Brian A. Cooper

LANDSCAPE-SCALE RELATIONSHIPS BETWEEN ABUNDANCE OF MARBLED MURRELETS AND DISTRIBUTION OF NESTING HABITAT

Abstract We used radar to count numbers of Marbled Murrelets (Brachyramphus marmoratus) flying inland within 10 river drainages on the Olympic Peninsula, Washington, during 1998–2000. We tested whether the numbers of murrelets entering drainages could be predicted from the amount and spatial configuration of low-elevation, late-seral forest (potential murrelet nesting habitat) within drainages. The maximal number of murrelet radar targets was positively correlated with the amount of late-seral forest in each of the three years sampled; this relationship persisted in 1999 and 2000 when controlling for drainage size. Murrelet radar counts were not correlated with the combined amounts of harvested, developed, and agricultural lands in any year. Numbers of murrelets increased as the amount of core area of late-seral forest and proximity of patches increased, and decreased with increasing amounts of edge of late-seral patches. Numbers were not correlated with the percent of late-seral forest, patch density, patch size, road density, or the overall diversity of all habitat types within landscapes. Neither the maximal nor the mean number of inbound Marbled Murrelets differed among years; the effect of year was small relative to the effect of habitat on murrelet numbers. Our results suggest that changes in the amount or distribution of nesting habitat should result in detectable changes in murrelet numbers at the scale of individual drainages. Thus, the amount and distribution of nesting habitat may play a role in the regulation of Marbled Murrelet populations, supporting the contention that providing nesting habitat is an effective conservation and restoration technique for this species. Relaciones a Escala del Paisaje entre la Abundancia de Brachyramphus marmoratus y la Distribución de Hábitat de Nidificación Resumen. Durante 1998–2000 utilizamos radares para contar el número de individuos de Brachyramphus marmoratus que volaron tierra adentro a lo largo de 10 cuencas de ríos que desaguan en la Península Olímpica, Washington, USA. Evaluamos si el número de individuos de B. marmoratus que entran por las cuencas puede ser predicho por la cantidad y configuración espacial de bosques de baja elevación que se encuentran en estadíos sucesionales tardíos (potencial hábitat de nidificación para estas aves) en cada cuenca. En cada uno de los tres años, el máximo número de individuos de B. marmoratus detectados estuvo positivamente correlacionado con la cantidad de bosque sucesional tardío; luego de controlar por el área de las cuencas esta relación persistió en 1999 y 2000. Durante todos los años, los conteos de B. marmoratus mediante radares no se correlacionaron con la cantidad combinada de tierras cosechadas, desarrolladas y agrícolas. El número de individuos de B. marmoratus aumentó con el área núcleo de bosque sucesional tardío y con el aumento de la proximidad entre parches, y decreció con el aumento de la cantidad de borde en los parches sucesionales tardíos. El número de aves no se correlacionó con el porcentaje de bosque sucesional tardío, densidad y área de parches, densidad de calles, ni diversidad total de todos los tipos de hábitats en el paisaje. Ni el número máximo ni el promedio de individuos de B. marmoratus que volaron en dirección tierra adentro diferió entre años; el efecto del año fue pequeño en comparación con el efecto del hábitat o del número de aves. Nuestros resultados sugieren que los cambios en la cantidad o distribución de hábitat para la nidificación deberían resultar en cambios detectables en el número de individuos de B. marmoratus a la escala individual de cada cuenca. Por lo tanto, la cantidad y distribución de hábitat para nidificación puede jugar un papel importante en la regulación de poblaciones de B. marmoratus, lo cual apoya la idea que proveer de hábitat para nidificación es una técnica efectiva para la conservación y restauración de esta especie.

RADAR-BASED MONITORING OF MARBLED MURRELETS

Abstract We used radar to measure daily, monthly, and annual patterns of Marbled Murrelet (Brachyramphus marmoratus) abundance and movements at 12 major river valleys in the Olympic Peninsula of Washington. Landward movements of murrelets peaked from ∼75 min to ∼20 min before sunrise, followed by a seaward exodus from ∼20 min before sunrise to ∼65 min after sunrise. This general pattern of a landward movement followed by a seaward exodus varied little, but the timing of the seaward exodus gradually became later from May to July. Within a morning, numbers of landward radar targets averaged twice the numbers of seaward targets, and morning counts were approximately five times evening counts. Species identification error rates were lower for landward radar counts than for seaward counts. Radar counts varied through the season, with numbers increasing from May to July, then dropping in August. Seaward counts were more variable than landward counts. There was wide overlap among months in the amount of daily variation in both landward and seaward counts. Radar appears to be a powerful, cost-effective, and non-intrusive tool that can establish an index of abundance for murrelets at specific inland breeding areas.

Patterns of Movement of Dark-Rumped Petrels and Newell's Shearwaters on Kauai

We used ornithological radar and night-vision scopes to study movement patterns of Dark-rumped Petrels (Pterodroma phaeopygia sandwichensis) and Newells Shearwaters (Puffinus auricularis newelli) on the island of Kauai, Hawaii, from 1992 to 1994. Movement rates on radar (targets/hr) for both species peaked for ∼2 hr around sunset and sunrise and were low in the middle of the night. Dark-rumped Petrels generally moved during crepuscular periods, whereas Newells Shearwaters were strongly nocturnal. Movement rates were much higher in fall 1993 than in fall 1992, probably because of effects of Hurricane Iniki in 1992, and were higher in summer than in fall, probably because of the presence of nonbreeding birds in summer. Movement rates increased through time in summer, probably because numbers of nonbreeding birds visiting colonies increased through time, but declined through time in fall because fewer adults returned to the colony as fledging progressed. Effects of the moon on movement rates appeared to be small. Movement rates varied geographically, generally being much higher on eastern and northern Kauai than on southern Kauai. Movements were predominantly inland in the evening, predominantly seaward in the morning, and both directions in the middle of the night. Birds flew between 8 and 800 m above ground level (agl) and averaged 142 m agl for all procellariid species combined. There was no relationship between elevation of a site and flight altitude of birds at that site. Flight altitudes at a site generally were highest during the evening peak of movement and lowest during the morning peak in summer but were not different among three periods of the night in fall. Dark-rumped Petrels flew at significantly higher altitudes than did Newells Shearwaters in fall 1993 and summer 1994 but not in summer 1993.

DECLINE OF TOWNSEND'S (NEWELL'S) SHEARWATERS (PUFFINUS AURICULARIS NEWELLI) ON KAUAI, HAWAII

Abstract We compared trends in the number of Hawaiian Petrels (Pterodroma sandwichensis; formerly Dark-rumped Petrels [P. phaeopygia sandwichensis]) and Newells Shearwaters (Puffinus auricularis newelli) seen visiting Kauai, Hawaii, on ornithological radar in June 1993 and 1999–2001 and summarized and evaluated trends in the number of young Newells Shearwaters recovered in the “Save Our Shearwaters” (SOS) Program on Kauai, 1979–2001. After pairing sampling dates at each site to remove temporal effects, radar data indicated that the number of Newells Shearwaters visiting Kauai declined significantly between 1993 and 1999–2001. The mean change from 1993 numbers of radar targets across 13 sites was −59.8 ± 7.2% (SE) in 1999, −62.1 ± 5.5% in 2000, and −61.5 ± 5.4% in 2001, with all sites except one showing decreases of 38–93% in 1999 and all sites showing decreases of 31–96% in 2000 and 37–92% in 2001. Our data suggest that the decline is concentrated in Newells Shearwaters, whereas the Hawaiian Petrel population actually appears to have increased. The SOS fallout data exhibited a consistent 72% overall decline in Newells Shearwater recoveries from 1993 to 2001. Although we believe that the SOS data only generally reflect population size and productivity of shear-waters on Kauai, we conclude from the radar data that there has been a significant decrease in the number of Newells Shearwaters visiting Kauai since 1993.

TRENDS IN RADAR-BASED COUNTS OF MARBLED MURRELETS ON THE OLYMPIC PENINSULA, WASHINGTON, 1996–2004

Abstract ABSTRACT The Marbled Murrelet (Brachyramphusmarmoratus) is a highprofile, federally threatened seabird, but noreliable estimates of population trends at inlandbreeding areas exist for this species. We conductedland-based radar studies of Marbled Murrelets at3–7 sites on the Olympic Peninsula,Washington, in 1996–2002 and 2004 to estimatepopulation changes and to examine relationshipsbetween our counts and oceanographic conditions,murrelet productivity, and regional at-sea countsof murrelets. Morning radar counts of murreletsvaried significantly among and within sites but didnot decline from 1996–2004, suggesting thatthe inland breeding population of murrelets isstable in this area. A retrospective power analysisindicated that we had a 25% and 56%chance of detecting 2% and 4% annualdeclines, respectively. Thus, if relatively smallannual declines did occur during our study period,there is a high probability that they would havegone undetected, even though they could add up to abiologically important decline over time. It isunlikely that murrelets on the Olympic Peninsuladeclined by ≥6% annually, however,because retrospective analyses indicated that powerto detect such declines was >88%. Therewas no significant relationship between radarcounts and at-sea counts or productivity ofmurrelets in the nearby San Juan Islands during thestudy period. We also did not detect a relationshipbetween radar counts and mean sea-surfacetemperatures or the Northern Oscillation Index,suggesting that variation in oceanographicconditions (e.g., the strong 1998 ElNiño event) was not associated withvariation in morning radar counts of MarbledMurrelets. A prospective power analysis indicatedthat small (2%–4%)annual declines could be detected with reasonablyhigh power (≥80%) with thecurrent radar sampling design by extending thestudy to 11–15 years.

Movement of the Hawaiian Petrel to Inland Breeding Sites on Maui Island, Hawai’i

Abstract We studied nightly movement rates, behavior, flight directions, and flight altitudes of Hawaiian Petrel (Pterodroma sandwichensis) and possibly Newell’s Shearwater (Puffinus auricularis) at 15 sites on Maui, Hawaiian Islands, in June 2001. We observed no Newell’s Shearwaters visually, but saw Hawaiian Petrels at all of the nine sites around eastern Maui and at two of the six sites around western Maui. Mean nightly movement rates on radar generally were higher in eastern Maui than western Maui, although movement rates in the northeastern part of western Maui were comparable to those at several sites in eastern Maui. The highest movement rates occurred at the Ke’anae Valley, Mokuia Point, Nu’u Bay, and Kaupo sites, all of which are located on the northeastern or southeastern slopes of Haleakala in eastern Maui. Hawaiian Petrels (identified visually) flew inland primarily between 10 min after sunset and the point of complete darkness (about 30 min after sunset), with no movements observed beyond 50 min after sunset. Radar movements peaked just before the point of complete darkness, but a substantial number of radar targets also flew inland at 30-50 min after sunset, with some movement occurring even after that period. These later movements suggest that small numbers of Newell’s Shearwaters are flying inland at several locations. Further, there was a higher proportion of these late flights in western Maui than in eastern Maui, suggesting that Newell’s Shearwaters, if present, form a higher proportion of the two species in western Maui than in eastern Maui. Mean flight directions at all sites were in an inland direction, with little variation in flight directions at most sites. Mean flight altitudes of the Hawaiian Petrel were 190 m above ground level, similar to those at Kaua’i Island. The data suggest that the number of Hawaiian Petrels on Maui may be higher than the current estimate of 1,800 birds.

Declining population trends of Hawaiian Petrel and Newell's Shearwater on the island of Kaua‘i, Hawaii, USA

ABSTRACT The island of Kaua‘i, Hawaii, USA, holds a large breeding populations of the endangered Hawaiian Petrel (Pterodroma sandwichensis) and a majority of the world population of the threatened Newells Shearwater (Puffinus newelli). We evaluated island-wide population trends of both species. For Newells Shearwaters, we considered radar counts at 13 sites between 1993 and 2013 and annual island-wide tallies of fledglings retrieved after being grounded by light attraction in 1979–2015 (Save Our Shearwaters [SOS] program). For Hawaiian Petrels, we considered radar counts alone. Radar data indicated a 78% decline overall in numbers of Hawaiian Petrels (at an average rate of ∼6% per year) and a 94% decline overall in numbers of Newells Shearwaters (at an average rate of ∼13% per year) during the survey period. Most (92%) radar sites showed significant declines of Newells Shearwaters across the entire survey period, as did 62% of sites for Hawaiian Petrels. The SOS recovery effort collected 30,522 Newells Shearwater fledglings between 1979 and 2015. When we compared this dataset in pre- and post-Hurricane Iniki (September 1992) periods, we found a significant downward trend after Hurricane Iniki, similar to the trend seen in the radar data. The large-scale declines found in this study are not surprising, considering the significant threats facing both species on Kaua‘i, which include powerline collisions, light attraction, introduced predators, and habitat modification—threats which were potentially exacerbated after Hurricane Iniki. Improved conservation initiatives and an increased understanding of the various threats facing the 2 species are key to reversing these declines.