Birds of a feather sleep together: Use of communal roosts by a charismatic raptor

Birds, like other animals, need safe and warm places to sleep. Cozying up in groups can be an effective way to maintain vigilance, conserve heat, and gather information about where to find their next meal. A new study published in the Journal of Raptor Research titled “Use of GPS Telemetry System to Study Communal Roosts in a Neotropical Raptor”tracked 24 Chimango Caracaras (Milvagro chimango) to study their resting, or “roosting” behaviors during the breeding season. Studies like this shed light on what is called the “spatial ecology” of an animal, meaning how organisms are distributed, how they use and move through space, and how interactions between other caracaras and other species unfold as a result. Such information helps biologists understand the importance of particular habitats, as well as how species adapt to changing landscapes.  

Caracaras are charismatic, scrappy members of the falcon family. They look and act like classic raptors but are also champion scavengers. As a result, they are thriving across Argentina in both rural and suburban areas. They are social and gregarious, sometimes breeding in large groups of up to 75 nests at one site and forming communal roosts, described here as “an aggregation of more than two birds that sleep together in the same place.” Author of the paper Claudina Solaro, from UNLPam and the National Research Counsil of Argentina, sought to investigate how consistently Chimango Caracaras use their communal roosts during the breeding season, and whether there were any differences in roost use between sexes or habitat types. 

To achieve this, she trapped 24 individual birds and fitted them with telemetry systems that collected their locations for up to 30 days. She tagged some individuals from a rural site where they roosted in a grove of exotic trees, and some individuals from a suburban site which consisted of native forest patches with trees partially inundated with water from a lake that contained treated wastewater. Ten males and 14 females were tagged in total. 

The birds in Solaro’s study were actively nesting. Both male and female caracaras participate in caring for the young, and therefore all the individuals in this study were roosting within four kilometers of their nest site. Solaro found that females slept in communal roosts less frequently than males, possibly because they are slightly more involved in parental care. The two areas in this study were very different from each other, suggesting that Chimango Caracaras are flexible in site selection for roosting activities. This trait likely aids them in adjusting to environmental change and has perhaps contributed to their widespread presence across Argentina. 

This novel study underscores the importance of behavioral flexibility in shaping the distribution of a raptor species. “This flexibility may allow the Chimango Caracara to inhabit a wide range of environments with different levels of disturbance,” says Solaro. She suggests future studies focus on establishing long-term datasets on the movement ecology of raptors for better understanding on “the processes by which species adapt to anthropogenic disturbance, or fail to do so, leading to potential range contraction.” Such shifts to animal populations are increasing in frequency, and understanding the mechanisms that drive a species to either adapt or falter is crucial to protecting biodiversity on all scales. Solaro emphasizes the importance of focusing on behavioral flexibility in future raptor studies, noting that species that “do not exhibit this flexibility may have their survival and long-term persistence threatened in habitats undergoing constant human-driven transformation.”   

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Paper:

Solaro, Claudina (2026). Use of GPS Telemetry System to Study Communal Roosts in a Neotropical Raptor. Journal of Raptor Research, 60(1):1-7. 
DOI: 10.3356/jrr254

Notes to Editor:

1. The Journal of Raptor Research (JRR) is an international scientific journal dedicated entirely to the dissemination of information about birds of prey. Established in 1967, JRR has published peer-reviewed research on raptor ecology, behavior, life history, conservation, and techniques. JRR is available quarterly to members in electronic and paper format.

2. The Raptor Research Foundation (RRF) is the world’s largest professional society for raptor researchers and conservationists. Founded in 1966 as a non-profit organization, our primary goal is the accumulation and dissemination of scientific information about raptors. The Foundation organizes annual scientific conferences and provides competitive grants & awards for student researchers & conservationists. The Foundation also provides support & networking opportunities for students & early career raptor researchers.