The Decline
of the Red
Knot
Lawrence Niles Ph.D Amanda Dey Ph.D
NJ Division of Fish and Wildlife, US
Humphrey Sitters Ph.D
International Wader Study Group, UK
Clive Minton Ph.D Victoria Wader Study
Group, Aus.
The red knot makes
one of the longest
Breeding Area migrations of any bird
Breeding Area
Northbound Flight
Breeding Area
Stopover
Wintering Area
Wintering Area
South Bound Flight
Wintering Area
The Delaware Bay
is one of four major
shorebird stopovers
in the
world
Shorebirds on the
Delaware Bay gain up to
10% of bodyweight/day
Until 1992, the harvest
of horseshoe crabs
was a tradition harvest
to supply bait for a
small eel fishery
By 1996 millions of
crabs were being
killed to supply bait
for a coast-wide
conch fishery
R ecent H orseshoe C rab Landings (N M FS)
7000000
6500000
6000000
5500000
VA
MD
DE
NJ
NY
5000000
4500000
Pounds
4000000
3500000
3000000
2500000
2000000
1500000
1000000
500000
0
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Year
In 1998 the ASMFC created management
plan for horseshoe crabs that froze harvest
at 25% of peak harvest without any
understanding of population size or
recruitment
DE DFW 30-foot Trawl Survey - Horseshoe Crab Index
Horseshoe Crabs, catch/unit effort
14
CPUE Total HS Crabs
12
Geo. mean Horseshoe Crabs
.
The only data available, a baywide trawl,
was dismissed although it documented a
90% drop in stock
10
8
6
4
2
0
1990
1992
1994
1996
1998
N = 350
Year
2000
2002
2004
Egg densities on bay beaches fell from average
counts of 40,000 egg/m in the early 1990’s to
4000 eggs/m in 2000
Egg density eggs/m
Mean Egg Density 2000-2005
6000
5000
4000
3000
2000
1000
0
2000
2001
2002
2003
Year
2004
2005
The number of red knots reaching weights >=185g
fell dramatically between 1997-2003
40000
33741
35000
30000
25000
20509
19922
20000
17340
15000
12075
10000
5376
5000
813
0
1997
1998
1999
2000
2001
2002
2003
The Delaware Bay stopover population has been declining
since 1997. Peak numbers of red knots of over 100,000 in
the 1980’s have fallen to 13,315 in 2004
Red Knot Surveys 1997-2004
number of birds
60000
50000
40000
30000
20000
10000
0
0
5
10
15
20
25
30
35
40
Daynum
1997
1998
2003
2004
1999
2000
2001
2002
We expanded our study
to the primary South
Breeding AreaAmerican wintering areas
Breeding Area
in 2000
Northbound Flight
Breeding Area
Stopover
Wintering Area
Wintering Area
South Bound Flight
Wintering Area
We compared populations of the red knot
and hudsonian godwit, an arctic breeder that
does not stopover on the Delaware Bay
.
Red knot numbers declined 68% in the
period of our study
Species
Red Knot
Godwit
Region
Tierra del Fuego
Tierra del Fuego
1982/86
Atlas
53232
31132
2000
51255
31090
2002
27242
46088
Numbers fell dramatically this year
2003
29915
42470
2004
30778
66840
2005
17653
53725
We expanded our study
to the primary breeding
area in 1999
Breeding Area
Breeding Area
Northbound Flight
Breeding Area
Stopover
Wintering Area
Wintering Area
South Bound Flight
Wintering Area
The red knot was compared to the golden plover, a
long distant migrant that does not stopover on the
Delaware Bay
Between 2000 and 2004 nest densities fell
from 1.2 nest/km to .5 nest/km
Table 2. Breeding density of red knot and American Golden Plover
on Southampton Island study site, Nunavut, Canada, 2000 through 2004.
Year
Species
2000 Red Knot
2001* Red Knot
2002 Red Knot
2003 Red Knot
2004 Red Knot
2001 Am. Golden Plover
2002 Am. Golden Plover
2003 Am. Golden Plover
2004 Am. Golden Plover
# Nests on
Study Site
11
7
9
3
5
Breeding
Density
(Nests/sq. km)
1.155
0.765
0.984
0.328
0.547
7
5
10
9
0.765
0.547
1.093
0.984
* 2001 - early hatching year, seven knots with broods found on study site
We expanded our study to the east
coast in 2004
East Coast Red Knot Resightings May 22 - 28, 2004
Ma isonnette, New Brunswick, Canada
( 3 ) M ay 12; ( 8 ) Ma y 24, 2004
Quebec
Ontario
New Brunswick
Maine
Nova Scotia
Ver mont
N ew H ampshire
New York
Michigan
Massachusetts
ConnecticutRhode Island
Pennsylvania
Long I sland, NY ( 12 ) May 27, 2004
Ohio
N ew Jersey
West Vir ginia
Maryland
Delaware
D istrict of Columbia
-
Chincoteague NWR, VA ( 3 ) Ma y 25, 2004
Kentucky
Virginia
Tennessee
Pea Isla nd NWR ( 10 ) & ( 3 ) May 25 ; ( 2 ) May 27, 2004
North Carolina
Cape Hatteras, NC ( 4 ) May 24, 2004
Ocracoke Island, NC ( 32 sca ttered ) M ay 27; ( >200 ) Ma y 28, 2004
Cape Lookout, NC ( 115 ) Ma y 27, 2004
South Carolina
Georgia
Turtle Isla nd, GA ( 270 ) May 27, 2004
Legend
Cumberland Isla nd, GA ( 0 ) M ay 27, 2004
U.S.A.
Canada
Fort Georg e Inlet, FL ( 33 ), ( 127 ), ( 21 ), & ( 133 ) May 27, 2004
Under 100
101 - 500
Florida
501 - 1000
Over 1000
Scale 1:11,667,279
0
95 190
380
570
760
Kilometers
The differences in population counts in Tierra del
Fuego and Delaware Bay indicates the knots that
bypassed the bay in 2003 and 2004 died in 2005
year
2000 2002
Tierra del 51255 27242
Fuego
Delaware 43145 31695
Bay
2003
29915
2004
30778
2005
17653
16025
13315
15300
The decline of the red knot represents
a general decline and threat of all
species that stopover on the bay
Peak counts of Red Knot, Ruddy Turnstone & Sanderling,
Delaware Bay 2000 - 2004
100,000
90,000
Number of Birds
80,000
70,000
60,000
Red Knot
50,000
Ruddy Turnstone
40,000
Sanderling
30,000
20,000
10,000
0
2000
2001
2002
Year
2003
2004
Birds must now move about the bay in search of
any significant source of eggs
Why An emergency?
• Sudden decline in 2003 without corresponding
declines in Tierra del Fuego suggest birds are
now by passing the bay
• The subsequent failure to breed and poor
mortality caused a 40% decline in Tierra del
Fuego in 2005
• As yet unreleased data on the ocean trawl for
crabs point to continuing declines in the
horeshoe crab population despite 50%
reductions in harvest.