-on, inquiry-based science. Together these various networks help raise awareness of key environmental issues, such as climate change and loss of biodiversity, while at the same time promote development of scientific skills among the general population. In addition, they provide valuable scientific data by which to track environmental change. Here we examine the role of citizen science in monitoring biodiversity in Ireland and conclude that some of the data collected in these networks can be used to fulfil Ireland's statutory obligations for nature conservation. In addition, a bee thought previously to be extinct has been rediscovered and a range expansion of a different bee has been confirmed. However, it also became apparent that some of the networks play more of an educational than a scientific role. Furthermore, we draw on experience from a range of citizen science projects to make recommendations on how best to establish new citizen science projects in Ireland and strengthen existing ones.

Citizen Science Reveals an Extensive Shift in the Winter Distribution of Migratory Western Grebes

Marine waterbirds have shown variable trends in abundance over the past four decades with some species displaying steep declines along the Pacific coast from British Columbia through California. One of the most dramatic changes has been that of western grebes (Aechmophorus occidentalis) in the Salish Sea. This region was a former core of the species wintering distribution but they have become increasingly rare prompting calls for conservation action. A more thorough understanding of this situation requires the analysis of trends at broader geographic scales as well as a consideration of mechanisms that might have led to a change in abundance. We used hierarchical modeling with a Bayesian framework applied to 36 years of Audubon Christmas Bird Count data to assess continent-wide and regional population trends in western and Clark’s grebes (A. clarkii) from 1975 to 2010. Our results show that the North American wintering population of Aechmophorus grebes decreased by ∼52% after 1975, but also that western grebes displayed strongly opposing regional patterns. Abundance decreased by about 95% over 36 years in the Salish Sea but increased by over 300% along coastal California. As a result, the mean centre of the species distribution shifted south by an estimated 895 km between 1980 and 2010. Mechanisms underlying this shift require further study but we hypothesize that it may be related to a change in the abundance and availability of their forage fish prey base. Since the mid-1980s, the Pacific sardine stock off the California coast increased from a few thousand metric tonnes to over two million. At the same time both the abundance and availability of Pacific herring declined in the Salish Sea. Studies are needed to examine this hypothesis further and additional consideration should be directed at other changes in the marine environment that may have contributed to a range shift.

Where Are the Bluebirds of the Bluegrass? Eastern Bluebird Decline in Central Kentucky

Eastern bluebird (Sialia sialis) populations are increasing across most of the species' range; however, we document a decline in a bluebird population in central Kentucky, where state and local Christmas Bird Count and Breeding Bird Survey data indicate bluebirds are declining throughout the Ohio River valley region. We examined several possible hypotheses for this decline, including habitat loss, nest cavity loss, increased competition from other species, and variation in winter temperature using long term nesting data gathered at one study site in central Kentucky. We found that bluebird abundance was positively correlated with mean temperature during the previous winter. Our data suggest bluebirds in central Kentucky are declining because they are susceptible to cold winters and are experiencing increased nest box competition.

71st Annual Saskatchewan Christmas Bird Count - 2012

71st Annual Saskatchewan Christmas Bird Count - 2012

Recent Trends in Western Screech-Owl and Barred Owl Abundances on Bainbridge Island, Washington

In an ongoing 15-y study concerning population dynamics of Barred Owls (Strix varia) on Bainbridge Island, Kitsap County, Washington, I documented a steep decline in the Western Screech-Owl (Megascops kennicottii) population and a steady increase in the Barred Owl population. From 1995 through 2010, I conducted 358 auditory playback surveys that showed both changes in abundance and spatial distribution of both species on the island. Statewide Christmas Bird Count data from the same time period also reflect an overall decline in the Western Screech-Owl population and an increase in the Barred Owl population. Further, at least 2 other studies have shown Western Screech-Owl to be prey for Barred Owl, also contributing to the body of evidence that leads to a possible correlation between the increasing number of Barred Owls and the decline of Western Screech-Owls.

Mapping Functional Traits: Comparing Abundance and Presence-Absence Estimates at Large Spatial Scales

Efforts to quantify the composition of biological communities increasingly focus on functional traits. The composition of communities in terms of traits can be summarized in several ways. Ecologists are beginning to map the geographic distribution of trait-based metrics from various sources of data, but the maps have not been tested against independent data. Using data for birds of the Western Hemisphere, we test for the first time the most commonly used method for mapping community trait composition – overlaying range maps, which assumes that the local abundance of a given species is unrelated to the traits in question – and three new methods that as well as the range maps include varying degrees of information about interspecific and geographic variation in abundance. For each method, and for four traits (body mass, generation length, migratory behaviour, diet) we calculated community-weighted mean of trait values, functional richness and functional divergence. The maps based on species ranges and limited abundance data were compared with independent data on community species composition from the American Christmas Bird Count (CBC) scheme coupled with data on traits. The correspondence with observed community composition at the CBC sites was mostly positive (62/73 correlations) but varied widely depending on the metric of community composition and method used (R2: 5.6×10−7 to 0.82, with a median of 0.12). Importantly, the commonly-used range-overlap method resulted in the best fit (21/22 correlations positive; R2: 0.004 to 0.8, with a median of 0.33). Given the paucity of data on the local abundance of species, overlaying range maps appears to be the best available method for estimating patterns of community composition, but the poor fit for some metrics suggests that local abundance data are urgently needed to allow more accurate estimates of the composition of communities.

Shorter migration distances associated with higher winter temperatures suggest a mechanism for advancing nesting phenology of American kestrels Falco sparverius

Global climate change has affected avian migration patterns and nesting phenology. Changes in one phase of a bird's cycle will most likely affect other stages, but few studies focus simultaneously on multiple life‐history events. We used western North American ringing records and Christmas Bird Counts to examine whether changes in migration patterns were concordant with advancing American kestrel Falco sparverius nesting phenology. Consistent with previous findings, male kestrels migrated shorter distances than female kestrels, and kestrels nesting in southern latitudes migrated shorter distances than kestrels nesting in more northern areas. In addition, kestrel migration distance decreased significantly from 1960 to 2009 and was negatively associated with winter minimum temperatures. Christmas Birds Counts from the same time period showed increasing indices of overwintering kestrel abundance in northern states (Washington, Idaho, and Utah), where winter minimum temperatures have increased significantly, and concomitant decreases in southern states (California and Arizona). Finally, changes in nesting phenology of kestrels in southwestern Idaho were best explained by warmer winters, not springs. Warmer winters may decrease energetic demands on migrants by allowing for shorter migration distances, decreasing thermoregulatory costs, or both. Decreased energy demands during winter may allow birds to gain resources necessary for reproduction earlier in the nesting season. Higher winter temperatures that decrease (former) constraints on early nesting may be a particularly important mechanism leading to advancing nesting phenology for species with strong seasonal declines in fecundity or intense early season competition for high‐quality nesting areas.