30.04.2018 – Spotting with shearwaters

One of the main indicators of possible marine mammal activity for our spotter is the presence of marine birds. The clues on what lies beneath the deep blue blanket of the ocean can be interpreted in their behavior; if they glide in a compact circle around an area for instance, marine predators may be hunting underwater.

The species that aids us the most in our search for cetaceans is the Cory’s shearwater (Calonectris borealis), the Atlantic cousin of the Scopoli’s shearwater (Calonectris diomedea) that nests in the Mediterranean region. Like several other migratory bird species, these animals are monogamous and travel in pairs and, like several marine predators, they enjoy a diet that includes a variety of schooling fish. Corys opportunistically follow cetaceans that signal not only the potential presence of prey, but also ease the hunt for the birds by bringing the school of fish closer to the surface. This is why we often rely on these birds for our sightings and often approach areas where they assemble in large numbers. Apart from their abundance during sightings, the birds make their presence felt, or better said heard, through their unique calls at night in Madeiras dramatic cliffs, where they nest in large numbers during the summer months.

Under windy conditions at sea our partial reliance on marine birds is often challenged as they also congregate in areas which are more shielded from uncomfortable gusts. In the morning we were able to locate Bottlenose dolphins (Tursiops truncatus) with the help of shearwaters and seagulls near Madalena do Mar. The guests on the afternoon trip were not so lucky; we returned to the marina without cetacean sightings but were able to spot a basking Loggerhead turtle (Caretta caretta).

By Paula Thake

Sightings of the day

Ribeira Brava

10:00 Bottlenose dolphins

14:30 No sighting