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Black-footed albatross “dynamic soaring” in the breeze near Southeast Farallon Island, 1979.

If someone had told us then that researchers would be putting geo-loggers on birds and using computers to track their wanderings across the ocean in the early part of the next century, we would probably have laughed. But, sure enough, it’s all come to pass and it’s shedding a whole new light on seabirds’ dependence on olfaction.

In a wonderful book, The Seabird’s Cry: The Lives and Loves of the Planet’s Great Ocean Voyagers by Adam Nicholson, the award-winning author takes you through the lives of a dozen seabirds, with revelations about early and recent findings in seabird research.

Black Storm-Petrel @ Tom Blackman

As highlighted by Nicholson, studies show that birds are using their sense of smell at multiple scales and for different reasons. At the ocean basin level, it’s used to find food. Closer to home, they find burrows or nests and it can also help in mate or chick recognition. As stated in an abstract by Milo Abolaffio and his co-authors in a recent paper on shearwater movements:

“After foraging in the open ocean pelagic birds can pinpoint their breeding colonies, located on remote islands in visually featureless seascapes. This remarkable ability to navigate over vast distances has been attributed to the birds being able to learn an olfactory map on the basis of wind-borne odors.”

There’s even anatomical evidence of the importance of olfaction in ocean-going seabirds in that some researchers have shown that the relative size of the olfactory bulb in the brain is especially large in Procellariformes, the order of birds incuding shearwaters, petrels, fulmars, storm-petrels and albatrosses. (1) Gabrielle Nevitt reports that northern fulmars have twice the number of mitral cells (a type of olfactory cell) as rats and six times as many as mice. (2)

Nevitt has “proposed that natural scent cues in the marine environment present guideposts to aid seabirds in foraging and navigation.” Importantly, Nevitt and other researchers have determined that a chemical, dimethyl sulfide (DMS), can be detected by a variety of marine organisms including procellariiforms. And where does this come from? It turns out that DMS is a byproduct of phytoplankton consumption by zooplankton – and when it’s released into the surface waters it volatilizes sufficiently for seabirds to detect it. Apparently, even harbor seals and whale sharks can detect trace concentrations of DMS. In short, it’s an “Eat Here” sign in the ocean environment. She proposes a conceptual model like this in her paper to better understand how an albatross might find an ”odor feature” indicating the potential presence of food.

“It’s an Eat Here sign!”

Anna Gagliardo and her colleagues have done amazing work on Cory’s shearwaters (and its close relatives) in the Atlantic Ocean and Mediterranean Sea. In one group, they used “olfactory deprivation” which consisted of a chemical treatment that temporarily knocked out the birds’ sense of smell for a few weeks. In another group, they attached magnets to disrupt any ability to use the earth’s magnetic fields as spatial guidance. And a third group was the “control” group that had neither treatment. All birds were fitted with GPS data loggers to see where they’d go after being released at specified distances from their breeding islands in the Azores.

The birds with their sense of smell knocked out were essentially unable to find their way back to the island in a timely manner, whereas “all of the control shearwaters were able to fly back to the breeding colony” and all but one of the birds wearing the small magnets made it back just fine.

Other researchers are working on understanding how adult birds can find burrow or nests in wildly chaotic colonies consisting of thousands of pairs of birds. Procellariiforms are known to be smelly birds as a certain musk is infused into their feathers, body, eggs and nest material. It’s thought that these smells help adults and chicks find home burrows or nests.

Laysan albatross @ Tom Blackman

This research into seabird foraging and nesting strategies is complicated because there are surface nesting and burrowing species as well as those species that use “opportunistic” or “commuter” strategies to find food in a vast ocean. That said, researchers are beginning to unravel some of the mysteries to seabird movements.

Aboard Searcher on Baja Whalewatching or on Pelagic trips, you can see both Laysan and black-footed albatrosses as well as several species of shearwaters, petrels, and storm-petrels. Next time you see one of these birds, I hope you’ll think about their amazing ability to fly hundreds or thousands of miles in what we think of as a featureless ocean and yet manage to get to tiny islands that are their homes – and once on land – locate their exact home burrow or nest site.

1. Corfield, J. R. et al. Diversity in olfactory bulb size in birds reflects allometry, ecology, and phylogeny. Front. Neuroanat. 9 (2015)
2. Journal of Experimental Biology 2008 211: 1706-1713; doi: 10.1242/jeb.015412

An arm starting from the trunk of a large adult. Photo by Paul Jones.

Many of you will be familiar with cardón’s northern cousin of the Sonoran desert, the saguaro cactus. While cardón is nearly endemic to Baja, it can be found on the mainland. However, unlike its cousin, cardón is not frost tolerant and is, therefore, saguaro’s ecological counterpart in warmer climes.

On the Searcher tour, the most majestic and impressive cardón forest can be found on the arroyo walk on Isla Santa Catalina. When we stop there, you will want to walk quietly up that canyon as you look at hundreds of individuals towering as high as 50 or 60 feet in total height. Atop the tips of their arms, we will look for birds such as the northern cardinal, white-winged dove, phainopepla, verdin, black-throated sparrow, gila woodpecker, and raven. Not only can hawks nest on the cardón arms, but woodpeckers can drill holes to make nest cavities. The plant responds by creating a callous, which when hardened, makes for a perfect “nest box” for the woodpeckers and owls, such as the elf owl or the rare Cape pygmy-owl. When the plant dies, these callosities can be found on the ground amidst the decomposing pulp and ribs and are known as “desert boots.”

Take a good close look at these wonderful giants on our trip as they are the desert counterparts to the giant sequoias or redwoods of the temperate forest.

An example of a “nursery plant” relationship. This larger individual might be older than 50 years while the smaller ones are “millenials.” Photo by Paul Jones.

Standing at the base of one of these giants, imagine the shallow network of roots which, with the help of a single short tap root, can support as much of 25 tons of weight. These are really slow-growing and long-lived plants. To get started in the harsh desert environment, many species need a “nursery plant” that the seedling grows up next to for protection from herbivores and the sun, and to help with water storage. A seedling might grow only an inch or so per year, meaning a plant that’s a few feet tall could be 40 years of age, which is roughly the age when they start their first arm. Some specimens are thought to be over 300 years old!

Several generations of cardón in a wash on Isla Santa Catalina. Photo by Paul Jones.

You will notice that the arms are fluted, allowing its thick waxy skin to flex like an accordion to take up the rains that fall with the onset of summer storms or chubascos. This allows them to store as much as a ton of water for the dry season. Associated with each ridge is a rib on the interior of the plant and in the middle is the pulp. The epidermis is photosynthetic as this plant has no leaves, just spines and flowers that emerge from the surface of the plant.

The white flowers have a rosy hint, and are in bloom from late winter into June. They open only at night to allow for bats, their primary pollinator, to feed at night. However ‘early birds’ and bees can have at it until the flowers closed up by midday. Once mature, the flowers turn into fruits with a spiny outer layer. These fruits were important to indigenous peoples who used the ribs with small hooks attached at the tip to reach up to the top of the cactus and pull them down. They either ate the pulp or dried it and later poured water through to produce a beverage as it’s purported to have medicinal or palliative effects. In addition cardón can provide a cactus band aid as locals put thin slices of the plant’s epidermis on skin wounds. Cardón ribs were used for a variety of purposes (in addition to the fruit gathering) – fuel for fires, fencing, roofs rafters, wall studs, and even fish spears.