We call them layovers, birds call them stopovers

Bird migration is awe-inspiring. Animals mostly made of feathers take to the sky and complete round-trip journeys up to 40,000 kilometers long. The extremists migrate nonstop. Some fast the entire way. Most migratory species, however, engage in what ornithologists refer to as “stopovers” to refuel, rest, and wait out storms. A new literature review published in the Journal of Raptor Research emphasizes the need for more investigation into the importance of these stopover sites, newly defined in the review as places where individuals “pause their migratory movements for at least twenty-four hours.” Raptors are top predators with far-reaching impacts on their surrounding habitat, and they respond quickly to environmental change, making them effective bioindicators. Bolstering our knowledge of which areas are most crucial to the success of these long-distance journeys is therefore necessary, and increasingly possible as tracking technology improves. 
 

The review, titled “Why Does Studying Migratory Raptor Stopover Sites Matter?”, analyzed 61 peer-reviewed publications from all over the world that studied raptor stopover sites, from the 1980’s through 2024. The reviewers’ aim was to summarize the current state of knowledge on stopover sites, specifically for diurnal raptors, meaning species active during the day. 
 

The authors revealed 35 focal raptor species across the publications, with the Osprey (Pandion haliaetus) being the most studied. Many studies were conducted in Europe or North America, and satellite telemetry was the most frequently use methodology. 

Lead author on the review Adelaida Pérez Cadavid and her coauthor Ernesto Ruelas Inzunza from the Institute of Biotechnology and Applied Ecology at Veracruz University, were surprised to see how little research has been conducted on stopover sites and that even less has been done to propose conservation initiatives for high impact sites. “Conservation is an intuitive, logical derivation of studying stopover sites,” says Ruelas Inzunza, “and one of our calls is for experts to identify and recommend more decidedly what threats should be addressed at these locations in the future.”
 

The reviewed studies mentioned an array of human-caused threats to raptors including climate change, acidification of water bodies, direct persecution such as shooting and poisoning, exposure to pollutants, human and predator-induced disturbance, renewable power development, collisions such as vehicle hits, and habitat loss and fragmentation. The latter was the incentive for conducting this review, as Veracruz Mexico has lost over 80% of its tropical dry forest, now one of the rarest habitat types on the globe, and an important forest for raptors traveling through that region on their way further south. “Habitat scarcity is an issue when you have a large proportion of the total global population of some species migrating through one bottleneck,” says Ruelas Inzunza. 
 

Many migratory species of raptors are on the decline globally. Yet, most studies and conservation actions of migratory raptors occur during breeding season, leaving migration and the non-breeding season comparatively understudied. Ruelas Inzunza and Pérez Cadavid hope their work will inspire raptor researchers to engage in more international partnerships, prioritize research on this topic, and better inform managers in charge of delineating conservation areas that could support these struggling species. Protecting stopover sites will likely require collaboration between policy makers, conservationists, and biologists, sometimes internationally. Birds don’t see borders, and many species such as Osprey, Cooper’s Hawks (Astur cooperii), Oriental Honey-buzzards (Pernis ptilorynchus), Sharp-shinned Hawks (Accipiter striatus), Turkey Vultures (Cathartes aura), and Broad-winged Hawks (Buteo platypterus) will benefit if decisionmakers protect stopover sites across geopolitical lines. 

###

Paper:

Pérez Cadavid, Adelaida and Ruelas Inzunza, Ernesto (2026). Why Does Studying Migratory Raptor Stopover Sites Matter? Journal of Raptor Research, 60(1):1-12. 
DOI: 10.3356/jrr251

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.