Estimating the Size of a Transient Population

Routledge, Richard; Smith, G. E. J.; Sun, Li; Dawe, Neil K.; Nygren, Emma; Sedinger, James S.

doi:10.1111/j.0006-341x.1999.00224.x

Cited by 7 publications

(7 citation statements)

References 12 publications

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“…Group 1 contained band data for birds observed only once within a year (hereafter single-sight data), and group 2 contained data for birds observed multiple times (hereafter multi-sight data). Notwithstanding that we may have missed some single-sight birds during searches, these groups represented 2 qualitatively distinct staging patterns consistent with previous observations of brant staging in the Strait of Georgia (Routledge et al 1999). Single-sight brant did not seem to use staging sites to accumulate body reserves but moved quickly through the area.…”

Section: Multi-strata Model Of Brant Residencysupporting

confidence: 86%

“…We speculate that a higher proportion of multi-sight birds were actually observed only once on the FRD compared with PQ because of fewer vantage points for viewing bands. Routledge et al (1999) estimated the volume of springstaging brant using the PQ study site in 1990. Similar to our study, the volume estimate was based on daily counts and records of marked birds.…”

Section: Discussionmentioning

confidence: 99%

“…Week 7 is approximately 17 February; week 20, approximately 18 May. approach, Routledge et al (1999) estimated the population size by exploiting the ratio of the estimated total number of days that birds stayed in the site to estimated mean LOS. Using a mean LOS of about 6 days, Routledge et al (1999) estimated the volume of brant to be 12,100 (95% CL, 8,600-16,000), or roughly one-half to one-third of our volume estimates for 1999 and 2000.…”

Section: Discussionmentioning

confidence: 99%

“…As such, the true effective sample size is smaller than the actual number of marked birds and results in an underestimation of true variance (Schmutz et al 1995) unless, as we have done, a correction for overdispersion is applied. Finally, our method requires a less onerous field effort than the Routledge et al (1999) method because observers do not need to record the number of birds checked for bands.…”

Section: Discussionmentioning

confidence: 99%

“…Previous volume estimates for Arctic geese have been generated through statistical (e.g., Routledge et al 1999) and modeling approaches (e.g., Frederiksen et al 2001). The statistical approach uses estimates of mean residency (or length of stay [LOS]) and counts.…”

mentioning

confidence: 99%

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Estimating Numbers of Black Brant Using Sequential Spring‐Staging Sites

2008

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Estimating total number of birds using a particular staging site during migration is challenging because counts alone do not account for turnover in the local population. Robust statistical methods are needed to more fully assess the conservation value of such sites. We used the multi‐strata model in Program MARK to estimate time‐dependent transition probabilities between sequential staging sites to estimate lengths of stay for spring‐staging Pacific black brant (Branta bernicla nigricans) on the Fraser River delta and Parksville‐Qualicum areas in the Strait of Georgia, British Columbia, Canada. Using resightings of marked individuals in combination with ground counts, we estimated the total number of brant, with associated uncertainties, staging at these sites during the spring migrations of 1999 and 2000. We estimated between 28,927 and 33,181 individual brant transited the Fraser River delta and Parksville‐Qualicum sites in 1999 and between 21,621 and 25,405 individuals in 2000. These totals correspond to approximately 18–26% of the entire Pacific Flyway brant population, suggesting the need for continued conservation and management efforts at these sites. Given the importance of staging sites to migratory populations, we believe this method could be applied to other species and locations.

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Section: Multi-strata Model Of Brant Residencysupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Estimating Numbers of Black Brant Using Sequential Spring‐Staging Sites

2008

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Stopover duration of fall‐migrating dabbling ducks

O’Neal

Stafford²,

Larkin

2012

J Wildl Manag

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The amount of time migrating birds spend at stopover sites, or stopover duration, partially determines an individual's access to resources, the environmental conditions encountered, and the exposure to predation, which in turn affect survival and fecundity. As such, migratory behaviors such as stopover duration can have a considerable effect on populations of migrants and plans for their conservation. This is especially true for migrant waterfowl, which are explicitly conserved through Joint Venture (JV) partnerships under the North American Waterfowl Management Plan. Although waterfowl are one of the most heavily studied taxa, little is known about their stopover behavior due to the scope of migration. Consequently, conservation plans of many mid-migration JVs either omit estimates of stopover duration or rely on antiquated data to estimate energetic requirements. We used weather surveillance radar to identify and enumerate ducks emigrating from an important stopover area in central Illinois. By using radar data in combination with data from weekly aerial inventories, we estimated an average stopover duration for fall-migrating dabbling ducks (tribe Anatini) of 28 days (SD ¼ 12) over 8 years (). Our estimate was similar to the historical estimate of 28 days , which serves as the primary reference for the Upper Mississippi River Great Lakes Region JV conservation plan. In addition to a corroborative mean, we also found considerable inter-annual variation in stopover duration. Estimated annual stopover duration was correlated positively with an index of annual foraging habitat quality (Spearman's rank correlation; r s ¼ 0.83), suggesting ducks may have assessed local conditions and adjusted the spatiotemporal course of fall migration. If the stopover behavior of fall-migrating ducks is flexible and forage-dependent, it is possible ducks allocate their time among sites in a somewhat ideal and optimal fashion, which could substantially affect the way resources are allocated within the spatial context of a JV region. ß 2012 The Wildlife Society.

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Trends in volume migration chronology in spring staging Pacific black brant

Smith

Hagmeier²,

Boyd

et al. 2011

J Wildl Manag

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We used a robust dataset of count and mark‐resighting data for Pacific black brant from 1989–2004, and a novel mark‐recapture model capable of analyzing such data, to calculate the annual variability and timing of brant as they migrated through the Parksville–Qualicum Beach area, a traditional spring staging site in coastal British Columbia, Canada. Our analysis indicated that the date of departure from this site to northern breeding sites advanced between 10 and 20 days over this period because of a combination of earlier arrival and shorter residence times. Given this change in migration behavior, and the potential implications for population dynamics, we recommend that targeted research on brant wintering, migration, and reproductive strategies should be examined within a greater Pacific‐wide context. In this way, the consequences of proximate factors (e.g., disturbance, food, and climate) can be understood in terms of individual fitness and population dynamics. Finally, at the local level, conservation actions are needed to ensure the long term sustainability of Parksville–Qualicum Beach as an important spring staging site for Pacific black brant. © 2011 The Wildlife Society.

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Estimating the Size of a Transient Population

Cited by 7 publications

References 12 publications

Estimating Numbers of Black Brant Using Sequential Spring‐Staging Sites

Estimating Numbers of Black Brant Using Sequential Spring‐Staging Sites

Stopover duration of fall‐migrating dabbling ducks

Trends in volume migration chronology in spring staging Pacific black brant

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