For the Love of an Ovenbird

Citizen Science in Latin America

A peculiar little bird with an odd-shaped nest has inspired people across Latin America to help with the study of Argentinian biologists finishing their Ph.D. at the Max Planck Institute for Ornithology in Seewiesen, Germany.

The first time that I heard about citizen science was at a conference in marine science held at my university. The concept of doing science as a community sounded like a perfect way to get people aware and directly engaged with environmental issues and with the underlying science. 

A colleague of mine remarked in a recent article (Balza, 2019), that the results of current scientific work are usually only read or distributed among those who work in the field—only scientists specialized in our niche of study. That is a bit frustrating, especially when doing conservation or basic science. Citizen science creates a way to involve the rest of the population not only in the process of making science but in sharing it as well. This expands the reach of our work making more people aware of it. 

‘Hornero’ is a project that has all the ingredients to enable great citizen science. The project’s data collection process is easy and accessible: anyone with a phone and good observation skills is able to participate. The project is also inclusive as age, location, educational background or professional credentials do not matter.

© Nicolas Andreani and Lucia Mentesana

The Hornero project was born like any other scientific project, with a question: What are the factors that determine where the bird places the entrance to its very distinctive oven-shaped nest? 

That is the question that Lucia Mentesana and Nicolas Andreani—the brains behind the project—wanted to investigate. Lucia and Nicolas are Argentinian biologists finishing their Ph.D. at the Max Planck Institute for Ornithology in Seewiesen, Germany. The idea, says Lucia, came after attending a colleague’s presentation about asymmetries in scale-eating fish. The presentation described how some fish have their mouths towards one side of the body and how it affects their feeding behavior (Takeuchi et al., 2016). Then, Lucia and Nicolas recalled that the suboscine ovenbird (Furnarius rufus, or Rufous Hornero) also deals with a natural asymmetry, but one that is characteristic of its nest structure rather than of the morphology of the bird itself (Gmelin, 1788).

The nest of the ovenbird consists of a mud structure with a curved entrance that separates the breeding chamber from the outside (Turienzo et al., 2019). Nests can be positioned on top of a variety of supports such as statues, trees, lamp posts or even the ceiling of your house. The entrance of these nests can be either on the right or on the left of their support. Both the male and the female partake in the building of the nest whose entrance is positioned late during the construction process. 

A pair of ‘horneros’ building their nest | © Mario Oscar Roqueta

While doing initial research, Mentesana and Andreani found a study about the orientation of the entrance of the nest related to the earth (Schaaf et al. 2018) but nothing about the asymmetry of the nest. This prompted the idea of the project.

The success of ‘Hornero’ as a citizen science project lies in that the bird is a species easy to study: its nest is easily recognizable, and the bird is widely distributed across several countries of South America. It can be found in urban, rural and natural areas (Souza & Santos, 2007). Furthermore, the bird is an important part of the culture in all the countries where it can be found. Musicians and poets from different countries have written about the ovenbird (e.g., Maria Elena Walsh, Atahualpa Yupanqui, and Adrian Maggi, among others).

One hypothesis about the asymmetry of the nest is that the bird chooses randomly where to position the entrance (on the left or right side of the nest). Nicolas and Lucia were not satisfied with this hypothesis and proposed another one: “We consider four possible scenarios: (1) Nest asymmetry is a random phenotype; (2) Nest asymmetry is determined by environmental variables (e.g., temperature, winds, and rainfall, among others); (3) Asymmetry is a consequence of a learning process, or (4) Asymmetry is genetically determined”.

Analyzing all these variables would imply recording lots of measurements and taking abundant visual data in the field in order to get a representative sample of the nests under a variety of environmental and from genetically isolated populations. In the beginning, they considered carrying the fieldwork themselves. However, this approach raised a couple of major issues. First, it would amount to a lot of work for only two people. Secondly, the sampling area that they could reasonably cover would be very small in comparison with the wide distribution of the species. Instead, they implemented a  citizen science project, including the development of a data recording app. The intent was to gather as many observations as possible over a much wider geographical area than originally considered. In October 2018 they launched the project in both Argentina and Uruguay. 

Citizen scientist visual recording of a nest | © Lucia Mentesana and Nicolas Andreani

The data recording app prompts citizen scientists to answer a few questions about the nest. Observers locate the side of the entrance of the nest; they document the height and the natural context of the nest (e.g, urban or countryside environment, on natural vs. man-made structure); they record the cardinal direction of the entrance (information that can be found using the compass of the phone), and they provide a picture of the nest. The principle is easy: If you find yourself on a trail of a natural reserve near your home doing some outdoor activity and spot a nest, then you can open the app (free), answer all the questions relating to what you are looking at. it’s also gratifying as each observation contributes to a cutting edge study about this bird with such a particular behavior.

The project was intended to document the hornero ovenbirds in Argentina and closeby Uruguay. But this species is widely spread all around South America  (Massoni et al., 2012), and is truly a charismatic bird for many, so the project expanded on its own. After releasing the app both in Argentina and Uruguay, Lucia and Nicolas started receiving messages from other countries asking that the app be available there as well. And so the project got data from a much wider range including from Paraguay, Brazil, and Bolivia.

The data collection phase has been completed. Lucia and Nicolas are currently analyzing the information that was collected during 2018-2019. They already have some preliminary results. 

  • More than 1,000 observers from 5 different countries participated in the study using the app (Argentina, Uruguay, Paraguay, Brazil, and Bolivia).
  • About 13,325 nests were documented. Special mention: A single user from Entre Rios, in Argentina, documented more than 1,000 nests! 
  • On average 1,000 nests were documented monthly.
  • Data quality checking showed that on a sample of a thousand observed nests, 95% of those were correctly documented (this includes correct reporting of the nest asymmetry, completion of the building of the nest structure,  and its situational data).
  • More than 60 % of the documented nests have their entrance on the right side of the nest.

Soon, we will more when Lucia and Nicolas publish their findings and reveal what they have learned about the bird’s nest-building behavior. Meanwhile, one can seek information about the project on and get news and updates through the project’s social media (Facebook, Twitter, and Instagram).

As is usually the case with citizen science projects, “Project Hornero builds a bridge between science and society” (Mentesana). Anyone can do science while building an answer to a question born out of curiosity. As a result, more questions can surface just by observing our surroundings. 

Field citizen science is great at connecting people to their immediate and surrounding natural habitat, as well as making observers aware that in most cases, we are sharing our home with many other species. What we all learn when we are out there documenting nature is that respect and tolerance are the keys to coexistence. 


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April 10th, 2020 | by  Carolina Pantano 

Banner and References section photos © Natalia Allenspach

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