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Folivory by a tropical tanager: species of plants used and the relationship between leaf consumption and fruit abundance

Authors

  • Tomás A. Carlo,

    Corresponding author
    1. Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802, USA
      Corresponding author. Email: tac17@psu.edu
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  • Raúl A. Pérez-Rivera,

    1. Departamento de Biología, Universidad de Puerto Rico-Humacao, Humacao, Puerto Rico 00791, USA
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  • Jason M. Gelditsch

    1. Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802, USA
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Corresponding author. Email: tac17@psu.edu

Abstract

ABSTRACT Folivory, or eating leaves, is unusual for small passerines. Puerto Rican Spindalises (Spindalis portoricensis, Thraupidae), tanagers endemic to the island of Puerto Rico, are known to feed on leaves, but little is known about the possible importance of leaves in their diet. Our objectives were to determine the different species of leaves eaten, the percentage of their diet consisting of leaves, and the relationship between leaf consumption and fruit abundance. We used data from previous studies where the foraging activity of Puerto Rican Spindalises was systematically sampled, and from additional observations made throughout the island. We documented 160 records of folivory, with spindalises feeding on 44 plant species in 25 plant families, including monocots, dicots, gymnosperms, and pteridophytes. Spindalises fed on young leaves of 26 plant species, and mature leaves of 19 plant species. Spindalises were primarly frugivorous (83.9% of diet), but leaves were the second most frequent food item in their diets (8.9% of diet). We also found that leaf consumption was negatively correlated with the abundance of ripe fruit, suggesting that leaves were particularly important food items when less fruit was available. The frequency of folivory by spindalises in our study was less than reported for other folivorous passerines such as plantcutters (Phytotoma spp.) and saltators (Saltator spp.). Nonetheless, folivory may help spindalises cope with human-dominated landscapes and other environmental changes on small islands.

RESUMEN

La folivoría, entiéndase el consumo de hojas, es poco usual en pequeños Passeriformes. La Reina Mora (Spindalis portoricensis) es un ave endémica a la isla de Puerto Rico que se conoce por consumir hojas, pero se sabe poco al respecto. Los objetivos de este estudio lo fueron el determinar la variedad de especies de planta que consume esta ave, determinar el porcentaje de la dieta compuesto por hojas, y examinar la relación entre la frecuencia de récords de folivoría y la abundancia de frutos en el ambiente. Para esto juntamos datos observacionales provenientes de estudios sistemáticos sobre la alimentación de la Reina Mora, así como datos de observaciones informales colectados en distintos puntos de la isla. Documentamos 160 récords de folivoría en la Reina Mora que incluyeron hojas de unas 44 especies de planta pertenecientes a 25 familias que incluían monocotiledóneas, dicotiledóneas, gimnospermas, y pteridófitas. La Reina Mora es principalmente frugívora (83.9% en promedio), pero las hojas constituyeron el segundo tipo de alimento más importante en su dieta (8.9% en promedio). Hallamos que el consumo de hojas estuvo negativamente correlacionado con la abundancia de frutos en el ambiente. La proporción de la dieta de la Reina Mora compuesta por hojas es menor que las reportadas para otros Passeriformes folívoros como los cortarramas (Phytotoma spp.) y los Saltator (Saltator spp.). Sin embargo, es posible que la capacidad de la Reina Mora de consumir hojas sea uno de los factores que ayuda a esta especie a sobrevivir en paisajes antropogénicos, así como de lidiar con cambios y fluctuaciones ambientales en islas.

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