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Unveiling the Secrets of Balearic Shearwater: From Behavior to Conservation

The Balearic Shearwater, scientifically known as Puffinus mauretanicus, is a bird species that belongs to the shearwater family. This species is a pelagic seabird and is found in the Mediterranean Sea and Eastern Atlantic Ocean.

In this article, we will delve into the identification of the Balearic Shearwater, including field identification and similar species, as well as plumage and molts.


Field Identification

The Balearic Shearwater has a distinct appearance that sets it apart from other birds. This species measures around 30-38cm in length, with a wingspan of 71-83cm.

It has a dark “M” shape on its upperwings, which is a defining feature of this bird. The head and upperparts are dark brown, while the underparts are white.

The legs and feet are pale pink, and the bill is black. The bird’s eyes are dark, and there is a light-colored crescent-shaped patch around the eye.

Similar Species

The Balearic Shearwater is similar in appearance to other shearwater species, which can make it challenging to differentiate. The Yelkouan and Manx shearwaters are two species that closely resemble the Balearic Shearwater.

However, the Yelkouan Shearwater has a paler “M” shape on its upperwings, while the Manx Shearwater has two white patches on its upperwings instead of the “M” shape.


The Balearic Shearwater has two primary plumages: breeding and non-breeding. During the breeding season, adults have a darker plumage, with a grey-brown head, and some birds develop a white throat patch.

The underparts are white and the upperparts are brown. During the non-breeding season, the plumage of adult birds fades to pale-grey, and the throat patch disappears.


Shearwater species undergo a unique molting process, which can sometimes cause confusion when identifying these birds. The Balearic Shearwater has a partial pre-alternate molt, which leads to plumage differences between breeding and non-breeding conditions.

During the pre-alternate molt, the bird replaces its innermost primaries and central tail feathers, which are retained through the breeding and non-breeding plumages. The retained feathers enable the bird to conserve energy and optimize its physical endurance during long flights over the open ocean.

In conclusion, the Balearic Shearwater is a fascinating bird species with unique characteristics. We have explored the field identification and similar species, as well as the plumage and molting patterns of this bird.

Understanding these features can help with accurate identification of the Balearic Shearwater and provide insight into its life cycle and behavior.

Systematics History

The Balearic Shearwater, also known as Puffinus Mauretanicus, first gained the attention of naturalists in the late 19th century. Since then, extensive studies have been conducted on the species, with the aim of understanding their systematics and evolution.

Through these studies, researchers have been able to identify the genetic and morphological changes that differentiate the Balearic Shearwater from other shearwater species.

Geographic Variation

The Balearic Shearwater is a widespread species, found primarily in the Western Mediterranean and adjacent Atlantic waters. Individuals breed on rocky islets of the Balearic Islands, Columbretes, and the Chafarinas archipelago, as well as on the south coast of France.

During the non-breeding season, they are widely dispersed throughout the Atlantic and Mediterranean Oceans. The populations of Balearic Shearwaters are relatively stable, although there are variations in their distribution.

For example, during the breeding season, birds from the Balearic Islands tend to migrate to the Atlantic, whereas those found in the Chafarinas and Columbretes spend the winter in the Mediterranean.


Several subspecies of the Balearic Shearwater have been identified, based on their geographical location and morphological differences. These subspecies are named after their breeding locations:


Puffinus mauretanicus mauretanicus: This subspecies breeds in the Balearic Islands. 2.

Puffinus mauretanicus bannermani: This subspecies breeds on the Chafarinas Islands, off the coast of Africa. 3.

Puffinus mauretanicus olsoni: This subspecies breeds on the Columbretes Islands, off the coast of Spain. Research has shown that these subspecies differ only slightly in their external appearance, and there is minimal variation in their vocalization patterns.

The subspecies’ genetic analysis demonstrates that they are all closely related and form a single panmictic population.

Related Species

The Balearic Shearwater shares a lot of similarities with other shearwater species, particularly those found in the Atlantic Ocean. These species include the Cory’s Shearwater, Manx Shearwater, and Great Shearwater.

However, recent genetic studies suggest that the Balearic Shearwater is most closely related to the Yelkouan Shearwater, which is mainly distributed in the Mediterranean Sea.

Historical Changes to Distribution

Over the years, the distribution of the Balearic Shearwater has seen significant changes, mainly due to human activities. During the 20th century, hunting and the introduction of mammal predators led to a decline in the species’ population.

Additionally, habitat destruction and pollution have had a significant impact on the birds’ breeding grounds. Conservation measures have been put in place to mitigate the challenges that the Balearic Shearwater faces.

These measures include the enactment of laws prohibiting hunting, reduction of human disturbance on breeding grounds, and the restoration of breeding sites. Recent evidence indicates that these measures have resulted in an increase in the species’ population.


In conclusion, the Balearic Shearwater is a unique species that has undergone extensive study over the years. Its fascinating systematics history, including the identification of its subspecies and related species, has provided valuable insight into the evolution of the species.

The changes in the species’ distribution patterns over the years also highlight the need to prioritize conservation efforts. Ultimately, the Balearic Shearwater serves as an excellent example of how scientific knowledge can be used to protect and preserve the natural world.


The Balearic Shearwater is a pelagic species, and its habitats are primarily offshore. During the breeding season, they nest on rocky cliffs and islets in the Mediterranean and nearby Atlantic Ocean.

The nests are made of soil and grass, and the female lays a single egg per breeding season. After hatching, chicks are fed a regurgitated oily food mixture that is rich in protein and fat.

Because the Balearic Shearwater is a pelagic species, it spends most of its life at sea. These birds are often observed over deep waters, where they feed primarily on small shoaling fish and squid.

They prefer warm water ranging from approximately 16 to 27 degrees Celsius, and their distribution is influenced strongly by sea-surface temperature.

Movements and Migration

The Balearic Shearwater is a migratory bird and undertakes broad-scale movements throughout the year. After breeding, they embark on long migration journeys and travel to different areas in the Atlantic and Mediterranean Oceans to feed.

During the winter months, the Balearic Shearwater leaves its breeding sites and flies to the central Atlantic, where they congregate over the 3000 m depth line. It is thought that these birds undertake a three-stage migration pattern, beginning with a pre-migration movement, followed by a long-distance migration phase, and finally, a post-migration dispersal phase.

Adults do not return to breed until they are around five years old. Juveniles undertake their first migration when they fledge from the nest.

Studies suggest that these first-year birds spend their first few months on the African coast, before heading out to open ocean. It is still unclear whether these birds return to their breeding sites or remain in the open ocean until they are mature enough to breed.

The movements of the Balearic Shearwater are dependent on a range of environmental factors, including currents, wind direction, and weather patterns. For example, strong westerly winds can carry Balearic Shearwaters far from their typical migration routes, and the species can be found as far north as Newfoundland and Iceland.

Conservation Implications

The migration and movement patterns of the Balearic Shearwater highlight its vulnerability to a range of threats, including climate change, fisheries, and habitat degradation. Climate change is expected to alter ocean currents, which could have significant impacts on the species’ distribution and movement patterns.

Furthermore, the Balearic Shearwater is also threatened by bycatch in various fishing gears. Conservation measures aimed at reducing the impacts of fishery impacts have been put in place, including the adoption of best practice guidelines and the use of mitigation measures such as tori lines.

Additionally, efforts such as marine protected areas have been developed to safeguard breeding sites and feeding grounds.


In conclusion, the Balearic Shearwater is a remarkable bird species that undertakes extensive movements throughout its life. Its breeding, feeding, and migration habitats are widely dispersed across the Atlantic and Mediterranean Oceans.

The species’ migratory behavior and dependence on multiple habitats highlight its vulnerability to a range of threats, including climate change and anthropogenic activities. Conservation measures are necessary to minimize these threats and safeguard the species for future generations.

Diet and Foraging


The Balearic Shearwater is a highly adapted species and has several behavioral and morphological features that are well-suited to its pelagic lifestyle. These birds have a narrow set of abilities, which allow them to exploit the sea’s resources efficiently.

Balearic Shearwaters feed mainly on small schooling fish and squid, which they capture by surface plunging by pattering across the surface of the water and diving down to great depths. They are also known to feed on crustaceans and cephalopods.


Balearic Shearwaters exhibit some degree of prey specialization, primarily feeding on a narrow range of fish species. Their diet is known to vary seasonally, with several species of lanternfish remaining a staple in their diet throughout the year.

During the breeding season, Balearic Shearwaters are known to feed on larger fish, such as the flying fish and sauries. Studies suggest that water temperature and prey availability may influence the dietary preferences of the species.

Metabolism and Temperature Regulation

The Balearic Shearwater is a highly efficient organism and has several physiological mechanisms for maximizing energy intake. To meet their energy demands, they rely primarily on the oxidation of lipid reserves.

Their metabolic rates decrease when at rest, and they reduce their body temperature slightly in response to thermal stress.

Sounds and Vocal Behavior


Balearic Shearwaters are known to produce diverse vocalizations that they use as a means of communication. These birds produce a range of vocalizations, including grunts, cackles, coos, warbles, and shrieks, which are used in a range of contexts.

Vocalizations are thought to be important for pair bonding, territory defense, and communication during courtship. The vocalizations of Balearic Shearwaters are used for several purposes.

These include:

1. Courtship and bonding: Balearic Shearwaters use a range of vocalizations during courtship and signaling their commitment to a mate.

For example, males use cackling and warbling vocalizations to signal their availability. 2.

Territorial behavior: These birds use vocalization to defend their territories against intruders. When defending territories, they produce explosive, gurgling vocalizations, which are aimed at aggressive behaviors.

3. Alarm calls: Balearic Shearwaters use alarming calls to warn others of potential danger.

These calls are thought to be produced in response to threats from predators or aggressive individuals. In conclusion, the Balearic Shearwater is a remarkable species that exhibits several adaptations that enable it to exist in a highly specific environment efficiently.

Their feeding and foraging behaviors, diet, and metabolism all play an essential role in their existence. Additionally, their vocalizations and communication behaviors offer fascinating insights into the species’ social interactions and reproductive behaviors.

Further research on these behaviors will be invaluable in devising effective conservation measures for this unique species.



The Balearic Shearwater is an accomplished flier and spends most of its life in the air or at sea. During flight, these birds use their broad wings, which have significant wing loading, to soar and glide over vast expanses of water efficiently.

They are also capable of high-speed, acrobatic flight, and are known to respond quickly to changes in wind direction and speed. On land, Balearic Shearwaters are somewhat awkward in their movements, but are capable of walking relatively long distances on their short legs and webbed feet.

These birds are also highly adapted to underwater swimming and diving, where they use their wings as flippers.


Balearic Shearwaters exhibit several behaviors related to self-maintenance. They are known to preen their feathers actively and to maintain their plumage, which is essential for insulation and flight.

Additionally, when entering and leaving the water, Balearic Shearwaters will shake off excess water to keep from being weighed down.

Agonistic Behavior

Balearic Shearwaters are known to exhibit a range of behaviors aimed at addressing intra and inter-specific conflict. During breeding, the birds engage in ritualized behaviors such as head shaking, beak-poking, and bill-clapping.

They are also known to engage in aggressive behaviors aimed at driving intruders from their breeding sites.

Sexual Behavior

Male Balearic Shearwaters use a range of vocalizations and displays in courtship aimed at attracting a mate. For example, males will produce low-frequency calls that increase the female’s level of arousal, initiating courtship.


The breeding patterns of Balearic Shearwaters have been extensively studied, and researchers have made numerous observations of their breeding behavior. During the breeding season, these birds will arrive at their breeding grounds and select a suitable site for nesting.

After pairing up, the female lays one egg, and both parents will take turns incubating the egg for approximately 50 days. Chicks hatch covered with down feathers, and are fed by their parents over an extended period.

Once the chicks reach their juvenile stage, the parents will abandon them, and they will lose their down feathers and become independent.

Demography and Populations

The Balearic Shearwater has a relatively stable population, although the species is at risk due to human threat pressures on breeding sites and feeding areas. The population in the Balearic Islands is thought to be around 3,000 breeding pairs, with around 200 breeding pairs on the Chafarinas and Columbretes islands.

With the species’ dependence on a narrow range of food types and severe threats from human activities, there remains a risk factor for their population in the long term. To address these concerns, numerous conservation measures have been put in place aimed at protecting these birds.

These measures include the establishment of marine protected areas, the regulation of fishing practices, and habitat restoration efforts aimed at preserving feeding grounds for the birds. These efforts aim to ensure that this unique species continues to exist for future generations to come.

In conclusion, the Balearic Shearwater is a remarkable species with unique behaviors and adaptations that make it uniquely adapted to its pelagic life. Understanding the species’ behavior patterns, breeding stances, and demographic patterns will be vital in designing effective policies to conserve and protect Balearic Shearwater populations, reducing the threats from human activity and ensuring a future for these remarkable birds.

The Balearic Shearwater is a remarkable bird species that exhibits unique adaptations and behaviors that enable it to exist in a highly specific environment efficiently. The article has covered several critical aspects of the Balearic Shearwater, including its systematics history, habitat, diet, vocalization, and behavior, especially locomotion and breeding.

The species’ vulnerability to various threats indicates that responsibility is necessary to minimize these threats and safeguard the species for future generations. Understanding the behavior patterns, breeding strategies, and demographic patterns of the Balearic Shearwater is fundamental in designing effective measures to conserve and protect populations of this remarkable species.

Overall, conservation and protection of Balearic Shearwaters are crucial for the long-term survival of this unique species.

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