FEBRERO 2020

Documenting the nesting biology of a secretive Neotropical bird

Two days after I graduated with my bachelor’s degree from the University of Idaho in 2015, I was on a plane heading south from rural northern Idaho to the Colombian cloud forest. There, I worked with Dr. Gustavo Londoño and his incredible colleagues at the Zygia Research Station to document the ecology and breeding biology of Neotropical birds in the Andes.

Each day was an adventure. I woke up with the sunrise and spent the day hiking to search for nesting birds. Luckily for my colleagues and I, not all birds nest high in the canopy. Nope—some will nest in arms reach. Birds can nest in the crooks of trees, inside decaying stumps, on the undersides of fern fronds, or elsewhere. For example, I found a nest of the Black-throated Tody-tyrant (Hemitriccus granadensis) in a low-hanging moss ball next to an underused trail. Surprisingly, there was scarce information about this species’ breeding biology and I had the opportunity to describe its nest for the first time in the Wilson Journal of Ornithology (McCullough and Londoño 2018).

Different types of nests we found in 2015 at the Zygia Research Station. A) Gray-breasted Wood-wren (Heinicorhina leucophrys); B) Green-and-black Fruiteater (Pipreola riefferii); C) Black-throated Tody-tyrant (Hemitriccus granadensis) from McCullough and Londoño 2018; and D) Blackish Tapaculo (Scytalopus latrans) from McCullough et al. 2019. 

Small passerines will also nest underground. This is the case for the Blackish Tapaculo (Scytalopus latrans), which is a small, dark, secretive songbird that lives in the Andes cloud forests of Colombia, Ecuador, and Peru. Tapaculos are difficult birds to study, as their reclusive behavior and monomorphic plumage makes it difficult to find and correctly identify them. This difficulty also applies to studies of their reproductive behavior because many tapaculos build nests underground. For the nest we found of Blackish Tapaculo, Wieland flushed an adult out of its nest while walking along a trail. Just by sight alone, we never would have found the nest as the entrance looked like any other leaf litter (McCullough et al. 2019). Flushing birds off nests while walking along trails was the single best way we found nests.

The nest, eggs, and nestlings of the Blackish Tapaculo. A) The nest’s entrance was in a bank near a trail. B) The dome nest, made of rootlets and fibers, was underground. We excavated the nest after successful fledging. C) The two eggs were pale white. D) The nestlings hatched 13 days after discovery and the nestlings were covered in gray down. E) The day of fledgling at 13 days old. Figure adapted from McCullough et al. 2019.

As our tapaculo nest progressed from eggs to fledglings, Wieland and I measured and photographed the nestlings each day. Though the nest and eggs of Blackish Tapaculo has been described previously, we were the first to document its nestlings, their growth, and the parent’s incubation behavior. We also installed a motion sensor camera to passively monitor adult behavior and observe the exact timing when the nestlings walked out of the nest for the first and final time. In the process, we recorded 543 hours and >56,000 photos of the parent’s behavior as the nestlings hatched and matured. Back in the United States, I reviewed the thousands of photos and counted the number of trips and food deliveries made by the parents. Of the food delivered to the nestlings, most were small flying insects. But I was surprised to discover an adult delivering a small frog to the nestlings! This was quite exciting for me, as it is the first record of any tapaculo species taking a vertebrate as a prey item. Our observations suggest that tapaculos could be more opportunistic than we once thought. It’s also a lesson for myself to sort through camera trap photos, no matter how many thousands, because I may be surprised at what I find. 

Camera trap photos of a parent provisioning the nestlings with a small frog. Look closely! It’s easy to miss the frog in the top right photo. Adapted from McCullough et al. 2019.

Even after nearly five years since my time in the Colombian Andes, I still fondly reminisce about my time at Zygia research station: the beautiful sunrises, spectacular flowers, interesting insects, and of course, the many birds that I was able to observe and measure. For fun, I made a little YouTube video about my time in at Zygia when I returned home in fall 2015. But on a more serious note, the opportunity to collaborate with Dr. Londoño on two papers regarding breeding biology of Neotropical birds was a particularly formative experience for my research career. Truly, the time I spent nest searching in the Colombian Andes were some of the best weeks of my life.

Jenna McCullough, the writer, is a 2nd year PhD student in the Biology Department and Museum of Southwestern Biology at the University of New Mexico. She studies avian evolution in the South Pacific’s many island archipelagoes.