After the Flood: What Happened to our Native Waterbirds on Kaua‘i?
We asked the experts how Hawai‘i’s waterbirds could have survived April’s historic flooding on Kaua‘i.
‘Alae ‘ula (Hawaiian moorhen)
When a record-setting 50 inches of rain pounded Kaua‘i in 24 hours this past April, it created waterfalls never before seen in Hanalei. Lightning striated the night sky while thunder quaked the walls of houses. The rain continued to cascade, forcing the Hanalei River over its banks and turning the valley’s picturesque scene of quilted taro fields into one big brown lake across which emergency first responders zipped on Jet Skis. Trees, fences and even a house got swept downriver as water blew out old lava tubes, creating sinkholes in roads. In town, mud busted into businesses, reaching knee-high in some places. Today, Black Pot Beach Park at the mouth of the river is nearly unrecognizable.
When the rain broke long enough to take a look around at Hanalei National Wildlife Refuge, home to numerous taro farmers and five endangered waterbird species, things looked ratty but also pretty normal. The raw river told the story of high water with its gash of exposed dirt and flattened vegetation along the banks. But taro still stood upright; their geometric patches remained intact. At least one farmer was harvesting the day after floodwaters receded. Surprising to me, no caches of dead birds were visible.
“Well, they are waterbirds,” Kim Uyehara reminded me. Uyehara is the biologist at a 917-acre refuge where we walked among taro patches looking for dead and injured birds. Meanwhile, helicopters buzzed overhead, ferrying people out of the communities of Wainiha and Hā‘ena, stranded due to numerous rockslides and sections of Route 560 being ripped out by rushing water.
We didn’t find any dead birds on our search, but birds were clearly missing. Not a single ae‘o (Hawaiian stilt) hovered over us and squawked as we walked, a concern because it was their nesting season. No ‘alae ke‘oke‘o (Hawaiian coot) and few ‘alae ‘ula (Hawaiian moorhen) scurried for cover. A survey taken a couple of weeks later revealed a drop in numbers of 40 to 70 percent for these species. However, the same survey revealed little change in counts of two other waterbird species at the refuge—nēnē and koloa maoli (Hawaiian duck).
Only seven bird carcasses were eventually found—even with the help of Solo, the scent detection dog featured in the April issue of HONOLULU, and his handler, Kyoko Johnson. “Kyoko and Solo were brought in as a preventative measure to make sure we weren’t missing any major carcass piles in debris and ditches,” Uyehara told me. “They were a substantial help in a time of need.”
Uyehara thinks the missing birds may have simply used their ability that notably distinguishes them from us humans—flight—and evacuated to safer locales. “My best guesses are they found more productive refugia in the Alaka‘i [Wilderness Preserve on Kaua‘i], Ni‘ihau or O‘ahu, in that order.”
Of course, some birds were likely lost and their bodies flushed out to sea by the force of the water. With time, a clearer image of the storms’ impact was revealed.
Ae‘o (Hawaiian stilt)
Few young birds and no nests were observed postflood, capping an already dismal breeding season. In the first four months of 2018, the Kaua‘i Emergency Management Agency issued 10 flash flood warnings, so it wasn’t just the April 15 flood that caused problems. But the historic April flood did rip out an estimated 2,600 feet of fence line, allowing destructive feral pigs easier access to the refuge.
And on closer examination, the April flood redistributed sediment, scouring taro patches and wetlands in some places and dumping soil in massive piles in others. It was as if a snow globe of Hanalei Valley had been shaken. For taro farmers, that messed with their nutrient values. For the endangered waterbirds, after surviving the onslaught of water, they now were left with the challenge of finding food.
“It’s fair to say that the invertebrate population and aquatic vegetation was pretty much swept away,” Michael Mitchell, deputy project leader for the Kaua‘i National Wildlife Refuge Complex, told me.
It’s true that all five of the waterbird species found at the refuge in Hanalei may re-clutch—that is, lay eggs in a new nest after a failed first attempt. So the breeding season may be salvaged. However, females need a great amount of protein to do so. According to Uyehara, a renesting koloa hen has about 24 hours between ovulation and laying and must eat protein equal to what she puts into an egg every day while she is laying the eight to 10 eggs in her clutch. That could equal 2,400 to 4,300 invertebrates per day. If she cannot find enough food, she won’t renest.
But waterbirds, like the Hanalei community, are resilient, having adapted over centuries to the varying dynamics of life on a floodplain. However, with predictions by climate scientists of stronger storms occurring at greater frequencies, was 2018 an indication of the new normal? And can Hawai‘i’s native waterbirds survive year after year of continued flooding?
Uyehara is hopeful. “They’ve got innate adaptations beyond what we know,” she said. “It’s what keeps people intrigued and always wondering.”
Kyoko Johnson and Solo work on Kaua‘i.
Photo: Tor Johnson, u.s. fish and wildlife service