Trends in tricolored blackbird colony size: 2008 through 2017

Meehan, Timothy D.; Arthur, Samantha; Michel, Nicole L.; Wilsey, Chad B.; Langham, Gary

doi:10.1002/jwmg.21664

Cited by 6 publications

(3 citation statements)

References 24 publications

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“…For example, areas with greater seasonal abundances of Eastern and Western bluebirds estimated from long‐term eBird observations (2004–2016; Fink et al 2018) mirror the strata with higher than average occupancy estimates from our short‐term analysis incorporating climate suitability. In addition to climate, habitat availability, land‐use pressures, ecoregional differences, and human population density (Opdam and Wascher 2004, Tingley et al 2012, Meehan et al 2019) play a role in determining species’ distributions and likely explain some of the among‐strata variation in occupancy.…”

Section: Discussionmentioning

confidence: 99%

“…We also controlled for large‐scale spatial variability in occupancy (i.e., due to land‐use and ecoregional differences) across species’ breeding and non‐breeding ranges using a strata‐level random effect:

logit false(ψ_{i, 1} false) = {normalα}_{ψ_{1}} + {normalβ}_{CS . {normalψ}_{1}} (CS . 2020_{i}) + {normalβ}_{Strata [i]},

where

β_{Strata (][, i)}

is the strata‐level random intercept effect centered around zero with a variance (τ) that is estimated along with the other parameters. Random effects have been included in other analyses based on widespread data collected by volunteers (Sauer and Link 2011, Saunders et al 2018, Meehan et al 2019). We opted to account for additional spatial variability (i.e., not captured by the fixed effect of CS.2020) in initial occupancy by attributing each site i to an analytical strata (which are the intersections of U.S. states and Bird Conservation Regions) because they are ecologically distinct regions with comparable bird communities, habitats, and resource management issues (Sauer et al 2003).…”

Section: Methodsmentioning

confidence: 99%

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Community science validates climate suitability projections from ecological niche modeling

Saunders

Michel

Bateman

et al. 2020

Ecological Applications

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Climate change poses an intensifying threat to many bird species and projections of future climate suitability provide insight into how species may shift their distributions in response. Climate suitability is characterized using ecological niche models (ENMs), which correlate species occurrence data with current environmental covariates and project future distributions using the modeled relationships together with climate predictions. Despite their widespread adoption, ENMs rely on several assumptions that are rarely validated in situ and can be highly sensitive to modeling decisions, precluding their reliability in conservation decision‐making. Using data from a novel, large‐scale community science program, we developed dynamic occupancy models to validate near‐term climate suitability projections for bluebirds and nuthatches in summer and winter. We estimated occupancy, colonization, and extinction dynamics across species’ ranges in the United States in relation to projected climate suitability in the 2020s, and used a Gibbs variable selection approach to quantify evidence of species–climate relationships. We also included a Bird Conservation Region strata‐level random effect to examine among‐strata variation in occupancy that may be attributable to land‐use and ecoregional differences. Across species and seasons, we found strong evidence that initial occupancy and colonization were positively related to 2020 climate suitability, illustrating an independent validation of projections from ENMs across a large geographic area. Random strata effects revealed that occupancy probabilities were generally higher than average in core areas and lower than average in peripheral areas of species’ ranges, and served as a first step in identifying spatial patterns of occupancy from these community science data. Our findings lend much‐needed support to the use of ENM projections for addressing questions about potential climate‐induced changes in species’ occupancy dynamics. More broadly, our work highlights the value of community scientist observations for ground‐truthing projections from statistical models and for refining our understanding of the processes shaping species’ distributions under a changing climate.

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Section: Discussionmentioning

confidence: 99%

logit false(ψ_{i, 1} false) = {normalα}_{ψ_{1}} + {normalβ}_{CS . {normalψ}_{1}} (CS . 2020_{i}) + {normalβ}_{Strata [i]},

where

β_{Strata (][, i)}

Section: Methodsmentioning

confidence: 99%

Community science validates climate suitability projections from ecological niche modeling

Saunders

Michel

Bateman

et al. 2020

Ecological Applications

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“…The range of the tricolored blackbird Agelaius tricolor (Figure 1) is limited, with more than 99% of the population occurring in California, and it is listed as Threatened under California's Endangered Species Act (Beedy et al 2020). Recent statewide surveys and analyses of eBird records, an electronic repository of crowd-sourced bird observations, showed an alarming decline of approximately 40% from 2008 to 2016 (Meese 2014;Robinson et al 2018;Meehan et al 2019). The species has low fecundity, averaging fewer than two fledglings per nesting attempt (Meese 2013;Holyoak et al 2014;, making recovery challenging.…”

Section: Introductionmentioning

confidence: 99%

Bioacoustic Monitoring Reveals Details of Tricolored Blackbird Breeding Phenology

Schackwitz

Airola

Greene

et al. 2020

Journal of Fish and Wildlife Management

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Bioacoustic monitoring has been used to study behaviors of organisms from insects to whales. Studies using multiple vocalizations of a single species have the potential to determine detailed phenology, but to date are rare. We tested whether bioacoustic monitoring of multiple gender- and age-specific vocalizations of the imperiled tricolored blackbird Agelaius tricolor could provide detailed information on reproductive phenology and breeding success. Using inexpensive cell phones and free software applications, we collected audio recordings of tricolored blackbird colonies during their breeding season. Adding solar panels enabled the stations to run autonomously, and use of cellular data enabled remote uploading of recordings. Analysis of the presence or absence of three vocalizations (male song, female song, and nestling call) provided a rich and detailed description of the breeding phenology, including the dates for courtship, onset of nest building, incubation, nestling hatching, and fledgling departure from nesting colonies. The resulting detail was more granular and accurate than comparable data from field monitoring, although field monitoring provides data such as abundance counts that bioacoustic monitoring does not. This information has a wide range of applications to research and conservation, from enabling more accurate abundance estimates, to assessing colony success or failure with fewer visits, to providing stronger guidance for when a colony must be protected from disruption.

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Dramatic recent declines in the size of monarch butterfly ( Danaus plexippus ) roosts during fall migration

Davis,

Croy,

Snyder

2024

Proc. Natl. Acad. Sci. U.S.A.

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The conservation status of monarch butterflies in North America is a topic of intense scrutiny and debate. It is clear that winter colonies in Mexico are declining, yet some recent studies suggest that summer breeding populations are relatively stable and similar to historical abundances. One possible explanation for these discordant patterns is that fall migration success has been recently disrupted. Here, we use a relatively unexplored citizen-scientist dataset on the size of monarch “roosts,” which are resting aggregations on vegetation, to infer changes in monarch abundance along the fall migration route over the last 17 y. We found that the timing of migration remained relatively unchanged while the flyway has generally become warmer and greener. Warmer and greener conditions were associated with larger roosts, yet we found steady, dramatic declines in roost sizes through time that were independent of climate and landscape factors. Roost sizes have declined as much as 80%, with losses increasing from north to south along the migration route. These findings suggest that failure during the fall migration could explain the apparent drop in monarch numbers from summer breeding to overwintering populations. This in turn suggests that conservation efforts that support fall migration success are most needed, such as providing high quality nectar plants along the migration route or limiting the planting of nonnative milkweeds that enhance monarch parasite loads. Overall, it appears the fall migration of monarch butterflies is under imminent threat, even if the species’ overall survival is not.

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Trends in tricolored blackbird colony size: 2008 through 2017

Cited by 6 publications

References 24 publications

Community science validates climate suitability projections from ecological niche modeling

Community science validates climate suitability projections from ecological niche modeling

Bioacoustic Monitoring Reveals Details of Tricolored Blackbird Breeding Phenology

Dramatic recent declines in the size of monarch butterfly ( Danaus plexippus ) roosts during fall migration

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