Tegan’s Science Notes #9: The Galápagos

Dave RearickAs I write this, I am less than 100 miles from Panama where I will commence a whole new adventure by traversing the Panama Canal. 

I do have a few more observations to share about my time in the Galapagos, but while I write those up, I’d like to hand-off here to our ocean scientist colleague Tegan Mortimer, who will share with us yet another in her wondrous series of “Science Notes” (See them all here!) – this new one on the Galapagos, naturally… as seen through the awesome lens of science! Take it away Tegan!

:: Tegan’s Science Notes #9 – The Galapagos

Tegan MortimerSailors called them the Enchanted Isles because strong currents and swirling mists could cause the islands to disappear and reappear right before their eyes. The Galápagos were made famous by Charles Darwin’s visit in 1835 during his voyage on board the HMS Beagle. The observations Darwin made on the islands had a direct impact on the development of his theory of evolution. Today these islands are still an unmatched source of biological wonder and continue to contribute to our study and understanding of the process of evolution.

Despite straddling the equator, the Galápagos do not have a tropical feel. In fact this archipelago is home to the northernmost penguin colony in the world, the only native penguins to be found in the Northern Hemisphere (though the penguins do spend most their time in the Southern Hemisphere, as only the most northern island is above the equator). You’ll remember from my African Penguins post (again, they are all listed on the Citizen Science page) that the KEY is in the water: cold, nutrient-rich water.

Source: http://cmi2.yale.edu/galapagos_public/data.html

The Galápagos Islands are located in a unique area in which can be found the convergence of several currents of tropical and subtropical waters that upwell around the islands. For a long time oceanographers thought that the cold waters surrounding the Galápagos came from the Humboldt Current (also known as the Peru Coastal Current) which runs along the western coast of South America carrying cold Antarctic water northward. However another type of current, called an undercurrent, which runs below and opposite to a surface current, was discovered in 1956. This current, called the Equatorial Undercurrent or Cromwell Current after its discoverer, is now seen as the reason for the island’s cool waters. The Cromwell Current flows eastward the entire length of the equator in the Pacific Ocean at a depth of about 100 meters below the westward flowing surface currents. As the current approaches the Galápagos, it is forced upwards by underwater seamounts forming an upwelling system. The waters then flow westward again as part of the South Equatorial Current.


There is a reason why Darwin’s visit to the Galápagos (as well as other islands) had such an effect on his ideas about evolution and natural selection. Islands often have a large number of endemic species, i.e., those that are found nowhere else. The Galápagos are no exception to this. But why do islands have so many unique animals? Geologically, the Galápagos are fairly young, they are volcanic islands formed sometime between 80 and 90 million years ago. In that time animals had to colonize the newly formed islands from the closest landmass, which is the mainland of South America, over 500 miles away. Of all the animal colonizers that reached the Galápagos, only a few would be able to survive and establish populations, which are the animals that still survive today – many of which Dave talked about in his updates.


When animals colonize islands, a few things often happen. These animals have been ‘released’ from pressures like competition and predation that they were under in their original locale. so they can quickly diversify to take advantage of the many different ecological niches that are available in their new home. These animals often don’t have to worry about predators any longer so they lose many of their anti-predator behaviors. Dave’s story about the baby sea lion illustrates this very point. The parent seals can leave the babies alone while they go hunting, knowing that no predator will attack the vulnerable babies. It may also help explain why the baby sea lion in Dave’s story came right up to the tour group without any hesitation. Among birds, this absence of predators can account for why birds may become flightless (like the cormorant) or lay their eggs on the ground, just as the blue-footed booby does.

These traits make islands very susceptible to the effects that follow from introducing animals like cats, dogs and rats which can easily prey on native animals. Humans too have had a heavy impact on island populations by hunting some animals to extinction. Luckily, today we have come to realize just how fragile these ecosystems are, which has caused many people and organizations to take up the work of protecting such special and “endangered” places… including the Galápagos.

Darwin’s Finches

There’s one group of animals from the Galápagos that needs a special mention. Darwin’s finches are a group of 15 species of birds found throughout the islands which Darwin specifically mentions in his Origin of Species. In this way, these birds became an important part of the scientific history of evolutionary thought, and as I will explain still maintain an important role in our modern understanding of evolution and the ways humans can impact it.


These birds are the classic example the adaptive radiation I mentioned earlier. A colonizer species to the island, the finches diversified into these 15 species all of which have different shaped beaks, each of which is related to what type of food that particular species eats. These birds are thought to be the fastest evolving animals on earth, which means that researchers can follow them, year to year, and track the natural selection pressures which define which species thrive and which do not.

However, another pressure is being placed on them as well. Human foods, like rice, are now widely available in much of these finches’ range. Birds that feed on human foods can lose the characteristics that make them evolutionary ‘fit,’ as earlier selection pressures are no longer being placed on them. The loss of these characteristics can erode the differences between the various species of finches leading to a loss of biodiversity. So instead of 15 different species, which are highly evolved to eat different food sources, it’s possible we may end up with just a few species that feed on human scraps. It would be tragic loss of such an amazing group of birds.

This study of the finches is actually a research project that my colleagues at Earthwatch are conducting in the Galapagos not far from where Dave moored Bodacious Dream. You can find out more about their project called Following Darwin’s Finches in the Galapagos at the link.

- Tegan 

:: For more exciting science insights and opportunities, please check out our BDX Explorer Guides or stop by our Citizen Science Resources page, where you can also find all of Tegan’s previous Science Notes, Also, we welcome your input or participation to our BDX Learning and Discovery efforts. You can always reach us at …  <oceanexplorer@bodaciousdreamexpeditions.com>

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Tegan’s Science Notes #6 – Seabirds

Dave RearickSome days are made interesting merely by their simplicity. Today looks to be one of those. The last 36 hours have made for some demanding sailing. Even though we’ve made good time, it’s taken a lot of patience and effort as the wind has increased, decreased and repeatedly switched directions. Each one of these changes has required that I adjust the course or trim the sails.

Today by dawn, things had settled down and we are now sailing steadily on course, which both simplifies my life onboard and gives me a chance to catch up on other things.

It’s pretty desolate down here in the Southern Ocean. There appears to be little visible sea life other than the mysterious bioluminescence I see occasionally at night and the plethora of seabirds that accompany me on my journey. For the first few days, there were a dozen or so albatross around, floating like soft music in the wake of the boat. Yesterday, I sailed through a flock of smaller white seabirds, but there were many of them – maybe 100 or so, and they kept up with me for several hours.

so_polar_skuaToday, the crowd has moved on. In its place was one lone, dark brown bird, (I’m going to guess it’s a South Polar Skua) which circled us for quite a while. As if we had entered a courting dance, he would land on the boat, I would chase him with my camera and he would fly off … and shortly resume his same pattern – coming up from behind, drifting a bit, then swooping around behind the sails and stalling just in front of the boat before falling back along the weather side. I would follow him around the boat, probably a couple dozen times before I would give into dizziness and allow him another victory in our simple game.

hemingway_175The days move along out here. I sail, navigate, check systems, watch out for ships, eat, sleep … and repeat. I’m grateful for the routine, as it has given me time to digest some reading material … one of which has been Ernest Hemingway’s Moveable Feast, a selection of short stories of his days in Paris. Two years ago, I found myself in the Lilas Café in Paris that he mentions. I sat on his dedicated stool, watching the many comings and goings of interesting people, just as it happened back in the 1930’s.

In the meantime, our ocean scientist, Tegan Mortimer has another wonderful science note for you directly below here – this one appropriately on seabirds! I strongly encourage you to give it a read. As I watch the birds soar day in and day out, I stand amazed before their beauty and the skill they bring to their aquatic lives.

Sailing along here … oh, let’s see … at coordinates … 46.81776S, 161.104W

- Dave


Tegan MortimerTegan’s Science Notes #6: Seabirds

Of about 9,700 species of birds on earth, only about 350 are considered seabirds. Think about that – 9,350 species occupy only 30% of the surface on the earth while those 350 species of sea bird ply the vast oceans which constitute 70% of the surface of the globe!

What is a seabird?

The definition of a seabird is a tricky one. Many people use the technical definition that a seabird is a bird which feeds in salt water. However, many coastal and wading birds feed in salt water, but aren’t considered seabirds because they don’t spend enough time at sea. However gulls are considered seabirds though they are strictly coastal and return to land regularly.

Sea BirdThe majority of sea birds spend the bulk of their time at sea and only return to land to nest. Therefore they depend on the marine environment for their food and float on the ocean’s surface to rest. The enormous wandering albatross will spend the first seven years of its life at sea before returning to remote islands to breed for the first time.

Who are the seabirds?

I mentioned albatrosses, which are the quintessential seabirds, and gulls which many of us who visit the coast are familiar with. The seabirds also include the petrels, shearwaters, storm-petrels, auks, pelicans, gannets, boobies, skuas, cormorants, shags, frigatebirds, tropic birds and last but certainly not least the penguins.

Many seabirds like the albatrosses and gannets have evolved strong, long wings which allow them to fly long distances without expending much energy, while other seabirds like the auks and penguins have sacrificed flying ability in favor of evolving features which allow for strong swimming ability.

Razorbill and Auk

Auks: Razorbill and Puffin

So what birds has Dave seen so far?

Dave has had some fantastic bird sightings. Unfortunately, seabirds can be very difficult to identify, especially the albatrosses of which I am sure Dave has seen more than one species. But this is the list so far of what we’ve been able to identify.

birds_1-2_named birds_3-4_named birds_5-6_named birds_7-8_named birds_9-10_named

Many of these seabirds are common and widespread in the oceans. In fact, the Wilson’s storm-petrel is believed to be the most numerous bird species in the world with around 12 to 30 million individuals! On the other hand, the gray-headed albatross, cape gannet, and African penguin are classed as endangered because they either have small geographic ranges, small populations or are experiencing significant population declines. So this makes a great list of both common and rare species. Dave spotted a white tern (actually it almost landed on his head!) off the coast of Brazil which is a very unusual sighting for that species in that area.

Dynamic Soaring

Albatross and some other seabirds use a peculiar flying pattern where they make large looping turns which take them up into the air and then they swoop down to almost touch the water and back up again. This is called “dynamic soaring” and it allows these birds to fly without expending much energy. These birds are using the difference in wind speed at different heights to soar. The wind is slower closer to the surface of the ocean due to friction and it becomes faster higher up. The bird starts by climbing up to higher wind speed, and then turns away from the wind and gains airspeed as it soars down the wind gradient. When it turns back into the wind at the water’s surface, the bird has extra energy which allows it to climb back up to higher windspeeds again. Birds which use dynamic soaring have evolved long, thin wings which they hold rigidly in the air as they soar a bit like the wings of a glider.

Dynamic Soaring

Additional Resources:

:: Source and good article: whoi.edu/oceanus/feature/a-robotic-albatross

:: Another interesting article: whoi.edu/oceanus/feature/of-wings–waves–and-winds

Seabird Conservation

While it may seem that seabirds that roam the vast oceans are less touched by human impacts that threaten other bird groups, the fact is that seabirds are the MOST threatened group of birds on earth! Of the 346 species of seabird, 101 species (that’s 29%!) are threatened globally and another 10% are classed as “Near Threatened.” And almost half of all seabirds are known or thought to be declining in population. The albatrosses in particular are the most threatened with 17 of 22 species classed as “Threatened by Extinction.” To put it into a little context, of the 10 species that Dave has seen, 30% are threatened and 70% have declining populations!

What’s happening here? Human activities are the greatest contributor. Historically, many seabirds breed on remote islands that are relatively free from land predators, so they often nest on the ground. When ships would occasionally land on these islands, pests like rats were unintentionally introduced. Rats are very destructive to ground nesting birds, eating both eggs and preying on chicks. Luckily, efforts have been made to eradicate such introduced pests from many of these islands.

Today however, other more menacing threats face seabirds. Drowning in fishing gear is one of the greatest threats to seabirds. In the open ocean, fishermen set long lines, miles of baited hooks, which unfortunately catch much more than the fish the fishermen want. Many seabirds hunt from the air, diving to catch prey they have spotted with their sharp eyes. When these baited hooks lay near the surface the birds take the bait, get hooked, and drown. This situation is bad for the birds, but the fishermen don’t want it either as that is a lost piece of bait. Organizations like Birdlife International are working with fishermen in the most affected areas to modify fishing practices to reduce this “bycatch.” The good news is that simple changes can dramatically reduce the number of birds being caught and lost in this manner.

Another threat to seabirds is marine pollution. Laysan albatross are particularly affected with 97% of chicks being found with plastic in their stomachs. The adults are attracted to plastic objects floating at the surface, likely mistaking them for fish eggs or squid. They carry them back to the colonies where they feed them to their chicks. Forty percent of chicks born each year will die due to plastic blocking their guts or other effects of consuming plastic objects. :

::The heavy cost of marine pollution: ocean.si.edu/laysan-albatross-plastic-problem

Seabirds are majestic, elusive and true ocean wanderers, the lone occupants of the air above the ocean, but they could all too easily disappear from these winds. We all have a role to play to protect the ocean and its life, whether it is learning more about marine debris, attending a beach clean up, buying seafood caught with sustainable practices or any other action which improves the ocean environment for all.

- Tegan

(Tegan Mortimer is a scientist with Earthwatch Institute. Contact Tegan directly at Tegan Mortimer <tmortimer (at) earthwatch (dot) org>)

:: For more great science insights and opportunities, please check out our BDX Explorer Guides or stop by our Citizen Science Resources page, where you can also find all of Tegan’s previous Science Notes. Also, we welcome your input or participation to our BDX Learning Discovery efforts. You can always reach us at …  <oceanexplorer@bodaciousdreamexpeditions.com>

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Tegan’s Science Notes #2 – Wind and Weather

(This is the second in a series of “Science Notes” from from our ocean scientist colleague, Tegan Mortimer, who works with Earthwatch Institute. These postings follow from encounters with nature that I have on the water. Tegan’s first Science Notes was onBird Migrations” – and can be found at the link or on our Citizen-Science Resource Page. Tegan’s Science Notes support our “Learning and Discovery” agenda, which we will keep expanding on over the course of the circumnavigation. Such “custom-made” reports we feel are particularly appropriate for sharing with the younger learners in your world. Please Contact Us if you have questions or suggestions on how we might better serve the interests of young learners and their mentors. Thank you, and take it away, Tegan!)

Today we’re going to talk about a very important topic; wind and weather. Dave spends a lot of time paying attention to the wind and weather patterns that control his journey. There are two types of weather patterns that Dave is confronted with: global weather and local weather.

Let’s start with global weather. These are weather and wind patterns which occur over very large parts of the globe and don’t change very much if they change at all. These are things like the trade winds and the doldrums.

So how does it work? Let’s start with the most basic concept of weather: warm air rises and cold air sinks. Understanding this concept is the first key to understanding weather and wind. Imagine that the air around you isn’t all this one big cloud of, well, air; instead it’s lots of pockets or parcels of air like cushions all packed together. By the way, this same phenomenon happens under the ocean with seawater as well as inside the earth’s core with magma.

Now, going back to the atmosphere, these different pockets can have different properties; different temperatures, different moisture contents and they can move independently of each other. A pocket that’s close to the surface of the earth is going to receive more heat from the earth than a pocket of air higher up in the sky. This warm pocket of air will start to rise and as it rises, it cools down until it reaches a point where it starts sinking again. This process than will start all over again as parcels of air keep going up and down. This movement of air upwards is sometimes called an updraft.

Now what does this all have to do with winds? First we have to imagine that we have a parcel of warm air at the ground. Like a balloon this air is going to rise, but as it rises, its temperature goes down. Eventually this air cools enough that it will start sinking back down. So we end up with our air going up and down over and over.

Let’s imagine this process of air rising and then sinking stretched over a longer distance, so that once the air sinks, it flows across the surface picking up heat until it rises again. The surface of the earth is covered by a series of these rising and sinking cells.

Global Wind Patterns
Source: wiki.flinthill.org

If we look at the diagram above we see that there are three major cell types. I’m going to talk about the Northern Hemisphere here, but it is exactly the same in the Southern Hemisphere - just flipped the other way! Hadley Cells transport air from the tropics towards the equator where it rises and is carried northward aloft. The Ferrel Cells cover the mid-latitudes and carry air which sinks at the tropics north to the Polar Cells which transport cold air south from the poles. This system helps to distribute the excess heat in the equator and tropics out to the mid-latitudes and polar regions.

What you’ll also notice is that this system of circulation gives rise to the major winds, especially the trade winds which Dave has been experiencing, and which are so essential to trans-Atlantic crossings.

Now it’s time to introduce the second major concept: high and low pressure. When you have a steady stream of air rising, it’s not going to be able to sink back down because there is more air pushing up behind it; instead it flow outwards before sinking down again. Where the air rises and disperses is a low pressure and where the air converges and sinks is a high pressure. Air will always flow from an area of high pressure to an area of low pressure. This “pressure” concept is found throughout biology and chemistry as well.

If we look at the equator, between the two Hadley cells, we see that air is traveling towards the equator, rising, and then flowing outwards. This is a Low Pressure area. Conversely, when we look at the area between a Hadley cell and Ferrel cell we see that the air converges aloft, sinks and then flows outwards, this is a High Pressure. What this means is that there is a low pressure all the way around the equator, a high pressure around latitude 30° and another low around latitude 60°. Air naturally flows from areas of high pressure to areas of low pressure. When this is combined with the revolution of the earth you get the major winds.

highs and lowsSource: rgsweather.com

You’ve probably heard about high and low pressures in your local weather reports too. High and low pressure areas occur when the surface pressure is either higher or lower than the surrounding “sea level pressure” which can happen for a variety of reasons. These pressure systems are responsible for most of our local weather. The same process that I described early is occurring here as well, a low pressure is air moving up and away and a high pressure is air moving down to the earth.

The GENERAL RULE is that air flows into a low pressure and away from a high pressure. In the northern hemisphere winds flow clockwise around a high pressure and counter-clockwise around a low pressure, and it’s the opposite direction in the southern hemisphere. Low pressure systems are usually associated with cloudy, wet, and “unsettled” weather while high pressure systems bring dry and clear conditions.

So, let’s finish off with a problem. Below is a picture of winds (taken from a very cool site) which are forming a weather system. Based on this map we can say a lot about the local weather. Are we looking at a high pressure or a low pressure? What types of weather are associated with low pressures? What types of weather are associated with high pressures? What do you think the conditions are like in the area shown?


Let’s break it down based on what we’ve learned. So we are in the northern hemisphere so we can figure out if this is a high or a low pressure based on the circulation of the winds. They are circulating counter-clockwise which means that this is a low pressure. Another clue is that the winds are circulating into a tight center rather than out of an area like we can see to the left. The bolder lines on this map show stronger winds so we can see that there are strong winds around the low pressure and lighter winds around the higher pressure to the west. We also know that low pressures being rain and cloudy weather. So looking at this map we can say that most of the northeastern United States is experiencing rainy or stormy weather with high winds. In fact this is a map showing wind conditions during Hurricane Sandy last year.

(Tegan Mortimer is a scientist with Earthwatch Institute. Contact Tegan directly at Tegan Mortimer <tmortimer (at) earthwatch (dot) org>)

Breezy Angles and Inner Debates

Catching up with you all on the weekend out here in the watery world. Decent breezes and good angles kept us averaging around 9 and 10 knots for most of the last few days – just the right speed for providing you that sense of forward progress! At the moment, as dawn rises on Saturday after the full moon sets, I’m closing in on the waypoint where I’ll start to make the big turn east and set up the final 2200 mile run to Cape Town.

http://goo.gl/maps/V5eeM26.92078W, 29.67041S

After consulting with our weather gurus at Commander’s Weather this morning, it’s looking like I should arrive at the waypoint just about the same time as a passing front that may give me some weather issues, but they don’t look to be really bad ones. The winds will be from the North (by northwest) and then switch to the southwest, but either of those directions should push me towards Cape Town, so that’s good. I may have to endure another day or two of squalls and higher winds, but the results should prove all positive. We’ll see how it all plays out by the beginning of the week. The thing about weather that you have to get used to out here is that it never stops! It just changes either slowly or quickly from one state to another, from weaker to stronger and back again … and those changes may proceed as predicted, or they might not. There’s never a guarantee that nature will play nice with your human plans.

Friday was a great day for drying out things, and I’ve got lots of foul weather gear and clothes strewn around the cockpit to give them a chance to fully dry out.  Regardless of what they say, nothing out here is water-proof and breathable … you’re either sweating faster than it can breathe or the water inevitably works its way through whatever material is covering you. I expect my pants could stand up by themselves with all the salt dried into the weave!!

A toastThe photo on the right here, that’s from last weekend, on the evening after we crossed the equator … when I opened the bottle of Irish Cream that my friend Joe Harris had thoughtfully provided. You can see the splash there … as tradition requires … a little onto the deck as a toast to Neptune, to the good ship that bears you and to this newbie equatorial crosser.

The other night, a visit from a bird initiated what would be a long night’s encounter. It hovered around the high corner of the stern for a while, then flew to the bow and jumped out in front and led us on for a while. Then it circled around a few times before trying once again to land on my head! I got some great photos of him flying by, but I can’t upload them (perhaps) until I get to Cape Town, as our KVH satellite system is out of range this far south of the Equator. Nonetheless, he did land and settled into a spot on the sail that is sitting on the weather rail trying to block some of the water that comes into the cockpit. Not more than 20 minutes later, another bird arrived and did the same thing, this time settling in on the edge of the splash guard where he could check out the first bird. From time to time all night long, they’d get up, fly around, dart in and out of the rigging and then settle back down and rest. Not sure where they might be headed or coming from, but it was nice to have some company through the dark and windy night. I thought all the spray might drive them away, but it never seemed to phase them. We are all clearly a bunch of tough old birds out here.

32.7234W, 1.8690S
Not exactly the bird in the story … similar but different … This one at 32.7234W, 1.8690S

Some days keep you busy, other days, you spend the extra time doing battle with your own mind. Yesterday, I was experiencing frustration with the wind and the instability of the boat, not to mention my desire to just point the bow to Cape Town. A lot of arguments ensued with both sides of the argument being vigorously debated by me, and all of which I won handily. I’ve learned that when frustrations arise, it usually means I’m either tired, hungry or in need of a break in the routine. Last night, I did my best to shut down my thoughts and I spent the night napping in my standard 15-20 minute intervals. I didn’t even try to do any writing, reading or other work, just tried to relax and rest … and this morning, I felt a lot better and pretty refreshed!

Today, Saturday … has been a good day and I’ve only a couple of hours left until sunset. These middle of the day hours, it’s necessary to get out of the cockpit and out of the sun. The cockpit is just too hot, because the sun is behind the boat and the cockpit coverings block the breeze. I generally spend a few hours below doing some work, thinking, napping, reading or writing.

Today has included a bit of everything, not to mention coaxing the wind to increase some, so I don’t have to change sails! If I were racing, I’d be changing sails without question, but today, the sail options all fell into the “overlapping” part of the chart, meaning I could go with any of three different sails. However, if the wind lets up even a knot or two, I really should have the spinnaker up, but if it increases a knot or two, jib and main would be best. I was feeling like I wanted a day off, and as it was almost Sunday, I did my best to talk the wind up a few knots which meant we stayed with what we had up.

Having wiggled my way out of that chore, I did add some water to the ballast tanks to help offset the wind. There are two ballast tanks on each side of the boat – the bigger one is 480 liters and the smaller one 270 liters, which makes for 750 liters total on each side. This ballast water weight makes the boat more stable and faster, and helps balance out the boat against the force of wind in the sails. At capacity then, the weight is roughly equivalent to having 10 guys sitting on the rail.

As I write this, I’m now sailing at about 9 knots which should translate into about 225 miles for the day, which is just what I need to make that waypoint by Monday and still stay ahead of the front! Typically, the winds ease up about sunset, and then come back a couple of hours later. Maybe I’ll have an easy night of it and not have to work so hard. If so, think I’ll go out for a movie and a pizza! (LOL!)

So, on we go…. sailing through the South Atlantic on our way to the southern tip of Africa!

- Dave, Bodacious Dream and the especially convivial Franklin
26.92078W, 29.67041S

Tegan’s Science Notes: #1 – Bird Migrations

So, while I’m out here at … oh, let’s see … 32.74017W, 0.61875N, getting pretty close to the equator … and still spending a lot of time dealing with the unruly elements, it seemed like a good time to introduce you to Tegan Mortimer. Tegan is an ocean scientist with Earthwatch who you might remember from the Boston Harbor whale watch videos. Tegan is helping us on the expedition on several levels.

  • Curating our Citizen Science Resources page
  • Advising us on our Explorer Guides (working to get them up there soon!) 
  • Fielding my questions and helping with identification of wildlife sightings
  • Posting those wildlife sightings to a cool site named iNaturalist.org
  • Receiving and recording all the research data that we gather

Thank you Tegan, it’s great to have you along for the trip!

Yellow Rump WarblerNow, if you recall, when I was 200 miles off the coast of New Jersey, a bird landed on the boat. Tegan helped us to identify it as a yellow-rumped warbler. The whole issue of bird migrations struck a spark and we asked Tegan to tell us more about bird migrations – because after all it is that time of year. This then is the first of her series of “Science Notes” … and I think you’ll find it worth your while to follow along … and especially good to share with the young’uns.. Take it away, Tegan!


A songbird over 200 miles from land? That seems like an unusual sighting! How could a little bird get that far from land? Did it get caught in a storm? It’s certainly true that birds can get blown off course and end up in strange places; this is usually followed by storms of excited bird watchers camped out in the hopes of catching a glimpse of a rare sighting!

Dave’s visit from a Yellow-Rumped Warbler on his way to Bermuda was probably not one of these lost birds. If you read my response in a recent post, then that you know that this tiny songbird is probably migrating; heading south to the Caribbean Islands to spend the winter while food in its northern summer home is hard to find.

Warbler PatternsSome yellow-rumped warblers fly farther than others; the maximum distance is about 2,500 miles from right up at the top of the tundra down to the Caribbean, but that’s really nothing compared to species that fly 8,000 to 12,000 miles in a single migration.

Some yellow-rumped warblers, like those that summer here in New England might only go as far south as the Carolinas, but those that spend the summer farther north tend to go much farther south. Still other varieties can survive a cold winter where other species of warbler would just starve. This is because they have a secret weapon! They are some warblers which are able to digest the waxes found in wax-myrtle berries and bayberries, thus providing themselves a wintertime food source without needing to fly as far south as other warbler species.

Bird AltitudesEvery fall millions of birds ranging in size from small warblers like Bodacious Dream’s visitor, to shorebirds and hawks fly to the Caribbean, Central America and South America to wait out the winter. These huge flocks of migrating birds often go unnoticed because they fly very high up in the air and often fly at night. Flocks of songbirds crossing stretches of water, like the Gulf of Mexico, usually fly around 10,000 feet up, but they have been recorded flying twice as high as that! Migrating birds have even been identified by passenger jets at cruising altitude. An amazing example is the bar-headed goose which migrates over the highest mountains in the world, the Himalayas, at heights of 29,500 feet. Even more amazing is that these geese fly over the mountains in a single day!

So how do these birds find their way, especially if they’re flying over the water? It was thought for a very long time that migrating birds flew at night so that they could use the stars for navigation, but then researchers realized that these birds are still able to navigate on cloudy nights. How exactly they navigate over such long distances is still a mystery, but scientists think that they may use many different senses to navigate including using the stars. Pigeons have been proven to be able to use their sense of smell to navigate and birds contain small amounts of the mineral Magnetite which is thought to help them sense the earth’s magnetic fields and see polarized light which can all help to navigate.

Animals that migrate are of special conservation concern because they travel so far and often traverse many countries with different laws. A species that is protected in one country may be hunted heavily in another. Luckily, the yellow-rumped warbler and many other migratory birds are protected by a treaty between the United States and other countries which protects these birds and their habitats as collective natural heritage. Additionally, the yellow-rumped warbler is widespread and has a large population so for conservation purposes it is considered to be of “least concern.” This species is not expected to face extinction any time in the near future. However that does not mean that climate change, habitat destruction, and human impacts won’t have effects on it which could possibly lead to declines or even extinction.

Earthwatch scientists are studying migratory songbirds that nest in the Rocky Mountains. Over the past 5 years these researchers and Earthwatch volunteers have seen a trend which indicates that many of these common and widespread songbirds are less successful nesting closer to human development. Human development is pushing further and further into “wild” land in some parts of the world, what could this mean for even our most common animals and birds?

Birds might be the most remarkable migrators, but they are hardly the only animals that Dave will see mid-migration. Can you think of some other ocean animals that migrate? Where are they going and why are they going there?

(Tegan Mortimer is a scientist with Earthwatch Institute.  Contact Tegan directly at Tegan Mortimer <tmortimer (at) earthwatch (dot) org>)