Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Little information is available on the impact of pueo predation on populations of native birds. The
pueo has been implicated as a predator of nestlings of various endangered bird species in Hawai„i
such as the „ākohekohe (VanGelder et al. 2001) and Maui parrotbill on Maui (Mounce 2008), palila
on Hawai„i (Pratt et al. 1998), and puaiohi on Kaua„i (Snetsinger 2005). Pueo are also known to prey
upon „apapane, common „amakihi, „i„iwi, and kōlea (Snetsinger et al. 1994).
Little is known about the breeding biology of the ground nesting pueo, but nests have been found
throughout the year. Nests are constructed by females and are comprised of simple scrapes in the
ground lined with grasses and feather down. Females also perform all incubating and brooding, while
males feed females and defend nests. The young may fledge from nest on foot before they are able to
fly and depend on their parents for approximately 2 months (Mitchell et al. 2005).
At the HFU, pueo are found only in the open areas and pastures of the reserve (Jeffrey, pers. comm.).
The pueo is rare in the KFU of the Hakalau Forest NWR (Ball, pers. comm.).
Similar to other native Hawaiian birds, loss and degradation of habitat, predation by mammals, and
disease threaten pueo. Pueo appear particularly sensitive to habitat loss and fragmentation, as they
require relatively large tracts of grassland and are ground nesters. Ground nesters are more
susceptible to the increased predation pressure that is typical within fragmented habitats and near
rural developments (Wiggins et al. 2006). These nesting habits make them increasingly vulnerable to
predation by rats, cats, and Indian mongooses (Mostello 1996, Mitchell et al. 2005).
Mortality of the pueo on Kaua„i has been attributed to the “sick owl syndrome,” which may be
related to pesticide poisoning or food shortages. They may be vulnerable to the ingestion of poisoned
rodents. However, in the one study conducted, there was no evidence that organochlorine,
organophosphorus, or carbamate pesticides caused mortality in the Hawaiian short-eared owl. Other
causes of death on Maui, O„ahu, and Kaua„i have been attributed to trauma (apparently vehicular
collisions), emaciation, and infectious disease (pasteurellosis) (Work and Hale 1996). However, their
persistence in lowland, nonnative and rangeland habitats suggests that they may be less vulnerable to
extinction than other native birds, especially because they may be resistant to avian malaria and avian
pox (Mitchell et al. 2005).
4.6 Endangered Hawaiian Waterbirds
The Hawaiian Island archipelago supports six species of endangered waterbirds: the koloa maoli,
„alae ke„oke„o, „alae „ula, ae„o, nēnē, and Laysan duck. All of these species, except for the nēnē,
require wetlands for their survival. As a result, the loss and degradation of Hawai„i‟s coastal wetlands
have been a significant factor in the decline of four endemic waterbirds in the main Hawaiian Islands.
From 1780-1980, the area of coastal wetland habitat in the main Hawaiian Islands declined by
31 percent. Coastal wetlands were filled for commercial, residential, and resort developments and
drained for agriculture. These developments have also degraded the water quality of the wetlands
(Evans et al. 1994, USFWS 2005a). Predation by introduced animals, disease, and environmental
contaminants have also contributed to the population decline of Hawai„i‟s endangered waterbirds.
Furthermore, nonnative plants, such as mangroves and grasses, have encroached on wetlands and
4-40 Chapter 4. Refuge Biology and Habitats