Parrots (Order Psittaciformes) are secondary cavity-nesters that depend on existing cavities for nest sites, and consume plant resources of fruits, seeds, and flowers that are highly variable, but little is known of resource selectivity by parrots, or how they deal with variable environments. We reviewed published studies of nest-cavity use by parrots, and those evaluating parrot diet and their relationship with food resources. Most studies have been conducted within the last 20 years and these present data on resource use for only one-third of parrot species worldwide. However, basic information on resource requirements is lacking for the vast majority of Psittaciformes, particularly for species from the Asian region. Nesting studies have found that parrots use nest cavities in large trees, high above the ground, with large nest chambers, of 0.5-1 m deep, and entrance diameters related to body size of the parrot species. A few studies demonstrate that parrots select nest sites based on cavity characteristics, which may influence nest success, but a complete evaluation of adaptive nest site selection by Psittaciformes is lacking. Parrots have varied diets and may employ a combination of strategies of diet switching, habitat shifts, and movements to track food resources. This plasticity in diet and foraging strategy may influence the extent to which parrots can respond to anthropogenic pressures of global change. Parrots may also play an important functional role in forest ecosystems, yet little is currently known of plant-animal interactions of parrots, or the impact of parrot populations on forest dynamics. Based on our review of the literature, we suggest that to meet their resource requirements, parrots employ resource selection strategies of hierarchical nest site selection to increase the likelihood of nest success, and plasticity in diet and foraging strategy to track variable food resources. Future studies need to evaluate resource selection and the consequences of this for fitness in order to assess the potential impacts of global change on parrot populations, and to identify characteristics which make species vulnerable to human pressures.
Background: Dietary specialization should arise when there is a relatively high abundance of a particular resource, where animals may select food items to obtain an optimal diet that maximizes energy intake. Large-bodied psittacines frequently exhibit a narrow dietary niche with specific habitat use, but few studies have determined whether psittacines select food resources, and how this influences habitat use. Methods: We established fruiting phenology transects to evaluate food resource availability for the large-bodied Military Macaw (Ara militaris) in semi-deciduous, deciduous, and pine-oak forest at two sites along the coast of Jalisco, during the dry season when macaws are nesting. We also determined Military Macaw diet by observations of foraging macaws along transect routes, and conducted bromatological analysis of the nutritional content of the most consumed resource. Results: Military Macaws used six plant species as food items during the dry season, and had a narrow dietary niche (Levins' B = 0.28), with 56% of foraging macaws consuming the seeds of Hura polyandra. No food resources were recorded in pine-oak forest during the dry season, with food resources and foraging by macaws concentrated in tropical deciduous and semi-deciduous forest, where H. polyandra was the most abundant fruiting tree species. When considering the proportional availability of food resources, we determined a broad Hurlbert dietary niche breadth of H = 0.67, indicating that Military Macaws consumed food resources according to their availability. Furthermore, the seeds of H. polyandra were an important source of protein, carbohydrates, minerals and moisture, and the hard fruitcasing means that these seeds are exclusively available for macaws. Conclusions: By concentrating their diet on the most abundant resources, Military Macaws may increase foraging efficiency in the dry season. The high nutrient content also means that concentrating the diet on seeds of H. polyandra may be an optimal foraging strategy for Military Macaws to meet their energy requirements during the breeding season.
ResumenMás del 26% de las especies de aves que habitan en México está declinando. Los ornitólogos han propuesto diversas acciones para conservar algunas de ellas; sin embargo, se han hecho pocos esfuerzos por difundirlas. En este escrito, tomando en cuenta las nueve pláticas presentadas en un simposio científico realizado en 2015, resumimos la información sobre los esfuerzos de conservación de aves que se están llevando a cabo en el país. Dividimos los estudios en tres categorías: los que analizan cómo se hace la conservación en México, los que hacen conservación práctica y los que constituyen investigación ecológica básica tendiente a la conservación de dichas especies. Concluimos que los esfuerzos de conservación de aves en el país son insuficientes y que se necesitan realizar más acciones para evitar la pérdida de la diversidad de aves en México.Palabras clave: avifauna mexicana, esfuerzos de conservación, especies de aves en peligro, especies de preocupación para la conservación, extinción de aves, monitoreo de aves. AbstractMore than 26% of bird species inhabiting Mexico are in decline. Ornithologists are developing different actions to conserve some of these species, but there have been few efforts to comprehensively describe these activities. In this paper, we summarize nine current bird conservation efforts being done in Mexico, which were first presented in a scientific symposium in 2015. We divide the studies into three categories: those that assess how avian conservation is conducted in the country; those that are examples of practical on-the-ground conservation, and those that are conducting ecological research on bird conservation. We conclude that current conservation efforts are insufficient to effectively halt the declines of most of these species and more actions are needed to reduce the loss of avian diversity in Mexico.
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