RED KNOT
Biology
On a sandy beach along the Delaware Bay, scientists and birders are gathered to
catch a glimpse of a very special shore bird known as the Red Knot. Thousands of
these birds will be arriving, exhausted and hungry after flying for four long days,
-over 4,000 miles- without stopping. Landing gracefully in the sand, the birds
immediately begin gorging
on protein-rich horseshoe crab eggs, eating as many as 18,000 eggs each day!. It
is important the birds eat up because they have only two weeks to double their
weight and prepare for the next leg of their journey, one that will take them an
additional 1,800 miles,
flying non-stop to the Red
Knots’ summer breeding
grounds in the Arctic
tundra. If world records
were awarded to animals,
this small bird the size of
cafeteria milk carton would
win a prize for one of the
longest migratory trips on
the planet. Red knots
travel an astonishing 9,300
miles in one season,
stopping only two to three
times to refuel.
Image: Public Domain: US Fish & Wildlife
Fun Facts about
the Red Knot:
The red knot makes one of
the longest migratory
trips of any bird – 9,300
miles along the Atlantic
Flyaway from its wintering
grounds in South America
to its high Arctic breeding
grounds. It only stops 2-3
times for refueling!
It’s estimated that 90%
of the population of red
knots (sub species C. c.
rufa) can be present in a
single day in the Delaware
Bay during spring
migration!
Once reaching the tundra, a treeless habitat with short summers, cool
Within two weeks of its
temperatures and perma-frost (permanently frozen soil underneath the surface
springtime arrival at
layer), red knots quickly find mates and make a nest. They make a nest on the
Delaware
Bay, the Red
ground in a shallow hole that the male bird excavates with his feet. The female
Knot will have doubled its
usually lays four brown and green camouflaged eggs in the nest and then both
weight from eating so
birds take turns incubating the eggs. Within 3 weeks, the eggs hatch and the
many horseshoe crab eggs!
young red knots emerge from the egg covered in down and with eyes wide open.
They are ready to leave the nest and follow their parents within a day! Growing
quickly is important because summers are short in the arctic and the birds must
be ready for the fall migration – another 9000 mile journey – within a month of hatching. By early August, when
Connecticut is still in the midst of summer, red knots are already on their way south.
Global Changes
Red knots have lived this way for a long time, probably thousands of years. But recently, something has changed,
and it is affecting these birds in a very serious way. In the past twenty-five years, the population of Red Knots
has crashed. This species is showing the most rapid decline in numbers ever recorded – down almost 70%, causing
much concern among scientists. The red knot is being considered for protection under the Endangered Species
Act. What is to blame for the loss of one of the world’s most amazing birds?
Some of the things that make this bird so unique also place them in danger. Red knots travel together in large
flocks, a behavior that helps them to survive when they are facing natural predators such as hawks and foxes. But
traveling in large flocks puts them at risk in countries where humans still hunt these birds. It can also increase the
loss of birds in areas where their habitat has been developed and there are no longer enough resources for the
large numbers of birds.
RED KNOT
Another reason for the steep drop in the Red Knot population has to do
with their eating habits during migration. Because the knots fly such long
distances, and stop to eat so infrequently, it is important for them to find
enough food at each stop along the way. Without enough to eat, the birds
will not be strong enough to reach the arctic, lay eggs and raise their
young. Perhaps their most important refueling stop is the Delaware Bay,
which divides Delaware from southern New Jersey. It is here that the
red knots find the energy they need to complete their journey to the
arctic. They get that energy from horseshoe crab eggs, which are being
deposited about the same time the red knots arrive each spring.
Horseshoe crabs have been around longer than the dinosaurs, each spring
finding a shore somewhere to crawl up on to lay their eggs. There were
always plenty of eggs for the red knots and plenty more that would hatch
into young horseshoe crabs. But then something changed.
Humans had sometimes collected horseshoe crabs to use as food for
livestock or as fertilizer for farm crops, but they had other choices as well and didn’t have to rely only on
horseshoe crabs for these needs. But beginning in the 1990’s, many horseshoe crabs began to be collected for use
as bait for eels and whelk. Scientists also began to collect them to extract some of their blood, which has special
properties that can help in medical research. Perhaps most importantly, the sandy beach habitat where horseshoe
crabs lay their eggs was rapidly changing, being developed into beach front homes and resorts. To protect many of
these homes, sandy beaches were replaced by stone or concrete walls to prevent erosion and flooding. The walls
also prevent horseshoe crabs from crawling up on shore to lay their eggs. Many factors contributed to fewer
horseshoe crab eggs being available for the red knots. Without this important food source, many red knots died
during migration, and the population dropped quickly.
Conservation:
Once biologists and wildlife managers began to discover the important ecological link between horseshoe crabs and
red knots, they urged local, state and the federal government to put strict regulations in place. Laws were passed
to limit the number of horseshoe crabs that can be caught for bait and for medical research. Also, much of the
remaining shore habitat is now protected from development. These controls will help the red knot and the
horseshoe crab, but further research must be done to study other factors that can have a positive effect on this
important migratory bird.
Sources:
http://www.allaboutbirds.org/guide/Red_Knot/lifehistory
http://www.dnr.md.gov/education/horseshoecrab/threats.html
http://www.fws.gov/northeast/climatechange/stories/redknot.html
http://www.nytimes.com/2012/06/06/nyregion/red-knots-horseshoe-crabs-and-fight-to-survive-in-delawarebay.html?_r=0
Willis, N.C. (2006). Red Knot: A Shorebird’s Incredible Journey. United States: Birdsong Books