Bird O'clock

Soaring Secrets: Exploring the Fascinating Behaviors of Cape Verde Shearwaters

The Cape Verde Shearwater, also known as Calonectris edwardsii, is a medium-sized seabird that breeds on the Cape Verde Islands, a group of volcanic islands in the Atlantic Ocean. This fascinating species belongs to the family Procellariidae and is well-known for its incredible endurance and adaptation to life at sea.

In this article, we will explore the identification, plumages, and molts of the Cape Verde Shearwater.

Identification

Field Identification

The Cape Verde Shearwater is a medium-sized seabird, measuring approximately 36-40 cm (14-17 inches) in length and having a wingspan of 90-104 cm (35-41 inches). Their plumage is mostly dark brown with a contrasting white belly, throat, and undertail coverts.

They have a distinctive dark cap on their head that extends down to their eyes, contrasting with a whitish or cream-colored face. The sheen of their plumage has a bluish tint under direct sunlight, making it possible to identify them from a distance.

Similar Species

The Cape Verde Shearwater can sometimes be confused with other shearwater species, such as the Cory’s Shearwater or the Scopoli’s Shearwater, which are also found in the same region. However, several differences help distinguish the Cape Verde Shearwater from these two species.

Cory’s Shearwater is slightly larger than Cape Verde Shearwater, and they have a more extended bill, a longer tail and more greyish barring on their underparts. Scopoli’s Shearwater, on the other hand, is similar in size, but they have a different bill shape and structure, with a more curved bill tip and a distinct tube nostril.

Plumages

The Cape Verde Shearwater has a distinctive plumage that changes throughout the year due to molting. Molting is the process of shedding old feathers and replacing them with new ones.

The Cape Verde Shearwater undergoes two molts a year – prebasic and pre-alternate. During the prebasic molt, which occurs from June to September, the Cape Verde Shearwater sheds and replaces all of its feathers, including its wing feathers, tail feathers, and body feathers.

As a result, they look much darker during this molt period, with a brownish-black plumage and white underparts. During the pre-alternate molt, which occurs from December to May, the Cape Verde Shearwater replaces only the feathers that are necessary for breeding.

This molt affects the sheen of their plumage, which appears more blueish in color because of the new feathers. Additionally, their underparts are more creamy-white, and their cap color is restored to a darker shade.

Molts

The molting process influences the appearance of the Cape Verde Shearwater. During the prebasic molt, the new feathers will look brighter in color and more contrasting than the old ones, which will be paler and more worn out.

Due to the loss of their flight feathers, the birds become flightless for a short period of time, which leaves them more vulnerable to predators and starvation. During the pre-alternate molt, the Cape Verde Shearwater replaces only the necessary feathers for breeding.

As the feathers grow, they can take on a slightly different shape or size, which can affect the flight and swimming behavior of the bird. Molting is an essential process for seabirds, providing them with the opportunity to replace old and worn-out feathers, which affect their ability to fly, swim, and stay warm.

In conclusion, the Cape Verde Shearwater is a fascinating seabird species, with distinct plumages and molts that affect their appearance, behavior, and survival. The identification of this species can be challenging but the key features such as the dark cap and bluish plumage are some of the prominent features to look for.

Molting is a fundamental process for all seabirds, and understanding the Cape Verde Shearwater’s molting cycle can provide insights into their life history and ecology. The Cape Verde Shearwater (Calonectris edwardsii) is a seabird species belonging to the family Procellariidae.

It is endemic to the Cape Verde Islands, a volcanic archipelago located in the Atlantic Ocean, off the coast of West Africa. In this article, we will explore the systematics history, geographic variation, subspecies, related species, and historical changes to the distribution of the Cape Verde Shearwater.

Systematics History

The Cape Verde Shearwater was first described by British ornithologist Leonard Jenyns in 1842, based on a specimen collected from the Cape Verde Islands. Jenyns named the species after the famous ornithologist William Edwards, who was an expert on the birds of the Cape Verde Islands.

The Cape Verde Shearwater is a member of the genus Calonectris, which consists of four species, including the Cory’s Shearwater (Calonectris borealis), the Scopoli’s Shearwater (Calonectris diomedea), and the Streaked Shearwater (Calonectris leucomelas). The genus Calonectris is part of the subfamily Puffininae, which includes other seabirds such as puffins, guillemots, and murres.

Geographic Variation

The Cape Verde Shearwater is a monotypic species, meaning that it does not have any recognized subspecies. However, there is some evidence of geographic variation in its plumage and measurements, which could be indicative of local adaptation or evolutionary differentiation.

One of the most noticeable differences in plumage is the color of the bill, which can vary from dark brown to yellow. Birds from the southern and eastern islands of the Cape Verde archipelago tend to have a darker bill, while birds from the northern and western islands have a lighter bill.

Another difference is the size of the birds, with birds from the southern islands being slightly larger than those from the northern islands.

Subspecies

Despite the evidence of geographic variation, there are no recognized subspecies of the Cape Verde Shearwater. This could be due to the limited sample size and the lack of detailed studies on the genetic and morphological differences among the populations.

However, future studies could shed more light on the potential subspecies of the Cape Verde Shearwater.

Related Species

The Cape Verde Shearwater is part of a group of birds known as the “little shearwaters” or the “gray shearwaters” that belong to the genus Calonectris. This group includes three other species:

– Cory’s Shearwater (Calonectris borealis)

– Scopoli’s Shearwater (Calonectris diomedea)

– Streaked Shearwater (Calonectris leucomelas)

These species share many characteristics with the Cape Verde Shearwater, including a similar size, wing shape, and foraging behavior.

They also have a similar plumage pattern, with a dark cap and contrasting white underparts. However, each species has its unique features, such as bill shape, tail length, and vocalizations.

Historical Changes to Distribution

The Cape Verde Shearwater is endemic to the Cape Verde Islands and has a restricted range, with a total breeding population estimated at around 45,000 pairs. However, there is evidence to suggest that the distribution of the species was much more widespread in the past, with historical records indicating the presence of the species on nearby islands and mainland Africa.

For example, there are reports of Cape Verde Shearwaters nesting on the Desertas Islands, a group of uninhabited islands off the coast of Madeira, Portugal. This suggests that the species had a wider distribution in the past, but the presence of humans and feral animals may have restricted their range to the Cape Verde Islands.

Furthermore, studies have shown that the Cape Verde Shearwater has experienced a decline in population size and breeding success due to a combination of factors, including habitat loss, predation by introduced species, and overfishing of their prey species. These threats have led to the species being classified as “Vulnerable” by the International Union for Conservation of Nature (IUCN) and highlight the importance of conservation measures to protect the species and its habitat.

In conclusion, the Cape Verde Shearwater is a unique and endemic seabird species that has a fascinating systematics history, exhibiting geographic variation in plumage and morphology. There are no recognized subspecies of the species, but further studies could reveal local differentiation.

The Cape Verde Shearwater is also related to other little shearwater species and has experienced historical changes in its distribution due to human activities and environmental factors. Its current status as a “Vulnerable” species emphasizes the urgent need for conservation measures to ensure its survival.

The Cape Verde Shearwater (Calonectris edwardsii) is an endemic seabird species that breeds in the Cape Verde Islands, a group of volcanic islands in the Atlantic Ocean off the coast of West Africa. In this article, we will explore the habitat of the Cape Verde Shearwater and its movements and migration.

Habitat

The Cape Verde Shearwater is a pelagic species that spends most of its life at sea, foraging for fish and squid in the open ocean. However, during the breeding season, which runs from February to September, the birds come to land to breed and nest in colonies on the cliffs and slopes of the Cape Verde Islands.

The breeding habitat of the Cape Verde Shearwater is typically in rocky crevices, holes and ledges, forests, and even in buildings. The breeding colonies are mostly located on steep cliffs and slopes, which provide protection from predators, and overlook the sea.

The birds will often return to the same breeding sites year after year and will form long-term monogamous pair bonds.

Movements and Migration

The Cape Verde Shearwater has a varied movement and migration pattern that is closely linked to the availability of food and ocean currents. During the breeding season, the birds remain in the Cape Verde Islands, where they forage in the surrounding waters and return to their nesting sites at night.

After the breeding season, the Cape Verde Shearwater undertakes a post-breeding migration to foraging grounds off the coast of Mauritania and Senegal, which have highly productive waters and abundant prey. During this period, the birds can travel over 2000 km (1242 miles) northwest to their feeding grounds and back.

The Cape Verde Shearwater is also known to undertake long-distance migrations, particularly during the non-breeding season. Recent studies have shown that the species can travel as far as the coast of Brazil and Argentina, covering a distance of over 5,000 km (3,106 miles) from the Cape Verde Islands.

The birds make this incredible journey aided by the trade winds and ocean currents, which save them the energy required to fly such long distances. The exact reason for undertaking such a long migration is unclear, but it’s believed that the reasons for such journeys could be influenced by factors such as ocean currents, prey availability, and competition with other species.

Climate change is having a significant impact on the movement and migration patterns of the Cape Verde Shearwater, as it is causing changes in ocean currents, sea surface temperature, and prey distribution, which are all factors that influence the species’ movements. These changes could lead to declines in populations and affect the overall health of the ecosystem in which the Cape Verde Shearwater is found.

In Conclusion, the Cape Verde Shearwater, as a pelagic species, spends most of its life at sea, but always returns to land to breed and nest. Its breeding habitat is in rocky crevices, holes, ledges, and forests, while its foraging habitat is the open ocean.

The Cape Verde Shearwater has a unique movement and migration pattern, closely linked to the availability of food and ocean currents, and covering vast distances, including post-breeding and long-distance migrations. Climate change is affecting the movements of the Cape Verde Shearwater, emphasizing the importance of conservation efforts to ensure the survival of the species and its ecosystem.

The Cape Verde Shearwater (Calonectris edwardsii) is a seabird species that breeds on the Cape Verde Islands and spends most of its life at sea, foraging for fish and squid in the open ocean. In this article, we will explore the diet and foraging behavior of the Cape Verde Shearwater as well as its sounds and vocal behavior.

Diet and Foraging

Feeding

The Cape Verde Shearwater is a pelagic predator that feeds on a variety of small marine organisms, including fish and squid. The birds locate their prey by sight and plunge dive into the water from the air to catch their prey.

They are also known to feed on fish and squid that come to the surface at night, using their sharp eyesight to locate the silhouettes of their prey against the dark sky.

Diet

The diet of the Cape Verde Shearwater changes depending on the season and the location of its hunting grounds. During the breeding season, the birds feed on small fish species such as flying fish and sauries that are abundant close to the Cape Verde Islands.

Outside the breeding season, the birds migrate to foraging areas off the coast of Mauritania and Senegal, where they feed on larger fish species such as sardines, mackerel, and squid that are found in the highly productive waters of the upwelling zones.

Metabolism and Temperature Regulation

The Cape Verde Shearwater has a unique metabolism and temperature regulation system that allows it to survive in the open ocean’s harsh conditions and fluctuating temperatures. They have a high metabolic rate, which enables them to digest food quickly and efficiently, but they also have a low core body temperature, which helps conserve energy.

The birds can regulate their body temperature by adjusting their metabolic rate and using countercurrent heat exchange, where heat is transferred from the arterial blood to the veins, allowing it to circulate, preventing heat loss to the environment.

Sounds and Vocal Behavior

Vocalization

The Cape Verde Shearwater is a vocal species that uses a variety of vocalizations during various situations. The birds typically vocalize more in breeding colonies, where they use a range of calls and songs to communicate with mates and offspring.

Some of the vocalizations that the Cape Verde Shearwater is known to make include:

– Contact calls: These are used by birds to maintain contact with each other while at sea and during migration. They are short, high-pitched calls that are repeated at short intervals.

– Alarm calls: These are used by birds when they perceive a threat from predators or human disturbance. The calls are loud and repetitive, acting as a warning to other birds in the colony.

– Mating calls: These are used by males to attract a mate, and they are usually louder and more complex than other calls. Males use these calls to proclaim their availability and to attract females to nest sites.

– Chick calls: These are used by chicks to communicate with parents and beg for food. They are high-pitched calls that increase in intensity and frequency when the chick is hungry.

In Conclusion, the Cape Verde Shearwater is a pelagic predator that feeds on a variety of small marine organisms such as fish and squid. Its diet changes depending on the season and the location of its hunting grounds.

The Cape Verde Shearwater is also able to regulate its metabolism and body temperature to survive in the open ocean’s harsh conditions. Finally, the species has a range of vocalizations, including contact calls, alarm calls, mating calls, and chick calls, which are used for communication.

The Cape Verde Shearwater (Calonectris edwardsii) is a seabird species that shows a wide range of behaviors, including locomotion, self-maintenance, agonistic behavior, sexual behavior, breeding, and demographic characteristics of populations. In this article, we will explore these behaviors in more detail.

Behavior

Locomotion

The Cape Verde Shearwater is a highly adapted pelagic species that is built for long and efficient flights over the open ocean. They have narrow, pointed wings and streamlined bodies that enable them to soar and glide effortlessly over the surface of the sea.

They are also capable of rapid and sustained flapping flight when necessary, such as during takeoff or when pursuing prey. The birds can fly at speeds of up to 55 km/h (34 mph) and can cover vast distances in search of food or breeding sites.

Additionally, the Cape Verde Shearwater can dive underwater to depths of up to 25 meters (82 feet) to catch its prey.

Self-Maintenance

The Cape Verde Shearwater has a range of self-maintenance behaviors that help keep its feathers and body in good condition. These include preening, bathing, and sunbathing.

Preening involves the bird using its bill to clean and condition its feathers, removing any dirt or parasites. Bathing is another self-maintenance behavior, where birds dip into the sea to wet their feathers, again, helping to keep them clean.

Sunbathing is a behavior where birds sit on the rocks and stretch out their wings, enabling them to dry their feathers and remove any excess water.

Agonistic Behavior

The Cape Verde Shearwater shows a range of agonistic behaviors, which are related to competition for resources such as food, nesting sites, and mates. These behaviors include aggressive displays, chasing, and physical interaction, such as bill-pecking and wing-flapping.

Sexual Behavior

The Cape Verde Shearwater shows a range of sexual behaviors related to the breeding season. These include courtship rituals, mate selection, and copulation

Popular Posts