Notes on the breeding biology of Rufous Potoos in lowland Ecuadorian Amazon

Potoos are some of the most intriguing birds of the Neotropics. Strictly nocturnal and very hard to see, they hunt insects from a perch, with a technique similar to the used by flycatchers. During the day they perch upright on tree stumps, camouflaging so good that they look like part of the stump or like a dead leaf. There are seven species of Potoos⁠—all from the new world—and five of them inhabit Ecuador. From these, the Rufuos Potoo (Nyctibius bracteatus) is the smallest of the species and perhaps the least known. Rufous Potoos are named after their reddish-brown coloring, that resembles the color of rust or oxidized iron. They have white spots that look like the fungus that sometimes grows on plants. When threatened, they rock back and forth to make themselves look like leaves fluttering in the breeze. This makes them almost impossible to be noticed by an untrained eye.

In August of 2018, while on a night hike in the forest of Tiputini Biodiversity Station in the Ecuadorian amazon, we noticed a bird flying slowly among the understory. When we carefully approached, it turned out to be an individual of a Rufuos Potoo, that was perched on a broken trunk of Rinorea sp. (Violaceae). It stayed there until the next day. This was an incredible finding, since these potoos are usually extremely hard to spot without previous knowledge of a roosting site. Having a resting site identified is a great opportunity to gather data on poorly known species. In the case of the potoo, only little is known about their reproductive ecology and nesting behavior. Subsequent visits revealed the bird on the same tree most of the time, suggesting a possible nest site.

We decided to conduct observations opportunistically for a few days, and things got very interesting. After two weeks, on 27 August, we observed that there was a nestling! It was hard to distinguish because it was almost completely covered by the adult’s ventral feathers, but it was there. A few days later, by 5 September, the nestling was completely visible and appeared to have doubled in size. Two days later, it was observed alone for the first time, remaining motionless even as we approached. We decided to use a camera trap to record every time the potoos (adult(s) and nestling) moved during both day and night and record nestling behavior and parental care. We obtained more than 2000 videos over the subsequent two months, were the nestling was on the trunk most of the time usually perched motionless on the tree. The adult was perched next to the nestling most of the time, but also engaged in other activities, including feeding the nestling. Over time, the adult starting to spend less and less time brooding the nestling. Thanks to the data recorded by the camera trap, we were able to obtain important information on different categories of behavior of both the chick and the adult, like preening, feeding or foraging and also behavior related to physical development, like exercising of flight muscles or stretching. On October 16th, after 51 days, the bird decided to move to a different place in the forest and fledged.

Thanks to the continuous monitoring, in the later days we recorded another Rufous Potoo on the same nest-site trunk. Based on the length of the tail and its behavior we were able to tell that it was not the fledgling. We were lucky enough to record a few vocalizations in the next few days. To our surprise, one day, immediately after a call a second Rufous Potoo came and copulated with the one already perched! To our knowledge, this was the first time an event like this has been recorded.

Rufous Potoos have always been a mystery to birdwatchers and scientists. They are rarely spotted in the wild and no one had much information on where they made their nests, how they take care of the nestling or simply what they do during the day. Our observations suggest that the reproductive and nestling behaviors of Rufous Potoos are similar to those reported for other Nyctibius species. Our study provides new insights on the behavior of this amazing species, but additional and more complex studies are required to get a better knowledge of this always elusive species.

 

This research was recently published in the Journal of Field Ornithology:

Vinueza‐Hidalgo, G. S., D. Mosquera, and J. G. Blake. 2019. Notes on the breeding biology of Rufous Potoos (Nyctibius bracteatus) in lowland Ecuadorian Amazon. Journal of Field Ornithology. https://doi.org/10.1111/jofo.12304.

 

Guest post by:

Diego Mosquera
Estación de Biodiversidad Tiputini,
Colegio de Ciencias Biológicas y Ambientales,
Universidad San Francisco de Quito