The pros and cons of offering supplemental food: important decisions for the next stage of ‘alalā reintroductions
Every morning for nearly the past 3 years, San Diego Zoo Global (SDZG) field team members and our partners trek into the Hawaiian forest to put out food for one of the island’s rarest inhabitants and one of the world’s rarest birds.
Regardless of whether the team is greeted with dew glistening in the early morning light, or with torrential rain cascading in large droplets from every leaf, they have persevered against the elements and continued to support recovery efforts for the ‘alalā, the Hawaiian crow. Over these years, multiple cohorts of ‘alalā have been reintroduced onto the landscape, spreading farther across the Pu‘u Maka‘ala Natural Area Reserve. Each day in the field can be unpredictable, as the team searches for birds, collects data, and learns about the encounters ‘alalā are having with new food resources, with predators, and with potential mates.
The one constant through all of this has been the daily provisioning of food. But why put so much focus on the food?
Supplemental food is one of the few support tools that we can use to help reintroduced animals adjust to their new life in the wild. By providing food after reintroduction, we can anchor animals to the reintroduction site, which allows for easier monitoring, and responding to any acute health issues that may crop up. Supplemental food can also provide much needed nutrition as animals learn how and where to forage on their own in their new environment, with all of its seasonal fluctuations, predators, and unknown spaces. Many studies on other species have shown that this support can benefit survival, and improve the prospects for breeding. We’ve seen many of these benefits for ‘alalā, as we’ve been able to easily keep track of birds and monitor their health and survival.
However, there are also potential costs to providing an artificially stable and reliable food source, if it is continued for too long. If not managed well, food stations can increase the likelihood of aggression between territorial animals, such as the ‘alalā, or inhibit natural dispersal in ways that can impact the forest or increase the risk of predation. Also the team’s daily treks could take time away from supporting ‘alalā in other ways. We, as a program, have tried to mitigate many of these costs, by moving food stations around, optimizing the time we spend in the forest, and responding to predation risks as best we can.
However, now that some of the birds have been flying free in the forest for multiple years, it is time they start to gain more of their independence.
By slowly reducing the amount of food we provide, we can help the birds become more wild, one step closer to being a self-sustaining population. Since ‘alalā are a key seed-disperser of the Hawaiian forests, encouraging them to focus on native fruits, seeds and insects will help them build forests for future generations of birds. Finally, we have an incredible opportunity to learn about what plants ‘alalā seek out on the landscape, to help us better pick future reintroduction sites and understand how they should naturally move up and down the mountain slopes with the seasons.
With these common goals in mind, we recently gathered with our partners to chart a course for helping wean the birds from supplemental food. Over the coming months, the team will be using the data they collect to monitor birds’ progress through the weaning process, ensuring that we strike an optimal balance between providing needed nutrition and helping the birds realize the benefits of natural foraging. While the team will continue their morning treks for now, it may not be long before the team instead has to turn to the sky and the surrounding forest to look for foraging ‘alalā.