The Secret Lives of Scarlet Macaws: Why Parents Favor Older Chicks and How Science Is Stepping In to Save the Youngest

Scarlet macaws, known for their lifelong mating bonds, are seen by many as a symbol of devotion. Yet, when it comes to parenting, these vibrant birds reveal a surprisingly ruthless side: macaw parents consistently neglect their youngest chicks, even when food is abundant. Thanks to a new “foster program” developed by scientists at Texas A&M University, however, these vulnerable chicks now have a better chance of survival.

Dr. Donald Brightsmith and researchers at Texas A&M’s College of Veterinary Medicine and Biomedical Sciences discovered that scarlet macaw parents often starve the younger members of their brood. Even in nests with plenty of resources, only one or two of the strongest chicks survive. “We found that 26% of second chicks and nearly all third and fourth chicks die before fledging,” Brightsmith explained, referring to the process where young birds learn to fly and gain independence.

The team’s research showed that the decision to ignore younger chicks isn’t due to sibling rivalry or a lack of food; instead, it’s based on the age difference within the brood. “Macaws lay eggs over several days, so chicks hatch on different days,” said Dr. Gabriela Vigo-Trauco, the project’s lead researcher. “If a chick hatches several days after the first, it’s more likely to be neglected and may die of starvation.”

To understand why these younger chicks face such harsh odds, Brightsmith and his team monitored food resources in the Tambopata National Reserve in Peru, confirming that resource scarcity was not the issue. They also installed cameras in macaw nests to observe parenting behavior over 10 years, witnessing firsthand how female macaws often prioritized feeding the oldest chicks, sometimes even burying the youngest chicks with nest material. The father macaw, however, would sometimes unbury and feed the neglected chick, showing that parenting decisions are complex even in the animal kingdom.

Seeing the struggle of these youngest chicks inspired the team to develop a foster program, placing neglected chicks with new macaw foster families. By placing chicks in nests with similarly aged chicks, they found that foster macaws accepted the younger birds without hesitation. “The foster parents may look at the new chick like they’re thinking, ‘Did I walk into the wrong house?’ but they start feeding it shortly afterward,” Brightsmith noted.

Since the program launched, 28 chicks have been successfully fostered over three breeding seasons. Published in Diversity, this foster program represents a promising approach to help not only scarlet macaws but potentially endangered parrot species worldwide.

Parrot populations continue to decline globally, making it essential to understand and address behaviors like brood reduction in conservation efforts. Brightsmith and his team hope that by fostering orphaned or neglected chicks, they can help protect macaws and other endangered parrots, ensuring a brighter future for these colorful symbols of the rainforest.