Diets of Scarlet Macaw chicks in the Peruvian Amazon: 
Donald Brightsmith, Ph.D.
Department of Biology, Duke University

 Introduction

Knowledge of wild animals diets is still relatively poor for most species. As a result, many animals held in captivity are fed diets designed for domestic fowl, dogs, cats and monkeys. Even parrots, which have been kept and bred in captivity for hundreds of years (Greiser 1995), have been the subject of surprisingly few dietary studies and the studies that have been done have not been made available to the general public. As a result, parrot owners, including zoos, breeders and pet owners, often use diets formulated with little knowledge of the birds’ actual requirements and preferences in the wild. 

Diet studies are also an important tool to help us understand the ecology and conservation of many wild species. In the Amazon basin of southeastern Peru, hundreds of parrots gather daily at river edge clay licks to consume soil. The behavior of the birds suggests that this is an important part of their diet (Brightsmith 2004), but the exact dietary functions of the soil remains unresolved. The soils bind to toxins found in the birds’ diets and provide a significant source of dietary sodium ([Gilardi et al. 1999, Brightsmith 2004). However it is unknown which of these is driving clay lick use. In the Tambopata region, lick use peaks during the breeding season for at least 10 different parrot species (Brightsmith in prep.). Data from crop samples show that Scarlet and Red-and-green Macaws feed their chicks clay lick soil (D. McDonald and D. Brightsmith unpublished data). So the increased lick use by adults is presumably to collect soil to feed to their young.

 Diet studies of wild herbivores are often hampered by the fact that it is difficult or impossible to tell exactly what part of the plant an animal is eating by watching a foraging individual. Even by following marked individuals throughout the day it is impossible to know the exact proportions of different food items consumed. As a result, analyzing the food plants does not provide information on the exact nutritional content of the birds’ diet. Psittacine birds provide an ideal opportunity to study diets because the chicks are easily accessible (unlike flighted adults that are difficult to trap) and hold undigested food in a non-muscular crop, which can be repeatedly sampled with relative ease. This provides the opportunity to analyze the nutritional content of exactly what the birds are being fed and follow the change in diet as chicks develop.
  

As part of the ongoing study of macaw and parrot ecology in Tambopata, Peru we collected crop samples from Scarlet Macaw chicks in January and February 2004. These preliminary data showed that the amount of soil fed by parents was greatest in young chicks and decreased with age (Table 1). The reasons for this are unknown, but it could be that the soil is mixed with the food and fed to the young to help reduce the toxicity of the seeds in the diet. Alternatively it could be that the soil is fed as a sodium supplement. The crop sample data show that the amount of sodium fed to the young declined with age, independent of the amount of clay in each sample (Figure 1). While the trend was the clearest for the sodium, concentrations of iron and calcium may have also decreased with the age. The nutrient analyses presented here are based on only seven conglomerate samples taken from 7 different nests over the course of a single breeding season. Obviously there is a great need to continue this work and determine if these trends are robust.

 In the current study, I plan to analyze crop samples taken from Scarlet Macaw chicks in Tambopata Research Center in southeastern Peru with the following goals:

1. Determine the levels of protein, fiber, ash, lipids and minerals (Na, P, Mg, Ca, Fe, Zn, S, Cu, and Se) in the diets of Scarlet Macaw chicks so that this information can be compared to the diets currently being fed to birds in captivity.
2. Determine the ages at which Scarlet Macaws feed clay lick soil to their chicks.
3. Determine how the concentration of sodium and minerals in the chicks’ diets changes with the age of the chick.
4. Determine how the toxicity of the chicks’ diets changes with the age of the chick.

Methods

The study is being conducted in Tambopata Research Center as part of the Tambopata Macaw Project, which has been ongoing under the direction of Dr. Donald Brightsmith since November 1999. Crop samples will be taken January – March 2005. Scarlet Macaw chicks from about 10 different nests will be sampled once every 7 days (approximately), from age 20 – 70 days, following the protocol presented in Enkerlin-Hoeflich et al. (1999).

 Samples will be field dried in an oven at approximately 50 – 60 deg C and then stored for up to 3 months in a dry area then shipped to laboratories in the USA for analysis. Toxicity analyses will be conducted at Texas A&M University in the laboratory of Dr. Tim Phillips a toxicologist in the Department of Veterinary Medicine. The dietary analyses will be conducted at the Palmer Research Center at the University of Alaska. 

Anticipated results and benefits of the study

Scarlet Macaw is a very common species in captivity and hundreds or more are raised annually in captivity. This study will increase our knowledge of wild parrot diets and provide information useful for improving the nutrition of parrots raised in captivity. As this work will be published in scientific journals and distributed through popular articles in magazines and on the Internet (see the Tambopata Macaw Project web page www.duke.edu/~djb4 for examples). As a result, all zoos, breeders, food companies and pet owners will have access to this information and its implications for raising macaws and parrots in captivity.  

This information will also provide further insight in to why birds use clay licks and their importance to breeding macaws. This question is complex and potentially very important. Throughout the tropics, most breeding parrots and macaws do not use clay licks. Even in southeastern Peru where clay lick use is common, many pairs do not consume soil while breeding or feed it to their chicks. Understanding the dietary role the clay plays will give us the first indication of how important the clay is in raising chicks. The clay licks of Peru are a valuable ecotourism resource and great foci of conservation activities due to the huge numbers of psittacines that use them. As a result, any information we can gain on the role these sites play in the lives of these birds is of great import to conservation in this area.

Literature Cited

Brightsmith, D. J. 2004. Effects of weather on avian geophagy in Tambopata, Peru. Wilson Bulletin 116: 134 -145.

Brightsmith, D. J. and R. Aramburú. 2004. Avian geophagy and soil characteristics in southeastern Peru. Biotropica 36: 534-543.

Brightsmith, D. J. and A. Figari. In prep. Seasonal patterns of avian geophagy in Tambopata, Peru.

Enkerlin-Hoeflich, E. C., J. M. Packard and J. J. Gonzalez-Elizondo. 1999. Safe field techniques for nest inspections and nestling crop sampling of parrots. Journal of Field Ornithology 70: 8-17.

Gilardi, J. D., S. S. Duffey, C. A. Munn and L. A. Tell. 1999. Biochemical functions of geophagy in parrots: detoxification of dietary toxins and cytoprotective effects. Journal of Chemical Ecology 25: 897-922.

Greiser, S. T. 1995. The sacred bird. In: Abramson, J., B. L. Spear and J. B. Thomsen (eds), The Large Macaws: Their Care, Breeding and Conservation, Raintree Publications, Ft. Bragg, CA, pp. 497-510.

Table 1: Presence of clay in crop samples from Scarlet Macaw chicks in Tambopata, Peru (January – February 2004). “N” indicates the number of crop samples. Chicks could not be sampled before 20 days because they were too small. Chicks fledged at approximately 90 days of age.

 
 Figure 1: Sodium concentrations in crop samples taken from Scarlet Macaw chicks in Tambopata, Peru (January – February 2004).