Bird banding provides an opportunity to document the return of migratory birds to the same sites, highlighting the importance of conserving their habitats throughout every stage of their annual cycle.
Each year, bird monitoring at Uaxactún and Las Guacamayas Biological Station, within the Maya Biosphere Reserve, helps identify which species use these forests during the nonbreeding season. But some records reveal something more: birds returning to the same sites after months or even years.
Photos by WCS Guatemala. All birds are handled by trained personnel following strict ethical and safety protocols.
Both stations are part of the Monitoring Overwinter Survival (MoSI) Program, an international network of stations that collects data to study bird survival, physical condition, and fidelity to their wintering sites. WCS Guatemala has participated in this effort since 2017.
MoSI stations use fine-mesh mist nets to temporarily capture birds for identification and measurement. Each newly captured individual receives an aluminum band with a unique number, allowing researchers to identify it if it is captured again. When a bird is recaptured, its band number makes it possible to reconstruct part of its history. All procedures are carried out by trained personnel with the appropriate permits, and the birds are released after data collection.
One notable example is a Kentucky Warbler (Geothlypis formosa) first captured in a net at the Uaxactún station during the 2022–2023 season, recaptured in 2023–2024, and again in 2025–2026. This record is part of a broader pattern: individuals of several migratory species, including Wood Thrush, Ovenbird, and Worm-eating Warbler, have been encountered again at the same sites over periods of three, four, or even five years.
“Having these birds in our hands has been an incredible experience because we can observe their characteristics up close. But what is most remarkable is recapturing individuals from previous years, knowing the tremendous effort they make to travel from the United States and Canada. Sometimes, we have even recaptured the same bird in the very same net,” says Marcial Córdova, Bird Program Coordinator at WCS Guatemala.
Results from the 2025–2026 Season
Between November 2025 and March 2026, six monitoring sessions were conducted at the two stations, recording 21 migratory bird species. The most frequently recorded species were Wood Thrush (Hylocichla mustelina), Kentucky Warbler (Geothlypis formosa), and Ovenbird (Seiurus aurocapilla), followed by Hooded Warbler (Setophaga citrina), Gray Catbird (Dumetella carolinensis), and White-eyed Vireo (Vireo griseus).
One of the most significant findings was the recapture of 30 individuals previously recorded in earlier seasons, each at the same station where it had originally been documented: 16 at Uaxactún and 14 at Las Guacamayas. These returns are consistent with interannual fidelity to wintering sites and provide evidence of the birds' repeated use of these forests.
Some of the species recorded have declining populations. One example is the Wood Thrush, for which habitat loss and fragmentation in both its breeding and wintering areas are among the main threats. Conserving this species requires protecting these habitats, as well as the stopover sites it uses for resting and feeding during migration.
Information That Becomes More Valuable Over Time
A single capture documents the presence of a bird; recaptures make it possible to track the same individual over time. This is why monitoring becomes increasingly valuable with each season, revealing patterns of site use and return that could not be identified through isolated records.
At these stations, we have also begun collecting information on resident birds, which inhabit the region year-round. With sustained monitoring, we hope to build a more detailed picture of their populations, how they use the forests of the Maya Forest, and their conservation needs.
From a Bird Band to a Broader Migratory Connection
Feather samples have also been collected during monitoring sessions for genetic studies aimed at understanding migratory connectivity—that is, linking specific populations to the areas they use during different stages of their annual cycle. We hope these samples will contribute to the Bird Genoscape Project, an initiative that uses genetic tools to investigate connections between breeding and nonbreeding areas.
A Long-Term Effort Rooted in Local Communities
During the 2025–2026 season, members of the Caoba Birders Club and participants from the communities of Uaxactún, Yaxhá, La Máquina, and La Pólvora took part in monitoring activities, having received training through various conservation and monitoring initiatives. Their participation helps sustain this work and strengthens local capacity to identify, band, and determine the age of birds by examining their plumage.
This effort is carried out in collaboration with local stakeholders and organizations such as the Cornell Lab of Ornithology, National Audubon Society, Zumbro Valley Audubon, the Biodiverse Landscapes Fund (BLF), and GIZ (German Agency for International Cooperation), among others.
The program welcomes students, researchers, and local and international collaborators interested in visiting the stations and contributing to the monitoring and conservation of resident and migratory birds that use the forests of the Maya Forest.