Greater Ani Research

Please visit Dr. Christie Riehl's website for more information about Greater Anis!

In collaboration with Christie Riehl and her grad students, Drs. Maria Smith and Amanda Savagian, I undertook fieldwork initially aimed at studying collective decision-making in the Greater Ani. Christie has a long-term project on the species based out of the Smithsonian Tropical Research Institute's Barro Colorado Island field station in Panama. The Greater Ani is a unique Neotropical cuckoo, exhibiting obligate communal cooperative breeding. The species' social breeding system involves core groups of two or three (and rarely four) unrelated socially monogamous pairs that lay their eggs in a single nest and cooperate to care for the young. This means that adults are caring for young to which they are not genetically related, and Christie has previously demonstrated that the parents are unable to recognize and preferentially care for their genetic offspring within the nest. Pretty neat, eh? 

The obligate group-living of Greater Anis means that they have interesting evolutionary conundrums and social problems that they have had to overcome and/or currently need to solve. My work with the species was initially focused on one feature of the ani social life, collective decision-making. Unfortunately, the SARS-COV-2 pandemic scuttled that project and all the progress we had made. Much of the work required some heavy lifiting during the non-breeding season to individually mark (i.e., color-band) adult anis. In 2019 and early 2020, I (working with Maria and Amanda) had made great strides towards improving capture rates and building back up the population of marked adults. Summer of 2020 was going to be our first breeding season where we'd collect some of the actual decision-making data. And then...well...the pandemic had other plans. I was not able to return to Panama until the 2022 breeding season. Given the new constraints imposed, we had to shift gears. I was still able to work with Maria to help her tackle the question of whether Greater Anis exhibit division of labor (Smith et al. 2024). For my own work, I shifted to playback experiments. 

Thanks to some keen observations by Dr. Savagian (and some previously excellent published work on the Smooth-billed Ani), we had a hunch that Greater Anis exhibit what is known as referential signaling. In a nutshell, referential signaling is the production of a signal (typically a vocalization) by an individual to inform other individuals of something about the environment. In non-human species, referential signaling frequently takes the form of referential alarm-calling, wherein an individual alerts conspecifics to the presence of a specific type of threat by means of a vocalization only given in the context of that threat. For example, Dr. Leanne Grieves and colleagues demonstrated that Smooth-billed Anis use two different types of referential calls to indicate the presence of aerial and non-aerial predators. Dr. Savagian undertook detailed study of the Greater Anis vocal behavior and noticed a call that they only seemed to give in the presence of raptors, including local threats like Common and Greater Black Hawks. We followed up these observations with playback experiments to see if Greater Anis respond appropriate even in the absence of the actual threat. The results? Greater Anis indeed have a referential alarm-call that appears to mean something like "aerial threat!" or "flying raptor incoming!" Most birds immediately dove or flew to cover when they heard a playback of the call, even though no aerial threats were present during playbacks (LaPergola et al. 2023). What's more, they almost exclusively produce this alarm call in response to true aerial threats, though they occasionally make mistakes (like calling when a Turkey Vulture suddenly appears from behind the canopy). I am now leveraging the Greater Ani's aerial alarm call to ask how these birds utilize personal and social information, including whether they prioritize or integrate information.