Declining Scaup Populations: A Retrospective Analysis of Long-Term Population and Harvest Survey Data

Afton, Alan D.; Anderson, M.

doi:10.2307/3803028

Cited by 107 publications

(154 citation statements)

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“…Diet data were included from 22 scaup collected in 2000-2001 at Thief Lake and Roseau River (Anteau and Afton 2006) for reference; those data were included into subsequent analyses as a separate region (Northwestern Minnesota 2000-2001). Samples were pooled over years and it was assumed that annual variation was less important than spatial variability Anteau and Afton 2006;Anteau and Afton 2008b).…”

Section: Statistical Analysesmentioning

confidence: 99%

“…The continental scaup population (Lesser [ Aythya affinis ] and Greater Scaup [ A. marila ] combined) has declined markedly since 1978 (Austin et al 1998;Afton and Anderson 2001); population estimates were lowest on record in 2006 (Wilkins et al 2007). Afton and Anderson (2001) concluded that the decline in the continental scaup population likely is driven by declines in the Lesser Scaup population and caused by reductions in recruitment.…”

mentioning

confidence: 99%

“…Afton and Anderson (2001) concluded that the decline in the continental scaup population likely is driven by declines in the Lesser Scaup population and caused by reductions in recruitment. The segment of the continental scaup population that winters in states bordering the Gulf of Mexico and migrates along the Mississippi River valley and through the upper-Midwest, comprises a major component of the continental population and this segment is experiencing the largest decline (Afton and Anderson 2001).…”

mentioning

confidence: 99%

“…The Spring Condition Hypothesis (SCH) states that reproductive success of scaup has declined because females currently are in lower body condition during spring migration than in the past (Afton and Anderson 2001). Female scaup currently have fewer lipid reserves than did those historically (Anteau and Afton 2004;Anteau and Afton 2008a) and catabolize those lipid reserves as they migrate throughout the upper-Midwest in spring (Anteau 2006).…”

mentioning

confidence: 99%

“…Specifically, we tested the prediction that forage quality has declined by comparing percentages of Gammarus lacustris (hereafter Gammarus ) and Hyalella azteca (hereafter Hyalella ) amphipods in diets (mean aggregate percent dry mass of taxa) of scaup collected during spring migration throughout the upper-Midwest in [2003][2004][2005] to those of scaup in Northwest Minnesota in -2001. We used data from NW00 for reference because these data are the only data set available that are quantitatively referenced to historical diets of scaup during spring migration in the upper-Midwest.…”

mentioning

confidence: 99%

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Diets of Lesser Scaup during Spring Migration throughout the Upper-Midwest are Consistent with the Spring Condition Hypothesis

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2008

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Section: Statistical Analysesmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Diets of Lesser Scaup during Spring Migration throughout the Upper-Midwest are Consistent with the Spring Condition Hypothesis

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Understanding the demographic drivers of realized population growth rates

Koons

Arnold

Schaub

2017

Ecological Applications

133

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Identifying the demographic parameters (e.g., reproduction, survival, dispersal) that most influence population dynamics can increase conservation effectiveness and enhance ecological understanding. Life table response experiments (LTRE) aim to decompose the effects of change in parameters on past demographic outcomes (e.g., population growth rates). But the vast majority of LTREs and other retrospective population analyses have focused on decomposing asymptotic population growth rates, which do not account for the dynamic interplay between population structure and vital rates that shape realized population growth rates (λt=Nt+1/Nt) in time-varying environments. We provide an empirical means to overcome these shortcomings by merging recently developed "transient life-table response experiments" with integrated population models (IPMs). IPMs allow for the estimation of latent population structure and other demographic parameters that are required for transient LTRE analysis, and Bayesian versions additionally allow for complete error propagation from the estimation of demographic parameters to derivations of realized population growth rates and perturbation analyses of growth rates. By integrating available monitoring data for Lesser Scaup over 60 yr, and conducting transient LTREs on IPM estimates, we found that the contribution of juvenile female survival to long-term variation in realized population growth rates was 1.6 and 3.7 times larger than that of adult female survival and fecundity, respectively. But a persistent long-term decline in fecundity explained 92% of the decline in abundance between 1983 and 2006. In contrast, an improvement in adult female survival drove the modest recovery in Lesser Scaup abundance since 2006, indicating that the most important demographic drivers of Lesser Scaup population dynamics are temporally dynamic. In addition to resolving uncertainty about Lesser Scaup population dynamics, the merger of IPMs with transient LTREs will strengthen our understanding of demography for many species as we aim to conserve biodiversity during an era of non-stationary global change.

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Lincoln estimates of mallard (Anas platyrhynchos) abundance in North America

Alisauskas

Arnold

Leafloor

et al. 2013

Ecology and Evolution

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Estimates of range-wide abundance, harvest, and harvest rate are fundamental for sound inferences about the role of exploitation in the dynamics of free-ranging wildlife populations, but reliability of existing survey methods for abundance estimation is rarely assessed using alternative approaches. North American mallard populations have been surveyed each spring since 1955 using internationally coordinated aerial surveys, but population size can also be estimated with Lincoln's method using banding and harvest data. We estimated late summer population size of adult and juvenile male and female mallards in western, midcontinent, and eastern North America using Lincoln's method of dividing (i) total estimated harvest, , by estimated harvest rate, , calculated as (ii) direct band recovery rate, , divided by the (iii) band reporting rate, . Our goal was to compare estimates based on Lincoln's method with traditional estimates based on aerial surveys. Lincoln estimates of adult males and females alive in the period June–September were 4.0 (range: 2.5–5.9), 1.8 (range: 0.6–3.0), and 1.8 (range: 1.3–2.7) times larger than respective aerial survey estimates for the western, midcontinent, and eastern mallard populations, and the two population estimates were only modestly correlated with each other (western: r = 0.70, 1993–2011; midcontinent: r = 0.54, 1961–2011; eastern: r = 0.50, 1993–2011). Higher Lincoln estimates are predictable given that the geographic scope of inference from Lincoln estimates is the entire population range, whereas sampling frames for aerial surveys are incomplete. Although each estimation method has a number of important potential biases, our review suggests that underestimation of total population size by aerial surveys is the most likely explanation. In addition to providing measures of total abundance, Lincoln's method provides estimates of fecundity and population sex ratio and could be used in integrated population models to provide greater insights about population dynamics and management of North American mallards and most other harvested species.

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Declining Scaup Populations: A Retrospective Analysis of Long-Term Population and Harvest Survey Data

Cited by 107 publications

References 7 publications

Diets of Lesser Scaup during Spring Migration throughout the Upper-Midwest are Consistent with the Spring Condition Hypothesis

Diets of Lesser Scaup during Spring Migration throughout the Upper-Midwest are Consistent with the Spring Condition Hypothesis

Understanding the demographic drivers of realized population growth rates

Lincoln estimates of mallard (Anas platyrhynchos) abundance in North America

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