Estimating the Total Number of Birds Using a Staging Site

Frederiksen, Morten; Fox, Anthony D.; Madsen, Jesper; Colhoun, Kendrew

doi:10.2307/3802907

Cited by 43 publications

(44 citation statements)

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“…The model estimates densities averaged for the date of the single survey, and future work should model stopover time and estimate total numbers of birds using each site during the entire season (Frederiksen et al 2001;Cohen et al 2009). However, these density values are the first data ever presented that allow detailed comparisons among river deltas within the study area.…”

Section: Discussionmentioning

confidence: 99%

Residence Probability and Population Size of Red Knots During Spring Stopover in the Mid‐Atlantic Region of the United States

et al. 2009

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Weekly counts of western Atlantic red knots (Calidris canutus rufa) at their Delaware Bay migration stopover site have suggested a major decline since the 1980s. We estimated red knot spring passage population size in the New Jersey Coast‐Delaware Bay region (DENJ; 2004 and 2006) and Virginia (VA; 2006 and 2007), USA, by correcting weekly aerial counts for mean daily residence probability between counts in a Monte‐Carlo simulation. We used daily telemetry relocations in mark‐resight models to estimate mean daily residence probability. Average daily residence probability was approximately 1.0 in mid‐May, 0.96–0.97 in the week of 22 May, and 0.64–0.77 after May 28 in DENJ in 2004 and 2006 and in VA in 2006. Average daily residency was approximately 0.88 in VA in 2007 from 22 May to 5 June. No birds moved from VA to DENJ in 2006 and only 2 birds (5.5%) moved in 2007. Stopover population sizes (±SE) in DENJ were 17,108 ± 1,322 in 2004 and 19,555 ± 831 in 2006, and in VA were 7,224 ± 389 in 2006 and 8,332 ± 718 in 2007, significantly greater than peak aerial counts. Years with similar peak counts had different residence probabilities; hence, adjustments for turnover should be used in the future to assess annual population changes. Our results suggest that VA can support a significant portion of this red knot subspecies during migration in at least some years. Managing red knots for recovery should entail improving our understanding of the use of other Atlantic Coast sites and protecting key coastal habitat from disturbance and development.

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Section: Discussionmentioning

confidence: 99%

Residence Probability and Population Size of Red Knots During Spring Stopover in the Mid‐Atlantic Region of the United States

et al. 2009

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“…Less well recognized is that changes in the LOS alter the number of birds censused, even if the total population does not change. To estimate the true number of birds (N T ) stopping over at Sidney Island, we incorporated our LOS estimates with the N C values in an arrival-stopover-departure model (Frederiksen et al 2001). The outcome (figure 4) provides no evidence for a drop in N T .…”

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confidence: 99%

Western sandpipers have altered migration tactics as peregrine falcon populations have recovered

Ydenberg

Butler

Lank

et al. 2004

Proc. R. Soc. Lond. B

149

171

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The presence of top predators can affect prey behaviour, morphology and life history, and thereby can produce indirect population consequences greater and further reaching than direct depredation would have alone. Raptor species in the Americas are recovering since restrictions on the use of dichlorodiphenyltrichloroethane (DDT) and the implementation of conservation measures, in effect constituting a hemisphere-wide predator-reintroduction experiment, and profound effects on populations of their prey are to be expected. Here, we document changes in the behaviour of western sandpipers (Calidris mauri ) at migratory stopover sites over two decades. Since 1985, migratory body mass and stopover durations of western sandpipers have fallen steadily at some stopovers in the Strait of Georgia, British Columbia. Comparisons between years, sites and seasons strongly implicate increasing danger from the recovery of peregrine falcons (Falco peregrinus) as a causal factor. A decade-long ongoing steep decline in sandpiper numbers censused on our study site is explained entirely by the shortening stopover duration, rather than fewer individuals using the site. Such behavioural changes are probably general among migratory shorebird species, and may be contributing to the widespread census declines reported in North America.

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“…To date, the assessment of the importance of stopover sites for waterbirds has typically been based on peak counts of any species, which underestimate the total number of birds using the site over a season because of the turnover of individuals (Frederiksen et al 2001). This method highlighted the importance of conserving large wetlands that commonly support big flocks of a species during migration, whereas it underestimated the importance of small wetland areas that do not support large numbers of migratory birds.…”

Section: Introductionmentioning

confidence: 97%

Do systematic daily counts reflect the total number of birds using stopover sites during migration? A test with Eurasian Spoonbill

Navedo

Garaita²

2012

Journal for Nature Conservation

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Estimating the Total Number of Birds Using a Staging Site

Cited by 43 publications

References 0 publications

Residence Probability and Population Size of Red Knots During Spring Stopover in the Mid‐Atlantic Region of the United States

Residence Probability and Population Size of Red Knots During Spring Stopover in the Mid‐Atlantic Region of the United States

Western sandpipers have altered migration tactics as peregrine falcon populations have recovered

Do systematic daily counts reflect the total number of birds using stopover sites during migration? A test with Eurasian Spoonbill

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