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What happened to the red knot rufa population?

ABSTRACT

The red knot of the subspecies rufa is an endangered shorebird. It reproduces in the Canadian Arctic during the month of June. It then flies thousands of kilometres to winter in Brazil, during its first year of life, or in Argentina, during its adult life. Travelling from one end of the planet to the other, this bird is a real athlete.

The red knot rufa population has dropped by 70% since the year 2000! Researchers from across the Americas have come together to study this exceptional bird and find answers to their questions. They followed the red knot rufa along the Atlantic coast: in Argentina, in Brazil, in the United States, in Canada, and even in the Canadian Arctic! Researchers use the capture-mark-recapture method to obtain detailed information about the remaining red knot rufa population.

During its southern migration, the red knot rufa stop in the Mingan Archipelago National Park reserve of Canada (MANPRC) for 2 to 3 weeks. They take advantage of this time to rest and feed themselves before starting their long migration to the southern tip of Argentina. For the adults, this trip can be over 10,000 km long, which means six days of continuous flying with neither food nor rest!

The studies conducted between 2005 and 2010 have demonstrated that the Mingan Archipelago is a very important stopover area for several bird species. It is the only place in North America where young (juvenile) red knot rufa born in the Arctic can be observed. Each year, researchers get an idea about the population’s growth or decline by evaluating the number of juvenile red knot rufa that have survived the arid conditions in the Arctic. This scientific research clearly shows the importance of the studies carried out in the Mingan Archipelago!

During its northern migration from Argentina, the red knot rufa is obliged to stop in Delaware Bay. Once there, it must double its weight in only two weeks if it wants to be able to reach its final destination: the Arctic. To feed efficiently, it must ingest huge quantity of horshoe crab eggs. These eggs are easy to digest. However, overfishing of horseshoe crabs has decreased the available egg supply. It has been prohibited to catch horseshoe crabs in New Jersey, but recovery could take time since it takes on average 10 years before a horseshoe crab is mature enough to lay eggs. Therefore, several red knot rufa do not have enough fat reserve to get to their final destination. They are dying along the way.

A great number of natural and human disturbances are threatening the red knot rufa throughout its long migration. In protected areas, like those managed by Parks Canada, human disturbances are greatly reduced. These havens provide wildlife with suitable habitats and protection from human threats. But thanks to an international effort to create awareness and better understanding of the bird’s decline, collaborative efforts have been undertaken to help the red knot rufa’s population.

Video 1 : Populations

Fact sheet

Genus: Calidris
Species: Calidris canutus
Sub-species: rufa
Common name: Red knot
Size: 23 to 25 cm
Wingspan: approx. 54 cm
Weight: 110 to 215 g
Beak colour: Black
Plumage colour:
Breeding plumage: Grey-brown, speckled with black along the back/Brick red face, chest, and belly
Wintering plumage: Pale grey along the back/White face, chest, and belly

The red knot rufa is a shorebird that breeds in the humid tundra. There are six subspecies, each one representing a distinct population: piersmai, rogersi, roselaari, rufa, islandica, canutus

Each population follows its own migratory route or “flyway”:
Roselaari from Alaska to California and Florida;
Rufa from the Canadian Arctic to Tierra del Fuego in Argentina, flying along the east coast of Americas;
Islandica from the Canadian Arctic to Europe;
Canutus from the north-west of Russia to the to the west coast of Africa;
Piersmai from the north-east of Russia to the west coast of Australia;
Rogersi from the north-east of Russia to the east coast of Australia and New-Zealand.

In early April, the red knot rufa departs from the southern tip of Argentina en route for the Canadian Arctic, where it reproduces in early June.

Though the weather conditions are harsh and food is less abundant, there are fewer predators at this latitude: for the red knot rufa, the long migration represents a survival strategy.

Predators: jaegers sp., snowy owl, Arctic fox, peregrine falcon

Prey: lemmings sp., red knot rufa

There is a correlation between the population cycles of predators and their prey. Populations of birds of prey and lemmings go through ups and downs together, in a cycle that repeats itself every 3 to 4 years. These populations patterns are called biological cycles. To compensate for the decline of such primary prey as lemmings, some predators may turn to the red knot rufa as a food source.

A clutch of eggs begins to hatch at the beginning of July.

The adult females usually begin flying south a few days after their eggs have hatched, thus avoiding the migrations of predatory birds that will be taking the same flyway a few weeks later. Unfortunately, the same cannot be said for their young, who will have to contend with these predators during their own migration.

The females will remain a few weeks ahead of the others all the way along the flyway. In some years, harsh weather conditions may limit the number of eggs hatched. Without any young to care for, the males may take flight at the same time as the females, in search of a location where food supplies are more abundant.

It’s instinct! – It’s time to go!

First stop is the Mingan Archipelago National Park Reserve.

Video 2: Trophic Relationships, Mingan Archipelago Flats

The yield of primary productivity of the marine environment can impact the richness of the flats. This biodiversity and abundance of food is a primary asset for the Mingan Archipelago.

Upon arrival, the red knot rufa undergo a series of physiological transformations. They will double their weight, from 110 grams to 220 grams, within two to three weeks. The body parts that are responsible for flying, such as the breast, the back muscles and the heart, will undergo a period of atrophy in order to make room for the feeding-related parts of the body, such as the gizzard, stomach, liver, intestines, and leg muscles. The muscles related to the gizzard play an important role as they allow the red knot rufa to crush the shells of the molluscs that are part of its diet. The bird becomes an eating machine.

Amongst the benthic wildlife of this archipelago, the red knot rufa can feed and gain the necessary weight for their next migration.

Trophic network presentation :

  • Producers : seaweeds and micro-seaweeds, phytoplankton;
  • Consumers : periwinkles, zooplankton, scuds, shrimps, mussels, crabs;
  • Consumers: red knot rufa;
  • Consumers : peregrine falcon, merlin;
  • Dead organic matter.

In order to increase their chances of survival against predators, the young learn the importance of moving in flocks across the vast flats, and of staying away from the vegetation surrounding the islands. Moving as a group both in the sky and on the ground is fundamental. Such clumped distribution allows the birds to maintain a heightened awareness of predators, thus reducing the chances of any one bird being caught.

Video 3 : Measuring the Size of a Population, Mingan Achipelago

The red knot rufa population has dropped by 70% since the year 2000.

During the ’80 the population of the red knot rufa was as high as 150,000 individuals. Of the 53,000 birds estimated in 2000, only 16,000 remained by 2010. Researchers around the world have united their efforts to learn more about this endangered bird.

At the Mingan Archipelago National Park Reserve, researchers use the capture-mark-recapture method to obtain detailed information about the remaining red knot rufa population. Once the birds are captured, researchers do the following steps:

  • Blood test for sex determination;
  • State of plumage to evaluate the moulting stage;
  • Beak measurement to evaluate growth;
  • Oral and anal sampling to evaluate the state of health;
  • Weigh the bird to evaluate the fat reserves.

The flag’s color helps to identify the location of the initial capture: white for Canada, green for the United States, orange for Argentina, blue for Brazil and red for Chile. In the future, other researchers will be able to collect data from the red knot rufa without having to recapture them. Certain birds, especially juveniles, about whose movements and ecology little is known, are outfitted with geolocator devices.

Near the end of their stay in the Mingan Archipelago, the red knot rufa have sufficiently augmented their fat reserves for their long flight ahead. However they must first, undergo another transformation which lasts approximately 3 days. Those body parts needed for flight (heart, muscles) recover so that once again, the bird becomes a flying machine.

Video 4 : Human Disturbances

The red knot rufa encounters few protected areas along its flyway. A great number of obstacles exist throughout its long migration. Human disturbances represent a major threat to its survival.

Urban and tourist developments near red knot rufa habitat have been a major source of disturbance.

These disruptions can prevent the bird from feeding properly in order to gain the necessary fat reserves to survive its long migration.

Here is a list of specific human disturbances:

  • Destruction of habitats, unplanned construction and development on the East coast of the United States and Argentina;
  • Disturbances during feeding periods due to an increase in tourism and leisure activities: walkers, runners, fishermen, dogs, ATVs, motorcyclists;
  • Shorebird hunting: in the Caribbean and the central region of Brazil’s north coast.
  • It is likely that a red tide killed over 300 red knot rufa on the Uruguayan coast in 2007.
  • Pollution from hydrocarbons and sea transport: Delaware Bay, -Tierra del Fuego and Gulf of St. Lawrence.
  • Industrial development and industry: Rio Grande and Bahia Blanca, Argentina.

But thanks to an international effort to create awareness and better understanding of the bird’s decline, collaborative efforts have been undertaken to help the red knot rufa population.

Video 5 : Natural Disturbances

Natural disturbances:

  • Increase of the number and strength of tropical storms due to global warming;
  • Diseases and parasites;
  • Predation;
  • Elevation of sea level due to global warming;
  • Increase of precipitations in the Arctic due to global warming.

With the help of geolocator devices, researchers have discovered that certain red knot rufa are able to divert up to 1,000km from their paths to avoid heavy storms. As a result of global warming, tropical storms are stronger and more frequent.

Global warming has increased precipitation levels, which means increased snowfalls in the Arctic. This makes it harder for the red knot rufa to find good nesting conditions. The birds sometimes have to move to higher latitude in search of better conditions, which leaves less time for breeding once they arrive.

Sometimes it’s impossible to reach these higher latitudes, and weather conditions prevent the birds from producing offspring. While the adults have migrated to Tierra del Fuego - which means “Land of Fire” - at the southern tip of Argentina, the young red knot rufa will spend almost a year on the Atlantic coast of Brazil.

The following year, some of the adults en route to Tierra del Fuego will make a short stop in Brazil. The young red knot rufa will take this opportunity to accompany them once they resume their migration to Argentina.

Video 6: B-95 in Tierra del Fuego, Argentina

B-95: Tudo bom? (How’s it going?)

DC-3: Estou numa boa ! (All good!)

B-95: He he he.

DC-3: What’s new with you?

B-95: We just avoided two storms – makes for a long flight but I’ve seen worse.

DC-3: So, Tierra del Fuego – is it like Mingan?

B-95: Well, it’s not a protected area. You need to be on your toes in Argentina. There are much more human disturbances to watch out for.

DC-3: Them again?

B-95: Yeap! Our population keeps dwindling and these scientists strongly suggested that we should be identified as an endangered species, you know! Argentina is the only place along our migratory path where we are all together in one place - makes us easier to count! Everything they learn about you will help other researchers, no matter where you end up.

(Exclamations from the scientists: Oh!)

DC-3: What’s all the commotion about?

B-95: I’m one of the oldest rufa here. Thank’s to my flag, they’ve been following me for 17 years, not to mention that I’ve flown more than 500,000 km – that’s further than going to the moon!

DC-3: Wow!

Video 7 : Overfishing of Horseshoe crabs, United States

In the Delaware Bay, researchers have found a strong link between the red knot rufa and the horseshoe crab, a living prehistoric arthropod.

The horseshoe crab’s eggs are an important source of food for red knot rufa. Unlike molluscs, these eggs have no shell and allow the bird to feed even with an atrophied gizzard. However, overfishing of horseshoe crabs in the ‘90s has decreased the available egg supply.

The horseshoe crab’s eggs per square metre decreased from 33,000 eggs/m2 in 1985 to 3,000 eggs/m2 in 2005, while red knot rufa’s population decline from 100,000 to 17,000 individuals.
Since 2007 it has been prohibited to catch horseshoe crabs in New Jersey.

Barring any further threats, the population should be able to recover, although this could take time since it takes on average 10 years before a horseshoe crab is mature enough to lay eggs.

Video 8 : Breeding and Feeding, Canadian Arctic

Red knot rufa arrive in the Canadian Arctic to breed in early June.

In some years, favourable weather conditions help the red knot rufa find nesting areas that are ideal for their needs, areas which are devoid of snow and the right size for a nest, areas which offer enough ground cover to camouflage them from danger.

After the eggs are laid, both male and female will share nesting duties for the next 22 days.

The eggs hatch just in time for the season’s insects to emerge and provide extra food before the bird’s departure.

In early August, when the young birds are able to fly, most of the males will leave the Arctic for the Mingan Archipelago. A few males will remain with the young for an additional 1 to 3 weeks until they are ready for their first migration.

Video 9: Role of protected areas, Mingan Archipelago National Park Reserve

Human disturbances are greatly reduced in protected areas such as those managed by Parks Canada. These havens provide wildlife with suitable habitats and protection from human threats.

Furthermore, the research that is conducted in the Mingan Archipelago National Park Reserve is part of an international initiative that allows scientists to better understand the ecology of this remarkable bird. In fact, the Mingan Archipelago is the only destination on the red knot rufa’s itinerary where we can get an indicator of breeding success.

Whenever a bird bearing an identification flag is spotted, scientists scour existing records to determine the sex of the bird.

The arrival of both males and females around the same time in the Mingan Archipelago is an indicator of a poor reproductive year for the red knot rufa.

However, when females arrive in the Mingan Archipelago first, to be followed by the males three weeks later, this indicates a good reproductive year.

Such occurrences give us hope that the red knot rufa population will recover one day.

Glossary:

Atrophy

A decrease in size or mass of a body part, an organ, or a tissue.


Biological cycle

Cycle composed of alternating periods of rise and fall in the size of a population. These periods are fixed in duration and are repeated continually.


Biomes

Large regions of the world with distinctive climates, wildlife and vegetation.


Chemical recycling

Natural phenomenon by which decomposers make inorganic matter available in an ecosystem by breaking down organic matter.


Community

Set of populations of different species sharing the same habitat.


Competition

Interaction between living organisms that seek access to the same resource in their habitat. Competition can be:

  • Intraspecific when competition occurs between individuals of the same species;
  • Interspecific when competition occurs between individuals of different species.

Consumers

Heterotrophic organisms that feed on other living organisms. Consumers can be divided in:

  • Primary, or first-order, consumers: herbivores, including granivores and frugivores;
  • Secondary, or second-order, consumers : carnivores eating herbivores;
  • Tertiary, or third-order, consumers : carnivores eating second-order consumers;
  • Omnivores: feed on several orders at once, they feed on producers and other consumers.

Decomposers

Organisms that feed on the waste and remains of other living organisms.


Disturbance

Event that damages an ecosystem. It can lead to the elimination of organisms and alter the availability of resources.


Ecological factors

Aspects of a habitat that can affect the organisms living there. Ecological factors can be:

  • Abiotics (nonliving) when they are of physical or chemical origin;
  • Biotics (living) when they are related to the actions of living organisms.

Ecosystem

Community of living organisms interacting with one another and with the nonliving components of the environment they inhabit.


Food chain

Series of living organisms in which each organism feeds on the one preceding it in the chain.


Geolocator

Tracking device recording data about a bird’s flight. The data are recovered and read when the bird is recaptured.


Habitat

Area inhabited by a species which offers survival conditions.


Juveniles

Young immature birds which are not fully grown or developed.


Population

Group of individuals of the same species, living in a shared space at a specific point in time. These individuals will interact during breeding season. Three main characteristics are used to describe a population: size, density and distribution.


Population density

Number of individuals per unit of area or volume.


Population distribution

Way in which individuals are dispersed within their habitat. There are three main patterns of distribution: clumped, uniform or random.


Population size

Number of individuals in a population.


Population study

Research revealing how various species evolve. It gives an indication as to whether a species is thriving or in decline.


Predation

Interaction between two living organisms in which one feeds on the other.


Producers

Autotrophic organisms with the ability to create organic matter from inorganic matter in an ecosystem.


Red tide

Abnormal algal bloom of toxic plankton named dinoflagellates. Algae become so numerous that they give coastal ocean waters a reddish color. The toxins released by the algae pass from one trophic level to another during feeding periods and might therefore kill animals.


Species

Set of individuals with common characteristics, able to reproduce among themselves and bearing offspring that are also able to reproduce.


Subspecies

Set of individuals isolated from other groups of the same species. Individuals that belong to different subspecies of the same species are capable of interbreeding, but they do not interbreed in nature due to geographic, ecological or anatomical isolation.


Trophic level

Position of a living organism in a food chain. Food chains contain three main trophic levels: producers, consumers and decomposers.


Trophic network

Representation of the trophic relationships in an ecosystem. It is also called food web.


Trophic relationships

Feeding interactions among the living organisms in an ecosystem.



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