Southern California – Naturalizing in La Jolla

Last week I had the opportunity to give a seminar at the Scripps Institute of Oceanography in La Jolla, California. The Scripps campus is a collection of research buildings perched on a steep slope above the ocean. Tall palms wave in the breeze. A resident osprey fishes from the concrete pier that services Scripps’s research vessels.  Many Scripps students and faculty keep surfboards in their offices and catch waves at lunch or during a break.

Scripps Institute of Oceanography

Scripps Institute of Oceanography

My host for the trip was PhD student Eric Keen – a college contemporary who was involved in the infamous Sewanee Natural History Society. Eric is studying the ecology of whales that forage in the fjords of central British Colombia. He is trying to learn as much as possible about how the whales use the sounds and inlets before those areas are altered by oil tankers that may soon service the Enbridge Northern Gateway Pipelines – a project that would bring natural gas from the oil sands of Alberta. Eric’s field seasons will involve months of living on and making observations from a 36-foot sailboat, which he plans to learn how to operate this summer en route.

I enjoyed exploring a bit of the southern California coast during my visit. The chaparral was in full-bloom; bush sunflowers (Encelia californica), black sage (Salvia mellifera), and coast monkey flower (Mimulus aurantiacus) were exploding along the sides of the trail. One notable difference from the chaparral in Santa Cruz was the profusion of cacti – barrels, prickly pears, and cholla gave the area a distinctly southwestern vibe.

Coastal chaparral at San Elijo Lagoon

Coastal chaparral at San Elijo Lagoon

In the pickleweed around a restored estuary (San Elijo Lagoon), I spotted two Belding’s Savannah Sparrows (Passerculus sandwichensis). This subspecies is a darker, larger-billed cousin of the familiar Santa Cruz variety. I also found a California Gnatcatcher (Polioptila californica) just before sunset in a spot that Eric suggested (my first two tries were busts). The kazoo-like call gave away the presence of this dark-tailed denizen of the chaparral.

In addition to the natural history, some of the highlights of my trip were a visit to the Birch Aquarium (where I learned that some deep-water fish have to have their air sacs deflated with a needle before they can be safely brought to the surface), fantastic burritos at Don Carlos, and some great conversations with UCSD and Scripps students and faculty. I had a particularly fun time talking with PhD student Chris Kopp and legendary marine ecologist Paul Dayton. I am indebted to my host Eric for a wonderful introduction to southern California.

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Evidence that Applied Nucleation is Working

When people set out to restore a rain forest, they usually start by planting a lot of trees. In a new paper in the Journal of Applied Ecology, Zak Zahawi demonstrates that there might be a better way. The method that we have been testing in southern Costa Rica is called applied nucleation. In short, applied nucleation entails planting small patches of trees instead of extensive, expensive plantations. In the paper, we report that seedling density is equivalent in applied nucleation compared to traditional tree plantations despite the fact that only 20% of their total area planted with trees (compared to 100% in plantations). Mean seedling density was about one seedling per two square meters – twice as high as in areas with no seedlings planted. By replicating the spatial pattern of natural succession, applied nucleation represents a cheaper and less intensive way to turn cow fields back into rain forests.

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Omnivore dilemmas in Guanacaste

What should I eat today? Where will I get it? How will I catch it? These are the questions that a Tropical Kingbird asks itself everyday.

Tropical Kingbirds are small, flying omnivores. From Santa Cruz, California (occasionally) to Argentina, Tropical Kingbirds are a common sight in open habitats like marshes, savannas, and parking lots. Tropical Kingbirds have low wing loading and a low aspect ratio, so they are quite maneuverable in the air. They use this morphology to their advantage to capture insects in mid-air or glean them from vegetation.

Tropical Kingbird (Tyrannus melancholicus) – pondering its next meal

This week I helped students on an undergraduate study abroad course design and implement a two-day study to determine the factors that predict foraging success for Tropical Kingbirds. To do so, we observed kingbirds in Palo Verde National Park in Guanacaste, Costa Rica. For each time a kingbird attacked an insect, we recorded the type of perch it was on, the height of the perch, the habitat the bird was in, the type of foraging behavior it employed (i.e., aerial hawk, sally glean, perch-to-ground), and the direction that the bird swooped to attack its prey (up, down, or even with the height of the perch). We also recorded whether or not the attack was successful.

USAP students on the Palo Verde airstrip watching a Tropical Kingbird (the tiny point at the top of the tree). Photo courtesy of Erika Deinert.

We found that the type of foraging maneuver is an important predictor of foraging success for Tropical Kingbirds. Kingbirds were much more successful when they gleaned insects from vegetation than when they hawked insects out of mid-air. This makes sense – insects in the air are moving targets, and many of them have a wide range of vision allowing them to sense kingbirds approaching from a distance (dragonflies, for example, only have a 1-degree blind spot directly behind them). Additionally, the initiation of escape behavior is easier for an insect already moving.

So why do kingbirds go for insects in the air at all? We suspect that kingbirds are primarily searching for prey in foliage and on the ground – higher odds – and only taking flying prey opportunistically when a better option doesn’t present itself right away.

The marsh in front of the Palo Verde Biological Station. Kingbirds in the open marsh seemed to have much higher attack rates than birds in other habitats like Typha-dominated marshes, yards, dry forest, and rice fields.

We also noted that individual birds varied considerably in their ability to consistently capture insects. Whether this is due to the random chance associated with short observations or due to real differences in the foraging abilities of different kingbird individuals is up for debate.

As always, working with the OTS USAP course was a tremendous pleasure. The students were highly engaged (I think each of the 25 students asked me a question during one of my two lectures), and Palo Verde is a beautiful place to visit.

Green-breasted Mango (Anthracothorax prevostii) – a hummingbird that would certainly make a fine tattoo.

Aside from Tropical Kingbirds, Groove-billed Anis (Crotophaga sulcirostris) were one of the most common open country birds around Palo Verde.

Limpkins (Aramus guarauna) were common in the Palo Verde marsh. I watched them peck into the mud like feathery sewing machines, but I never saw one capture an apple snail.

Northern Jacanas (Jacana spinosa) wander through the marsh calling loudly and flashing yellow feathers on the underside of their wings. For what purpose, I do not know. There were lots of juveniles present during my visit.

Roseate Spoonbills (Platalea ajaja) and Wood Storks (Mycteria americana) are two of the most charismatic waders at Palo Verde. Here we found some in a slough adjacent to some rice fields just outside of the park entrance. (The most charismatic wader is the Jabiru (Jabiru mycteria), which we did not see this week).

We found a Double-striped Thick-knee (Burhinus bistriatus) incubating a big, cream-colored egg with brown splotches in front of the entrance station at El Negrito. A nearby mate attempted to run a distraction, but it didn’t do a broken wing display.

Scissor-tailed Flycatchers (Tyrannus forficatus) outnumbered Tropical Kingbirds at El Negrito. Perhaps these two species competitively exclude one another?

 

 

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UCSC’s Newspaper Rock

This afternoon I rode my bike past the water tanks at the junction of West, Red Hill, and Chinquapin Roads on UCSC’s Upper Campus. The water tanks are like a modern Newspaper Rock. The rotating art exhibit changes whenever someone paints over the previous work.

The current manifestation of the Upper Campus water tanks is a protest against the campus’s Long Range Development Plan (LRDP), which includes campus expansion into current natural areas.

Close-up of Sammy Slug and the Lorax

These murals are a beautiful and effective form of activism. They are also likely to reach a sympathetic audience: recreationalists like bikers, joggers, hikers, and mushroom hunters who enjoy Upper Campus in its undeveloped state.

Sammy, with consternation etched upon his brow as he reads a pamphlet on the LRDP

The debate over where UCSC will get the water to supply a campus extension has been contentious.

 

 

 

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Palo Verde: A Visit to Guanacaste

Next Sunday I am flying to Palo Verde National Park in northwestern Costa Rica to teach a short segment of an undergraduate study abroad course. The course is run by the Organization for Tropical Studies, and it is one of the premier biological field courses in the world. I was a student on the course in 2005, and it’s a great honor to return as visiting faculty.

The view from Palo Verde Biological Station towards the Rio Tempesque.

Palo Verde is comprised of two major ecosystems: tropical dry forest and seasonal wetland. During the dry season, December – April, the park is dry as a bone and very hot. Animals congregate around shrinking water holes, and bask in the shade of a mango orchard.

But during my visit next week, the park will be at the height of rainy season. In May-December the Rio Tempesque swells and overflows its banks, filling an enormous wetland with stagnant water. This has two important implications.

First, the wetland becomes a wonderland of waterbirds. When ducks migrate south in the fall, this is one of the places that they end up. There they join the ranks of some impressive waders like Double-striped Thick-Knee, Roseate Spoonbill, Limpkin, Wood Stork, and the king of Neotropical waders: the Jabiru.

The second implication of the seasonal flooding is that the park becomes lousy with swarms of blood-thirsty mosquitoes. They are infamous, and they strike fear in the hearts of students and faculty alike.

A black Ctenosaur (Ctenosaura similis) chills out on the roof of the dormitory in 2005.

A Wood Stork (Mycteria americana) glides over the marsh (Feb 2012).

Tropical Kingbirds are abundant and conspicuous at Palo Verde, making them a tempting study organism.

This is one bug that I was happy to see dead, though I would have been happier if it had been dead somewhere besides the floor of my cabin. Kissing bugs (Reduviidae) are a vector for Chagas disease, a gnarly, life-threatening ailment caused by Trypanosoma cruzi (Feb 2012).

 

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Applied Nucleation: What It Is

If you ask me what I study, I’ll usually tell you that I study ecology – the science of interactions between organisms and the environment. That’s enough for some people. A lot of people, actually. If you ask for details, I’ll say that I study restoration ecology – the science of assisting of the recovery of damaged ecosystems. I’ll also tell you that I do field work in Costa Rica, and that the objective of my research there is to learn how to turn beat-up cow pastures back into rainforest. That much detail is enough for almost everyone.

But, if you are one of the few who is really persistent or has already formulated a few opinions about the best strategies for turning cow pastures in rainforests, I’ll sometimes mention that I study Applied Nucleation. If you’ve found this blog, you may fit into one of those categories.

This is what we want to turn back into rainforest.

Before I tell you about Applied Nucleation though, I need to tell you a little bit about ecological succession.

Imagine yourself inside of a mature rainforest. There are tall trees all around you, and each one is a different species. There are lianas (woody vines) the size of your thigh hanging from the canopy. The understory where you are standing is dark and humid, and you could easily walk off of the trail because there is very little vegetation down on the ground. Maybe there are monkeys eating figs up in the treetops. Maybe there’s a Scarlet Macaw croaking overhead.

This is what it looks like inside a mature rainforest.

Now, imagine yourself in the same forest after a Category Four hurricane.

The trees have all been broken off or uprooted. It is hot without the shade from the canopy. You should put on some SPF because the tropical sun is intense. The forest has become a brush pile, and there is no way to walk through it without a machete and a chainsaw. No monkeys, no macaws.

Almost immediately, the forest will begin to regenerate. Gradually and predictably, it will become more and more like the rainforest that was there before the storm. This process is called ecological succession. The first trees to come back will be light-loving pioneer species like Cecropia. These spindly trees produce bajillions of tiny seeds, which manage to find their way (via the digestive tracks of birds and mammals) to every conceivable place that a Cecropia tree might be able to grow. As the brush pile diminishes and the canopy closes in, more species of trees, herbs, lianas, and animals will return to the site.

A horizontal view of ecological succession

So the recovery of species composition following a disturbance is reasonably predictable. There is also a well-documented pattern for how forests recovery spatially.

Imagine looking down at the recovering forest from a helicopter. At first, right after the storm, it’s just a mess of downed trees, but if you fly over again after a couple of years, there will be a few isolated tree canopies. Under those sparse canopies, the climate will be a little bit cooler and a little bit moister than in the surrounding area. Those canopies will also attract seed-carrying birds that will defecate from the branches, adding to the pool of tree seeds down below. Over time, those few scattered tree canopies will act as nurseries, and other trees will germinate and grow underneath and around the edges – expanding the size of the canopy patch or nucleus. Eventually, those patches will meet one another and coalesce, closing the canopy and making a continuous forest over what was just recently more like a brushy savanna. This pattern of patch formation and expansion is called the nucleation model of succession.

A helicopter view of nucleating ecological succession.

Now you’ve got the Nucleation. Here I’ll tell you about the Applied.

Hurricanes, despite their hugely destructive power, are a relatively benign disturbance in intact ecosystems. Trees blow over, but there are still seeds in the soil that can germinate and grow up to become the next generation of trees. Fires, floods, and landslides fall into the same category. Other disturbances are more insidious.

When forests are cut down by humans, for example, we generally don’t let them regrow, at least not right away. First we like to grow some crops. Make some money. In southern Costa Rica, where I do my fieldwork, the crop of choice was coffee. In the 1950s-70s, much of the Coto Brus Valley was deforested for coffee production. But in the 1990s and early 2000s, coffee prices bottomed out – a result of failed negotiations in the International Coffee Organization. Farmers were forced to try something else, and for many of them, something else was cattle.

A Coto Brus farmer and his cows. Twenty years ago, this was a coffee plantation. (Photo by Jim Reid)

For various reasons, various people now want to turn some of those cow pastures back into rainforest. Some farmers want to regrow forest in order to protect springs, prevent erosion, and preserve a little piece of the natural world to pass on to their grandchildren. Others want to restore rainforest to keep endangered species from going extinct and to mitigate the worst effects of global climate change by sequestering atmospheric carbon inside of wood.

This is easier said than done. After years of intensive agriculture, tropical cow pastures generally have few or no tree seeds left in the soil. And birds and mammals are not likely to bring new seeds either; pastures are hot, dangerous, and virtually devoid of food resources. Simply removing cows from the land may not be enough. In some cases, you could fly your helicopter over an abandoned pasture every year for decades and see nothing but an itchy carpet of exotic pasture grasses.

To get one of these pastures back on its successional track towards a mature rainforest, the most obvious thing to do is plant some trees. You can plant a lot of trees, as in a tree plantation, but this is expensive. It’s also a lot of work, and it tends to have a long-lasting influence on the overall diversity of the new forest. (Remember standing in the mature rainforest eleven paragraphs ago? Remember how every tree was a different species?)

Instead, my research group is exploring the possibility of planting just a few trees in small patches. The premise of the strategy is that the small patches will create favorable conditions for new trees to arrive and grow. Ultimately, we think that the patches will get bigger and bigger until they meet and form a new, highly diverse rainforest. We call this strategy Applied Nucleation, after the nucleation model of succession.

If you’ve made it to the end of this post, you might as well keep reading. Check out our lab website for more information!

Here is one of our study sites from Costa Rica. The plot on the right is the one that represents the applied nucleation approach.

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Sequoia Scrabble

Over the weekend I took a trip to Yosemite National Park with two friends from Central America. We spent two nights in Yosemite Valley, carefully sequestering anything with an odor inside of the heavy-duty bear lockers. On Saturday we day-hiked in the high Sierra around Mount Hoffman and saw a variety of high-elevation bird species including Clark’s Nutcracker and Mountain Chickadee.

Mount Hoffman from May Lake. Mount Hoffman is near the geographic center of Yosemite National Park.

On Sunday morning we hiked from Highway 120 down the old Yosemite wagon road to the Merced Grove – a group of about 20 giant sequoias (Sequoiadendron giganteum). Sequoias are famous for their enormous size; the largest known individual is 84 meters (275 feet) tall and 9.8 meters (32 feet) in diameter. Lesser appreciated is the fact that the common name, sequoia, is among the shortest words in the English language that use all five standard vowels with no repeats (the shortest is eunoia).

Two giant sequoias in the Merced Grove at Yosemite National Park. Freezing cold Salvadorian for scale. (It was not that cold; 13°C or 55°F)

One of the distinctive qualities of giant sequoia is its thick, soft bark. It feels a little like fuzzy Styrofoam. Looking up at the side of a sequoia (like looking at the side of a barn), the trunk is pocked with small cavities, presumably excavated by animals. To roost in a giant sequoia would likely be a fine existence. For one thing, the bark provides excellent insulation. Giant sequoias require forest fires in order to regenerate, and their bark protects the xylem from damaging flames. Some species of bats take advantage of this adaptation by overwintering behind the bark in tree cavities that maintain non-freezing temperatures year round. Another benefit of sequoia roosting is that your home is unlikely to be demolished – more than 90% of all sequoia groves are protected. The principle trade-off is a lack of privacy; Mariposa Grove in Yosemite, for instance, receives hundreds of thousands of visitors per year.

Mountain dogwood (Cornus nuttallii) has beautiful red leaves in the fall. We did not notice major evidence of the anthracnose that has decimated eastern flowering dogwood (Cornus florida), although apparently it was first discovered in this species.

It’s hard to hug a sequoia.

Dramatic light and campfire smoke in a meadow in Yosemite Valley. The looming cliff in the background is Half Dome.

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Presidential Leking Behavior

Last night during the second presidential debate, Barack Obama and Mitt Romney performed a carefully choreographed display in a small arena at Hofstra University. They strutted. They gesticulated. They butted heads. They produced elaborate vocalizations. Meanwhile, an alert audience of somewhat less gaudy individuals looked on, evaluating the candidates’ speech and movements for small variances that might connote greater quality in a national leader.

In outward appearance, the comportment of the debaters was similar to a leking behavior – ecological terminology for the extravagant  competitive displays that males of some species produce in order to mate with females. Famous lekers of the animal world include the Greater Prairie Chicken (Tympanuchus cupido) and the Andean Cock-of-the-rock (Rupicola peruvianus). Male prairie chickens gather in early spring in areas with sparse vegetation and display to females by puffing out orange air sacs on the sides of their necks and making booming noises. Presidential candidates, in contrast, gather in early fall in university auditoriums. The displays are otherwise similar.

Leking Behavior by Presidential Candidates

Leking Behavior by Greater Prairie Chickens

In the case of the debate, Obama and Romney were competing for votes rather than mating opportunities. Aside from their political platforms, small differences in the quality of their displays that were picked up by the national media included spicy zingers (like Obama’s pension comment) and awkward imagery (like Romney’s binders) as well as movements around the arena described in The Economist as “turkey-cocking and stiff necked strutting.” In classical leks, males contribute almost nothing to females except for sperm; nesting and chick rearing is left entirely to the females. Whether the presidential debate metaphor extends this far seems to be a matter of personal opinion.

 

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