Search for: All records

Sex‐related differences in vital rates that drive population change reflect the basic life history of a species. However, for visually monomorphic bird species, determining the effect of sex on demographics can be a challenge. In this study, we investigated the effect of sex on apparent survival, recruitment, and breeding propensity in the Adélie penguin (Pygoscelis adeliae), a monochromatic, slightly size dimorphic species with known age, known sex, and known breeding history data collected during 1996–2019 (n = 2127 birds) from three breeding colonies on Ross Island, Antarctica. Using a multistate capture–mark–recapture maximum‐likelihood model, we estimated apparent survival (), recapture (resighting) probability (), and the probability of transitioning among breeding states and moving between colonies (; colony‐specific non‐juvenile pre‐breeders, breeders, and non‐breeders). Survival rate varied by breeding status and colony, but not sex, and pre‐breeders had higher survival rates than breeders and non‐breeders. Females had a higher probability of recruiting into the breeding population each year and may enter the breeding pool at younger ages. In contrast, both sexes had the same probability of breeding from year to year once they had recruited. Although we detected no direct sex effects on survival, the variation in recruitment probability and age‐at‐first reproduction, along with lower survival rates of breeders compared to pre‐breeders, likely leads to shorter lifespans for females. This is supported by our findings of a male‐biased mean adult sex ratio (ASR) of 1.4 males for every female ( proportion of males = 0.57, SD = 0.07) across all colonies and years in this metapopulation. Our study illustrates how important it can be to disentangle sex‐related variation in population vital rates, particularly for species with complex life histories and demographic dynamics.

 

Unlike in many polar regions, the spatial extent and duration of the sea ice season have increased in the Ross Sea sector of the Southern Ocean during the satellite era. Simultaneously, populations of Adélie penguins, a sea ice obligate, have been stable or increasing in the region. Relationships between Adélie penguin population growth and sea ice concentration (SIC) are complex, with sea ice driving different, sometimes contrasting, demographic patterns. Adélie penguins undergo a complete molt annually, replacing all their feathers while fasting shortly after the breeding season. Unlike most penguin species, a majority of Adélies are thought to molt on sea ice, away from the breeding colonies, which makes this period particularly difficult to study. Here, we evaluate the hypothesis that persistent areas of high SIC provide an important molting habitat for Adélie penguins. We analyzed data from geolocating dive recorders deployed year-round on 195 adult penguins at two colonies in the Ross Sea from 2017 to 2019. We identified molt by detecting extended gaps in postbreeding diving activity and used associated locations to define two key molting areas. Remotely sensed data indicated that SIC during molt was anomalously low during the study and has declined in the primary molt area since 1980. Further, annual return rates of penguins to breeding colonies were positively correlated with SIC in the molt areas over 20 y. Together these results suggest that sea ice conditions during Adélie penguin molt may represent a previously underappreciated annual bottleneck for adult survival.

 

ABSTRACT South polar skuas migrate from subtropical regions to breed along coastal Antarctica. In a fecal sample collected on Ross Island, Antarctica, we identified 20 diverse microviruses ( Microviridae ) that share low levels of similarity to currently known microviruses; 6 appear to use a Mycoplasma/Spiroplasma codon translation table. 

We conducted the first assessment of Adélie Penguin (Pygoscelis adeliae) chick survival that accounts for imperfect resighting. We found that when chicks are larger in size when they enter the crèche stage (the period when both parents forage at the same time and chicks are left relatively unprotected), they have a higher probability of survival to fledging. We investigated the relationships between growth, crèche timing, and chick survival during one typical year and one year of reduced food availability. Chicks that hatched earlier in the season entered the crèche stage older, and chicks that both grew faster and crèched older entered the crèche at a larger size. These relationships were stronger in the year of reduced food availability. Thus, parents increased their chicks’ chance of fledging if they provided sufficient food for faster growth rates and/or extended the length of the brood-guarding period. Early nest initiation (i.e., early hatching) provided parents with the opportunity to extend the guard period and increase chick survival. However, to extend the guard stage successfully, they must provide larger meals and maintain higher chick growth rates, even if just one parent at a time is foraging, which previous work has shown is not possible for all individuals. We show that the factors governing tradeoffs in chick-rearing behavior of Adélie Penguin parents may vary in accord with environmental conditions, a result from which we can better understand species’ adaptations to environmental changes.

 

Age-related variation in foraging performance can result from both within-individual change and selection processes. These mechanisms can only be disentangled by using logistically challenging long-term, longitudinal studies. Coupling a long-term demographic data set with high-temporal-resolution tracking of 18 Adélie penguins ( Pygoscelis adeliae , age 4–15 yrs old) over three consecutive annual cycles, we examined how foraging behaviour changed within individuals of different age classes. Evidence indicated within-individual improvement in young and middle-age classes, but a significant decrease in foraging dive frequency within old individuals, associated with a decrease in the dive descent rate. Decreases in foraging performance occurred at a later age (from 12–15 yrs old to 15–18 yrs old) than the onset of senescence predicted for this species (9–11 yrs old). Foraging dive frequency was most affected by the interaction between breeding status and annual life-cycle periods, with frequency being highest during returning migration and breeding season and was highest overall for successful breeders during the chick-rearing period. Females performed more foraging dives per hour than males. This longitudinal, full annual cycle study allowed us to shed light on the changes in foraging performance occurring among individuals of different age classes and highlighted the complex interactions among drivers of individual foraging behaviour. 

To fulfill their conservation potential and provide safeguards for biodiversity, marine protected areas (MPAs) need coordinated research and monitoring for informed management through effective evaluation of ecosystem dynamics. However, coordination is challenging, often due to knowledge gaps caused by inadequate access to data and resources, compounded by insufficient communication between scientists and managers. We propose to use the world's largest MPA in the Ross Sea, Antarctica as a model system to create a comprehensive framework for an interdisciplinary network supporting research and monitoring that could be implemented in other remote large‐scale international MPAs. Our proposed framework has three key components: (i) policy engagement, including delineation of policy needs and ecosystem metrics to assess MPA effectiveness; (ii) community partner engagement to elevate diverse voices, build trust, and share resources; and (iii) integrated science comprising three themes. These themes are: advancement of data science and cyberinfrastructure to facilitate data synthesis and sharing; biophysical modeling towards understanding ecosystem changes and uncertainties; and execution of observational and process studies to address uncertainties and evaluate ecosystem metrics. This proposed framework can improve MPA implementation by generating policy‐relevant science through this coordinated network, which can in turn improve MPA effectiveness in the Ross Sea and beyond.

 

Autonomous survey and aerial photogrammetry applications require solving a path planning problem that ensures sensor coverage over a specified area. In this work, we provide a multi-robot path planning method that can obtain this coverage over an arbitrary area of interest. We extend our previous method, path optimization for population counting with overhead robotic networks (POPCORN), by a divide-and-conquer scheme, split and link tiles (SALT), which drastically decreases the time needed for route planning. These POPCORN instances can be computed in parallel and combined with SALT in a scalable manner to produce coverage paths over very large areas of interest. To demonstrate this algorithm’s capabilities, we implemented our planning algorithm with a team of drones to conduct multiple photographic aerial wildlife surveys of the Cape Crozier Adélie penguin rookery on Ross Island, Antarctica, one of the largest Adélie penguin colonies in the world. The colony, which contains over 300,000 nesting pairs and spans over 2 km, was surveyed in about 3 hours. In contrast, previous human-piloted single-drone surveys of the same colony required over 2 days to complete. We also have deployed our survey system at several islets at Mono Lake, California, to survey a California gull colony as well as at a 2000-acre ranch in Marin, California. We provide this survey path planning tool as an open-source software package named wadl. 

Abstract Quantifying food intake in wild animals is crucial to many ecological and evolutionary questions, yet it can be very challenging, especially in the marine environment. Because foraging behavior can be inferred from dive recordings in many marine creatures, we hypothesized that specific behavioral dive variables can indicate food intake. To test this hypothesis, we attached time-depth recorders to breeding Adélie penguins also implanted with RFID tags that crossed a weighbridge as they traveled to and from the ocean to feed their chicks. The weighbridge reported how much mass the penguin had gained during a foraging trip. The variables that explained a significant amount of the change in body mass while at sea were the number of foraging dives per hour (46%) and the number of undulations per hour (12%). Most importantly, every increment of 1 in the rate of foraging dives per hour equated to a penguin gaining an average 170 g of mass, over the course of a 6–60 h foraging trip. These results add to a growing understanding that different metrics of foraging success are likely appropriate for different species, and that assessing the types and frequencies of dives using time-depth recorders can yield valuable insights. 

Abstract Group-size variation is common in colonially breeding species, including seabirds, whose breeding colonies can vary in size by several orders of magnitude. Seabirds are some of the most threatened marine taxa and understanding the drivers of colony size variation is more important than ever. Reproductive success is an important demographic parameter that can impact colony size, and it varies in association with a number of factors, including nesting habitat quality. Within colonies, seabirds often aggregate into distinct groups or subcolonies that may vary in quality. We used data from two colonies of Adélie penguins 73 km apart on Ross Island, Antarctica, one large and one small to investigate (1) How subcolony habitat characteristics influence reproductive success and (2) How these relationships differ at a small (Cape Royds) and large (Cape Crozier) colony with different terrain characteristics. Subcolonies were characterized using terrain attributes (elevation, slope aspect, slope steepness, wind shelter, flow accumulation), as well group characteristics (area/size, perimeter-to-area ratio, and proximity to nest predators). Reproductive success was higher and less variable at the larger colony while subcolony characteristics explained more of the variance in reproductive success at the small colony. The most important variable influencing subcolony quality at both colonies was perimeter-to-area ratio, likely reflecting the importance of nest predation by south polar skuas along subcolony edges. The small colony contained a higher proportion of edge nests thus higher potential impact from skua nest predation. Stochastic environmental events may facilitate smaller colonies becoming “trapped” by nest predation: a rapid decline in the number of breeding individuals may increase the proportion of edge nests, leading to higher relative nest predation and hindering population recovery. Several terrain covariates were retained in the final models but which variables, the shapes of the relationships, and importance varied between colonies.