AmericanOrnithology.org
Volume 121, 2019, pp. 1–7
DOI: 10.1093/condor/duy004

COMMENTARY

Evidence of Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii
Lindsay C. Young,1* Eric A. VanderWerf,1 Matthew McKown,2 Paige Roberts,2 Jeff Schlueter,2 Adam Vorsino,3
and David Sischo4
2

Submitted April 11, 2018; Accepted September 11, 2018; Published January 22, 2019

ABSTRACT

Hawaii’s only 2 endemic seabirds, Newell’s Shearwater (Puffinus auricularis newelli) and Hawaiian Petrel (Pterodroma
sandwichensis), are listed under the United States Endangered Species Act. Threats to both species include light attraction
and fallout, collisions with power lines and other structures, predation by invasive animals, and habitat degradation. Both
species were assumed to be extirpated from the island of Oahu despite limited survey effort. We used survey data from
Kauai (both species) and Maui (Hawaiian Petrel only) to model suitable habitat and light conditions. We then projected
this model onto Oahu to identify potential survey sites. From April to September of 2016–2017, we deployed automated
acoustic recording units at 13 potentially suitable sites across Oahu. We detected Newell’s Shearwaters at 2 sites; one
on the leeward slopes of Mount Kaala in the Waianae Mountains and another at Poamoho in the Koolau Mountains. We
detected Hawaiian Petrels at one location on the windward slope of Mount Kaala. All 3 sites were in nearly intact native
forest with steep slopes. The frequency of detections at these sites suggests that both species are regularly prospecting
on Oahu and potentially could be breeding there. If they are breeding, these individuals could represent missing links in
the population connectivity of both species among islands. Protecting any remnant breeding populations would be of
high conservation value given their recent population declines.

Keywords: acoustic monitoring, habitat suitability, Hawaiian Petrel, Hawaiian seabirds, Newell’s Shearwater, Oahu
Evidencia de Puffinus auricularis newelli y Pterodroma sandwichensis en Oahu, Hawái
RESUMEN

Las dos únicas especies de aves marinas endémicas de Hawái, Puffinus auricularis newelli y Pterodroma sandwichensis,
están incluidas en la Ley de Especies en Peligro de Estados Unidos. Las amenazas para ambas especies incluyen atracción
a la luz y caída, colisiones con líneas eléctricas y otras estructuras, depredación por animales invasores y degradación
de hábitat. Se asumía que ambas especies habían sido extirpadas de la isla de Oahu, a pesar de un esfuerzo limitado
de muestreo. Usamos datos de monitoreo de Kauai (para ambas especies) y de Maui (solo para P. sandwichensis) para
modelar el hábitat adecuado y las condiciones de luz. Luego, proyectamos este modelo sobre Oahu para identificar sitios
potenciales de muestreo. De abril a septiembre de 2016–2017, emplazamos unidades de grabación acústica automática
en 13 sitios potencialmente adecuados a lo largo de Oahu. Detectamos la presencia de Puffinus auricularis newelli en dos
sitios; uno en las laderas de sotavento de Monte Kaala en las Montañas Waianae, y otro en Poamoho en las Montañas
Koolau. Detectamos la presencia de Pterodroma sandwichensis en un sitio, en las laderas de barlovento de Monte Kaala.
Los tres sitios estuvieron en bosques nativos casi intactos con laderas abruptas. La frecuencia de las detecciones en
estos sitios sugiere que ambas especies están periódicamente presentes en Oahu y que podrían potencialmente criar
allí. Si estuviesen reproduciéndose allí, estos individuos podrían representar estabones perdidos de la conectividad
poblacional entre islas de ambas especies. La protección de cualquiera de las poblaciones reproductivas remanentes
sería de alto valor de conservación dadas sus disminuciones poblacionales recientes.

Palabras clave: aves marinas de Hawái, hábitat adecuado, monitoreo acústico, Oahu, Pterodroma sandwichensis,
Puffinus auricularis newelli
INTRODUCTION
Hawaii’s only 2 endemic seabirds, Newell’s Shearwater
(Puffinus auricularis newelli) and Hawaiian Petrel (Ptero-

droma sandwichensis), are listed as threatened and endangered, respectively, under the United States Endangered
Species Act (ESA; USFWS 1983). Threats to both species
include light attraction and fallout, collisions with power

Copyright © American Ornithological Society 2019. All rights reserved. For permissions, e-mail:journals.­
permissions@oup.com.

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

Pacific Rim Conservation, Honolulu, Hawaii, USA
Conservation Metrics, Santa Cruz, California, USA
3
U.S. Fish and Wildlife Service, Pacific Islands Office, Honolulu, Hawaii, USA
4
Hawaii Department of Land and Natural Resources, Division of Forestry and Wildlife, Honolulu, Hawaii, USA
* Corresponding author: lindsay@pacificrimconservation.org
1

 2  Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii 

thus information on their status and potential distribution
on the island is lacking. If either Newell’s Shearwaters or
Hawaiian Petrels are breeding on Oahu, those populations
would a represent missing link in the population connectivity of these species among islands, and thus protecting any
remnant populations would be of high conservation value
(Welch et al. 2012).
The purposes of this study were to (1) review historical records of Newell’s Shearwater and Hawaiian Petrel
sightings on Oahu to search for geographic patterns of
occurrence, (2) use models of habitat suitability and light
pollution to indicate areas most likely to support remnant
breeding populations, and (3) conduct island-wide auditory surveys across potentially suitable habitat.
METHODS
We used 3 methods to identify and survey locations on
Oahu where Hawaiian Petrels and Newell’s Shearwaters
were most likely to occur. First, we searched for historical records of petrels and shearwaters on Oahu by doing
an extensive literature search, conducting interviews with
local biologists, and by searching the database of bird records at the Bernice Pauahi Bishop Museum (BPBM; Pyle
and Pyle 2017). Second, we conducted a habitat suitability
and light modeling exercise to prioritize locations for surveying. Finally, we deployed automated acoustic recording
units (song meters) to survey for both species in locations
identified by the model as most suitable.
Habitat Modeling
We developed habitat suitability models for Newell’s
Shearwater and Hawaiian Petrel using presence-only data
acquired from auditory surveys, nesting site location data,
and expert opinion polygons. The data sets included 993
locations for Newell’s Shearwater on Kauai and 2,545 locations for Hawaiian Petrel on Kauai and Maui. If survey
points overlapped, only a single point per locality was used.
Auditory surveys for both species were conducted by the
Kauai Endangered Seabird Recovery Project (KESRP) from
2006 to 2012. The nest site location data was collected during surveys from the 1950s to 2008 by KESRP on Kauai
and by the National Park Service at Haleakala National
Park on Maui.
To develop the habitat suitability model for each species
from these presence locations, we selected a subset of variables from a set of 24 abiotic environmental variables using
a selection procedure that attempts to remove uninformative or correlated variables (Vorsino et  al. 2014, Vorsino
2016). Five variables were selected that best described the
distribution of both species (isothermality, precipitation
seasonality, slope, topographic roughness index, and wind
at 50 m elevation).

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

lines and other structures, predation by invasive animals,
and habitat degradation (Ainley et  al. 1997, Simons and
Hodges 1998, Ainley et al. 2001). These pressures have resulted in serious declines in both species over the last 20 yr,
particularly for shearwaters (Raine et al. 2017). The most
recent population estimates are 20,550 for Newell’s Shearwaters and 11,900 for Hawaiian Petrels (Pyle and Pyle
2017). On Kauai, ornithological radar surveys, combined
with returns of downed birds to the Save Our Shearwaters
program, show an apparent decline of 94% from 1993
to 2013 for shearwaters and 78% for petrels (Raine et  al.
2017). The population declines for shearwaters were corroborated by changes in at-sea population estimates, with
approximately 84,000 individuals estimated based on data
collected between 1984 and 1993 (Spear et al. 1995).
Both species are loosely colonial and nest in burrows,
crevices, or under vegetation in at least 2 habitat types:
middle to high elevation (160–1,200 m), wet native montane forest on steep slopes dominated by ohia trees (Metrosideros polymorpha) with uluhe fern (Dicranopteris
linearis) understory (Ainley et al. 1997). In addition, petrels are known to breed in open, rocky subalpine habitat
at high elevation (>2,000 m; Ainley et al. 1997). Historically, both species were found from sea level to the mountain tops on all the main Hawaiian Islands, and they were
among the most abundant seabirds in Hawaii (Olson and
James 1982). Their current breeding ranges have been
greatly constricted in area and habitat diversity compared
to the historical breeding range because of habitat loss
and predation by nonnative mammals. Virtually all extant
breeding colonies are located in areas that are inaccessible to mammalian predators, such as steep cliffs, or that
have low predator density, such as open lava fields at high
elevation. In addition, attraction of fledglings to artificial
light sources and subsequent grounding in urban areas is
a significant cause of juvenile mortality (Ainley et al. 1997,
Troy et al. 2011). Over time, reduced recruitment resulting from fallout of juveniles could cause colonies to dwindle in areas with greater exposure to artificial light.
More than 90% of the extant shearwater population is
found on Kauai, with scattered colonies on Maui and Hawaii (Ainley et al. 1997). While the population size of petrels
is thought to be smaller, they are more widely distributed in
similar-sized colonies on Kauai, Maui, Lanai, and Hawaii,
thus providing some level of protection against catastrophes and stochastic forces. For both species, identifying
and protecting colonies on other islands is one of the most
important actions to safeguard against natural disasters
(Holmes et al. 2015). Both species were historically known
from Oahu but were thought to have been extirpated from
the island prior to European contact in 1778, although dozens of grounded birds have been recovered from around the
island (Pyle and Pyle 2017). No systematic, targeted surveys
have been done for montane-nesting seabirds on Oahu, and

L. C. Young, E. A. VanderWerf, M. McKown, et al.

 L. C. Young, E. A. VanderWerf, M. McKown, et al. 

tion model after elevating them by 100 m (as conducted
by Troy et al. 2011) to account for possible light detection
during fledgling flight and projected onto a 0–100% visibility scale. The areas defined as lit (i.e. below the 3rd quartile
of light intensity) were classified as 100% visible, and thus
do not vary in intensity.
Song Meter Programming and Deployment Locations
Remote acoustic monitoring has been found to be an effective technique for detecting the presence of rare, nocturnal
seabirds like Hawaiian Petrels and Newell’s Shearwaters
(Buxton and Jones 2012). This method takes advantage of
the social behavior and frequent vocalizations that occur at
breeding colonies. To search for these cryptic species, we
deployed automated acoustic recording devices (Wildlife
Acoustics SM4 and SM2 song meters) at 16 locations on
Oahu. Recorders at 3 locations failed to make recordings,
resulting in 13 locations with data (Figure 1). We chose locations where Newell’s Shearwaters or Hawaiian Petrels
had been previously recorded on the island, or where suitable habitat existed based on modeling outcomes. We deployed song meters at 3 locations in 2016 and 15 locations
in 2017 for a total of 13 unique survey points (2 of the locations surveyed in 2016 were repeated in 2017). Five sites
were in the Koolau Range on the eastern side of Oahu and
8 were in the Waianae Range on the western side of the island. Of the 13 locations, we accessed 6 by helicopter and
7 by hiking. We deployed song meters from April to June
and retrieved them in September–November each year to
correspond with the breeding season of both species. We
visited every 1–3 mo during the deployment period to retrieve data and service the units.

FIGURE 1.  Historical and current observations of (A) Hawaiian Petrels and (B) Newell’s Shearwaters overlaid with projected suitable
habitat on Oahu.

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

Using the selected variables and presence locations, we
developed the habitat suitability model for each species by
combining 2 commonly used presence-only machine learning methods, MAXENT (Phillips et al. 2006) and Gradient
Boosting Model (Friedman 2001). Each projection from
MAXENT and the Gradient Boosting Model was then validated using a subset of the species presence data to define the Area Under the Curve (AUC), KAPPA, and True
Skill Statistic (TSS). An overall habitat assessment was developed from both methods that best described the relationship of shearwater and petrel locations to the various
topographic and climatic variables used in the assessment.
A weighted means ensemble of each validation metric definitive of both modeling approaches was then used to infer
habitat suitability, as projected onto Oahu.
Overlap of artificial light with otherwise suitable shearwater and petrel habitat is an important habitat modifier
that may limit the current breeding distribution of both
species. As such, it is an essential variable to include when
determining potential suitability of a site. As outlined in
Vorsino (2016), we developed a threshold from which light
was projected into unlit areas. This threshold was developed by extracting light intensity metrics for all seabird
auditory detections from the 15 arc-second Visible Infrared Imaging Radiometer Suite (NOAA 2018). The threshold from which light impact was projected was defined
using the 3rd quartile of a boxplot developed from the
extracted light intensity data. This threshold seemed to
best exemplify seabird sightings, maximized high-intensity light source areas, and minimized indirect sky glow
(Chalkias et al. 2006). A viewshed was then developed from
the periphery of this threshold across a 10 m digital eleva-

Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii  3

 4  Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii 

Data Analysis
Automated acoustic analysis of all field recordings was carried out using classifications based on the Deep Neural
Networks machine learning technique (Schmidhuber
2015). This approach detects sounds on field recordings
that have spectro-temporal properties similar to those
measured from signals produced by target species and
then splits field recordings into 2-second clips and extracts
measurements of 10 spectro-temporal features typically
found in animal sounds. A Deep Neural Network classification model was then trained for each species using training and cross-validation datasets containing examples of
positive sounds (vocalizations from Newell’s Shearwaters
and Hawaiian Petrels) and a representative example of
“negative” sound clips (i.e. sound clips from the soundscape at all survey sites that do not contain the species of
interest). Each classification model returns a probability
that a given 2-second window of field recordings contains
a sound produced by the target species. All events flagged
by the automated classification model were manually reviewed to confirm correctly identified Hawaiian Petrel or
Newell’s Shearwater calls.
RESULTS
Historical Records
For Hawaiian Petrels, the records of historical observations on Oahu were sparse: since 1991 at least 10 grounded
live birds were turned in to Sea Life Park for rehabilitation
(Pyle and Pyle 2017). Four more petrels were found dead;
two were close to Honolulu Harbor, one in Manoa Valley in
Honolulu, and one at the Kawailoa Wind Farm (Figure 1).
For Newell’s Shearwaters, there were at least 45
records of birds found throughout the island, with concentrations southwest of the Pali Highway Tunnel in upper
Nuuanu Valley, where strong trade winds force them
down, and on the northeast side of Pearl Harbor (Figure 1;
Banko 1980). The cause of the relatively large number of
observations from Pearl Harbor is unknown. Newell’s
­

Shearwater ­observations from the Pali Highway included
5 birds in 1967 (Sincock and Swedberg 1969), 3 birds from
1971–1975 (Banko 1980, Conant 1980), and 2 in 2008 (Pyle
and Pyle 2017). Shallenberger (1976) also reported seeing
Newell’s Shearwaters flying at night over the Pali Highway
in the early 1970s. In 2006, a resident in Kalihi Valley recorded calls of Newell’s Shearwaters passing over his house
regularly (E. VanderWerf personal observation). Of the 36
birds turned in to the Sea Life Park for rehabilitation from
1990 to 2003, approximately one-third died, and the rest
were banded and released alive (Pyle and Pyle 2017).
Habitat Suitability Analysis
Habitat modeling results indicated that more suitable
habitat was present on Oahu for Newell’s Shearwaters
than for Hawaiian Petrels and that suitable habitat is associated with upper-elevation forest (Figure 1). As all models showed relatively equivalent results, only the KAPPA
model is shown. All AUC, KAPPA, and TSS statistics were
indicative of an informative projection (i.e. on average
greater than 0.85 for AUC [values ranging from 0 to 1.0]
and greater than 0.5 and 0.5 for Maxent and GBM [values
range from −1.0 to 1.0]; Allouche et al. 2006). As the interest was primarily in habitat suitability, and not necessarily
in presence/absence categorization, the plots are projected
without a thresholding metric. As characterized in Vorsino
(2016), the threshold from which light was projected onto
the islands was defined as 0.2234 nano-Watts/(sr*cm2).
From this threshold, and using the Oahu based VIIRS and
DEM maps, the light viewshed was projected and plotted
with both species’ presence localities (Figure 2).
Auditory Detections of Newell’s Shearwaters and
Hawaiian Petrels
We made 320.04 hr of recordings on 220 nights at 3 sites
in 2016 and 4,730.68 hr of recordings on 829 nights at 10
sites in 2017. Recording time varied at each site as a result of deployment dates (which were limited by helicopter schedules and weather), and in some cases song meters
malfunctioned during the deployment period, resulting in
partial recordings.
We detected Newell’s Shearwater calls at 2 sites, one on
the leeward slope of Mount Kaala at 1,100 m elevation in
the Waianae Mountains, and another at Poamoho in the
Koolau Mountains at 650 m elevation (Table  1). All calls
detected at the Kaala Natural Area Reserve (NAR) site were
in May and June, while calls at Poamoho were detected in
September. Most calls were detected within a 3-hr period
before sunrise, except one night when calls were detected
99 min after sunset at Poamoho.
We detected Hawaiian Petrel calls at one site, Lower
Kaala NAR, on multiple nights in May and July 2017
(Table 1). Although the first calls were detected just before

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

Each song meter was programmed to record data each
day from sunset to 2  hr after sunset and for 1.5  hr starting 2  hr before sunrise. These correspond to the peak
calling periods when birds typically are either flying into
their burrows after sunset or departing their burrows just
before sunrise. For both species, more than 95% of vocalizations occur from sunset to 2  hr post sunset and from
2 hr to 30 min before sunrise (Ainley et al. 1997, Simons
and Hodges 1998). To increase the likelihood of detecting
birds, the song meters also were programmed to record
for 1 min of every 5-min block from sunset to 4 hr before
sunrise to capture sporadic calls throughout the night. The
total recording time was 5.2 hr per night per unit.

L. C. Young, E. A. VanderWerf, M. McKown, et al.

 L. C. Young, E. A. VanderWerf, M. McKown, et al. 

Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii  5

TABLE 1.  Summary of Newell’s Shearwater and Hawaiian Petrel calls detected on Oahu in 2017. Minutes from sunrise contains the range
of times over which calls were detected on each night. Moon illumination is the percent of the lunar face illuminated on each night.
Species
Shearwater
Shearwater
Shearwater
Shearwater
Shearwater
Shearwater
Shearwater
Shearwater
Petrel
Petrel
Petrel
Petrel
Petrel
Petrel
Petrel
a

Site
Kaala NAR
Kaala NAR
Kaala NAR
Kaala NAR
Kaala NAR
Poamohoa
Poamoho
Poamoho
Lower Kaala
Lower Kaala
Lower Kaala
Lower Kaala
Lower Kaala
Lower Kaala
Lower Kaala

Date
May 6, 2017
May 8, 2017
Jun 3, 2017
Jun 5, 2017
Jun 14, 2017
Sep 1, 2017
Sep 15, 2017
Sep 22, 2017
May 5, 2017
May 6, 2017
May 7, 2017
May 17, 2017
May 26, 2017
Jul 21, 2017
Jul 22, 2017

Time

Number of calls

04:40
04:43 to 04:49
04:07 to 04:15
04:40 & 04:44
03:12 & 03:17
04:32 to 04:39
20:13
04:10
20:42
20:52 to 21:34
20:16 to 21:15
20:02 & 20:12
19:56 to 21:05
20:05 to 22:30
19:49 to 20:17

1
4
3
2
2
5
1
1
2
4
6
2
18
15
8

Minutes from sunrise Moon illumination
−78
−74 to −68
−102 to −94
−69 and −65
−157 and −152
−103 to −96
−608
−131
+103
+112 to +154
+76 to +135
+58 to +68
+48 to +117
+50 to +195
+34 to +62

0.83
0.95
0.71
0.87
0.79
0.79
0.18
0.06
0.81
0.88
0.94
0.58
0.03
0.02
0.00

This site was not monitored before August 16, 2017, due to sensor failure

the full moon on May 10, subsequent calls were detected
during varying moon illuminations; all calls were detected
within a 4-hr period after sunset. The site where Hawaiian Petrels were detected was at 1,100 m elevation on the
windward slope of Mount Kaala, 1,500 m away from the
site of Newell’s Shearwater detections. All 3 sites were in
largely intact native forest with steep slopes.
DISCUSSION
Habitat modeling results indicated that more suitable habitat was present on Oahu for Newell’s Shearwater than for

Hawaiian Petrel, which corresponded to higher numbers
of both historical and contemporary sightings of shearwaters. It is unclear whether the difference in the amount
of apparently suitable habitat is a function of available
model parameters (i.e. only reflecting their extant range
rather than full historical range), or true habitat availability. Both species, but particularly petrels, once occurred
in high densities in coastal lowlands of Oahu (Olson and
James 1982). These locations were not represented in the
model parameters, which relied solely on extant sightings
from nesting locations on other islands. Historical sightings of both species appeared to be correlated more with

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

FIGURE 2.  Historical and current observations of (A) Hawaiian Petrels and (B) Newell’s Shearwaters overlaid with percentage light
visibility.

 6  Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii 

­ awaiian Petrel calls. We believe the sound was made by a
H
satellite communication facility located about 200 m from
the survey site. Petrels and other procellariform seabirds
can be attracted to a variety of sounds, including recordings of their calls and even human voices (Tennyson and
Taylor 1990, Podolsky and Kress 1992, Lawrence et  al.
2008). It is possible that the noise from the radar station,
which is similar to a portion of their call, is attracting Hawaiian Petrels to the site.
For Newell’s Shearwaters, the larger number of grounded
birds that have been found island-wide since the 1950s, especially in the proximity of the Pali Highway tunnel, has
caused speculation that a breeding colony may persist in
the Koolau Mountains near Honolulu (Pyle and Pyle 2017).
A  second concentration of historical sightings existed at
Pearl Harbor, a highly urban, well-lit area around a military installation. However, when the locations of downed
birds was overlaid with light sources and suitable habitat,
the association with light appears to be stronger than with
habitat (Figure 2). The song meter deployed in this region
in 2016 (which was also near the location where Newell’s
Shearwater calling was heard in 2006) did not detect any
Newell’s Shearwaters or Hawaiian Petrels. It is not out of
the question that birds may exist in high-quality habitat in
this region, as evidenced by the Poamoho detection farther
north, but the presence of so many lights and predators
makes their persistence in the mountains above Honolulu
unlikely.
ACKNOWLEDGMENTS
We thank C.  Miller and the Hawaii Division of Forestry
and Wildlife, and the U.S. Fish and Wildlife Service Oahu
Forest National Wildlife Refuge for permits and logistical
support. In particular, we thank the Oahu Army Natural
Resources Program and Matthew Burt for loaning this
project 10 SM2 song meters, and providing access and logistical support to several of the study sites. We thank the
Kauai Endangered Seabird Recovery Project for providing
seabird habitat information to contribute to the modeling
exercise, and all reviewers for helping to improve the manuscript.
Funding statement: We thank the National Fish and Wildlife
Foundation and the U.S. Fish and Wildlife Service for funding
this effort.
Ethics statement: This research followed all necessary state
and federal guidelines for work in natural areas and on listed
seabird species.
Author contributions: LY and EV conceived the idea, design,
experiment (supervised research, formulated question or hypothesis); LY, EV, and DS collected data; LY, EV, MM, AV wrote
the paper; LY, EV, AV, MM developed or designed methods;
LY, PR, JS, MM, AS analyzed the data; DS contributed substantial resources in the form of helicopter time.

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

high light intensity (100% of observations) than with suitable breeding habitat. Given the highly vagile nature of
both species, it is likely that birds nesting anywhere on the
island could be attracted to lights, or fallout, at any location
on the island. Thus their presence, particularly in urban areas, does not necessarily serve as a good indicator of potential breeding in that location.
We detected petrels at one site and shearwaters at two
sites where they could potentially be breeding on Oahu.
These detections in montane areas on Oahu were unexpected because both species were believed to have been
extirpated as breeders from the island prior to the arrival of
European explorers in 1778 (Olson and James 1982, Welch
et  al. 2012). Individuals of both species that have been
found on Oahu since then, often grounded in ­low-elevation
urban or suburban areas, are assumed to have been disoriented vagrants from other islands. These detections do
not provide evidence that either species is breeding on the
island, which might be indicated by regular acoustic activity across the entire breeding season, but the repeated detections at Mount Kaala over several months in 2 yr demonstrate that site is visited regularly by these species. The
birds we detected could be the last survivors of remnant
breeding populations on Oahu, or they could be young
birds from other islands that are prospecting for mates and
breeding sites.
Although it was surprising that we detected these species at all, the locations where we detected them were not
unexpected given the distribution of historical observations of downed birds moving between breeding sites
and at-sea foraging areas and suitable nesting habitat
indicated by modeling. The areas on all sides of Mount
Kaala and Poamoho are protected as Hawaii State natural
area reserves or forest reserves, and they contain some
of the least disturbed native forest habitat on the island.
Although predators including feral cats, mongooses, and
rats are undoubtedly present in these areas, the steep,
nearly vertical, slopes present in portions of these areas could provide nest sites that are relatively safe from
these predators. Both areas also are among the darkest
on Oahu, with little visible light pollution that can attract and confuse birds as they commute to and from the
mountains. The small number of Newell’s Shearwater
calls at the Poamoho site on the other side of Oahu is
also intriguing. Several biologists have reported Newell’s
Shearwater calls in Kualoa Valley and on the ridges in that
area over the last 20 yr (D. Duffy personal communication), possibly representing birds transiting to a remnant
colony at Poamoho.
Calls of petrels at the Lower Kaala NAR site were detected despite the presence of a constant low-frequency, man-made sound with a frequency (478–550 Hz)
that almost completely masked the first, tonal portion of

L. C. Young, E. A. VanderWerf, M. McKown, et al.

 L. C. Young, E. A. VanderWerf, M. McKown, et al. 

LITERATURE CITED

Podolsky, R., and S. W. Kress (1992). Attraction of the endangered
Dark-rumped Petrel to recorded vocalizations in the Galapagos
Islands. The Condor 94:448–453.
Pyle, R. L., and P. Pyle (2017). The Birds of the Hawaiian Islands:
Occurrence, History, Distribution, and Status. B.P. Bishop
Museum, Honolulu, HI, USA. http://hbs.bishopmuseum.org/
birds/rlp-monograph/
Raine, A. F., N. D. Holmes, M. Travers, B. A. Cooper, and R. H. Day
(2017). Declining trends of Hawaiian Petrel and Newell’s
Shearwater on the island of Kauai, Hawaii, USA. The Condor:
Ornithological Applications 119:405–415.
Schmidhuber, J. (2015). Deep learning in neural networks: An
overview. Neural Networks 61:85–117.
Shallenberger, R. J. (1976). Avifauna: Survey of North Halawa
Valley. ‘Elepaio 37:40–41.
Simons, T., and C. Hodges (1998). Hawaiian Petrel (Pterodroma
sandwichensis), version 2.0. In The Birds of North America
(A. Poole and F. Gill, Editors). Academy of Natural Sciences,
Philadelphia, PA, USA, and American Ornithologists’ Union,
Washington, DC, USA.
Sincock, J. L., and G. E. Swedberg (1969). Rediscovery of the nesting
grounds of Newell’s Manx Shearwater (Puffinus puffinus
newelli), with initial observations. The Condor 71:69–71.
Spear, L. B., D. G. Ainley, N. Nur, and S. N. G. Howell (1995).
Population size and factors affecting at-sea distributions of four
endangered procellariids in the tropical Pacific. The Condor
97:613–638.
R Core Team (2013). R: a language and environment for statistical
computing. Vienna, Austria. http://www.R-project.org.
Tennyson, A. J., and G. A. Taylor (1990). Behaviour of
Pterodroma petrels in response to “war-whoops.” Notornis
37:1–128.
Troy, J. R., N. D. Holmes, and M. C. Green (2011). Modeling artificial
light viewed by fledgling seabirds. Ecosphere 2:1–13.
[USFWS] U.S. Fish and Wildlife Service (1983). Hawaiian Darkrumped Petrel and Newell’s Manx Shearwater recovery plan.
Portland, OR, USA. http://kauaiseabirdhcp.com/mt-content/
uploads/2016/05/recovery-plan_hawaiian-dark-rumpedpetrel-and-newell_s-manx-shearwater_usfws-1983.pdf
Vorsino, A. E. (2016). Newell’s Shearwater landscape strategy.
Internal report. U.S. Fish and Wildlife Service, Ecological
Services, Honolulu, HI, USA. https://www.fws.gov/
pacificislands/documents/NESH%20Landscape%20Strategy_
Final_Feb17.pdf
Vorsino, A. E., L. B. Fortini, F. A. Amidon, S. E. Miller, J. D. Jacobi,
J. P. Price, S. O. Gon III, and G. A. Koob (2014). Modeling
Hawaiian ecosystem degradation due to invasive plants under
current and future climates. PLOS One 9:e95427.
Welch, A. J., A. E. Wiley, H. F. James, P. H. Ostrom, T. W. Stafford, and
R. C. Fleischer (2012). Ancient DNA reveals genetic stability
despite demographic decline: 3000 years of population
history in the endemic Hawaiian Petrel. Molecular Biology and
Evolution 29:3729–3740.

The Condor: Ornithological Applications 121:1–7, © 2019 American Ornithological Society

Downloaded from https://academic.oup.com/condor/article-abstract/121/1/duy004/5298327 by guest on 23 January 2019

Ainley, D. G., T. C. Telfer, and M. H. Reynolds (1997). Townsend’s and
Newell’s shearwater (Puffinus auricularis). In The Birds of North
America 297 (A. Poole and F. Gill, Editors). Academy of Natural
Sciences, Philadelphia, PA, USA, and American Ornithologists’
Union, Washington, DC, USA.
Ainley, D. G., R. Podolsky, L. de Forest, G. Spencer, and N. Nur
(2001). The status and population trends of the Newell’s
Shearwater on Kauai: Insights from modeling. In Evolution,
Ecology, Conservation, and Management of Hawaiian Birds: A
Vanishing Avifauna (J. M. Scott, S. Conant, and C. Van Riper III,
Editors). Studies in Avian Biology 22:108–123.
Allouche, O., A. Tsoar, and R. Kadmon (2006). Assessing the
accuracy of species distribution models: Prevalence, KAPPA
and the true skill statistic (TSS). Journal of Applied Ecology
43:1223–1232.
Banko, W. E. (1980). Part I. Population histories—species accounts.
Sea birds: Newell’s Shearwater (‘A’o). CPSU/UH Avian History
Report 5B: History of Endemic Hawaiian Birds. Cooperative
National Park Resources Studies Unit, University of Hawaii at
Manoa, Honolulu, HI, USA.
Buxton, R. T., and I. L. Jones (2012). Measuring nocturnal
seabird activity and status using acoustic recording devices:
applications for island restoration. Journal of Field Ornithology
83:47–60.
Chalkias, C., M. Petrakis, B. Psiloglou, and M. Lianou (2006).
Modelling of light pollution in suburban areas using
remotely sensed imagery and GIS. Journal of Environmental
Management 79:57–63.
Conant, S. (1980). Recent records of the ‘Ua’u (Dark-rumped Petrel)
and the ‘A’o (Newell’s Shearwater) in Hawaii. ‘Elepaio 41:11–13.
Friedman, J. H. (2001). Greedy function approximation: A gradient
boosting machine. Annals of Statistics 29:1189–1232.
Holmes, N., H. Freifeld, F. Duvall, A. Raine, M. Laut, J. Penniman,
D. Hu, and C. Bailey (2015). Newell’s Shearwater and Hawaiian
Petrel recovery: A five-year action plan. U.S. Fish and Wildlife
Service, Honolulu, HI, USA. http://kauaiseabirdhcp.com/mtcontent/uploads/2016/05/nesh_hape_banp_action_planfinal_usfws-2015-11-13.pdf
Lawrence, H. A., C. D. Millar, G. A. Taylor, L. D. Macdonald, and
D. M. Lambert (2008). Excess of unpaired males in one of the
world’s most endangered seabirds, the Chatham Island Taiko
Pterodroma magentae. Journal of Avian Biology 39:359–363.
[NOAA] National Oceanic and Atmospheric Administration (2018).
VIIRS cloud free composite. National Geophysical Data Center
Earth Observation Group. http://www.ngdc.noaa.gov/dmsp/.
Olson, S. L., and H. F. James (1982). Prodromus of the fossil
avifauna of the Hawaiian Islands. Smithsonian Contributions
to Zoology 365:1–59.
Phillips, S. J., R. P. Anderson, and R. E. Schapire (2006). Maximum
entropy modeling of species geographic distributions.
Ecological Modelling 190:231–259.

Newell’s Shearwaters and Hawaiian Petrels on Oahu, Hawaii  7