Far from Land: The Mysterious Lives of Seabirds. Michael Brooke. 2018. Princeton University Press: Princeton, New Jersey.
An interesting article in a recent British Birds (Smith 2018) describes how British ornithologists have tracked migrating Red-necked Phalaropes that breed in the Shetland Islands north of Scotland. In fall, these phalaropes first flew to the waters near the Outer Hebrides somewhat near the Shetlands, and then proceeded to the seas off northwestern Ireland. Instead of heading south, they flew far west across the Atlantic to Newfoundland and the Bay of Fundy in North America. Some of the tracking maps showed birds that were also along the coast of New England. From here they flew south along the coast of the United States, then across the Caribbean, most crossing Cuba. Then they crossed Panama to eventually winter off the coast of Ecuador. That means there is a slim chance that a Red-necked Phalarope you saw in Massachusetts waters in late summer could have originated in northern Scotland. This is a complicated migratory route that could not even have been guessed ten years ago. The ornithologists were able to precisely track these birds, who spend most of their non-nesting time far out at sea and out of sight, with tiny geolocator tags mounted on the birds' backs. Scientists retrieved the geolocators from the birds when they returned to the Shetlands to breed, and within an hour of retrieval they were at their laptops using a migrate technology decoder to look at maps the birds routed. This study published in British Birds has just reaffirmed earlier studies that are described in Far from Land.
Michael Brooke is the Strickland Curator of Ornithology at the University Museum of Zoology, Cambridge. He has spent his life as a seabird biologist, beginning when he became a seabird assistant at Fair Isle "in that interval between school and university." (p. ix) Far from Land is his latest book.
Far from Land begins with an interesting overview of what species Brooke defines as "seabirds." This includes all tubenoses, alcids, cormorants, gannets, frigatebirds, tropicbirds, pelicans, gulls, terns, skuas, and phalaropes. What all these species have in common is that they spend most of their life at sea, often out of the sight of ornithologists. Because scientists could only study birds on their nesting areas, and sometimes even those were on remote islands, there were huge gaps in our knowledge of the movements and behaviors of many of these species. In some cases we didn't even know where they bred. This all began to change, first slowly and then more rapidly, beginning 20 years ago with the use of sophisticated electronic monitoring devices.
"Modern electronics are revolutionizing our knowledge of the activities of seabirds at sea." (p. 1) Far from Land describes what we now know of what seabirds do at sea, and at the same time traces the evolution of the methods and devices by which we have gained that knowledge as well as the hard-working scientists who study the seabirds.
One of the most basic questions to ask about a seabird is: "where is it when it's not nesting?" Traditional ringing (banding) had only a limited use in answering these questions. A bird ringed at a nesting colony might be retrieved on the wintering ground, but we would have no idea where the bird was in between these two locations. Then came radio telemetry and radar and even the use of thermal imaging. New Zealand Petrels were thought to be extinct but were rediscovered in 2003. At that point we knew they were alive but had no idea where they nested. Scientists using radio telemetry discovered New Zealand Petrels' nesting burrows in 2013 on Little Barrier Island. Black-capped Petrel nesting areas in the mountains of Hispaniola have been found using thermal imaging and radar. But this was only the beginning of the electronic revolution in seabird monitoring.
"The overall impacts of VHF radio telemetry and radar have been slight compared to what has been learned from satellite telemetry." (p. 19) Satellite telemetry, or PTTs—platform transmission terminals—offers an accuracy of around 500 meters in locating the position of the birds and has been used in many seabird studies. Global positioning systems (GPS) are even more accurate and give the researcher more detailed information about where a bird flies. The one drawback is that the device needs to be retrieved from the bird in order to download the data stored on the GPS tag. Geolocators or GLS devices—global location sensing—are also used. They are cheap, weigh one gram, can run for two years, and can show the time of sunrise and sunset where the bird is located. Drawbacks are that their latitude information is poor around the equator and they are not as accurate as PTTs. These are just a few of the modern devices used to show us where seabirds travel.
We may now know where the birds are, but what are they doing while out to sea? Are the birds feeding, diving, or resting on the water? There are immersion loggers that can be attached to the legs of a seabird to tell if the bird was flying or sitting on the water at different times. Capillary tubes attached to seabirds can tell researchers how deep species of seabirds dive.
If the species is bobbing on the sea, it might well dive for food. How deep does it dive? Early in the quest for answers capillary tubes were attached to birds. Because the capillary is sealed at one end, the air within becomes compressed when a bird dives and water under pressure enters from the other end. The deeper the dive, the further the water moves. The movement was recorded by an indicator powder (e.g. icing sugar or water soluble dye) dusted on the inside of the capillary that changes as it gets wet. Thus, when the device is retrieved from the bird, the capillary gives an indication of the maximum depth reached by the bird and the device during the period of attachment. (p. 22)
Other modern devices include time-depth recorders that digitally record the data of how long the bird spends under water and how deep it dives.
How successful are the seabirds at catching prey on every dive? Technology originally developed for use on Weddell seals glues a "reed-contact and magnet" to the mouth that records when the electrical contact is broken when the seal or bird opens its mouth to chomp on some prey item. This has now been used in studies of penguins and cormorants. Small cameras (45 grams) have even been attached to the central tail feathers of gannets to record their interactions with fishing vessels. Far from Land describes well the details of even more technology used to investigate seabirds' lives. Just as we have witnessed an electronics revolution in data storage and presentation in the last two decades, ornithologists and other biologists have also seen a revolution in monitoring electronics. Everything has become more powerful, smaller, and more precise. But it's not just all about the electronics and other measurements that can be recorded using tissue samples. Non-electronic methods, such as stable isotopes extracted from minute samples of a bird's blood, muscles, bones, or feathers can provide supplementary information on diet and travels. (p. 45)
From the data, a picture of mastery emerges. Seabirds are not helpless morsels of life tossed hither and thither by wind and waves. Rather they employ strategies that enable them to cover huge distances and detect scattered food with relative ease, and with the advantage that they are less subject to day-to-day predation than are landbirds. (p. 27)
In each of its chapters, Far from Land follows different species through their lives, beginning with the birds' first trip out to sea from the colonies where they were hatched, through their acquisition of flying skills, to their first flights at sea. For many species, their immature years were considered lost to ornithologists because we knew nothing about where they went beyond the occasional anecdotal sighting. Species like albatrosses can fly around for a number of years before they are mature enough to breed. But where do they go during these lost years? The new monitoring technology is enabling ornithologists to fill in these formerly huge gaps in our knowledge with precise information. Some of what has been discovered is surprising:
Again using a combination of geolocators and immersion recorders, Jannie Linnebjerg of Lund University found that male Brűnnich's Guillemot [the European name for Thick-billed Murre] parents and their chicks achieved the autumn journey southward of almost 3,000 km entirely by swimming. (p. 33)
When Far from Land turns to seabird migration, the reader cannot help but get caught up in how amazing seabirds are. Short-tailed Shearwaters breed on islands around southeast Australia, including Tasmania. Every year they travel north to the Sea of Okhotsk and the west end of the Aleutians.
Immatures leave the breeding grounds in March, breeders follow in mid-April and fledglings make up the rear guard in late April-early May. The trans-equatorial movement north of perhaps 30 million of these shearwaters is surely one of the world's greatest bird migrations, a fluttering avalanche of 20,000 tonnes of sentient flesh, roughly half the weight of the Titanic. (p. 37-8)
It has been estimated that these shearwaters fly at about 50 km/hr for 20 hours a day, covering on the average 1,000 kilometers a day! Sometimes the distances traveled are difficult to comprehend. Arctic Terns are well-known long-distance migrants, but the distances traveled by certain well-monitored individuals are mind-boggling. This data was discovered using geolocators and a multi-national team of ornithologists that tracked 10 birds from Greenland and 1 from Iceland.
The numbers gathered from these travels are exhausting. The journey totaled at least 72,000 km, comprising 35,000 km southbound at about 330 km/day; 11,000 km while (relatively!) dawdling in Antarctic waters, and finally 26,000 km northbound at 520 km/day. (p 55-6)
Some species of seabirds have evolved specific physiological mechanisms to aid them in their long hours gliding at sea.
Sailors and biologists have long been fascinated by the ability of albatrosses to glide for hours with barely any movement of their wings. A key factor is anatomical; a shoulder lock in albatrosses and giant petrels has the effect of reducing or even eliminating the need for any muscle power to hold the wing outstretched and horizontal. (p. 113)
Gliding over the seas is next to effortless for species like albatrosses, even in heavy weather. As you might expect, researchers have done heart rate monitoring of albatrosses, and their findings are reported in detail in Far from Land.
Languid is the word that comes to mind when watching a gliding albatross. And the efficiency of albatross flight is confirmed by modern heart rate measurements of gliding Wandering Albatrosses. Combining information from externally-attached heart beat monitors, leg mounted immersion recorders that reported whether bird was afloat or airborne, and a satellite pack for relaying the information back to Toulouse in France, French scientist Henri Weimerskirch discovered that the heart rate of flying Wandering Albatrosses, around 80 beats/min, was barely faster than the rate of birds resting on the water, around 60 beats/min. But take-off, involving flapping, was seriously hard work. The heart rate then topped 200 beats/min. (p. 115)
Sometimes in Far from Land the ornithologists are just as surprising as the seabirds they study. For decades, nobody knew where the wintering grounds were of Ross' Gulls, a particularly difficult bird to study because of its Arctic haunts. Mark Maftei, Shanti Davis, and Mark Mallory used data from geolocators and satellite tags to track the gulls' movements. When they delivered their findings at the 2015 World Seabird Conference, it was done partly "in impeccable rap." (p. 59) The lyrics are reproduced in Far from Land. It is now known that Ross' Gulls can be found in winter off Labrador in seas just south of the Arctic Circle, an area rarely visited by researchers at that time.
The last chapter of Far from Land is devoted to all the dangers seabirds face. These include ocean-mounted wind farms, longline fishing, direct pollution of the oceans, light pollution, power lines near nesting colonies, the introduction of predators on breeding islands, and finally, climate change. This explains why so many species of seabirds are endangered or at risk of being endangered. The health of the world's oceans directly affects the health of all seabirds.
If you have ever enjoyed watching gannets plunge dive off the Cape in fall or marveled at the flight of Great Shearwaters on a local whale watch, Far from Land will give you a more complete picture of how these birds breed, migrate, and find food. We only may be able to enjoy these birds briefly from some beach or the deck of a ship, but thanks to the efforts of creative researchers, as well as the evolution of monitoring technology, we can now virtually follow these birds as they leave our sight and wander far from land.
This book has attempted to paint a picture of how modern devices have enabled researchers to discover more about the lives of seabirds at sea. That simple sentence undersells the reality. Posed 50 or even 20 years ago, certain questions would have been totally unanswerable. Now, for many birds, they can be answered with confidence. (p. 203)
- Smith, Malcolm et al. 2018. Further evidence of transatlantic migration routes and Pacific wintering grounds of Red-necked Phalaropes breeding in Shetland. British Birds 111|417-90: 428–37.