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

Cohen, Jonathan B.; Karpanty, Sarah M.; Fraser, James D.; Watts, Bryan D.; Truitt, Barry R.

doi:10.2193/2008-042

Cited by 22 publications

(41 citation statements)

References 46 publications

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“… Simulated median red knot abundance (solid black line) (2.5 and 97.5 percentiles, solid gray lines) from 1999 to 2008 under (A) model 1 with set at 3.0 × 10 −7 and (B) model 2 with set to 3.0 × 10 −9 in response to horseshoe crab abundance, and harvests in Delaware Bay during that time period, observed peak Red Knot counts from aerial surveys of Delaware Bay (dotted line, from K. Kalasz, personal communication), estimated red knot abundance in Delaware Bay (dashed lines, from Niles et al [2008] and Niles et al [2009]), and estimated Red Knot abundance in 2006 in the Delaware Bay using radio tracking data and stopover duration analyses (*, from Cohen et al [2009]). …”

Section: Resultsmentioning

confidence: 99%

Multispecies Modeling for Adaptive Management of Horseshoe Crabs and Red Knots in the Delaware Bay

McGowan¹,

Smith²,

Sweka³

et al. 2011

Natural Resource Modeling

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Adaptive management requires that predictive models be explicit and transparent to improve decisions by comparing management actions, directing further research and monitoring, and facilitating learning. The rufa subspecies of red knots (Calidris canutus rufa), which has recently exhibited steep population declines, relies on horseshoe crab (Limulus polyphemus) eggs as their primary food source during stopover in Delaware Bay during spring migration. We present a model with two different parameterizations for use in the adaptive management of horseshoe crab harvests in the Delaware Bay that links red knot mass gain, annual survival, and fecundity to horseshoe crab dynamics. The models reflect prevailing hypotheses regarding ecological links between these two species. When reported crab harvest from 1998 to 2008 was applied, projections corresponded to the observed red knot population abundances depending on strengths of the demographic relationship between these species. We compared different simulated horseshoe crab harvest strategies to evaluate whether, given this model, horseshoe crab harvest management can affect red knot conservation and found that restricting harvest can benefit red knot populations. Our model is the first to explicitly and quantitatively link these two species and will be used within an adaptive management framework to manage the Delaware Bay system and learn more about the specific nature of the linkage between the two species.

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Section: Resultsmentioning

confidence: 99%

Multispecies Modeling for Adaptive Management of Horseshoe Crabs and Red Knots in the Delaware Bay

McGowan¹,

Smith²,

Sweka³

et al. 2011

Natural Resource Modeling

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“…It has been hypothesized that the decline in TDF knots may also have been driven by the lack of sufficient horseshoe crab eggs in Delaware Bay (Baker et al 2004). Our study and other recent work explores this hypothesis linking red knot and crab declines as well as other possible hypotheses such as limiting factors at other northerly stopover sites (Cohen et al 2009, 2010 b ). Much work remains to be done to explore possible limiting factors on the knots' Arctic breeding grounds (Niles et al 2008).…”

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confidence: 59%

“…Peak knot numbers in Delaware Bay have continued to hold near steady and possibly increase between 2006 and 2009 according to a recent knot status update (Niles et al 2010). Similarly, the total red knot passage population size corrected for turnover between weeks did not decrease between 2004 and 2006 in Delaware Bay (Cohen et al 2009). If the horseshoe crab egg shortage caused the dramatic decline observed in the Delaware Bay stopover counts and TDF wintering counts of knots between the mid 1990s and 2003, and if crab eggs remain the limiting factor, then an increase in eggs available to red knots should result in an increase in the red knot population.…”

Section: Discussionmentioning

confidence: 96%

“…For example, the use of stopovers that were once apparently important final refueling areas for red knots, including coastal New Jersey, New York, and Massachusetts (Mackay 1893), is now much reduced (Niles et al 2008). The Delaware Bay now serves as the key refueling site for approximately two‐thirds of the Western Atlantic red knot population, with coastal Virginia hosting much of the remaining one‐third (Cohen et al 2009). Therefore, managers should also consider factors limiting red knot numbers at these alternate historic stopover sites, at their wintering sites, and on their relatively unknown Arctic breeding grounds in addition to those in Delaware Bay to best facilitate the recovery of red knots to historic numbers.…”

Section: Management Implicationsmentioning

confidence: 99%

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Sufficiency of horseshoe crab eggs for red knots during spring migration stopover in Delaware Bay USA

et al. 2011

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Horseshoe crab (Limulus polyphemus) eggs are a dietary staple of the red knot (Calidris canutus) during its spring stopover on the Delaware Bay. Numbers of knots stopping in Delaware Bay declined in the 1990s concurrent with a decline in horseshoe crabs, leading to the hypothesis that reduced horseshoe crab egg abundance limited the red knot population. Management efforts, including a seasonal harvest moratorium in the Delaware Bay, have been instituted to restore crab populations to levels of sustainable use by multiple users, including migratory birds. Our objective was to evaluate the sufficiency of horseshoe crab eggs in Delaware Bay in May–June 2004 and 2005 for knots to refuel for their migratory flight to the Arctic breeding grounds. We examined egg counts to determine if there were fewer high egg‐density sites later than earlier in the day and season, as migrating birds might deplete this resource. We studied foraging rates at red knot locations to determine if foraging probes increased with time of day and season as birds depleted surface eggs by pecking, then began probing for subsurface eggs. Finally, we experimentally tested whether red knots and their competitors depleted horseshoe crab eggs. Crab egg numbers at knot foraging sites did not decline throughout the day or season in 2004. In both years, we found no evidence that knots switched from pecking to probing with increases in time since sunrise or start of the stopover. Egg numbers were similar in exclosed and accessible plots on crab nesting depressions and in areas of open intertidal zone, but were significantly lower in accessible than in exclosed plots in the wrack line. Our results indicate that horseshoe crab eggs in Delaware Bay were sufficient to support the refueling of the present‐day stopover population of red knots. If an increase in the availability of crab eggs to foraging birds does not result in an increase in knot numbers, managers must prioritize mitigation of limiting factors at other historically important spring stopovers and on the poorly understood breeding and wintering grounds in addition to the Delaware Bay. © 2011 The Wildlife Society.

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“…Multiple studies indicate that Delaware Bay is not a singular terminal staging area but part of a broader network of sites centered on the mid-Atlantic coast , Smith et al 2008, Cohen et al 2009). Currently, most of the information available on spring stopover ecology of red knots has focused exclusively on Delaware Bay.…”

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confidence: 99%

Spring migration of red knots along the Virginia barrier islands

Watts

Truitt

2015

J Wildl Manag

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We conducted low-altitude, aerial surveys from the last week of April through the first week of June (1995, 1996,(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) to assess patterns in bird abundance, migration phenology, and habitat use of red knots (Calidris canutus rufa) staging along the Virginia barrier islands. During most years, knots arrived in early May, reached peak abundance during the third week of May, and were gone by mid-June. The peak period (10 May-3 June) accounted for >90% of detections for all years. The mean high count during the study was 7,373 AE 407 (SE). Decadal comparisons of high counts, accumulated numbers for the period of peak abundance and the season totals provided mixed results. Knots within the study area used peat banks and sandy beaches for foraging. Intertidal peat banks were patchily distributed and represented only 6% of the shoreline. Mean knot densities were comparable between the 2 habitats in the early period of migration but diverged rapidly such that by the third week of May, knot densities were 10-fold higher on peat compared to sand. Knots exhibited wide annual variation in habitat use; the number of knots observed on peat varied from 13% to 91% of the total birds for a given year, presumably reflecting the underlying population dynamics of respective bivalve populations. Potential prey dynamics coupled with the patchy distribution of peat appear to cause year-to-year variation in space use along the island chain. The Virginia barrier islands appear to be part of a terminal staging area for red knots that stretches from New Jersey south through the Outer Banks of North Carolina. Documenting red knot use within portions of this region beyond the well-studied Delaware Bay may lead to a more complete understanding of the sampling process used by red knots to make staging decisions. Ó 2014 The Wildlife Society.

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

Cited by 22 publications

References 46 publications

Multispecies Modeling for Adaptive Management of Horseshoe Crabs and Red Knots in the Delaware Bay

Multispecies Modeling for Adaptive Management of Horseshoe Crabs and Red Knots in the Delaware Bay

Sufficiency of horseshoe crab eggs for red knots during spring migration stopover in Delaware Bay USA

Spring migration of red knots along the Virginia barrier islands

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