COS 233-1 - Investigating the elusive 'akeke'e, a Hawaiian honeycreeper in peril

Abstract: Hawaiian honeycreepers are experiencing a wave of extinctions due to introduced mosquito-
borne diseases, notably avian malaria (Plasmodium relictum). Mosquitoes are not native to the
Hawaiian Islands and were first introduced by whaling ships in the 1800s. Since introduction,
these mosquitos have become the vector for transmission of disease to the endemic
endangered honeycreeper population. Climate change is increasing the prevalence of disease
within critical habitat for many species, especially on Kaua’i. The ‘akeke’e (Loxops caeruleirostris),
an endangered species endemic to Kaua’i, was estimated at about 1000 birds in 2018 after a
steep decline of >90% in recent decades, highlighting the need for urgent conservation action.
To determine the best conservation strategy, we attempted to capture, band, resight, and
radiotrack ‘akeke’e to better understand nesting biology, territory size, and movement patterns
since 2018. Despite many hundreds of netting hours, we caught only 19 ‘akeke’e. Most
radiotracked birds (N=4) disappeared within a few days of transmitter attachment, suggesting
large scale movements, which were corroborated by resight data. ‘Akeke’e often lay 3-4 eggs,
not 2 eggs as formerly reported. Nests are frequently attended by > 2 adults. Our observations
suggest that ‘akeke’e have retreated from lower elevation and are less common in the core of
their range. These data suggest that the ‘akeke’e numbers only several hundred birds and will
likely disappear by 2030, if not by 2025. However, landscape-level mosquito control is expected
to be deployed on Kaua’i in 2025 and, given how difficult it is to capture these birds and find
their nests, the probability of successful captive breeding or translocation was considered low.
Therefore, we determined that the best strategy is to continue to monitor this elusive species
with a combination of occupancy surveys and song meters to ensure they are persisting on the
landscape while we await mosquito control.