Prioritizing tropical habitats for long-distance migratory songbirds: an assessment of habitat quality at a stopover site in Colombia

Abstract

ABSTRACT. Long-distance migratory birds are declining globally and migration has been identified as the primary source of mortality in this group. Despite this, our lack of knowledge of habitat use and quality at stopovers, i.e., sites where the energy for migration is accumulated, remains a barrier to designing appropriate conservation measures, especially in tropical regions. There is therefore an urgent need to assess stopover habitat quality and concurrently identify efficient and cost-effective methods for doing so. Given that fuel deposition rates directly influence stopover duration, departure fuel load, and subsequent speed of migration, they are expected to provide a direct measure of habitat quality and have the advantage of being measurable through body-mass changes. Here, we examined seven potential indicators of quality, including body-mass change, for two ecologically distinct Neotropical migratory landbirds on stopover in shade-coffee plantations and tropical humid premontane forest during spring migration in Colombia: (1) rate of body-mass change; (2) foraging rate; (3) recapture rate; (4) density; (5) flock size; (6) age and sex ratios; and (7) body-mass distribution. We found higher rates of mass change in premontane forest than in shade-coffee in Tennessee Warbler Oreothlypis peregrina, a difference that was mirrored in higher densities and body masses in forest. In Gray-cheeked Thrush Catharus minimus, a lack of recaptures in shade-coffee and higher densities in forest, also suggested that forest provided superior fueling conditions. For a reliable assessment of habitat quality, we therefore recommend using a suite of indicators, taking into account each species' ecology and methodological considerations. Our results also imply that birds stopping over in lower quality habitats may spend a longer time migrating and require more stopovers, potentially leading to important carryover effects on reproductive fitness. Evaluating habitat quality is therefore imperative prior to defining the conservation value of newly identified stopover regions.Priorisation de milieux tropicaux visant des passereaux migrateurs de longue distance : évaluation de la qualité de l'habitat dans une halte migratoire en Colombie RÉSUMÉ. Les oiseaux migrateurs de longue distance sont en diminution sur la planète et la migration a été pointée du doigt comme source primaire de mortalité chez ce groupe. Malgré ce constat, notre manque de connaissance sur l'utilisation et la qualité de l'habitat aux haltes migratoires -c.-à-d. les sites où les oiseaux accumulent l'énergie en vue de la migration -limite notre capacité à déterminer les mesures de conservation appropriées, spécialement dans les régions tropicales. L'évaluation de la qualité de l'habitat aux haltes est donc urgente, de même que la détermination de méthodes efficaces et rentables pour s'y prendre. Étant donné que les taux d'accumulation d'énergie influent directement sur la durée de séjour aux haltes, la charge d'énergie au départ d'une halte et la vitesse subséqu...

Major stopover regions and migratory bottlenecks for Nearctic-Neotropical landbirds within the Neotropics: a review

“…Indeed, with time-minimiation emerging as the main currency shaping the evolution of migration strategies (Alerstam 2011), migratory birds are expected to seek out sites that maximize their fuel deposition rate and, accordingly, their speed of migration (Buler et al 2007, La Sorte et al 2014a. It follows that one of the fundamental needs of migratory birds is therefore the availability of high quality habitats (those supporting high fuel deposition rates), in specific regions along their migratory route (Weber et al 1999, Bayly et al 2016. These habitats Figure 1.…”

“…For example, in northern Colombia, where geolocators have identified a general region used by Veery for autumn stopover (Heckscher et al 2011, Hobson andKardynal 2015), it is possible to travel from snow-capped peaks, through humid montane forest, to xeric scrub in less than 100 km. Only through detailed mark-recapture studies within that region has the high value of foothill and pre-montane forest been demonstrated for Veery and other Nearctic-Neotropical migrants (Bayly et al 2012a(Bayly et al , 2016.…”

Habitat selection in transformed landscapes and the role of forest remnants and shade coffee in the conservation of resident birds

“…Shade coffee plantations have been promoted as a biodiversity‐friendly production system that can harbour communities intermediate between those of sun coffee monocultures and remnants of native forest (Jha et al, ; Perfecto, Rice, Greenberg, & VanderVoort, ; Philpott et al, ), so financial tools and social incentives have arisen to prevent their replacement by homogeneous land uses (Perfecto, Vandermeer, Mas, & Pinto, ; Philpott, Bichier, Rice, & Greenberg, ). However, most assessments of the conservation value of tropical agroforestry systems rely heavily on community‐level measures (Hughes, Daily, & Ehrlich, ; Petit & Petit, ), and while there is recent evidence on differences for migrant birds (Bakermans, Vitz, Rodewald, & Rengifo, ; Bayly, Gómez, Hobson, & Rosenberg, ), information on demography and persistence of resident species is still scarce (Gleffe, Collazo, Groom, & Miranda‐Castro, ; Irizarry, Collazo, Pacifici, Reich, & Battle, ; Komar, ; Sánchez‐Clavijo, Arbeláez‐Alvarado, & Renjifo, ).…”

Conservation of Nearctic Neotropical migrants: the coffee connection revisited

“…Indeed, the conservation value of shaded coffee may be higher in areas of high deforestation and those lacking protected areas, where plantations may be the only forest-like habitat suitable for migrants (Perfecto et al 1996, Bakermans et al 2009). Neotropical migrants have been forced into this agroecosystem in response to the loss of natural habitat, and the quality of shade coffee plantations relative to the native forests from where they were carved is still to be fully addressed (but see Bakermans et al 2009, Bayly et al 2016. While conservation efforts to maintain shade coffee plantations are critical, efforts to restore or protect remaining forest are also needed.…”