The many joys of tropical fieldwork

This week, Dispatches from the Field is excited to welcome guest blogger Zachary Kahn, who tells us about some of the trials, tribulations, and triumphs of his fieldwork in Costa Rica.  For more about Zach, check out his bio at the end of the post.

I was surprised the first time it happened, although I really shouldn’t have been. I had been warned many times. I had been told to wear bug spray and bring tape, but that it was inevitable. Still, I couldn’t help but feel a little shocked to see hundreds of tiny poppy seed-like critters crawling all over my body. Indeed, I had been “tick-balled”, a term referring to having an army of tiny ticks latch onto your clothing and spread across your body like a group of crazed protesters. The trick was to make a ring of duct tape, with the sticky surface facing outwards, and peel them off. Sadly, I didn’t have any tape that day. This was the first of many times I would be tick-balled, and my first introduction to one of the many joys of doing tropical fieldwork in Costa Rica.

I am currently a Masters student at the University of Windsor, and my research is focussed on the behavioural ecology of tropical songbirds. Why study birds in the tropics, you ask? Well, unlike in the temperate zone where it is primarily males that sing, often both males and females sing in the tropics, and sometimes combine their songs into cool vocal displays called duets by overlapping or alternating their songs. I became interested in studying the reasons birds in the tropics sing duets, and I have tried to do this this by studying a population of Rufous-and-white Wrens in Santa Rosa National Park, in northwestern Costa Rica. I have spent the past two field seasons in the tropical dry forests of Santa Rosa romping around and chasing birds like a crazy person, all the while getting tick-balled and falling down more times than I’d like to admit.

My study species: the Rufous-and-white Wren (Thryophilus rufalbus). Isn’t he pretty?

My day in the field is pretty similar to any other field ornithologist. I get up super early to record birds while they are singing, set up mist nets to catch and band birds for identification, and closely monitor their behaviour. I also need to check inside their nests in order to assess what breeding stage (i.e. eggs or nestlings, and how many) each pair is at throughout the field season. For many species, this is fairly straightforward. You find the nest, make a note of its location, look inside, and you’re done! Finding the nest is usually the most difficult part since many species have mastered the art of nest concealment and camouflage.

A Rufous-and-white Wren nest in a Bullhorn Acacia Tree (Vachellia cornigera). If you look closely, you can see some ants along the main stem, and a wren getting ready to leave the nest.

Luckily for me, I don’t have this problem. Rufous-and-white Wrens nest in Bulhorn Acacia trees over 80% of the time at my study site. Their nests are bulky conspicuous globs, and there are very few acacia trees in the forest, making it relatively easy for me to find their nests. Simple, right? Wrong. The funny thing about acacia trees is that ants like them too. In fact, many species of ants have a symbiosis with the trees: the tree provides the ants with food and shelter in return for defense from predators, other plants, and stupid field biologists. To get inside the wren nests, I have to use a ladder, open a hole in the back of the nest (they are enclosed domed structures instead of open cups), feel inside, then sew the nest back up, all while being bitten by a swarm of angry acacia ants and nearly falling off the ladder. My hands swell up like balloons every time I have to do this, giving me yet another visual reminder of the joys of tropical field work.

A Black-handed Spider Monkey (Ateles geoffroyi) snacking on a seed pod in Santa Rosa National Park.

I don’t mean to imply that all of my experiences in the tropics have been bad because overall it really has been amazing. I have been fortunate enough to see an incredible assortment of bird species, such as the Elegant Trogan, Blue-crowned Motmot, Keel-billed Toucan, and Long-tailed Manakin. And it’s not just birds. There are monkeys too. Yes, they throw sticks at you and sometimes try to pee on you (one missed me by about a foot last summer), but getting to watch them move through the trees each morning is more than worth it. It’s also really cool seeing different species of snakes (including some that are extremely venomous), frogs, lizards, and mammals like Tamanduas, Coatis, and Agoutis. We even saw a Tapir this summer! Having the opportunity to see so many cool animals on a daily basis is really awesome, and by far my favourite part of doing fieldwork in the tropics.

Perhaps the most incredible thing I have experienced during my time in Costa Rica is what my lab refers to as “Toad Day”. Once a year, for only 1-2 days after the first large rainfall of the year in May, huge numbers of frogs and toads congregate at previously dried-out ponds and rivers in the park as they begin to fill up with water. Hundreds of them come to the water and begin to chorus together in order to attract females to come and breed. Many species do this, including Cane Toads, Mexican Burrowing Toads, and several species of tree frogs, but the most interesting of them all is the Yellow Toad. For most of the year, males and females of this species look like your typical run-of-the mill toads, mostly brown in colour with the occasional splotch of grey or rufous. However, as soon as it starts to rain in early to mid-May, the males turn a spectacular lemon-yellow as they congregate at the breeding pools. This transformation corresponds with intense competition for females, and aggressive fights between 2,3,4 or more toads for a single female are common to see. This sight – hundreds of bright yellow toads and other species chorusing together all in one place – is one of the most incredible things I have ever seen, and is something I look forward to every time I go back to the field.

A group of male Yellow Toads (Incilius luetkenii) at a breeding pond in Santa Rosa National Park.

Anyone who has done field work knows  it can be a rollercoaster of highs and lows, an endless series of amazing experiences and unique challenges. This is especially true in the tropics. On one hand, there are tick balls, venomous snakes, valleys of slippery boulders, and hordes of biting ants to deal with. On the other, there are amazing animals to see, scenic beaches to swim at, and daily exposure to unique tropical ecology. I have had a blast over the past two field seasons in Costa Rica, and I would highly recommend that others  go down and do fieldwork in the tropics if they get the chance!

Zach Kahn is a 2^nd year Masters student in Dan Mennill’s bioacoustics lab at the University of Windsor, studying the behavioural ecology of tropical wrens in Costa Rica. He completed his undergraduate degree in 2015 at Queens University, where he studied interspecific competition in closely-related songbirds for his Honours thesis project under Paul Martin. He is passionate about wildlife ecology, natural history, and conservation, as well as being outdoors and playing softball and football.