Importance of Nest Predation by Alien Rodents and Avian Poxvirus in Conservation of Oahu Elepaio

Abstract

The Oahu elepaio (Chasiempis sandwichensis ibidis) is an endangered forest bird endemic to the Hawaiian island of Oahu (USA) and is threatened by nest predation from alien rodents and mosquito‐borne diseases. I investigated importance of these threats and evaluated success of conservation efforts from 1995 to 2008. I controlled rodents with snap‐traps and bait stations in 3 valleys and switched sites from non‐treatment to treatment over time. I mist‐netted and color‐banded 91 elepaio, inspected them for symptoms of avian poxvirus (Poxvirus avium), and estimated survival using multistate mark‐recapture models. I determined annual fecundity of each breeding pair and monitored success of 212 nests. The oldest known Oahu elepaio was ≥15 years old. Survival of females was higher with rodent control (0.82 ± 0.05) than without (0.55 ± 0.12), but survival of males was not affected by rodent control (0.86 ± 0.02 with vs. 0.84 ± 0.04 without). Survival of elepaio with active or inactive pox‐like lesions was 4–10% lower than survival of elepaio with no pox symptoms. Rodent control resulted in higher annual fecundity (0.69 ± 0.05 vs. 0.33 ± 0.06 fledglings/pair) and nest success (62% vs. 33%). Female site‐fidelity, mate fidelity, and female encounter probability were lower in the absence of rodent control because more females switched territories and mates after nest failure. Population growth calculated from survival and fecundity estimates was stable with rodent control (1.07 ± 0.04) but declining without rodent control (0.69 ± 0.05). Elepaio numbers have continued to decline despite rodent control, probably because some young birds disperse into adjacent unmanaged areas that act as sinks. The best immediate management strategy for Oahu elepaio is to conduct rodent control over larger areas. Restoration of native forest would benefit elepaio by providing nest sites that are less attractive to rodents. Construction of predator‐proof fences and eradication of predators would provide the best long‐term protection for elepaio.

Mitigating Future Avian Malaria Threats to Hawaiian Forest Birds from Climate Change

“…In Hawai’i, introduced mammals such as black rats, feral cats, and mongooses prey on eggs, fledglings, or even adult birds [71]. One study of Oahu Elepaio ( Chasiempis ibidis ) found that rodent control improved female survival (nearly 50%), fecundity (> 100%), and nest success (near 100%) [71].…”

“…In Hawai’i, introduced mammals such as black rats, feral cats, and mongooses prey on eggs, fledglings, or even adult birds [71]. One study of Oahu Elepaio ( Chasiempis ibidis ) found that rodent control improved female survival (nearly 50%), fecundity (> 100%), and nest success (near 100%) [71]. In contrast, no difference in nest success or abundance was detected in native forest birds during predator control at Hakalau Forest National Wildlife Refuge from 1996 to 1999 [71].…”

Stepping stone speciation in Hawaii’s flycatchers: molecular divergence supports new island endemics within the elepaio

“…The primary threats to elepaio are nest predation by alien mammals, diseases carried by alien mosquitoes, and loss and degradation of habitat caused by feral ungulates, invasive alien plants, human development, and wildfires (VanderWerf and Smith 2002;U.S. Fish and Wildlife Service 2006;VanderWerf et al 2006;VanderWerf 2008VanderWerf , 2009. Information about phylogeography and population structure of elepaio is needed to inform management decisions and help develop the best possible conservation strategy (U.S. Fish and Wildlife Service 2006).…”

Nest success and parental investment in the Critically Endangered Maui parrotbill Pseudonestor xanthophrys with implications for recovery

“…A large suite of environmental factors have been found or are thought to reduce Maui parrotbill productivity in the wild: predation by native and alien vertebrates (Mounce 2008, VanderWerf 2009), restriction to suboptimal habitat inferred by the fossil record (Olson & James 1982), severe wind and rain storms during the breeding season (Simon et al 1997), and potentially inviable eggs related to small population genetics (Stone & Scott 1985). The relationship between parental investment and nest success has not been previously explored, especially in relation to severe weather.…”