James Kendal Sheppard

Summary: The Thick-billed Parrot Rhynchopsitta pachyrhyncha is an endangered, cavity‑nesting psittacine restricted to increasingly fragmented high‑elevation pine forests of Mexico’s Sierra Madre Occidental, yet its non‑breeding ecology remains poorly known. We analysed multi‑year movement data from parrots to delineate the species’ overwintering range and seasonal habitat, and ground‑truthed predicted core areas during field surveys. The overwintering range lies 380–570 km south of the breeding range in the northern Sierra Madre Occidental, primarily in western Chihuahua and adjoining Durango and Sonora, and is dominated by cool, high‑elevation montane pine and mixed pine–oak forest. We observed large overwintering flocks of 300–900 birds and confirmed intensive use of these core habitats, suggesting that previous wild population estimates of c.2,500 individuals may be conservative. Only a small proportion of the overwintering range is currently under formal protection, with most habitat occurring within managed communal forest landscapes. Our findings provide the first empirical delineation of the Thick-billed Parrot’s overwintering range and highlight priority areas where strengthened habitat protection and conservation agreements with forestry communities will be critical for the species’ recovery.

The thick-billed parrot ( Rhynchopsitta pachyrhyncha ) inhabits highland pine forests in the Sierra Madre Occidental ranges of northwestern Mexico. Their populations have declined significantly to <2000 individuals due to habitat loss, illegal hunting and increasing predation. Despite their ecological and cultural importance and increasingly endangered status, the species is data deficient. Our study aimed to inform and enhance conservation management strategies for thick-billed parrots with information on their spatial ecology, habitat use, migratory behaviors and social associations. We deployed biotelemetry devices to conduct the first tracking study of wild thick-billed parrots. Our study revealed that thick-billed parrots are seasonal migrators, departing their breeding habitats around October and returning from southern habitats around April. Our research also identified previously unknown overwintering sites and migratory stopover locations, as well as a new nesting site. The parrots exhibited high spatial variability in range shifting behavior, but all tracked parrots exhibited range shifts during migration, with durations of 3 to 181 days and distances of 173 to 765 km. They traveled in close social groups and migratory routes primarily followed high-elevation forests along the Sierra Madre Occidental ranges. Home range analysis indicated smaller breeding site ranges and larger overwintering ranges, possibly reflecting nesting constraints and winter food resource dispersion. Parrot spatial associations favored high-elevation forest landscapes with tall and wide-trunked trees, underscoring the importance of preserving old-growth forests for nesting and foraging. Less than 20 % of parrot habitats have formal regulatory protections. Conservation management efforts must focus on increasing protections for nesting areas, overwintering habitats, and key migratory stopover sites. As climate change exacerbates regional threats, integrated management plans involving local stakeholders and communities are essential for the parrots’ long-term survival and the preservation of their old-growth forest habitats.

Summary: We report on what appear to be increasing predation events on nesting Thick-billed Parrots Rhychopsitta pachyrhyncha. Thick-billed Parrots are classified as ‘Endangered’ and their seasonal breeding range is restricted to increasingly fragmented and degraded high elevation mixed conifer forest habitat within the Sierra Madre Occidental region of north-western Mexico. Predation of established breeding pairs has recently contributed to the ongoing decline of Thick-billed Parrot populations by removing mature birds with high reproductive value, which has associated consequences for future recruitment. We observed increasing predation events on nesting Thick-billed Parrots by bobcats Lynx rufus accompanied by kittens throughout the 2018–2019 breeding seasons, and we speculate that recent reductions in bobcat habitat have pushed them into new ranges where they are supplementing their diet with nontraditional prey items.