Birds of a feather flock together, but what about their mites?


Birds are one of the most well-studied organisms in the world. To date, it is estimated that nearly 10,000 species of birds exist worldwide! In Las Cruces, a biological station found in southern Costa Rica, records indicate that there are over 400 species of birds from 71 different families that reside in the nearby 266 hectare forest.


Costa Rican’s national bird: Clay-Colored Robin; generalist feeder

Each bird species may have its own suite of ectoparasites including lice, mites, fleas, and ticks. Scientific literature shows that the biology of bird ectoparasites is still not well understood despite their important cost and role in a bird’s life (Proctor and Owens 2000). A bird’s feathers serve as a great habitat for ectoparasites, especially mites, and quantifying parasite type and number can be completed in several ways, many of which are non-invasive.


Checking wings for mite eggs.

According to Whiteman and Parker (2012), there is a positive relationship between host density and parasite infestation but I have found little literature examining the relationship between host feeding type and parasite infestation .The objective of my study was to investigate and see if there is a relationship between bird parasitism and bird feeding behavior. I hypothesized that bird parasitism would correlate with feeding behavior, e.g. nectarivore.


Rufous-Tailed Hummingbird; nectarivore

I captured a total of 81 birds representing 42 different species at two sites near Las Cruces Biological Station in Southern Costa Rica. Both sites were located approximately 4 km from the Panama border, site 1 was in an old coffee plantation and site 2 was in a privately owned 2 hectare section of primary forest.


Site 1- Old coffee field now used to grow bananas, peppers, yucca, and berries.


Site 1- Recently cleared paddock adjacent to old coffee plants.


Site 2- Primary forest.

Birds were safely captured using 20 mist nets each 12 m long. Birds were identified to species and classified as generalist, nectarivores, insectivores, frugivore or grainivore feeders. For each bird, I examined the first four primary flight feathers on one wing for mite eggs. The presence of mites was quantified on a scale of 0 to 5, where 0 signifies that no mite eggs were present and 5 signifies that eight or more mite eggs on average were found on each feather.


Blue Crowned Motmot; generalist feeder


Scaly-breasted Hummingbird; nectarivore

Common Pauraque

Common Pauraque; insectivore


Bay Headed Tanager; frugivore


Yellow Faced Grassquit; Grainivore

Using Tukey’s HSD test, I found a significant relationship (P˂ 0.001) between bird feeding behavior and the number of mites present! Specific significant differences in parasite loads were observed between nectarivores and frugivores (P˂ 0.001), nectarivores and generalist feeders (P ˂ 0.001), and nectarivores and insectivores (P˂ 0.001). Significant differences were not observed between other types of feeding behaviors.  These results are consistent with my hypothesis that bird feeding behavior correlates with bird parasitism.

So, why is it important to study and understand ectoparasite and bird host relationships? Parasitism over time can impose a long-term cost to their hosts (Brown et al. 1995). With little understood about the biology of some of these parasites it may be uncertain the actual cost faced by the bird host. It is vital that future research further investigate the relationship and effect of ectoparasites on their bird host(s).

Why did you choose the Gringos Field Ecology OTS course instead of the Latinos Ecología de Campo de OET???


This was an interesting question I was asked several times during the course so I have been thinking in the answer and I would like sharing it. I think my answer is divided in two parts, the first one includes the reasons why I chose Gringo’s course and the second one includes the reasons why I would recommend it since I survived it haha.


The main reason why I chose the Americans course was the language, English!!! After 15 years of English classes in Peru I still need English classes in real life, that real moments in which you have to think fast, open your mouth and move your tongue to express yourself in English. Also because I was feeling completely ready to stay out from my comfort zone… what could be worst?… I’m not anymore in my country, with my people, costums and food (oh my Peruvian food). And my third reason!!! American Tropical biologists many times talk about Latin-Americans countries and they don’t even have been there, they don’t really know our reality or our reasons to study our nature, but they are good people, they just need to spend more time with us haha a little piece of Latin-American’s pride!!!


Once in the course, definitely you will practice and improve your English, with no time to even practice a statement before an oral presentation, it’s just about to loosen up and try to enjoy the moment. However, the best part about languages is that many gringos could speak a little bit of Spanish and they would probably have cute accents and ways to speak our lovely language. Pienso que son adorables and listening to them is buenaaazooo…You not only will be out from your comfort zone, you will have a moment to know and test yourself, so be ready for the new things you could discover, at the end of the way you will see there was a positive side. Definitely you will meet nice American people, at the beginning they will be funny and will keep distance from you but at the end even the tough one will hug you and scratch your head. But don’t worry, if at some point you need Latino’s love for sure there will be one more Latin@ in the course to bother you as just we know or some Centro American that will tell you Pura Vida!


Last advice… come on Latinos go for the Gringos Field Ecology OTS course, DON’T BE BABIES!!!!

 Rossana (alias PERU)

Loss and recover of density dependent effects in the invasive ginger Zingiber spectabile


Invasive species are the second biggest threat for native biodiversity, after habitat destruction. Once introduced to a new habitat, exotic species can   reduce native species richness, abundance, and overall diversity. How it is possible? For instance, in new habitats they lose their specific herbivores and pathogens and only deal with generalist herbivory in the invaded range. However, they will lose this advantage over time, starting to accumulate new enemies. In addition, herbivory and pathogen impacts may depend on plant density and life stage.

There is one hypothesis about density dependent regulation of population growth, called the Janzen-Connell hypothesis. It considers that natural enemies prevent recruitment of offspring near their parent plants, thus facilitating coexistence among species, so it’s also a possible explanation of forest’s biodiversity. This hypothesis predicts more seeds close to the mother plant, but probability of survival increasing at a distance away from the mother. In this study, we wanted to test the Janzen-Connell hypothesis, testing whether the negative density dependent effects on invasive seedlings changed over time as the enemy release effects diminished over time. We expected that in newly invaded areas, there would be more seedlings close to the mother plants (loss of Janzen-Connell) than near the source of invasion.


We develop this study at Las Cruces Biological Station due to the invasive ginger Zingiber spectabile presents an ideal system to test the effects of enemy release and Janzen-Connell. Previously, we knew where the source (the Wilson Botanical Garden), and the invasion front are located. The spatial distribution of the invasive ginger was used as a chronosequence (space for time substitution) to test the variation in the strength of density-dependent seedling herbivory. We used the native ginger Renealmia cernua for comparison with the invasive one, expecting it to present stronger density-dependence akin to the Janzen-Connell hypothesis. Our methodology consisted in sampling 5 individuals of Z. spectabile and 3 of R. cernua, at the source and edge of the invasion. Placinga mother plant at the center, we surveyed seedlings radially every 1m outward to 8m, counting the number of seedlings, as you can observe in the images.

Screen Shot 2015-01-30 at 10.53.03 PMOur results showed the Janzen-Connell prediction near the source of invasion, implying that well-established individuals of Z. spectabile have started accumulating new enemies!!! On the other hand, we did not find the same pattern at the edge of the invasion. More specifically, in the source of invasion we saw more seedlings between 6–7 m from the mother plant, and fewer seedlings between 0–1 m. At the edge of the invasion we reported more seedlings between 2–3 m, and fewer between 4–5 m. However, unexpectedly we did not find Janzen-Connell in the native ginger, perhaps because of its low density throughout the surveyed area, or also because we did not capture the ideal distance from the mother plant to survey the seedlings. We did not find seedlings between 0–1 m both at the edge and source of invasion, but we counted a few more seedlings between 7–8 m at both sites.

Although the evidence shows that invasive gingers near the source are presenting signs of density dependent factors, the density at the source is larger than at the front. This could imply that it is still too early to see the jc3outcomes of population regulation in this invasive plant. Future studies on this system will inform us about the dynamics of population regulation of well-established invasive plants.

The Importance of Playing [with ants…]


Two free hours in the afternoon, and what to do? Take a walk, take a nap, journal my experiences? Why not play?

At Palo Verde, there is a large diversity of Acacia trees and acacia ants that form mutualisms with these trees. In exchange for housing and food provided by the tree, the ants defend the tree from herbivory. Some ant species will even eradicate any plants or seedlings that grow too close to the acacia tree so that it does not have to deal with excessive competition for light, space, and nutrients.

Dr. Kaspari and colleagues found an interesting pattern of salt limitation as one moves in an ecosystem from coastal to inland (Kaspari et. al 2008 PNAS). To investigate these patterns, Kaspari et. al used ant communities and bait traps of NaCl or sucrose. They found that, the further inland ant communities were, the more frequently they chose the NaCl baits over the sucrose baits.

At Palo Verde, we were given the opportunity to go into the field, make observations, and design a hypothetical research project. My group designed a proposal about the acacia ant system, to see whether acacia ants close to the gulf [salt water] were less salt limited than ants further inland. We designed two series of ‘salinity gradients’ – one from the coast inward at three distances, and then using sampling sites at three distances from brackish water and fresh water [the river] as well. We wanted to do both a field and lab component in which we presented ants with NaCl solution and sucrose solution, and count the number of visitations to each. If our hypothesis, that ants further from salt water [gulf/ocean] would be salt limited, was true, then we would expect to find ants further from salt water having a higher number of visitations to the salt baits versus the sugar baits.

Of course, this was just a hypothetical proposal – even if we had time to do independent projects at Palo Verde, one as complex as this would not be completed in time. As part of the feedback we got from our proposal, it was suggested that we do a pilot study first. So, when we suddenly had two free hours one afternoon, I decided to do just that.

I had it in my head to visit three to five patches of acacia trees, and do two salt/sugar trials at each patch. Suffice to say, the pilot study did not go exactly as planned, but I learned a ton in the process. This leads me to the importance of play.

After visiting two trees, I realized that I was working with two different species of acacia ants. Not being a myrmecologist, I will simply describe them as the black ants and the red ants. At first I thought that the black ants were the more active and aggressive ones [thus being better for my study], because they had an immediate reaction to my disturbance of their tree. However, after an initial flurry of activity when their branch or domatia were disturbed, they calmed down and retreated into hiding. It was all for show!! Whose show? I don’t know. Is a flurry of timid ants enough to ward off potential herbivores? When I repeatedly disturbed their branch, the flurries of activity became smaller and less frequent, until it was simply a little ant head peeking out from a domatia hole, or nothing at all.

So, first lesson learned, it was time to try the red ants. They were, on the whole, more aggressive and active. Even so, there were decided differences among different populations of the red ants [different trees with red ants in them]. Some were very active, but barely reacted to my disturbance of their tree, whereas a tree that looked totally empty suddenly had aggressive ants ready for battle when I brushed past a branch. This was the tree where I got the most observations in [oh yeah, remember I’m doing a pilot study about sucrose versus sodium solution preference?]. It is also where I got bit by an angry red Acacia ant. Let me tell you, it hurts! I would certainly be warded off if I was an herbivore [but not warded off as a tenacious scientist, haha!]. The pain is immediate and intense, but then dissipates. Oh, what a cool adaptive strategy, I though to myself, to invest only enough to inflict immediate annoyance. Silly scientist…about twenty four hours the pain came back along with oober intense itching!! Aha, so they invest in immediate deterrence followed by a delayed reminder of just what a bad idea it was to mess with acacia trees and their ants.



[Above: Acacia ants visit sugar (blue) and salt (orange) solution vials.

But back to my study – ahem, I mean, play. In total I checked out three different acacia trees. The black ants, during ten minutes of observation, made one visit to the vial with sugar solution and one visit to the vial with salt solution. I visited two trees with red ants, with very different personalities [or, if you will, behavioral patterns]. On the “too busy to be bothered” tree, the red ants made, well, zero visitations to either vial, even when vials were placed directly in their path. On the “curious and rapid defense” tree, the red ants made 12 visits to the sugar solution and 6 visits to the salt solution. One thing I realized as I observed them [play!!] was that the vials were so large that the ants, though curious, would only investigate solution on the lid and rim of the vial but would not go in. So I ran back to the classroom and put the solution into smaller vials, brought it back out to my star students. During the smaller vial trial, the red ants made 1 visit to the sugar solution and 3 visits to the salt solution.

My results are of course inconclusive, but do support an idea of doing a lab experiment prior to a complex field experiment, and I learned a lot more about my potential study subjects in the process. Playing with acacia ants – a great way to spend two free hours in the afternoon!

What questions will lead you to play today? 🙂

El bosque encantado Cuericí


There is a phrase in Spanish to express fondness for something, me encanta. In a language class, you’d learn the meaning as “I like…” but the literal translation is “it enchants me.” For me, these words describe my feelings towards Cuericí much better than any in English. The forest is truly enchanting.

DSCN3442There is something in the fresh mountain wind that fills me with excitement and peace at the same time. At an altitude of 2600 m, the air is cool and thin. It ascends along the Cordillera Talamanca, twirling its way across the páramo, and invites all plants it touches to dance along with it. It frolics, carrying along gusts of mist in an erratic, playful manner. The wind surprised me with its strength, when first I gazed across the entrance of the Rio Macho forest reserve. It inhabited my lungs in a refreshing embrace, and swept up my hair all around my face. You’re somewhere new, it whispered, come explore.

And then I met the flora of Cuericí. DSCN3544The plants are unique; many are even endemic species that exist nowhere else in the world except amongst these beautiful mountains. The Costa Rican black oak, for example, Quercus costaricensis, is a tall, majestic creature that reaches towards the sky with intertwining branches and delicate round acorns the color of dark-roasted café. I didn’t expect oak trees, a hardwood genus so familiar to the northeastern US where I’ve done most of my research. But these trees in Cuericí do not stand alone. IMG_4204They are home to a multitude of other organisms; lichens and mushrooms and epiphytes all use the strong branches and small bark crevices of the trees as substrates to grow. Some bromeliads glow red in the canopies, perched like colorful birds amidst the overflowing layers of greenery.

When I gaze up at these beautiful layers, so proliferous and dense and rich, I feel profoundly overwhelmed with awe. Awe of being one meager species amongst thousands of cohabitating, light-absorbing, oxygen-creating, life-giving producers. Awe of the sheer diversity, the variety in color and texture and size and form. Awe of being intimately connected to such a complex, dynamic, and longstanding system. Awe of the mystery that still resides within. This mystery is what sets aflame my passion to study these forests, to ask them why they are so complex and how they are changing and what we can do to make sure they still exist in the future.

I am undeniably connected to the forests of Cuericí. Something deep and inexplicable grounds me there, and I know I must return to unfurl the mysteries that lie within. Truly, me encanta el bosque Cuericí.DSCN3551

Tonight Only on Pay Per View: The Feisty Dermanura Watsoni takes on the Heavy Weight Champ Carrolia Perspisillata


Nights in Las Cruces can get a little wild, or at least you think they are when you have spent six nights in the jungle. Why would anyone want to do that you ask: bats of course! The only mammals that can fly. These awesome creatures are not only cute as hell, they also provide a massive amount of ecosystem services; from disease control, by hunting disease vectors like mosquitos, to pollinating fruiting plants essential for life. That’s right you can thank the Mexican long nosed bat for your tequila sunrise in the morning. Agave is pollinated by just that one species of bat. Bats are also the second most diverse mammalian order after rodents. It’s believed that the evolution of flight opened up new niche space for the ancestors of bats, leading to a rapid adaptive radiation. Now we have all sorts of crazy bats, from giant fruit eating flying foxes in Australia, to small blood sucking vampires here in Costa Rica. Of course the niche space that was opened by the evolution of flight filled rapidly, and we now have many species specializing on the same resources, as well as using the same fly space to access those resources. This leads to competition, which is where we come in. Two promising, up-and-coming researchers Paul Furumo and Kevin McCormick recently completed some work attempting to determine if a bat’s wing shape influenced where it foraged. During the study we noticed that we seemed to catch different bats at different times of the night. We knew that some of these species, like those in genus Carollia, specialize on pretty specific fruits like Piper. Therefore, we thought that the patterns we were seeing of different species showing up at our nets at different times might have something to do with how bats avoid direct competition over food and fly space. With this in mind we spent an extra three nights out in the jungle, looking for answers. We found that 80% of the bats we captured were just two species, Carollia perspicillata and Dermanura watsoni. Interestingly enough, these guys are both frugivores, but they are specializing on different kinds of fruit, so if they are competing it’s for flight space not food. Yes, bats actually do compete over flight space, because the echolocation frequencies they use to navigate can actually interfere or jam each other’s signals. However, this echolocation “jamming” has mostly been described within species, not between species. Therefore, it is not just competition, but the most anticipated match in the history of OTS Las Cruces. Who will win and go to roost with a full belly? Find out here (Click on photo below) exclusively on pay per view! Presentation2

As it turns out, the match ended in a tie. For whatever reason, the two fighters never appeared in the ring at the same time. One would come out, looking for challengers and find nobody. After retiring, the other contender would emerge, eager to battle it out, but alas, no one there with whom to tangle. This happened over and over, round after round, until the sun came up, and the crowd of researchers had gone home, tired from this unsynchronized affair, and wanting their money back from the cable company for hyping up such an event, and leaving them flat. The simple reason that these two forces never encountered, is a lesson of temporal niche partitioning. These two species seem to avoid each other during peak feeding times. The two contenders barely encountered one another in this cycling in and out of the ring because they were actually after different prizes. Dismayed, the researchers wrote a strong letter to the fight promoters, telling them to consider the motivations of their fighters next time, before making such a big deal about it on pay per view.

Bites of bats, birds, chiggers and mosquitoes- Whitney, the other white meat.


As an individual focused on conservation medicine, my future goals include conducting research that will reach and influence the scientific community as well as the non-scientific community on a global scale. At the time of applying for Field Ecology: Skills for Science and Beyond, my intensions were focused on learning new and valuable skillsets that would aid in the success of my future endeavors. After four intense and exciting weeks, I can successfully say that my expectations were not only met but surpassed and the knowledge I gained will go far beyond the classroom and used on a daily basis.

The journey started at a Palo Verde Biological station, a dry forest and one of the world’s largest protected wetlands. I was immediately pulled out of my comfort zone as I was taught how to use a statistical program called “R”. Anyone who has heard of or had the “privilege” of working with this program can immediately attest to the love/hate relationship that comes with it… but I digress. Palo Verde was also full of exploration of the natural world. 0500 bird watching, late evening walks, climbing up a mountain, and learning how to use camera traps from an expert were just a few of the exciting activities that took place. But with these exciting activities came “friends”, friends with wings and multiple sets of legs. These “friends” to most people are known as mosquitoes. I made over 300 friends while at Palo Verde and their parting gifts of itchiness, blotchiness, and swelling will forever be remembered even if their presence is no more.

After departing from Palo Verde, the journey continued on to La Selva Biological Station. La Selva is a neotropical rain forest that receives a little more than 4 meters ( >12 feet!) of rain each year. Although our 12 day visit was during the “dry season”, we got to experience the joy of daily rain storms and never having dry clothes. Nature usually tried to be kind and warn us when the rain was nearing. Howler monkeys would yell and birds would call out but when you’re a few hundred meters into the forest there isn’t much you can do but dance in the rain and make the most of it. When I wasn’t drenched from head to toe or sitting in on nightly lectures I was busy conducting research and simultaneously making movies. Using quality cameras and splicing footage together is a skill I’ve always wanted to have but never had chance to master. Thanks to OTS I have had the joy of successfully added this skillset to my “toolbox” in an ecosystem I’ve dreamed of visiting since a small child.

Aside from dancing in the rain and making amazing movies, La Selva produced opportunities of doing other new and exciting things like climbing high into the forest canopy and mist-netting bats! Learning to climb trees was simply amazing. Using a rope and pulley system I was able to ascend into the canopy 15 meters (~50 feet)! The view was gorgeous at sunrise and the observations and research we were able to conduct while in the air pushed me farther than I had ever been pushed. I would do it all over again in a heartbeat if I could. When I wasn’t scaling trees, or assisting my colleagues to do the same, I was learning to mist-net and handle bats (another lifelong goal). Bats are adorable and they do so much for ecosystems, every moment was exciting and I learned so much! I learned vital things about bat behavior, diet, and morphology. I also learned a lot about bat health and how to quickly, and politely, remove their tiny razor blade like teeth from my gloves and fingers. For an animal that weighs just a few grams they sure do pack a lot of personality and wit and I hope to work with these individuals again and again in the future!

After we said “ciao” to La Selva we headed south to Cuerici Biological Station. This place was like no other I have ever been to. Waking up to a montane cloud forest high in the mountains with the crispest air was definitely a God send and a drastic change to the hot, humid ways of the rain forest. Cuerici was filled with hikes lasting several hours with dozens of chiggers, several cups of the world’s best hot chocolate, storytelling by the locals and gracious hosts, sunrise yoga, and a fabulous tour of a sustainable, chemical free trout farm! Every hour of every day was cherished and I only wish that my pictures could do this blessed place justice!

All good things must come to an end, and my OTS journey concludes at Las Cruces Botanical Garden and Biological Station. This station offered many great things but in a much different setting to those previously visited.  This particular environment has been fragmented and changed by the hands of humans over recent decades but yet holds a wide range of fauna and flora biodiversity. I was able to experience some of this amazing biodiversity first hand during my 7 day stay as the research I conducted focused on bats and birds. Birds, like bats, are amazing in their own right and full of spunk! Birds may not have sharp detention like bats but if you’re not careful their beak may give you a nice pinch. Although the days and nights were long and my fingers are recovering from the nibbles of my new found friends, I’m still amazed and thanfkful that I was able to study and handle 14 species of bat and 42 species of bird!

This short blog is just a small view into my four week journey with OTS in Costa Rica and it wouldn’t have been possible without the emotional support of my family and friends as well as the monetary support of my university in the States. The journey, albeit stressful, went by way too fast and was full of so many amazing animals and people and gorgeous scenery.

Until next time, Costa Rica.


Whitney Collins