Mark Miller (College of Science and Engineering and Centre for Tropical Environmental and Sustainability Science, James Cook University, Australia, Cairns, Queensland, Australia) and colleagues have published in the journal Marine Ecology Progress Series on Wedge-tailed Shearwaters Ardenna pacifica (globally Least Concern) foraging in association with tuna.

The paper’s abstract follows:

“Foraging with tuna is a well-documented seabird strategy, referred to as facilitated foraging. However, despite this behaviour being considered almost obligatory in nutrient-poor tropical waters, little data exist on its relative importance to individual colonies. Therefore, to examine facilitated foraging under different patterns of nutrient availability, we tracked wedge-tailed shearwaters Ardenna pacifica from 2 colonies, one tropical and one subtropical, situated in waters of contrasting productivity. Shearwater foraging behaviour was assessed relative to oceanographic covariates and predicted distributions for multiple tropical tuna species and age-classes, simulated by an existing ecosystem model (SEAPODYM). Shearwaters from both colonies undertook long trips to deep, pelagic waters close to seamounts and foraged most often at fronts and eddies. Micronektonic and adult tuna age classes were highly correlated in space. Predation between these tuna age classes represents a likely source of facilitated foraging opportunities for shearwaters. At broad spatio-temporal scales, shearwaters consistently foraged in areas with higher predicted adult skipjack and micronektonic tuna densities and avoided adult bigeye tuna. At finer spatio-temporal scales, dynamic ocean features aggregated tuna of all sizes. Enhanced tuna density at these locations increased the likelihood of shearwater foraging activity. Long trips in the tropics targeted oligotrophic waters with higher tuna densities. Long trips in the subtropics targeted enhanced productivity, but in some years shifted to target the same oligotrophic, tuna-dense waters used by tropical conspecifics. We conclude that facilitated foraging with tuna is consistently important to the tropical breeding population and becomes increasingly important to the subtropical population in years of low marine productivity.”

Wedge-tailed Shearwaters

Reference:

Miller, M.G.R., Carlile, N., Scutt Phillips, J., McDuie, F. & Congdon, B.C. 2018. Importance of tropical tuna for seabird foraging over a marine productivity gradient. Marine Ecology Progress Series 586: 233-249. doi.org/10.3354/meps12376.

John Cooper, ACAP Information Officer, 22 January 2018

The Kapiti Island Nature Reserve near Wellington, New Zealand is administered by the Department of Conservation and is open to tourist parties. It has been free of introduced mammalian predators for two decades (rats were eradicated in 1996). Among its prolific birdlife is a breeding population of Near Threatened Sooty Shearwaters Ardenna grisea near the island’s western cliff tops. The island’s shearwaters have been a risk to Wekas Gallirallus australis, an endemic (and flightless) New Zealand rail, that prey upon its eggs and young chicks.

Sooty Shearwater, photograph by West Coast Penguin Trust

Not being an introduced species to New Zealand (although introduced to Kapiti in the 1890s), and having a global status of Vulnerable with a decreasing population, their elimination from the island is assumed not to be an option, so a Weka-proof fence has been constructed to keep them out of the shearwater’s breeding site.

“Departure ramps were included in the construction to allow tītī [Sooty Shearwaters] to safely launch back out to sea from their breeding grounds. Motion sensor cameras will also tell us if any cunning weka have found any weak spots along the fence line. The next steps are to install some small one-way tunnels along the fence line, to give juvenile birds an extra exit route when they fledge. Night surveys of the colony in the New Year will hopefully prove more tītī chicks get that chance this breeding season”.

Read more here.

John Cooper, ACAP Information Officer, 19 January 2018

Ryan Reisinger (Centre d’Etudes Biologiques de Chizé, Villiers-en-Bois, France) and colleagues have published in the journal Diversity and Distributions on a decade of at-sea tracing of marine predators, including seven ACAP-listed species, that breed on Marion Island in the southern Indian Ocean.

The paper’s abstract follows:

“Aim

The distribution of marine predators is driven by the distribution and abundance of their prey; areas preferred by multiple marine predator species should therefore indicate areas of ecological significance. The Southern Ocean supports large populations of seabirds and marine mammals and is undergoing rapid environmental change. The management and conservation of these predators and their environment relies on understanding their distribution and its link with the biophysical environment, as the latter determines the distribution and abundance of prey. We addressed this issue using tracking data from 14 species of marine predators to identify important habitat.

Location

Indian Ocean sector of the Southern Ocean.

Methods

We used tracking data from 538 tag deployments made over a decade at the Subantarctic Prince Edward Islands. For each real track, we simulated a set of pseudo-tracks that allowed a presence-availability habitat modelling approach that estimates an animal's habitat preference. Using model ensembles of boosted regression trees and random forests, we modelled these tracks as a response to a set of 17 environmental variables. We combined the resulting species-specific models to evaluate areas of mean importance.

Results

Real tracking locations covered 39.75 million km2, up to 7,813 km from the Prince Edward Islands. Areas of high mean importance were located broadly from the Subtropical Zone to the Polar Frontal Zone in summer and from the Subantarctic to Antarctic Zones in winter. Areas of high mean importance were best predicted by factors including wind speed, sea surface temperature, depth and current speed.

Main conclusions

The models and predictions developed here identify important habitat of marine predators around the Prince Edward Islands and can support the large-scale conservation and management of Subantarctic ecosystems and the marine predators they sustain. The results also form the basis of future efforts to predict the consequences of environmental change.”

A Grey-headed Albatross, one of the seven ACAP-listed species in the study, carries a tracker at Marion Island, photograph by Kim Stevens

With thanks to Ryan Reisinger.

Reference:

Reisinger, R.R., Raymond, B., M.N., Hindell, M.A., Bester, M.N., Crawford, R.J.M., Davies, D., de Bruyn, P.J.N., Dilley, B.J., Kirkman, S.P., Makhado, A.B., Ryan, P.G., Schoombie, S., Stevens, K., Sumner, M.D., Tosh, C.A., Wege, M., Whitehead, T.O., Wotherspoon, S. & Pistorius, P.A. 2018. Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean. Diversity and Distributions DOI: 10.1111/ddi.12702.

John Cooper, ACAP Information Officer, 18 January 2018

Rachael Orben (Department of Fisheries and Wildlife, Oregon State University, Hatfield Marine Science Center, Newport, USA) and colleagues have published open access in the journal Endangered Species Research on the post-fledging wanderings at sea of the globally Vulnerable Short-tailed Albatrosses Phoebastria albatrus.

The paper’s abstract follows:

“The ability of juveniles of wide-ranging species to locate distant foraging regions can rely on innate or learned information. Reliance on innate cues could be problematic when conservation actions facilitate reintroduction. In the North Pacific, the short-tailed albatross Phoebastria albatrus is recovering from extensive harvesting, and has recently benefited from translocation efforts. Yet little is known about how naïve juveniles disperse or about individual distributions of immature short-tailed albatrosses. The primary goals of this study were to quantify the ontogeny of movement patterns and spatial distributions and compare these between naturally reared and translocated short-tailed albatrosses. We tracked 51 albatrosses for up to 5 years post-fledging: naturally reared chicks from their natal colony on Torishima, Japan, and chicks that were translocated 350 km to the southeast to Mukojima, Japan. Initial, more northerly dispersal of translocated fledglings suggests the ability to adjust to a new departure location. Fledglings’ departure paths differed from previously tracked adults departing Torishima, yet like adults, the majority of fledglings (81%) reached the Bering Sea that first summer, further supporting large-scale innate orientation abilities. Juveniles showed strong seasonal changes in distributions, traveling more in winter and occupying regions not typically used by adults (e.g. California Current, Sea of Okhotsk). As they aged, juveniles began to exhibit habitat fidelity to shelf-break regions, as anticipated from prior studies, yet continued to explore new regions with low levels of spatial fidelity. Juvenile short-tailed albatrosses explored almost the entire species range, highlighting the impressive capacity of individuals to transverse the North Pacific.”

A fledgling Short-tailed Albatross takes its first flight

Reference:

Orben, R.A., O’Connor, A.J., Suryan, R.M., Ozaki, K., Sato, F. & Deguchi, T. 2018. Ontogenetic changes in at-sea distributions of immature short-tailed albatrosses Phoebastria albatrus. Endangered Species Research 35: 23-37.

John Cooper, ACAP Information Officer, 17 January 2018