From Solution to Problem: The Irony Of Invasive Species
U.S. Fish & Wildlife Service establishes control order on barn owls and cattle egrets to protect endangered native species
Staff Writer Rosannah Gosser
Photos courtesy of Wikimedia Commons
Over millions of years on the most isolated island chain on Earth, animals and plants reached Hawai’i floating on crests of waves and flying on currents of wind. These pelagic renegades found an organic oasis: plenty of rain and sunshine, fertile soil, and most importantly, no predators. They evolved here in a microcosm for biodiversity, until people arrived. Rats, dogs, chickens, and pigs accompanied the first settlers, as well as plants like sugarcane and bananas. With western contact, even more foreign species were brought to the islands, from mosquitoes to miconia, fire ants to “octopus” trees, albizias to coqui frogs.
All of these species have waged biological war against the endemic animals and plants, competing with them for resources, and in many cases, threatening them with extinction. In the past century, some species have been deliberately introduced as an effort to control invasive species’ impacts, but oftentimes have created their own issues and only added to the problem.
This is the predicament prescribed to barn owls (Tyto alba) and cattle egrets (Bubulcus ibis). Both species were brought to Hawai’i in the 1950s: barn owls were released to control rat populations in sugarcane fields, and cattle egrets as a remedy for horn flies on cattle. But their introduction achieved little of what they were originally intended to do; instead, barn owls and cattle egrets began to prey on endemic species of birds that had existed without predators for so long. This threat continues today. Native birds that are particularly in danger include: ae’o (Hawaiian stilt), ‘alae ‘ula (Hawaiian moorhen), ‘ua’u (Hawaiian petrel), and pueo (Hawaiian short-eared owl).
Many invasive species of animals in Hawai’i, like mongoose and feral cats, are not protected by legislation and therefore open to unrestricted predator control. However, barn owls and cattle egrets are covered by an international law called the Migratory Bird Treaty Act (MBTA), which is an agreement between the United States, Canada, Mexico, Japan, and Russia that mandates the protection of certain species of migratory birds wherever they occur in those areas. In an effort to preserve the endangered species of Hawai’i that are preyed upon by barn owls and cattle egrets, the U.S. Fish & Wildlife Service has issued permits for years that allow specific authorized agencies, such as the Department of Land and Natural Resources (DLNR) and the National Park Service, to use “lethal take” on the predatory birds. These permits have been given out only to qualified agencies and have required annual renewal
This past August, after several years of debate and public commenting, the Service installed a ruling for these authorized agencies to forego renewal of their permits every year. In other words, organizations like the DLNR can continue to execute predator control on barn owls and cattle egrets without having to file for a permit again and again.
The ruling states: “Cattle egrets and barn owls are invasive in Hawai’i and threaten native wildlife with extinction. Nonlethal methods have been unsuccessful in reducing the impacts caused by cattle egrets and barn owls. We, therefore, are making final a regulation that allows take by agencies that have functional and/or jurisdictional responsibility for controlling invasive species and protecting native species in the Hawaiian Islands.”
Jenny Hoskins, a wildlife biologist of the U.S. Fish & Wildlife Service’s Migratory Bird and Habitat Program, explains the control order. “Our goal in writing the rule is endangered species protection. What we’re going to be looking at is those specific waterbird and seabird colonies that have problems. Unfortunately we know where all of those colonies are because the endangered species numbers are so small. We didn’t write this with the goal of eradicating [barn owls and cattle egrets], we wrote this with the goal of preserving endangered species and hopefully we won’t have to take any more birds than necessary to protect those colonies.”
According to Hoskins, the control order will mostly be implemented on Kaua’i, O’ahu, and Maui. Here on the Big Island, several wetland areas with bird colonies threatened by barn owl and cattle egret predation will be targeted. Additionally, cattle egrets that roost at Keaukaha Beach Park will be addressed because of the hazards they pose on the airport runway.
When the ruling was proposed, some public concern arose over methods of lethal take and complaints that instead of intensifying barn owl and cattle egret euthanization, more attention needs to be given towards protecting endangered birds. “We have to accept that there’s been change in Hawaii,” states Sydney Ross Singer, director of the Good Shepherd Foundation. “To blame these birds for the entire problem is naive and to kill them is just so abhorrent to anyone who loves animals and nature and wildlife.” In the case of barn owl and cattle egret predation, there will be loss of life either way. Is it justification enough to kill animals that are killing other animals? Or is it just the circle of life?
As humanity continues to homogenize the global environment, it becomes harder to know where to draw the line between natural and unnatural. “If we do nothing, oftentimes [invasive species] are going to drive everything else to extinction, and we won’t have anything left,” says Dr. Patrick Hart of UH Hilo’s Biology Department. “It’s trying to balance how to maximize biodiversity.” Often deemed the “Endangered Species Capital of the World,” the Hawaiian islands exemplify the fragility that ecosystems face in modern times.
It’s true that change is inevitable, and that these islands will never be the same as they were pre-contact. But it’s difficult to ascertain the extent to which we should continue to mess around with nature and apply trial and error to our mistakes, such as that of barn owls and cattle egrets. One thing is for sure: the diversity of wildlife that evolved here on the Hawaiian islands is unparalleled, unique, and undoubtedly deserving of protection from destruction.