Saving Shorebirds: the Crusade for Red Knots

by Lanny McDowell


I realize that “Crusade” sounds overbearing, but the more you read my blog, the more you will know I throw words around rather loosely, hopefully for effect.  I wanted to get your attention.

I am involved with two other outdoorsy types, very good friends of mine, in seeking creative and significant solutions to the Red Knot’s race toward extinction in the Americas.  The population trend is so steeply downward that it occurred to us that some additional sources of food might be found to supplement the variable stocks of Horseshoe Crab eggs that are naturally found along the shores of Delaware Bay during May and early June each year, the “Limulus” eggs that the northbound shorebirds count on to fuel the last long leg in their annual journey to breed in the arctic.

We three spent a week at the end of May of 2008 assessing the situation in the Cape May area of New Jersey, talking with researchers and trying out a man-made food item we obtained from a zoo food supply company.  With a  grant from the Marine Conservation Action Fund at the New England Aquarium in Boston, Mass. we bought 500 pounds of this fish-based feed to try out on the shorebirds in their natural habitat.

On my regular blog page I will be referring to our ongoing involvement with the scary declines in shorebird populations.   There you can find an article I wrote for the Vineyard Gazette, called “Red Knot Project Update ”, down the list of my regular blog posts.  It’s dated 11/28/08.  And of course I will be posting photos from our times at the shores of Delaware Bay.   For an informal account of what we did this, 2009, at Delaware Bay, I am copying right here the text of a post I wrote on 06/06/09 after a week in New Jersey with the other members of GCA:


Our Pennsylvania-based associate John Patrick Brown arranged a just-in-time house rental which offered us the option of either staying in a nice old farmhouse once owned by Lucky Luciano or using the current owners’ beach house right on Delaware Bay at a place called Highs Beach, which is just south from Cook’s and Reeds beaches, both well known as annual shorebird feeding and resting sites situated up the bay coast from Cape May.

The permits for Global Conservation Alliance (GCA)  to conduct research this year specified Cook’s, Reeds, Moore’s and Gandy’s beaches as locations for our work.  The procedure to collect Horseshoe crab eggs involved sampling certain marked plots according to  protocols developed by Norm Famous, who has the credentials and background to do that sort of thing.  Three of the four beaches were associated with the outlets of estuary systems draining out of extensive marshlands emptying into Delaware Bay from the New Jersey side.  Two of the beaches were long uninterrupted stretches of sand.  Two contained a variety of bayshore surfaces and substrata, including clay and silt layers, sections of peat and areas of mixed sand and pebbles washed by strong tidal currents.

Our objective was to identify places on the beach that horseshoe crabs would prefer for egg nests and to dig “soil” samples of a given size, record their locations and measure the density of crab eggs found in the samples stored in zip-locked bags.  After collection on the beaches, the samples were transported to the beach house rental where three GCA members and associates washed, sifted and rebagged each sample, then counted the number of eggs in each labeled bag, then tallied the egg counts for later comparison.  This sampling protocol was chiefly designed to show how the number of eggs contained in an undisturbed sample of beach area would differ from a sample collected after the beach had been disturbed by raking up the sand from as deep as nine inches and from as shallow as four to six inches.   Each set of plots contained a control plot.  Our forthcoming experiment results will be prepared by Norm Famous as a requirement of the permit issued by New Jersey Department of Fish and Wildlife, so I will not elaborate further here.

A second experiment had to do with distributing Aquamax, the manufactured food we tried out in 2008 as a possible substitute for horseshoe crab eggs.  This experiment was chiefly a matter of observing the reaction of both shorebird and gull species to food alternatives and to the areas of beach that were disturbed (raked up) in the course of our egg sampling process.

Porter Turnbull and I had arrived in New Jersey on the 26th of May, when we were joined by John Patrick Brown, who assisted us last year.  Norm Famous and Pete Gilmore, who is new to the team in 2009, arrived late on the 28th.  Teams worked on the beaches everyday at one location or another, with the exception of May 30th, which was devoted mostly to egg processing and counting after one sampling set was taken in the morning.  The beaches were sampled in this order:  Moore’s, Gandy’s, Reeds.  Cook’s Beach was used exclusively for observation, whereas the other three provided egg density samples as well as opportunities for observation.  What we found during our late May stay this year was quite different from the scene we experienced last year.  In 2008 most Red Knots and Dunlin were concentrated at Moore’s Beach, feeding shoulder to shoulder at the mouth of the estuary; and spawning crabs were not that easy to find.  This year that location was dominated by Laughing Gulls and crabs were in abundance.  Feeding and resting flocks of shorebirds could turn up anywhere along the main beaches this time, working the water’s edge or gathering at the inside corners along the beach where an eddy or a jetty concentrated the horseshoe crab eggs.

Typically we would dig out samples and rake the plots to obtain more samples starting at a low or rising tide.  Then we would watch the feeding activities of shorebirds working the advancing edge of the rising tide.  In some cases we resampled our plots, which we had marked with poles in the four corners, to measure egg densities after the passage of the high tide and the predation of the feeding birds.

Overall, I would characterize the work as tedious and the data as useful.  The human company was well matched and the locations inspiring; and the birds as always were a miracle.

We were told fairly early on that the major northward departures of Red Knots occured on the 26th, our arrival date.  However, both the weather and the numbers of shorebirds in our vicinity, and Red Knot numbers in particular, all improved daily, right up until our own departures on June 1st.  We witnessed the largest aggregations of birds at Cook’s Beach on May 31st, with thousands of Semi-palmated Sandpipers and hundreds of Ruddy Turnstones and Red Knots present.  Dowitchers, Dunlin and Sanderlings had for the most part moved out earlier.

As to collateral birding this year, I would have to say that Clapper Rails and Seaside Sparrows were the the stars that held our attention the longest.  Both are considered hard to see, yet we found that both were quite willing to be seen extensively, given the right opportunity.

We will publish a formal report for 2009 in the future, but we wanted to keep you all in the loop.  And many heartfelt thanks to all for your encouragement,  advice and support.

Best wishes, Lanny McDowell

Learn more about The Red Knot Survival Project at GCA:


For a recent (June 19th, 2009) article by Mike Seccombe in the Vineyard Gazette about the status of horseshoe crabs in Massachusetts, use this link:


Following is the report which describes the “Crusade” past (2008) and future:

Red Knot Supplemental Feeding Program in Delaware Bay

Norman Famous and Porter Turnbull

Global Conservation  Alliance

September 24, 2008

Report submitted to the Marine Conservation Action Fund

1.0          Summary

A feasibility study to evaluate the supplemental feeding of the red knot (Calidris canutus) using prepared food (Aquamax) was conducted during May 2008 at Reed’s Beach on the NE shore of Delaware Bay in New Jersey.   The red knot migrates from South America to Delaware Bay where its weight doubles while “stopover feeding” for about three weeks on horseshoe crab (Limulus polyphemus) eggs before continuing to Arctic nesting grounds.  This refueling stop in Delaware Bay is vital to migration, breeding, and, ultimately, species  survival. The red knot population declined steadily from the 1970’s through the mid 1990’s, after which it decreased at a catastrophic rate of 70% over the last 10 years.  Already listed as endangered in Canada, the red knot is experiencing a catastrophic population decline, possibly leading to extinction, due to the depletion of its principal migration food, horseshoe crab eggs.

Due to the accelerated red knot population decline and recent legislative moratoriums on harvesting horseshoe crabs in New Jersey, sensitive ‘political’ concerns introduced several hurdles which limited access to the birds and affected the scale of our study.  The project gained logistical support and vital information on the local population status of the red knot and horseshoe crab through meeting with principle scientists and members of the horseshoe crab harvesting community.   In addition, it increased our sensitivity to the polarized relationship between the commercial fishing community and red knot conservationists.

The project had two components: 1) provide alternative food sources, monitor food selection, evaluate logistics, and identify potential problem areas for implementing a larger scale feeding program; and 2) establish a working coalition of stake-holders including federal and state agencies, red knot biologists, NGO’s, horseshoe crab fisherman, and the food supplement industry.  The study was timed to coincide with the spring lunar tidal cycle when horseshoe crab reproductive activities and red knot populations reach their respective peak levels.

The study brought together diverse groups with conflicting interests.  After several meetings with New Jersey state regulators, we agreed to a modified study design at two locations along Reed’s Beach.  Areas with high egg and bird densities were avoided because of on-going research by multiple research groups and potential disturbances.   After much discussion amongst scientists, the basic question we addressed was: “will the red knot and other horseshoe crab egg predators feed on artificial provisions while foraging in relatively low egg density conditions?”

2.0  Accomplishments:

(1) Important data on the feasibility of feeding the red knot and other shorebirds in population decline was collected;

(2) Data on food preferences (natural vs. artificial) and feeding behavior for the primary predators of the Limulus egg were collected;

(3) Artificial food was successfully used to feed and/or lure laughing gulls (Larus philadelphia) away from Limulus eggs and red knot groups.  Luring laughing gulls away from feeding red knots is crucial because they are the red knot’s most important competitor for Limulus eggs;

4) Information on local population movements and patterns for red knots, other shorebirds, and laughing gulls was gathered;

(5) Competitive and behavioral interactions among species competing for the same food resources were observed:

(6) A foundation for an alliance amongst red knot researchers, red knot conservationist, and commercial horseshoe crab fisherman was initiated, which is essential for cooperative, long-term management of both resources.

Although the sample size within the experimental design was too small for sound statistical analysis, we describe general trends.  Our conclusions and recommendations are based on repeated observations from 1) the 4 x 5 ft plots contained in the study design, 2) direct application of provisions on beaches, 3) observations at key red knot concentration areas which included large numbers of all birds in the horseshoe crab egg feeding guild, and 4) over 75 collective years of gull and shorebird feeding observations.

3.0          Methods

Pairs of 4 ft by 5 ft study plots were established at several locations along Reed’s Beach.  Although not heavily populated by red knots, the sites were free from human disturbance and provided excellent observation conditions.  In descending order of abundance, the members of the Avian horseshoe crab egg feeding guild in the vicinity of the paired plots included laughing gulls, sanderlings, semipalmated sandpipers, ruddy turnstones, red knots, dunlins, 1 to 3-year old herring gulls, and European starlings.  Low numbers of other shorebird and gull species were present (e.g., semipalmated plover (Charadrius semipalmatus), least sandpiper (Calidris minutilla), willet (Catoptrophorus semipalmatus), ring-billed gull (Larus delawarensis), and great black-backed  gull (Larus marinus).

Experiments were conducted primarily on the incoming tide for three days after permits were obtained; and conducting preliminary observations at key red knot and laughing gull concentration areas was conducted.  For the feeding experiments, we placed and secured screening material on the beach and covered it with about one inch of provisions. The provisions were comprised of round 2-4 mm dark-colored fish pellets (size designed for post-frey sized Atlantic salmon).  Pellets were approximately the size of the pale, light-colored translucent horseshoe crab eggs.

Bird use of the provisions was monitored until the plots  were inundated by the incoming tide.  On the last day of the study, a second set of plots was established on each beach after the first set was inundated.  Supplemental experiments were also conducted where we distributed provisions directly on the beach both parallel and perpendicular to the incoming tide line.  Data were collected at timed intervals by bird species and included:

1) Time of Arrival at the Plots (both within and surrounding the plots),

2) Number of Birds,

3) Use of the Plots,

4) Length of Stay,

5) Departure time if the species or most of the individuals departed (both from the plots and surrounding the plots),

6) Behavioral Interactions Among Species or Individuals Within the Same Species, and

7) Post-feeding/Post-inundation Behavior (e.g., Did the birds depart to other feeding areas or did they rest nearby.

4.0          Results

The results are presented to match the seven primary data gathering questions described in the methods section above (Section 2.0).

Time of Arrival at the Plots (both within and surrounding the plots),

Laughing gulls were the first species to arrive at and use the provision plots.  Generally, birds arrived about an hour after plots were established.  Laughing gulls continued to arrive in low densities (e.g., less than 30 birds) over the next hour.  Shorebirds did not typically concentrate around the plots until laughing gull densities reached maximum.

Number of Birds

After reaching densities ranging between 25 and 50 birds, laughing gull numbers increased to 300 to 500 birds and remained relative constant until feeding areas were inundated.  Larger Larids followed a similar pattern but were displaced when laughing gull densities reached more than 100 birds.  Shorebirds numbered from 1 to 5 individuals of each species as they associated with the Larid flocks.  When provisions were spread directly on the beach, 1 to 2 shorebirds fed regularly on the provisions.  Other individuals sampled provisions but returned to forage for crab eggs.  Egg densities were not sampled but were presumed to be lower than egg densities near beaches with known active horseshoe crab spawning.

Use of the Plots

Once high densities of Larids were in the plots, they remained until provisions were exhausted.  However, because of the small pellet size, provisions lasted several hours while gulls were at maximum density.  Based on qualitative observations, gull feeding behavior, in terms of packing density, arrangement while feeding, interactions among individual feeding birds, and density and interactions among surrounding non-feeding birds paralleled similar behaviors, distributions, and bird concentrations in the high-density horseshoe crab areas.  Parallel observations of shorebird-gull interactions at high-density crab egg locations were not possible because gulls and shorebirds typically fed in slightly separated locations and the total numbers of shorebirds were two orders of magnitude higher than those at Reed’s beach.

Length of Stay

Once gulls reached their highest densities and provisions were consumed, most birds rested within 50 meters of the plots until high tide.  The half-mile distance between study areas was typically devoid of gulls during feeding and post-feeding.  Concurrently, shorebirds continued to feed along gull-free sections of beach followed by roosting over the high tide period, approximately 1 ½ hours before and after high tide.

Departure Time of the Species or Time When Most Individuals Departed (both from the plots and surrounding the plots)

Once gulls reached maximum densities, they appeared to remain in the vicinity of the plots throughout the remaining incoming period.  When gulls departed feeding plot areas, the section of beach between study areas remained mostly devoid of gulls.

Shorebirds appeared to remain on the beach.  Their behavior is described above under ‘Use of the Plots’.

Behavioral interactions Among Species or Individuals Within the Same Species

Among the gulls, gull interactions appeared similar to those qualitatively observed at high egg concentration areas.  Inter-specific interactions at high crab egg concentration areas among members of the guild were not documented.  See ‘Use of the Plots’ above for a discussion.

Shorebird feeding behavior on their natural prey did not change when in the vicinity of provisions scattered on the beach.  Occasionally, individual sanderlings, ruddy turnstones, semipalmated sandpipers, dunlin, and red knots would forage in the provision zone between one to three wave-washes, after which they returning to crab-plucking behavior where they follow the in and out flow of the wave action.

In and surrounding the feeding plots, shorebirds were displaced by Larids both within and adjacent to the provision source.  Basically, shorebirds were at the bottom of the Larid-shorebird dominance.  Not enough data were available to assess a pecking order among shorebirds at the feeding stations.  However, while feeding on horseshoe crab eggs, ruddy turnstones showed a tendency to displace all shorebirds.  Among sanderlings and semipalmated sandpipers, the larger sanderling occasionally exhibited aggressive behavior toward semipalmated sandpipers.  No other species of shorebird displaced ruddy turnstones.

Post-feeding/Post-inundation Behavior (e.g., did the birds depart to other feeding areas or did they loaf nearby; question pertinent primarily to gulls)

After food was exhausted, the gulls remained rested within 50-75 meters of the study plots after food was exhausted.  Large Larids (herring and great black-blacked gulls moved to a distant jetty where they roosted).

5.0          Recommendations

5.1          Supplemental red knot feeding

The Aquamax food product provided by Mazuri foods did not appear to be easily identifiable to shorebirds as a food source. It is possible that there was not enough time for birds to acclimate to the provision type or insufficient food was presented. In addition, the small presentation plot may have been an adverse factor due to competition with laughing gulls, which displaced the shorebirds.  For example, paired 4 ft x 5 ft. plots presented a small target area to be detected on a rising tide.  Laughing gulls, which are a competitor with the red knot for Limulus eggs, readily accepted the Aquamax, and dominated the feeding stations.

It is not known if the red knot uses solely visual clues to identify food sources.  A follow-up with Mazuri Food to develop a provision that has the appearance and texture (as well as nutritional composition) is recommended.  Part of this development includes analysis of Limulus eggs with the assistance of Limulus researchers.

5.2          Feeding laughing gulls and other Larids

Because laughing gulls are direct competitors for Limulus eggs, feeding gulls should reduce competition, and make the food source more abundant and available for the red knot.  Experimental feeding of the Aquamax product demonstrated that gulls were quickly attracted to the provisions and their high numbers made the provision un-available to other species.  Gull feeding stations at locations distant from the red knot feeding areas is promising, thus being comparable to supplemental feeding.

5.3          Shallow tilling of the substrate

The use of a plow or harrow in red knot feeding areas will expose near-surface Limulus eggs.  Because red knots glean the Limulus eggs from the surface or by shallow probing, tilling or harrowing (disturbing) will render their natural food available.  In addition, these areas can be fortified with supplemental feeds if appropriate types are developed.  Accessibility and the sand/gravel character of the beaches make this approach logistically viable.  There will likely be questions as this technique will expose more of the Limulus eggs to predation.  However the areas disturbed will be small and rotational management can be used. As the overall population of Limulus and resultant egg production in Delaware Bay appears to be rebounding it is not likely that this technique will result in any serious threat to the crab.  As Limulus come ashore to spawn on several occasions including times in June after the red knot has departed, localized crab egg production will be preserved.  This approach may be the most cost effective and successful, as it uses the bird’s natural food preference and is logistically easy to accomplish.

5.4 Redistributing Limulus eggs to areas being utilized by feeding red knots.

Bird and horseshoe crab experts indicated that there are areas of high concentrations of limulus eggs that are not being utilized by the red knot.  Limulus eggs could be harvested and  then distributed to feeding red knot groups using a portable PVC pipe sluicing apparatus. Although this method is logistically more difficult than tilling it has the advantage of bolstering the egg food source in areas being heavily utilized by the birds: i.e we bring the provisions to them. Also this method cooperatively involves and employs the fishing community in harvesting, transporting and storing limulus eggs. An alliance with the local harvesters and fishing industry is critical in any successful outcome regarding the survival of the red knot.

5.5          Creating red knot high tide roosting/Resting habitat in Delaware

Red knots utilize roosting or resting areas distant from feeding beaches.  This daily commute requires significant energy expenditure.  Researchers communicate that although the Delaware side of the bay is richer in Limulus and their eggs, the majority of the red knots forage on the New Jersey side due to the proximity of suitable roosts.  Creating high tide resting areas close to various feeding areas will likely help the red knot by reducing the energy expenditure required by long-distant commuting as well as making more productive feeding areas readably available.

5.6          Captive feeding studies

Pen feeding trials of captive birds can be conducted to test the red knot’s acceptance of supplemental food sources and fat accumulation rates.  These studies can be performed by researchers or graduate students at the University of Delaware, Rutgers, or other accredited facilities.  Feeding programs may also be established at the Monterey Bay and New England Aquariums, who are equipped with academic facilities.  Dr. Theunis Piersma in Finland has been pen feeding red knots, and will be consulted.  There are constraints, however.  Red not foraging behavior in the wild may be not be the same as in captivity.  Furthermore such studies may push back direct action to help the red knot by years.  As it is accepted that the red knot population has experienced precipitous drops in recent years further delays may be contraindicated.

5.7          Creating alliances among competing interests

Currently there is a non-cooperative rift between the scientists and the fishing community because of the 2008 moratorium on Limulus harvesting in New Jersey.  It is crucial that all stake holders be included in the process of Limulus population restoration and management, which will allow red knots, horseshoe crabs, and fishermen to successfully coexist.  Support from the aforementioned groups as well as others such as government agencies, Non Governmental Organizations, and industry (e.g., medical and electrical generation industries) will insure the success of applied follow-up studies.

6.0          Conclusions

Red knot and horseshoe crab populations are sinking and time is of essence.  Already listed as endangered in Canada, red knot populations have faced catastrophic declines that may lead to broad regional extinctions due to reduced numbers of horseshoe crab eggs.  Red knots fly from South America to Delaware Bay where their weight doubles while they ‘refuel’ for about three weeks on horseshoe crab eggs.  Delaware Bay is a critical refueling or fat-accumulating location before continuing to their Arctic nesting grounds

A multi-disciplinary approach for red knot recovery and management is needed.  No single approach will provide a quick-fix with the capacity to reverse perilous declines because multiple independent and near-independent factors contribute to their demise.  Relevant factors include inadequate  food supplies, competition among members of the avian horseshoe crab egg-foraging feeding guild, unregulated harvesting of horseshoe crabs during the 1980s and 1990s, limited number of red knot high tide resting areas along the Delaware side of the bay, and relatively long distances between prime red knot feeding areas.  In addition, the importance of each factor may vary among locations and among years.  Without a coordinated multi-disciplinary approach to overcome these and other factors, full recovery may not be possible, or will be severely protracted.

Our plan is designed to provide a temporary ‘life boat’ to help red knot populations ride out the present food shortages while horseshoe crab populations rebound, which is expected to take 8-12 years.  Assuming a full or partial population recovery, the contingency plan can also be implemented over the long-term during years when spawning and the red knot migration are asynchronous, or when weather reduces egg availability.

Studies involving Limulus egg harvesting or substrate disturbance that may adversely impact Limulus populations will need review and approval by Limulus researchers.  Likewise, management methods that may adversely impact red knot populations will need review and approval by the appropriate federal and state agencies and red knot researchers.



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Birds are cool!  Lanny

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