The Red Knot (Calidris canutus) is a medium-sized shorebird that is found in both the western and eastern parts of North America. It is also known as the robin sandpiper and is a common migrant bird along many coastal areas of the world.
There are 6 subspecies, 3 of which are native to North America, including Alaska and Canada, into the Arctic Circle. The other 3 subspecies are native to Northern Europe and Russia including Siberia. In both cases they make a very long migration south for winter.
Red Knot Characteristics
The red knot plumage changes between breeding season and winter. During the winter months, their feathers are a pale grey on the upperparts and lighter grey-white on the underparts. This is the same across both the sexes. Adults of both sexes have a blackish cap in winter.
Their breeding and summer coat is different. The adult male has an orange-red face and breast during the breeding season, with a mottled brown across their upper parts. Females have a similar coat but less bright and distinctive.
The red knot’s bill is slightly upturned, usually no longer than the size of it’s head. It has a short neck and short, dark often black legs. It is the second largest of the sandpiper birds. In terms of size, they are roughly 23–26 cm (9.1–10.2 inches) in length with a wingspan around double that – 47–53 cm (19–21 inches).
Red Knot Location & Habitat
It typically inhabits mudflats, beaches, and tidal flats, but can also be seen in other habitats such as coastal marshes, pastures, and fields. The red knot is a common migrant bird along many coastal areas of the world and can be found in both the western and eastern parts of North America, particularly at stop off points on their long migration.
During the breeding season, they migrate to the Arctic tundra of Alaska and northern Canada. Here they will nest in dry tundra slopes, usually away from the coasts and surrounded only by sparse vegetation. They may also migrate to the southern parts of the United States, Central America, and South America in winter.
Of the subspecies that breed in Northern Russia and Siberia, they will migrate and winter on the coastal areas of West Africa, or Australia. These are exceptional long flight birds.
Red Knot Diet
The red knot primarily feeds on marine invertebrates, including molluscs, crustaceans, marine worms, and insect larvae. It also feeds on plant matter such as seeds and grains, but will prioritise meat when available. During staging periods, they may feed on terrestrial insects, spiders, and berries. The red knot can be seen in large flocks while they are feeding, where they are often seen probing and pecking in the sediment.
Their biggest and most important food source however, is the horseshoe crab. They require this large food source, and particularly their eggs, to help them put on the weight they need to endure their long migration.
Red Knot Behaviour
The males are first to arrive at a breeding site, and will mark territory with aerial song displays. They may even chase off other males in flight to defend their territory. The song flights are spectacular to witness, with the appearance of some expert choreography. It is believed that these birds are completely monogamous, but it is not clear if this carries over from season to season.
When traveling south for winter, red knots gather together in large flocks, and they will eat and sleep within these flocks. These are wading birds, and are known to both forage and rest in shallow water. Like many other shore birds, they will often rest on one leg, in shallow water, especially when roosting. The other leg is held up close to their body. They are diurnal birds, with most of their activity occurring during daylight hours.
Red Knot Reproduction
The red knot is a monogamous species and typically mates for life. During the breeding season, the male and female engage in a courtship display which involves preening and bill raising, as well as a ritualized running display.
The male will select 3 to 5 sites suitable for scraping a nest, then the female will choose one from the selection. The female will then prepare the chosen site with a ground nest, scraping a depression into the ground and lining it with the leaves and twigs from the surrounding willows, avens and sometimes mountain heather.
The female usually lays two to four speckled, olive-brown eggs in their scraped out ground nest. The eggs are incubated for 20-25 days, with both parents taking turns while the other forages. Once hatched, the chicks develop quickly and after the first day, they are able to leave the nest and forage with their patents. By their fourth week the chicks are able to fly and become independent.
Mothers will leave the site usually before the chicks have fledged, but the fathers stay on site until after their young have fledged. They will then set off alone, leaving the young to take their first migratory flight independently.
The red knot has an average lifespan of between 7-15 years in the wild, depending on a number of environmental conditions and human encounter. Some individuals have been recorded living up to 20 years.
Red Knot Predators & Threats
In general, the red knot is preyed upon by various species of birds, such as jaegers, owls, hawks, gulls, and skuas. Large birds of prey such as peregrine falcons are also a threat outside of their breeding grounds. Other land predators such as foxes and raccoons will take advantage of any opportunity that comes their way for a red knot meal too.
As well as the threat of predation, the red knot faces a range of different threats from human and environmental pressures. Climate change has a significant impact on their northern, coastal breeding grounds. Sea level rises and coastal erosion around their Arctic range are destroying their habitat, and fast.
Other human threats include unsustainable fishing practices, particularly of their major food source, the horseshoe crab. With less food, and less suitable breeding ground, the pressure is on for these birds.
Red Knot Conservation Status
Red Knots are not considered to be a species under threat yet, but they are listed as Near Threatened on the IUCN Red List. Some subspecies are more at risk than others however. All three of the subspecies that live in North America are in decline.
The Red Knot Rufa for example is listed as federally threatened on the United States Endangered Species Act with a rate of decline that may push the bird to extinction. In 2003, it was expected that the bird may only have a decade left. As of 2022, they are still an extant subspecies.
One measure of protection that has been introduced to try and alleviate some pressure from these birds, is the limiting of horseshoe crab harvests for human consumption. These birds are also protected by the AEWA agreement, in which signatories have responsibilities to protect the species from hunting, monitor the population numbers and to establish protected areas for the species.
Amazing Facts About The Red Knot
- The Red Knot has one of the longest migrations of any bird. One subspecies, the Calidris canutus rufa or Red Knot Rufa, travels almost 20,000 miles each year. They make a 9,000 mile (14,000 km) journey from the Arctic Circle to the other side of the world at the southern tip of South America. Then for the breeding season, they make the journey back.
- To prepare them for the long migration, these birds will reduce the size of their digestive organs, and take on lots of weight to fuel the trip.
- Red Knots have nerve-endings in their bill that help them to find molluscs buried under wet sand.
