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Vegetation dynamics and avian seasonal migration: clues from remotely sensed vegetation indices and ecological niche modelling

Authors


Correspondence and current address: M. Papeş, Oklahoma State University, Department of Zoology, 501 Life Sciences West, Stillwater, OK 74078, USA.
E-mail: papes@okstate.edu

Abstract

Aim  Regional movements of tropical birds are among the least understood patterns of migration, generally assumed to be related to seasonality of vegetation and food resources. We used readily available remotely sensed data to analyse this relationship in the three-wattled bellbird (Procnias tricarunculatus), an IUCN Vulnerable canopy frugivorous bird that undergoes localized altitudinal and latitudinal movements between several non-breeding and breeding ranges.

Location  Central America.

Methods  We generated ecological niche models (GARP and Maxent) based on remotely sensed vegetation indices (enhanced vegetation index, EVI; red index, RI; and normalized difference water index, NDWI) that were used as proxies for canopy characteristics and phenological changes between seasons. The variation in EVI was also analysed in relation to known bellbird seasonal migration patterns.

Results  Remotely sensed summaries of intra-annual vegetation variation could not explain known movement patterns of bellbirds breeding in Monteverde Cloud Forest Reserve, Costa Rica. The ecological niche modelling (ENM) framework used for exploring potential movement patterns of another population of bellbirds, observed in March 2004 in Corcovado National Park, Costa Rica, showed that the Atlantic and Pacific lowlands are suitable for the bellbirds year-round, while middle elevations, where breeding may occur, have limited suitability.

Main conclusions  Our findings suggest that: (1) the Corcovado population tracks similar environmental conditions during the non-breeding season; (2) migration to middle elevation breeding sites might be related to factors other than vegetation seasonality or breeding might not be restricted to these elevation ranges; and (3) the lowlands comprising most of the suitable areas for bellbirds are where anthropogenic pressure is highest, so conservation status should consider this threat, and conservation planning should emphasize these areas.

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