Banding age ratios reveal prairie waterfowl fecundity is affected by climate, density dependence and predator–prey dynamics

Specht, Hannah; Arnold, Todd W.

doi:10.1111/1365-2664.13186

Cited by 26 publications

(56 citation statements)

References 49 publications

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“…Annual survival in scaup increased with small‐mammal abundance. This result is consistent with an alternate prey hypothesis where predation on alternate prey such as ducks and their eggs and young declines as populations increase for primary prey species like small mammals (Brook et al , Specht and Arnold ). Contrary to our predictions, however, we did not find a relationship between apparent survival and small‐mammal index in scoters.…”

Section: Discussionsupporting

confidence: 88%

Annual survival in female white‐winged scoters and lesser scaup

Slattery

Clark

2019

J Wildl Manag

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Quantifying survival and understanding underlying sources of variation are important for developing population models and informing management decisions. We estimated apparent survival (i.e., true survival less permanent emigration) for adult female white‐winged scoters (Melanitta fusca) and lesser scaup (Aythya affinis) breeding at a northern boreal forest site in western Canada, 2002–2008. We also evaluated variation in survival relative to indices of breeding status, individual quality, spring weather conditions, local small‐mammal abundance, and overwinter climate. Breeding female scoters had higher apparent survival than did nonbreeding females, suggesting that breeders had higher survival or fidelity to the study area, or that more nonbreeders were transient birds that may have bred elsewhere in subsequent years. Apparent survival rate for breeding female scoters was unrelated to other individual and environmental covariates. Nest‐trapped female scaup had higher apparent survival rates than did prenesting females captured in decoy traps, implying that more pre‐nesters dispersed permanently or died after marking. Nesting female scaup with higher body condition or those in years when small mammals were more abundant had higher apparent survival; associations between survival and other environmental covariates were less certain. Overall, apparent survival rate of breeding adult female scoters was lower than reported for scoters from other North American locations or for other sea duck species, whereas estimates for nesting female scaup were comparable with those from other boreal and prairie‐parkland locations. Our results indicate that for scaup in this region, factors influencing female body condition, such as maintaining high‐quality habitat, areas with abundant food or low disturbance, could improve annual survival. © The Wildlife Society, 2019

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Section: Discussionsupporting

confidence: 88%

Annual survival in female white‐winged scoters and lesser scaup

Slattery

Clark

2019

J Wildl Manag

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“…These fecundity estimates complemented estimates of juvenile and adult survival that analysts have typically obtained from tag‐recovery data (Brownie et al., ; Siriwardena et al., ) and allowed me to construct models that included all of the demographic components of population growth. For pintails, data were sufficient to estimate annual variation in all three vital rates and these estimates suggested that observed population declines during 1970–1993 were driven primarily by reductions in annual fecundity, which is consistent with other recent studies of historical pintail data (Bartzen & Dufour, ; Specht & Arnold, ). For juncos, my estimate of adult survival (0.493, SD : 0.034) was slightly larger than estimates of apparent survival from constant‐effort ringing stations (0.453, SD : 0.030; DeSante et al., ), whereas my estimate of recruitment ( F × S juv = 1.889 × 0.276 = 0.521) was slightly lower than estimates derived from reverse‐time analyses (0.554, SD : 0.032; DeSante et al., ).…”

Section: Discussionsupporting

confidence: 86%

“…Wildlife managers have long used age ratios of harvested individuals ( H j,t / H a,t ) to measure annual fecundity, but because juveniles are often more vulnerable to harvest than adults, tag‐recovery data are needed to adjust these data for relative vulnerability to harvest:

{\overset{F}{true}}_{normalt} = \frac{H_{j, t} / H_{a, t}}{{\overset{f}{true}}_{j, t} / {\overset{f}{true}}_{a, t}}

where

{\overset{f}{true}}_{j, t} / {\overset{f}{true}}_{a, t}

is the ratio of juvenile to adult harvest rates (Zimmerman et al., ). Age ratios at capture can provide similar estimates of population‐level fecundity (Specht & Arnold, ), but if capture probabilities differ between age classes, fecundity estimates will be biased. However, live recaptures during the initial banding period could be used to assess age‐specific vulnerability to capture and estimate the true underlying age distribution, similarly to vulnerability‐adjusted age ratios at harvest (Alisauskas, Arnold, Leafloor, Otis, & Sedinger, ; Zimmerman et al., ).…”

Section: Introductionmentioning

confidence: 99%

“…Even if estimation of capture vulnerability is not possible, age ratios at capture might nevertheless provide a reliable index of annual fecundity. Although uncorrected age ratios at capture have been used to assess population‐level fecundity (Mazerolle, Dufour, Hobson, & den Haan, ; Ross, Alisauskas, Douglas, & Kellett, ; Specht & Arnold, ), models to estimate fecundity from initial capture data have not been formally developed for tag‐recovery studies, although Link and Barker () have addressed this issue for open‐population mark–recapture data.…”

Section: Introductionmentioning

confidence: 99%

“…I apply these models to two species of North American birds. Northern pintails ( Anas acuta ; Figure ) have experienced a prolonged population decline and previous studies have shown it cannot be explained by declining survival (Bartzen & Dufour, ), suggesting that lowered fecundity may be the cause (Specht & Arnold, ), but to date there have been no integrated analyses for pintails to identify relative contributions of different vital rates to observed population changes (Koons, Arnold, & Schaub, ). Dark‐eyed juncos ( Junco hyemalis ) are a widespread passerine that has been well‐studied at several localized and primarily southern breeding sites (Nolan.…”

Section: Introductionmentioning

confidence: 99%

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Using ring‐recovery and within‐season recapture data to estimate fecundity and population growth

Arnold

2018

Ecology and Evolution

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Tag‐recovery data from organisms captured and marked post breeding are commonly used to estimate juvenile and adult survival. If annual fecundity could also be estimated, tagging studies such as European and North American bird‐ringing schemes could provide all parameters needed to estimate population growth. I modified existing tag‐recovery models to allow estimation of annual fecundity using age composition and recapture probabilities obtained during routine banding operations of northern pintails (Anas acuta) and dark‐eyed juncos (Junco hyemalis), and I conducted simulations to assess estimator performance in relation to sample size. For pintails, population growth rate from band‐recovery data (λ = 0.93, SD: 0.06) was similar but less precise than count‐based estimates from the Waterfowl Breeding Pair and Habitat Survey (λ: 0.945, SE: 0.001). Models with temporal variation in vital rates indicated that annual population growth in pintails was driven primarily by variation in fecundity. Juncos had lower survival but greater fecundity, and their estimated population growth rate (λ: 1.01, SD: 0.19) was consistent with count‐based surveys (λ: 0.986). Simulations indicated that reliable (CV < 0.10) estimates of fecundity could be obtained with >1,000 within‐season live encounters. Although precision of survival estimates depended primarily on numbers of adult recoveries, estimates of fecundity and population growth were most sensitive to total number of live encounters. Synthesis and applications: Large‐scale ring‐recovery programs could be used to estimate annual fecundity in many species of birds, but the approach requires better data curation, including accurate assessment of age, better reporting of banding totals, and greater emphasis on obtaining and reporting within‐season live encounters.

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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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Banding age ratios reveal prairie waterfowl fecundity is affected by climate, density dependence and predator–prey dynamics

Cited by 26 publications

References 49 publications

Annual survival in female white‐winged scoters and lesser scaup

Annual survival in female white‐winged scoters and lesser scaup

Using ring‐recovery and within‐season recapture data to estimate fecundity and population growth

Community science validates climate suitability projections from ecological niche modeling

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