Scarlet Macaw Nesting Ecology and Behavior: Implications for Conservation Management

Abstract

Documenting parental care by wild birds is important for understanding reproductive success and promoting conservation. However, little is known about how wild parrots care for their offspring in the nest and how to use this knowledge to inform conservation actions. I documented wild Scarlet Macaw parental behavior in the lowland forests of southeastern Peru during 19 breeding seasons. I also tested using wild macaws as foster parents to increase chick survival. I found that females provide the majority of nestling care when the chicks hatch but the proportion of care given by the male gradually increases as the chicks age. I found that (1) chicks are fed on average 3.6 times per hour throughout the nesting period, (2) chicks are fed during the day and at night with major diurnal and nocturnal feeding peaks, and (3) macaw parents can store food in their crops for over 7 hours and use this to feed their chicks at night. I analyzed chick starvation due to brood reduction and found that chick starvation is the leading cause of chick mortality at my site: (1) 27% of all second hatched chicks starve, and (2) nearly all third and fourth hatched chicks starve. I found no evidence that death by starvation was caused by (1) sibling rivalry, (2) macaw food availability in the forest, or (3) hatch weight. I did find that (1) direct control of food distribution within the brood favors first hatch chicks but specifically disfavors second hatch chicks that starve to death and (2) the larger the age difference between brood members the more likely the second chick would starve. The technique of macaw foster parents was categorically successful. All relocated foster chicks were successfully accepted by their foster parents (N = 28 chicks across 3 seasons) and 89% of them fledged. Fostering increased fledging success per available nest from 17% (1999 – 2016) to 25% (2017-2019) and decreased chick death by starvation from 19% to 4%. This research has great potential benefits for in-situ and ex-situ macaw population management and conservation.