Macaws tend to lay three or more eggs on average. But why does the first chick survive while the younger ones often die? Is it food scarcity, sibling aggression, weather, predation, or parental preference? Researchers from the Macaw Society at Texas A&M University have been studying this issue and collecting data for over 10 years.
This is what they found. If the chicks hatch four or more days apart, they require a different kind of care which often leads to parental neglect – such as insufficient food or warming incubation. “Scientists have known for years that scarlet macaws hatch more chicks than they fledge,” said Dr. Donald Brightsmith, a professor in the Department of Veterinary Pathobiology at Texas A&M University. “We found that 26% of second chicks in scarlet macaw broods and nearly all third and fourth chicks die before fledging.”
“Scarlet macaws lay eggs over a period of several days instead of all at once, which means the chicks don’t hatch on the same day,” said Dr. Gabriela Vigo-Trauco, a post-doctoral researcher with Texas A&M’s Schubot Center for Avian Health, who led the project. “If the second chick hatches only a couple of days after the first, there is a good chance that the parents will feed it. However, if it hatches four, five, or more days after the first chick, the parents will probably neglect it and let it die.”
Image courtesy of Roshan Tailor.
Researchers installed cameras in the nests to better understand and document why some chicks survived while younger ones died. They found that some were overfed while others continued to beg for food and starve. They saw some other interesting behaviors as well. For example, the female might attempt to cover up a chick it no longer wanted to feed with nest substrate, and then the father would come back and unbury it. Parental disagreements!
Researchers also confirmed that in most cases there was no shortage of food resources, such as trees with fruit and flowers. So, they hypothesized that the chicks were not starving due to lack of food availability. They determined the chicks were starving simply because the parents did not want to take care of birds with different levels of development. It is the age difference, not predation, lack of food, or sibling rivalry that causes some chicks to die.
A Unique Approach To Fostering
As part of her doctoral research, Dr. Vigo-Trauco developed a program for saving neglected chicks. She found that these same neglectful parents can make good foster parents. If a neglected chick is raised in captivity and then placed back in a nest with another chick at the same developmental age, the parents are then more willing to take care of both chicks. So, the key to survival is to make sure they are at the same developmental stage, making it easier for the parents to provide equal care.
The foster chick program has successfully re-homed 28 chicks over three breeding seasons. “Parrots are one of the most endangered groups of birds in the world,” Don Brightsmith said. “We hope that this program, and the understanding of brood reduction behind it, can assist with the conservation of a broad array of parrot species across the tropics.”
The Macaw Society has been researching and advancing the conservation of the scarlet macaw (Ara macao macao) inside the Tambopata National Reserve, in southeast Perú, for over 20 years. Scarlet macaws, though not classified as under threat of extinction, are iconic. Unfortunately, they are under continual threat from habitat loss due to agriculture, mining, and logging. Therefore, they warrant continued conservation efforts. Since parrots to help disperse seeds to facilitate forest regeneration, their conservation is essential and benefits the whole forest ecosystem.
This month’s Lafeber donation goes to support the good works of the Macaw Society, which is dedicated to conservation, protection, rehabilitation, and release of a wide variety of special and endangered parrot species. To read more about the foster chick program, you can read the full study here (https://www.mdpi.com/1424-2818/16/11/657).