ABSTRACT
The cranio-mandibular complex is an important structure involved in food capture and processing. Its morphology is related to the nature of the food item. Jaw muscles enable the motion of this complex and their study is essential for functional and evolutionary analysis. The present study compares available behavioral and dietary data obtained from the literature with novel results from functional morphological analyses of the cranio-mandibular complex of the Guira cuckoo (Guira guira) to understand its relationship with the zoophagous trophic habit of this species. The bite force was estimated based on muscle dissections, measurements of the physiological cross-sectional area, and biomechanical modeling of the skull. The results were compared with the available functional morphological data for other birds. The standardized bite force of G. guira is higher than predicted for exclusively zoophagous birds, but lower than for granivorous and/or omnivorous birds. Guira guira possesses the generalized jaw muscular system of neognathous birds, but some features can be related to its trophic habit. The external adductor muscles act mainly during food item processing and multiple aspects of this muscle group are interpreted to increase bite force, that is, their high values of muscle mass, their mechanical advantage (MA), and their perpendicular orientation when the beak is closed. The m. depressor mandibulae and the m. pterygoideus dorsalis et ventralis are interpreted to prioritize speed of action (low MA values), being most important during prey capture. The supposed ecological significance of these traits is the potential to widen the range of prey size that can be processed and the possibility of rapidly capturing agile prey through changes in the leverage of the muscles involved in opening and closing of the bill. This contributes to the trophic versatility of the species and its ability to thrive in different habitats, including urban areas.
Subject(s)
Birds/anatomy & histology , Birds/physiology , Animals , Biological Evolution , Biomechanical Phenomena , Bite Force , Jaw/anatomy & histology , Muscle, Skeletal/anatomy & histology , Skull/anatomy & histologyABSTRACT
We studied stomachs contents of 50 specimens of four common cuckoo species (Cuculidae) from southern Brazil: Guira guira (Gmelin, 1788) (n = 21), Coccyzus melacoryphus (Vieillot, 1817) (n = 8), Crotophaga ani (Linnaeus, 1758) (n = 11), and Piaya cayana (Linnaeus, 1766) (n = 10). We measured stomach volume and prey were identified and quantified based in their dimensions. The size of the prey was associated with bill width and body mass. Diet items were analyzed and identified to the lowest possible taxonomic level, based on literature, scientific collection data, and specialists. The diet of the four species was composed by 100% animal species, with invertebrate dominance. Only in G. guira stomachs the presence of vertebrates was observed more than once (amphibian, reptile, and bird). C. ani, which had similar diet, ingested a large number of Arachnida and Orthoptera. Piaya cayana ate mostly Hemiptera. The predominance of caterpillars (Lepidoptera), suggested in the literature was not observed in the diet of C. melacoryphus. There was a statistically significant difference in bill width and body mass among the bird species, and there was no correlation between bill width and the proportion of medium and large-sized prey.
ABSTRACT
We studied stomachs contents of 50 specimens of four common cuckoo species (Cuculidae) from southern Brazil: Guira guira (Gmelin, 1788) (n = 21), Coccyzus melacoryphus (Vieillot, 1817) (n = 8), Crotophaga ani (Linnaeus, 1758) (n = 11), and Piaya cayana (Linnaeus, 1766) (n = 10). We measured stomach volume and prey were identified and quantified based in their dimensions. The size of the prey was associated with bill width and body mass. Diet items were analyzed and identified to the lowest possible taxonomic level, based on literature, scientific collection data, and specialists. The diet of the four species was composed by 100% animal species, with invertebrate dominance. Only in G. guira stomachs the presence of vertebrates was observed more than once (amphibian, reptile, and bird). C. ani, which had similar diet, ingested a large number of Arachnida and Orthoptera. Piaya cayana ate mostly Hemiptera. The predominance of caterpillars (Lepidoptera), suggested in the literature was not observed in the diet of C. melacoryphus. There was a statistically significant difference in bill width and body mass among the bird species, and there was no correlation between bill width and the proportion of medium and large-sized prey.
ABSTRACT
Feeding ecology of the Guira Cuckoo (Guira guira) in the northeastern Buenos Aires Province. We studied the diet and feeding ecology of the Guira Cuckoo (Guira guira), a bird that has a wide distribution in Argentina. We analyzed 62 stomachs, obtained between 1991 and 1997 (26 in spring, 13 in summer, 10 in autumn and 13 in winter), in the localities La Balandra and Punta Blanca, Magdalena district, Buenos Aires province. in order to establish the contribution of each prey item, we applied the relative importance index. The dietary contribution in terms of number and volume was also taken into account. This species feeds only on animals. The trophic spectrum was determined on the basis of the identification of 92 items, all of animal origin, principally insecta (98 %), Annelida, Mollusca, Arachnida, Crustacea, Amphibia, Reptilia and Aves. in conclusion, G. guira is a opportunistic species that consumes animal preys exclusively. Rev. Biol. Trop. 56 (4): 1883-1892. Epub 2008 December 12.
Se estudió la dieta y ecología alimentaria del ave conocida en Argentina como Pirincho (Guira guira), a través del análisis de 62 contenidos estomacales. Las muestras fueron obtenidas entre 1991 y 1997 (23 en primavera, 16 en verano, 10 en otoño y 13 en invierno), en las localidades de La Balandra y Punta Blanca, partido de Magdalena, provincia de Buenos Aires. Ambos sexos fueron analizados en conjunto debido a que no se encontraron diferencias significativas en el número y en el peso de las presas consumidas por machos y hembras (U de Mann-Whitney). La dieta estuvo compuesta en un 100 % por ítemes de origen animal, representada por 92 entidades taxonómicas. Los invertebrados constituyeron más del 96% de la muestra por número, y los vertebrados un 31% del peso total. Los insectos fueron hallados en el 98% de las muestras, representando el 85% y 59% en número y peso del total consumido, respectivamente. En los contenidos estomacales se hallaron además anélidos, moluscos, crustáceos, arácnidos, anfibios, reptiles y aves. Estacionalmente no se encontraron diferencias significativas en el número de las presas capturadas. En lo referente al peso, las muestras de invierno resultaron más pesadas que las de primavera y verano (Kruskal-Wallis). El Pirincho es un ave oportunista que consume exclusivamente presas de origen animal.