20.05.2019 - In the middle of the Sea of Cortez – Isla San Pedro Martir

Since we had calm weather conditions on our way north in the Sea of Cortez, we stopped at the most remote island in the Sea. Isla San Pedro Martir is located 51 km from Baja California and 53 km off the coast of Sonora on the mainland. The island is a UNESCO World Heritage Natural Site and a protected area since 2005. We hope to find a special place with lots of sea birds and are not disappointed. In the morning Isla San Pedro Martir appears as huge white rock in the distance and soon lots of sea birds swarm around the boat. The large bird population deposits enormous quantities of guano, resulting in the white appearance of the island. In the late 19th and early 20th century guano was heavily mined and shipped as far as Europe for use as fertilizer. Additionally the eggs of the birds were collected. As we come closer it is clear that we not only find birds but hundreds of Californian sea lions (Zalophus californianus). We can hear their noises from far away and after we anchor a group of about twenty sea lions show off around the boat. They are really curious and show us a lot of tricks. Later we notice four fishing boats – called pangas – which are looking for fish in the strong current on the northeastern side of the island. They use hook and lines and no nets. This is less invasive than nets and still provides a rich catch. Immediately masses of seabirds surround the fishing boats hoping for leftovers.

The water in the west, south and east of the islands is very green, probably because of the up-welling of very nutritious deep sea water. This nutrients are used by plant plankton organisms to grow. The plankton organisms multiply explosively and that is where the green water color comes from. Only on the northern side we find clear water and can see huge brown algae or kelp and steep rock face under water. The cliffs on the northern side are so steep that we only see a few sea lions.

With the dinghy we drive around the island and discover Heermann’s Gulls (Larus heermanni) and Brown Pelicans (Pelecanus occidentalis californicus) which sit in big groups on the rocks close to the water. Brown Boobies (Sula leucogaster) and the first Blue-footed Boobies (Sula nebouxii) since Galapagos sit scattered on the higher rocks and watch us. We think that they also might breed on the island but can not see any nests. On a ledge we identify a few Double-crested Cormorants (Phalacrocorax auritus). We even discover two Common Raven (Corvus corax) on our trips around the island. Above the island circle Red-billed Tropicbirds (Phaethon aethereus) which might nest high on the island and have a conspicuous high and loud call. Especially in the evenings we can observe groups of birds returning to the island to rest and sleep after looking for food. We think some of them also nest here since the rats were eradicated in 2007 to give them a place to build their nests. Also the collecting of eggs is prohibited. During our first trip we notice lots of walls made out of stones on the steep slopes. We find out that they were made by the Seri-Indians to attract nest building and ease of egg collection. There is only one place to go ashore at the northern side. But this small rocky beach is occupied by a sea lion rookery. At the moment the breeding season starts and the huge males, which can grow up to 2 m and a weight of 380 kg, can be aggressive. According to the internet it is not allowed to go ashore, although on the sign at the small beach it does not say so. On the top of the island grows a dense forest made of Cardon cactus. It really looks like a proper forest from farther away.

In the afternoon we see a cloud of seabirds in the east of the island. As we get closer we can see that the birds hunt for small crabs. When we look into the water we can see them swimming around in large quantities. Those are pelagic crabs (Pleuroncodes planipes) called pelagic red crab or tuna crab and are a species of squat lobster. They grow up to 13 cm and are bright red animals. Lots of Herrmann’s Gulls sit on the water and wait for the red crabs which drift by with the current. With a small movement of the head the birds catch a crab.

The Californian sea lions are very active since breeding season just started. The female ones are preparing to give birth and the biggest males try to conquer a territory to be able to mate with as many females as possible. We decide not to go snorkeling since the males can be quite aggressive. You even hear their loud shouts day and night, with which they want to draw attention to themselves.

After three days we have to continue on our way and have to say goodbye to the wonderful, but also strong smelling and loud scenery of San Pedro Martir.