Lindsay C. Young

Bringing Home the Trash: Do Colony-Based Differences in Foraging Distribution Lead to Increased Plastic Ingestion in Laysan Albatrosses?

When searching for prey, animals should maximize energetic gain, while minimizing energy expenditure by altering their movements relative to prey availability. However, with increasing amounts of marine debris, what once may have been ‘optimal’ foraging strategies for top marine predators, are leading to sub-optimal diets comprised in large part of plastic. Indeed, the highly vagile Laysan albatross (Phoebastria immutabilis) which forages throughout the North Pacific, are well known for their tendency to ingest plastic. Here we examine whether Laysan albatrosses nesting on Kure Atoll and Oahu Island, 2,150 km apart, experience different levels of plastic ingestion. Twenty two geolocators were deployed on breeding adults for up to two years. Regurgitated boluses of undigestable material were also collected from chicks at each site to compare the amount of plastic vs. natural foods. Chicks from Kure Atoll were fed almost ten times the amount of plastic compared to chicks from Oahu despite boluses from both colonies having similar amounts of natural food. Tracking data indicated that adults from either colony did not have core overlapping distributions during the early half of the breeding period and that adults from Kure had a greater overlap with the putative range of the Western Garbage Patch corroborating our observation of higher plastic loads at this colony. At-sea distributions also varied throughout the year suggesting that Laysan albatrosses either adjusted their foraging behavior according to constraints on time away from the nest or to variation in resources. However, in the non-breeding season, distributional overlap was greater indicating that the energy required to reach the foraging grounds was less important than the total energy available. These results demonstrate how a marine predator that is not dispersal limited alters its foraging strategy throughout the reproductive cycle to maximize energetic gain and how this has led to differences in plastic ingestion.

Successful same-sex pairing in Laysan albatross

Unrelated same-sex individuals pairing together and cooperating to raise offspring over many years is a rare occurrence in the animal kingdom. Cooperative breeding, in which animals help raise offspring that are not their own, is often attributed to kin selection when individuals are related, or altruism when individuals are unrelated. Here we document long-term pairing of unrelated female Laysan albatross (Phoebastria immutabilis) and show how cooperation may have arisen as a result of a skewed sex ratio in this species. Thirty-one per cent of Laysan albatross pairs on Oahu were female–female, and the overall sex ratio was 59% females as a result of female-biased immigration. Female–female pairs fledged fewer offspring than male–female pairs, but this was a better alternative than not breeding. In most female–female pairs that raised a chick in more than 1 year, at least one offspring was genetically related to each female, indicating that both females had opportunities to reproduce. These results demonstrate how changes in the sex ratio of a population can shift the social structure and cause cooperative behaviour to arise in a monogamous species, and they also underscore the importance of genetically sexing monomorphic species.

DEMOGRAPHY AND NATURAL HISTORY OF LAYSAN ALBATROSS ON OAHU, HAWAII

Abstract Laysan Albatross (Phoebastria immutabilis) began re-colonizing sites across the Pacific in the 1970s after severe population declines, and fledged the first chick on the island of Oahu in 1992. We report the status of Laysan Albatross populations at Kaena Point and Kuaokala on the island of Oahu, Hawaii and provide new demographic data for this species. Colonies on Oahu were monitored weekly from 2004 to 2008; all individuals were censused, banded, and genetically identified to gender. There was a population of 365 adults on Oahu in 2008 of which 47% were active breeders. The breeding population increased 27% annually since 1991. The high rate of increase was due primarily to immigration with some local recruitment. Recaptures indicate that seven birds were from French Frigate Shoals, one was from Midway Atoll, and 52 were from Oahu and returning to breed; all other adults were of unknown origin. Hatching rate (62%), fledging rate (78%), and overall reproductive success (48%) were comparable to other colonies despite occasional predation. The rate of adult dispersal was high with up to 10% of birds observed each day on Oahu visiting from Kauai. Adults occasionally changed breeding colonies between seasons, and even visited other islands while actively breeding on Oahu. While small, these colonies are at higher elevations and may serve as refugia in the event of sea level rise and, thus, should continue to be conservation priorities.

Estimating Survival and Life-Stage Transitions in the Laysan Albatross (Phoebastria immutabilis) using Multistate Mark—Recapture Models

ABSTRACT. Accurate estimates of demographic rates are fundamental to understanding population dynamics and can provide insights into the ecology and conservation of a species. We used multistate mark—recapture models to estimate apparent annual survival, encounter probability, and life-stage transitions in Laysan Albatrosses (Phoebastria immutabilis) at Kaena Point, Hawaii, from 2003 to 2010. Four-state models of prebreeders, breeders, failed breeders, and skipped breeders overestimated survival by 1–3% and underestimated skipped breeding by 5–6%, but five-state models that included a state for unobserved skipped breeders performed better. Survival did not vary among years and was highest in prebreeders (mean ± SE = 0.996 ± 0.010) and lower in successful breeders (0.932 ± 0.023) than in failed breeders (0.963 ± 0.018), suggesting a cost to reproduction. Survival was similar in males and females among prebreeders, breeders, and failed breeders, but survival of males was lower among skipped breeders. Encounter probability was related to monitoring effort; more frequent visits and use of field-readable auxiliary bands and remote cameras resulted in higher encounter rates. With sufficient effort, all skipped breeders were observed at the colony even though they did not breed. Recruitment averaged 24% in females and 21% in males and varied among years. Breeding frequency averaged 0.807 ± 0.028 and varied among years. Successful breeders were more likely than failed breeders to skip the next breeding season. Estimates of all demographic rates except recruitment were similar to estimates for Laysan Albatrosses from Midway in the 1960s despite differences in methodology. This information can help measure population dynamics, breeding population sizes, population trends, and efficacy of conservation actions.

As the egg turns: monitoring egg attendance behavior in wild birds using novel data logging technology.

Egg turning is unique to birds and critical for embryonic development in most avian species. Technology that can measure changes in egg orientation and temperature at fine temporal scales (1 Hz) was neither readily available nor small enough to fit into artificial eggs until recently. Here we show the utility of novel miniature data loggers equipped with 3-axis (i.e., triaxial) accelerometers, magnetometers, and a temperature thermistor to study egg turning behavior in free-ranging birds. Artificial eggs containing egg loggers were deployed in the nests of three seabird species for 1–7 days of continuous monitoring. These species (1) turned their eggs more frequently (up to 6.5 turns h−1) than previously reported for other species, but angular changes were often small (1–10° most common), (2) displayed similar mean turning rates (ca. 2 turns h−1) despite major differences in reproductive ecology, and (3) demonstrated distinct diurnal cycling in egg temperatures that varied between 1.4 and 2.4°C. These novel egg loggers revealed high-resolution, three-dimensional egg turning behavior heretofore never measured in wild birds. This new form of biotechnology has broad applicability for addressing fundamental questions in avian breeding ecology, life history, and development, and can be used as a tool to monitor birds that are sensitive to disturbance while breeding.

Adaptive value of same-sex pairing in Laysan albatross

Same-sex pairing is widespread among animals but is difficult to explain in an evolutionary context because it does not result in reproduction, and thus same-sex behaviour often is viewed as maladaptive. Here, we compare survival, fecundity and transition probabilities of female Laysan albatross in different pair types, and we show how female–female pairing could be an adaptive alternative mating strategy, albeit one that resulted in lower fitness than male–female pairing. Females in same-sex pairs produced 80% fewer chicks, had lower survival and skipped breeding more often than those in male–female pairs. Females in same-sex pairs that raised a chick sometimes acquired a male mate in the following year, but females in failed same-sex pairs never did, suggesting that males exert sexual selection by assessing female quality and relegating low-quality females into same-sex pairs. Sexual selection by males in a monomorphic, non-ornamented species is rare and suggests that reconsideration is needed of the circumstances in which alternative reproductive behaviour evolves. Given the lack of males and obligate biparental care in this species, this research demonstrates how same-sex pairing was better than not breeding and highlights how it could be an adaptive strategy under certain demographic conditions.

Response of Wedge-tailed Shearwaters (Puffinus pacificus) to Eradication of Black Rats (Rattus rattus) from Moku'auia Island after Reinvasion

Abstract: Moku‘auia is a 5-ha island off northeastern O‘ahu, Hawai‘i, that supports several thousand nesting Wedge-tailed Shearwaters (Puffinus pacificus) and several species of migratory shorebirds and is critical habitat for the federally endangered ‘ohai plant (Sesbania tomentosa). The island is separated from Mālaekahana State Recreation Area on O‘ahu by a channel 230 m wide and 1 m deep and receives numerous human visitors. Black rats (Rattus rattus) were first documented on Moku‘auia in 1967 and were eradicated in the 1990s, but rats recolonized the island and were eradicated again in 2006. We re-eradicated black rats in November 2011 following another recolonization, using snap traps and diphacinone in bait boxes spaced 25 m apart. Pre-eradication, 80% of tracking tunnels contained rat tracks. After 14 days, no more rats were trapped, bait take dropped to almost zero, and no rats have been detected since. Eradication of rats resulted in a doubling of Wedge-tailed Shearwater reproduction in 2006 and 2012 and is expected to enhance regeneration of native plants. Black rats may recolonize Moku‘auia periodically in the future because of its proximity to O‘ahu and the frequency of human visitation, but its small size and simple terrain make rats easy and inexpensive to eradicate, and the natural resources present warrant continued management.

Juvenile survival, recruitment, population size, and effects of avian pox virus in Laysan Albatross (Phoebastria immutabilis) on Oahu, Hawaii, USA

ABSTRACT Understanding population dynamics and determining conservation priorities in long-lived species with delayed breeding often is hampered by lack of information about younger age classes. Obtaining accurate estimates of juvenile survival and recruitment can be difficult because young individuals are infrequently observed. We used mark–recapture models to estimate age-specific survival, recruitment, population size, and encounter probability of Laysan Albatrosses (Phoebastria immutabilis) using a 14-yr dataset from Oahu, Hawaii, USA. We also measured the long-term effect of avian pox virus (Poxvirus avium) on the survival and recruitment of albatrosses infected as nestlings. Survival of juvenile albatrosses during the first year after fledging was 0.757 ± 0.042. We were able to estimate juvenile survival, the first such estimate in any long-lived seabird, because our high search effort revealed that some birds began visiting the natal colony at the age of 1 yr. The survival of prebreeders increased rapidly and reached a value in the second year (0.973 ± 0.008) that was similar to the survival of breeding adults (0.973 ± 0.017). The average age of first return to the natal colony was 4.24 ± 0.11 yr. The average age at first breeding was 8.44 ± 0.15 yr, with recruitment probability peaking at ages 9–10 yr and a single bird being recruited into the breeding population at the age of 4 yr. Pox virus decreased survival in the first year by 4%–13% and decreased recruitment probability up to age 12 by 4%–26%, depending on the severity of infection. The total size of the Laysan Albatross population on Oahu in 2015 was 555 birds, consisting of 270 active breeders, 231 prebreeders, and 54 birds that likely skipped breeding that year. The number of prebreeders constituted an average of 44% of the total population. These demographic estimates will be useful for population modeling exercises involving various threat and management scenarios, and for examining environmental factors that influence demography.

Data loggers in artificial eggs reveal that egg-turning behavior varies on multiple ecological scales in seabirds

ABSTRACT In most avian species, egg-turning behavior during incubation is vital for proper embryonic development and hatching success. However, changes in turning behaviors are rarely studied across different temporal scales (e.g., day–night or across incubation phases), though the timing of incubation behaviors affects reproductive success. We used data loggers encapsulated in artificial eggs to measure turning rates and angle changes of eggs in Western Gull (Larus occidentalis) and Laysan Albatross (Phoebastria immutabilis) nests. We examined diurnal and daily cycles in egg-turning behaviors across early, middle, and late incubation phases. Our results indicate that (1) egg-turning behaviors remain similar throughout incubation, resulting in a consistent environment for developing chicks; (2) egg-turning rates and angle changes vary according to diurnal cycles and day length in each species; and (3) egg-turning rates, but not angle changes, were similar between species. Egg-turning behaviors may vary among species according to seasonality and geography, and using consistent methodologies to measure egg turning will further clarify the role of egg turning in avian life history and ecology.

Predominance of Unbalanced Gene Flow from Western to Central North Pacific Colonies of the Black-Footed Albatross (Phoebastria nigripes)

Abstract: The Black-Footed Albatross (Phoebastria nigripes) breeds in two remote regions, approximately 4,000 km apart, in the North Pacific. The population in the central North Pacific region (Northwestern Hawaiian Islands), which contains >95% of the total population, is currently stable, although concerns exist about future declines. In contrast, the population in the western North Pacific (Izu and Ogasawara Islands in Japan) is rapidly increasing, and the breeding areas are expanding. To estimate possible gene flow caused by dispersal between populations, we performed genetic analysis on six colonies of Black-Footed Albatross using 10 microsatellite markers. The central and western North Pacific populations were genetically differentiated. However, an estimation of migrants per generation indicated directional dispersal from the western to the central North Pacific. In particular, the population on Kure Atoll, the westernmost atoll in the Hawaiian Islands in the central North Pacific, exhibited weak genetic differentiation from the western North Pacific populations, suggesting frequent immigration from the western North Pacific. The recent expansion of the western North Pacific population may be due to an increase in returning individuals, which may be caused by increased breeding success rates and/or survival rates. Range-wide and long-term monitoring of the Black-Footed Albatross population using genetic markers may help to uncover dispersal dynamics of this highly mobile but philopatric albatross species and to make appropriate conservation decisions in light of environmental changes.