Tricolored Blackbird (Agelaius tricolor)

Meese, Robert J.; Beedy, Edward C.; Hamilton, W. J.

doi:10.2173/bna.423

Cited by 10 publications

(28 citation statements)

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“…Likewise we do not know the extent of any decline during recent decades. Previous studies have tabulated population sizes but have not statistically analyzed population data (DeHaven et al 1975; Beedy et al 1991; Beedy and Hamilton 1997; Hamilton et al 1999). …”

Section: Introductionmentioning

confidence: 99%

“…The most extensive reports of tricolored blackbird population status indicate range-wide breeding abundance declines of ∼89% between the 1930s and 1980s (Beedy et al 1991). The species is the most colonial passerine in North America since the extinction of passenger pigeons (Bent 1958).…”

Section: Introductionmentioning

confidence: 99%

“…Since the 1930s, over 90% of the individuals nested in wetlands of California's Central Valley (Neff 1937; Orians 1961; DeHaven et al 1975). This area experienced wetland losses of greater than 90% between 1850 and 1980 (Frayer et al 1989), and ∼99% loss of grassland habitats that are used for foraging by tricolored blackbirds (Beedy and Hamilton 1997). For tricolored blackbirds, Beedy et al (1991) reported wetland loss and fragmentation as the principal reasons for decline.…”

Section: Introductionmentioning

confidence: 99%

“…This area experienced wetland losses of greater than 90% between 1850 and 1980 (Frayer et al 1989), and ∼99% loss of grassland habitats that are used for foraging by tricolored blackbirds (Beedy and Hamilton 1997). For tricolored blackbirds, Beedy et al (1991) reported wetland loss and fragmentation as the principal reasons for decline. Yet, the species has also changed from predominantly breeding in freshwater cattail ( Typha spp.)…”

Section: Introductionmentioning

confidence: 99%

“…and bulrush ( Scirpus spp.) marshes (Neff 1937) to increasingly include upland non-native and agricultural habitats as breeding sites (Beedy and Hamilton 1997). Such changes could complicate our interpretation and detection of population declines.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the contribution of habitats and regional variation to long‐term population trends in tricolored blackbirds

Graves¹,

Holyoak²,

Kelsey

et al. 2013

Ecology and Evolution

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Population trends represent a minimum amount of information required to assess the conservation status of a species. However, understanding and detecting trends can be complicated by variation among habitats and regions, and by dispersal connecting habitats through source-sink dynamics. We analyzed trends in breeding populations between habitats and regions to better understand the overall dynamics of a species' decline. Specifically, we analyzed historical trends in breeding populations of tricolored blackbirds (Agelaius tricolor) using breeding records from 1907 to 2009. The species breeds itinerantly and ephemerally uses multiple habitat types and breeding areas, which make interpretation of trends complex. We found overall abundance declines of 63% between 1935 and 1975. Since 1980 overall declines became nonsignificant and obscure despite large amounts of data from 1980 to 2009. Temporal trends differed between breeding habitat types and were associated with regional differences in population declines. A new habitat, triticale crops (a wheat-rye hybrid grain) produced colonies 40× larger, on average, than other breeding habitats, and contributed to a change in regional distribution since it primarily occurred in a single region. The mechanism for such an effect is not clear, but could represent the local availability of foodstuffs in the landscape rather than something specific to triticale crops. While variation in trends among habitats clearly occurred, they could not easily be ascribed to source-sink dynamics, ecological traps, habitat selection or other detailed ecological mechanisms. Nonetheless, such exchanges provide valuable information to guide management of dynamic systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Understanding the contribution of habitats and regional variation to long‐term population trends in tricolored blackbirds

Graves¹,

Holyoak²,

Kelsey

et al. 2013

Ecology and Evolution

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Using citizen science data in integrated population models to inform conservation

Robinson

Ruiz‐Gutiérrez

Fink

et al. 2018

Biological Conservation

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Low genetic diversity in a population of Tricolored Blackbird (Agelaius tricolor), a species pending Endangered status

Liu

Meese²

2020

Preprint

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The Tricolored Blackbird (Agelaius tricolor) is a colonial songbird, found almost exclusively in California, whose total population size has sharply declined over the past century. It is currently under review to be listed as Endangered under both the California and U.S. Endangered Species Acts. Here we assess the genetic diversity of a breeding population in California's Central Valley, comparing our findings with previously sampled conspecific and congeneric populations. First, we genotyped 50 adults at 9 microsatellite loci in our focal population and estimated allelic and Shannon diversity, observed and expected heterozygosity, and the inbreeding coefficient (FIS). Second, we compared our results to those of the one existing study on Tricolored Blackbird conservation genetics and found that levels of allelic diversity and heterozygosity in our focal population were similar to those of 11 previously studied populations. Unlike the earlier study, which found moderately high mean inbreeding coefficients, we detected no evidence of inbreeding in our focal population. Third, we used 7 of the 9 loci to compare the genetic diversity of our focal population with populations of 2 previously sampled Agelaius congeners. We found that allelic diversity, Shannon diversity, and expected heterozygosity in our Tricolored Blackbird population were most similar to those of an isolated Red-winged Blackbird (A. phoeniceus) population in the Bahamas. We discuss possible reasons for the different results from the conspecific study, outline why the collective findings from both studies support the need for protective measures, and urge conservation action to maintain existing genetic diversity and gene flow before ongoing population losses lead to adverse fitness consequences.

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Tricolored Blackbird (Agelaius tricolor)

Cited by 10 publications

References 0 publications

Understanding the contribution of habitats and regional variation to long‐term population trends in tricolored blackbirds

Understanding the contribution of habitats and regional variation to long‐term population trends in tricolored blackbirds

Using citizen science data in integrated population models to inform conservation

Low genetic diversity in a population of Tricolored Blackbird (Agelaius tricolor), a species pending Endangered status

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