Three, two, one! A man pulled a trigger and a net shot across the beach along the Delaware Bay.
photo permission: Maureen Barrett
photo permission: David Carter
What was he doing? What
was he trying to catch? Shorebirds! Scientists rushed down to the net,
eager to get to work. Underneath this mess, literally there were hundreds
of tiny shorebirds shrieking and struggling to be released out of the net.
While burlap covers calmed them, the shorebirds were hurried to dry sand.
The scientists moved very swiftly.
photo permission: David Carter
They reached their hands
underneath the net. With a bird in each hand, the scientists moved the
birds into collapsible cages. What was to come next? A detailed assessment,
bird by bird, by bird, by…. well, you get the picture.
The State of Delaware
has been working for four years monitoring birds. They have collected 4
years worth of data to date, and
have now committed monitoring resources to carryout the study for an additional
5 years, starting in the spring of 2001. They monitor the shorebirds by
banding and weighing them.
In the spring of 2000 a group of people from the British Trust for Ornithology, the Delaware Coastal Management Program, and the Wash Wader Ringing Group worked for two weeks counting and weighing shorebirds. These British scientists have come to Delaware for several years now to help state officials develop their own monitoring program. All around the world, scientists have been trying to find out the health of shorebird populations worldwide. Nigel Clark, one of the ornithologists from Britain, said, “Delaware Bay is vital for two weeks when the birds come to build fat reserves for their final leg of their journey up north.” The scientists believe that getting information on the shorebirds may be a useful tool in regulating the harvest of horseshoe crabs.
photo permission: David Carter
Some of the shorebirds that visit this area are: dunlins, ruddy turnstones,
semipalmated sandpipers, sanderlings, and of course, red knots. They are
headed for the Arctic from South America. This is a distance of about 8,000
miles. They need energy to fly that far, so they stop in Delaware and eat
the horseshoe crab eggs. David Carter, a scientist with the Delaware
Coastal Programs, said that if scientists knew on what beaches and under
what conditions the shorebirds feed the most, then they could control horseshoe
crab harvests better and concentrate on protecting those areas. They know
now "when" the birds come, but are still learning the details about exactly
what areas are most important to them.
In the spring of 2000
there were a few surprises for the scientists. Among the surprises were
that they found a shorebird that had been previously banded in Brazil and
two birds that were banded last year on the New Jersey side of the Delaware
Bay. They also found that the birds had a wide weight range this spring.
Some of the shorebirds had no fat whatsoever, and there were some birds
whose body weight was half fat!
Jacquie Clark, one of the people from England, had the job of examining the plumage of the red knots and measuring the wings of the red knots. She got to hold each dove-sized red knot in her hands at the monitoring. Sometimes she saw red knots with very thin structures. Their breastbones were sticking out from beneath their feathers. Sometimes she even felt the sharpness of new feathers growing.
After Jacquie Clark looked at the birds, a man named Simon Gillings, an ornithologist from the British Trust, measured the bills of the birds. He measured from the very tip of the bill to the head of the bird. He said these measurements are important because sometimes the body weight of the bird can fool you.
After that, the birds were gently put into a cut-off pipe on a digital scale, where they were weighed. In this process, they found that some of the birds weighed as little as 114 grams. Some of the other birds weighed as much as 180 grams. Jacquie Clark said that most of these shorebirds, before they continue their journey to the Arctic, would weigh in the range of 200 grams to 220 grams. She commented, “They weigh so much that they can scarcely fly. They are just like butterballs.” Scientists keep track of the height and weight of the birds, just like our doctors keep track of us on human growth charts.
Then, the shorebirds were handed to the banding team. Color-coded bands were put on the birds.
photo permission: David Carter
The
picture above is a shorebird called a redknot. This redknot was banded
in Tierra del Fuego, Argentina, and was caught 2 months later at Mispillion
Harbor in Delaware. Mr. Carter picked this bird to photograph because it
was banded in the farthest place south that the birds travel. As for the
colors of the flags, green is for the U.S., orange is for Argentina, blue
is for Brazil, and white is for Canada. (Mr. Carter had never seen one
of the white bands before this year, because it's very hard to find the
birds in their nesting area and very few have been marked with a white
flag.) The flag colors never change. The 2 lower color bands give specifics
about the site and year the birds were banded.
Mr.
Carter, who was helping with the banding, commented that in the 5 years,
including this one, that they have been monitoring the birds, they had
never seen the birds as large so early in the season before! He thinks
that the weather played an important role. Scientists believed that last
year when the birds arrived, a little later than usual, they never gained
enough body weight for their trip to the Arctic. They think that
the birds were a little later than they usually were due to having to migrate
through very stormy weather. They also think that they didn’t gain enough
body weight because they had a short stay. It had nothing to do with the
lack of horseshoe crab eggs. People in Delaware had documented that there
was a super abundance of eggs available. Although the shorebirds were light
in weight the previous year, they left the bay on time - near the end of
May. Carter speculates that because of the excellent weather this past
year, the shorebirds arrived more on time. He said this past spring
they caught birds that weighed more than the birds that left last
year. He also mentioned that the warm temperature early in May may have
led to the early heavy horseshoe crab spawning that fattened them, and
many birds may have been in exceptionally good shape in 2000 due to not
breeding succesfully in 1999, and having spent more time fattening up in
the wintering areas of Argentina. In nature, Carter says, the shorebirds
have good and bad years, much like our stockmarket and economy.
Now that you know the process of monitoring shorebirds, you must realize
it is important to keep scientific records of these birds. We can't just
guess about their health and their numbers. We must have facts.