{"id":580,"date":"2018-03-06T13:03:00","date_gmt":"2018-03-06T13:03:00","guid":{"rendered":"https:\/\/whalewatchingazores.com\/blog\/2018\/03\/06\/corys-shearwater-different-matter-over\/"},"modified":"2022-12-16T12:30:48","modified_gmt":"2022-12-16T13:30:48","slug":"corys-shearwater-different-matter-over","status":"publish","type":"post","link":"https:\/\/whalewatchingazores.com\/blog\/corys-shearwater-different-matter-over\/","title":{"rendered":"Cory\u2019s shearwater, a different matter over the sea"},"content":{"rendered":"
During winter time, even though we have great whale watching tours and encounters we can\u2019t forget a very good friend of us, the Cory\u2019s shearwater<\/a> or the \u2018cagarro\u2019 as we call them in Portuguese. This beautiful marine birds start accompanying our tours since middle spring to middle autumn, their fly is very special as they enjoy to touch with their wings the surface of the ocean and they lead us very often to different species of dolphins (mainly common <\/a>and also a summer time species the spotted dolphin<\/a>).<\/span><\/div>\n
Let\u2019s now learn a bit more about this very special species: who they are, which their main characteristics are, how their migration routes are and what the threats they face nowadays.<\/span><\/div>\n
We have compiled some information about this birds, as we think they deserve a bit of attention, even though they are not cetacean this is a very attached species to our whale watching tours.<\/div>\n
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Who are these Cory\u2019s shearwaters?<\/span><\/h2>\n
The Cory\u2019s (Calonectris borealis) is a large shearwater in the seabird family Procellariidae. Named Cory\u2019s in English because of the American ornithologist Charles B. Cory<\/a>. <\/span><\/div>\n
It is a very symbolic migratory seabird of the Azores, as it covers the world\u2019s largest breeding population of the species (Fig 1). They live in the open ocean, ranging from neritic zones (areas with water less than 200 meters deep) to continental shelves, and only come ashore during the breeding season.<\/span><\/div>\n
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Fig1: Cory\u2019s shearwater abundance. Graphic by Victor Martin<\/figcaption><\/figure>\n<\/div>\n
Their open ocean habitat covers warm waters of that are connected with high productive ecosystems[1]<\/span><\/a>, such as ocean fronts[2]<\/span><\/a>, deep-water springs and continental shelves[3]<\/span><\/a>.
\nThis creates a food source for many marine animals, like the Cory\u2019s shearwate<\/a>r. <\/span>This species has a complex system of sounds. The sounds are only produced during the breeding season, in their breeding colonies. Males only produce high-pitched tones while the females produce more deep tones. <\/span> This sounds have a very particular tone that can be heard specially at night time close to the cliffs were they nest.<\/span><\/div>\n
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Foto by Mariana Silva<\/figcaption><\/figure>\n

The genus name Calonectris<\/strong> comes from the classical Greek words kalos, meaning “Good<\/strong>” and nectris meaning “swimmer<\/strong>“. And, as might be expected, the Cory\u2019s shearwater <\/a>is a great swimmer! The species has webbed feet as well as long and straight wings that are adapted to allow the birds to use the updrafts of wind on the waves to \u201cshear\u201d over the water\u2019s surface (hence the name \u201cshearwater\u201d). <\/span>But, not only the wings are perfectly adapted to an oceanic lifestyle, the species is also adapted to drink seawater due to the existence of highly developed nasal tubes. They have desalination glands that extract and dispose of the salt. This is reason why this birds can spend months in the ocean without coming back to land. They also have an unusually strong sense of smell. This is very handy, since they can find their food over large ocean surfaces and also relocate their colonies.<\/p>\n<\/div>\n

<\/a>Cory\u2019s shearwaters<\/a><\/span> and common or spotted
\ndolphins or even other species like tunas are very often seen around the Azores, and also on our whale watching tours, all feeding together in a \u2018feeding area\u2019 were the dolphins surround the school of fish forcing them to \u2018make\u2019 a ball and other species including Cory\u2019s profit of this feast diving directly into the ball of fish.<\/span><\/div>\n
The diet of Cory\u2019sshearwaters<\/a> in the Azores has been studied and found to be very diverse. Several species of octopus, squid, fish and crustaceans have been found in their stomach contents. The birds are able to catch these prey by diving up to 15 meters deep using their wings as flippers!<\/div>\n
When they are not feeding this birds rest on the surface of the ocean, creating big island of birds that are just \u2018floating’, it is something very beautiful just to observe them taking off using the water as a runway with their legs!<\/span><\/div>\n
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Albert Cama<\/figcaption><\/figure>\n<\/div>\n
This marine bird has a \u201cMediterranean cousin\u201d, the Scopoli\u2019s shearwater<\/strong> (Calonectris diomedea).<\/div>\n
For a long time researchers thought that the Cory\u2019s shearwater<\/a> (Calonectris diomedea borealis) was a subspecies from Scopoli\u2019s (Calonectris diomedea). But now, they are considered by researchers as two different species. <\/span><\/div>\n
Although their appearance is very similar, they still have important differences that result in them being distinguished as a separate species: <\/span><\/div>\n
The most important difference is their different and very marked breeding distribution<\/strong>:<\/span><\/div>\n
\u2022   <\/span>Scopoli\u2019s shearwater<\/span> Mediterranean distribution: <\/span>Algeria, Croatia, France, Greece, Italy, Malta, Spain (excluding the Canary Islands), Tunisia and Turkey.<\/span><\/div>\n
\u2022    <\/span>Cory\u2019s shearwater<\/a> <\/span>\u00e0<\/span> Atlantic distribution: <\/span>Portugal (including the Azores, Madeira and Berlengas) and the Canary Islands. <\/span> <\/span><\/span><\/div>\n
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Fig 2: Geographical breading area of Scorpoli\u2019s and Cory\u2019s shearwater.<\/figcaption><\/figure>\n<\/div>\n
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Also their size<\/strong> is quite different:<\/span> the Cory\u2019s shearwater<\/a> has a bigger body-mass than
\nthe Scopoli\u2019s shearwater, with the different being about 46 percent.<\/span><\/div>\n
Genetics<\/span><\/strong> are a very important parameter to indicate if the species are different or not: figure 3 shows the two different populations based on genomic differences. The Scopoli’s shearwater is shown with a blue colour throughout the Mediterranean Sea and the Cory’s shearwater is shown by a red colour in the Atlantic Ocean.<\/span><\/div>\n<\/div>\n
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Fig 3. Population genetic structure of Cory\u2019s shearwater. Munilla I. et. al. (2016)<\/figcaption><\/figure>\n<\/div>\n
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However, genetic material gets mixed between both species if one individual travels from one population to another (e.g. from Baleares Islands to Azores Islands). This event is called gene flow<\/strong>, but in this case the gene flow is low, allowing us to think that there is not a big hibridation between the two species.<\/span><\/div>\n
There is another characteristic that the researchers use to differentiate the two different species, the bird song<\/strong>. Even though they use their special song for the same purposes: simple vocalization for calls and complex for mating, the sound between the two species is different, being the one of the Cory\u2019s with three syllables and the Scopoli\u2019s using two:<\/span><\/div>\n
Don\u2019t miss theirs incredible singing! Can you notice the difference?<\/span><\/div>\n