Letizia Campioni (Marine and Environmental Sciences Center, Instituto Universitário, Lisbon, Portugal) and colleagues have published in the Journal of Animal Ecology on tracking immature Cory's Shearwaters Calonectris borealis at sea.

The paper’s abstract follows:

1. “The processes that drive the ontogeny of migratory strategies in long‐lived animals with slow maturation remain enigmatic. While some short‐lived migrants are known or believed to repeat the same migratory patterns throughout their lives, little is known on the time required for immature long‐lived migrants to progressively acquire adult‐like migratory behaviours, or which aspects take longer to refine during the maturation process.
2. Here, we studied the ontogeny of long‐distance migratory strategies and related patterns of spatial distribution in a long‐lived seabird species during the annual cycle. To do so, we deployed light‐level geolocators on 4‐ to 9‐year‐old immature Cory's shearwaters (Calonectris borealis) and on breeding adults.
3. We revealed that migratory timings and destinations of young shearwaters progressively changed with age. The effect of ageing was remarkably evident on spring migratory performance and phenology. Birds gradually shortened the duration of the non‐breeding period by advancing departure date and reducing travelling time, which resulted in a sequential arrival at the colony of the various age contingents. Ageing immatures gradually changed from a more exploratory strategy to a more conservative way of exploiting resources, reducing both their year‐round spatial spread across oceanic domains and the total distance travelled. Immatures always performed a trans‐equatorial migration to the Southern Hemisphere, contrasting with 17% of the adults which remained in the North Atlantic year‐ Finally, during the breeding season immatures were widely dispersed through the North Atlantic reducing their overlap with breeding adults.
4. Our long‐term study provides empirical support to the hypothesis that in long‐lived species, the refinement of migratory behaviour and year‐round spatial distribution is a progressive process mediated by age and experience, where life stage constraints and competition for resources may also play a role. The emerging pattern suggests that for some avian taxa, the ontogeny of migratory strategy is a prolonged, complex and dynamic process.”

With thanks to Letizia Campioni.

Reference:

Campioni, L., Dias, M.P., Granadeiro, J.P. & Catry, P. 2019.  An ontogenetic perspective on migratory strategy of a long‐lived pelagic seabird: timings and destinations change progressively during maturation.  Journal of Animal Ecology doi.org/10.1111/1365-2656.13044.

John Cooper, ACAP Information Officer, 31 July 2019

Dimas Gianuca (Environment and Sustainability Institute, University of Exeter, Penryn, UK) and colleagues have published open access in the Journal of Animal Ecology on sex‐specific differences in the demography of Northern Macronectes halli and Southern M. giganteus Giant Petrels that breed sympatrically at South Georgia (Islas Georgias del Sur)*.

The paper’s abstract follows:

“·  Many animal taxa exhibit sex‐specific variation in ecological traits, such as foraging and distribution. These differences could result in sex‐specific responses to change, but such demographic effects are poorly understood.

• · Here, we test for sex‐specific differences in the demography of northern (NGP, Macronectes halli) and southern (SGP, M. giganteus) giant petrels – strongly sexually size‐dimorphic birds that breed sympatrically at South Georgia, South Atlantic Ocean. Both species feed at sea or on carrion on land, but larger males (30% heavier) are more reliant on terrestrial foraging than the more pelagic females. Using multi‐event mark‐recapture models, we examine the impacts of long‐term changes in environmental conditions and commercial fishing on annual adult survival and use two‐sex matrix population models to forecast future trends.
• · As expected, survival of male NGP was positively affected by carrion availability, but negatively affected by zonal winds. Female survival was positively affected by meridional winds and El Niño–Southern Oscillation (ENSO), and negatively affected by sea ice concentration and pelagic longline effort. Survival of SGPs did not differ between sexes; however, survival of males only was positively correlated with the Southern Annular Mode (SAM).
• · Two‐sex population projections indicate that future environmental conditions are likely to benefit giant petrels. However, any potential increase in pelagic longline fisheries could reduce female survival and population growth.
• · Our study reveals that sex‐specific ecological differences can lead to divergent responses to environmental drivers (i.e. climate and fisheries). Moreover, because such effects may not be apparent when all individuals are considered together, ignoring sex differences could underestimate the relative influence of a changing environment on demography.”

A Southern Giant Petrel on South Georgia (Islas Georgias del Sur)*, photograph by Kirk Zufelt

Reference:

Gianuca, D., Votier, S.C., Pardo, D., Wood, A.G., Sherley, R.B., Ireland, L., Choquet, R., Pradel, R., Townley, S.,  Forcada, J., Tuck, G.N. & Phillips, R.A. 2019.  Sex‐specific effects of fisheries and climate on the demography of sexually dimorphic seabirds.  Journal of Animal Ecology doi.org/10.1111/1365-2656.13009.

John Cooper, ACAP Information Officer, 30 July 2019

*A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Islas Malvinas), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur) and the surrounding maritime areas.

Johanna Wren (Joint Institute for Marine and Atmospheric Research, Honolulu, Hawaii, USA) and colleagues have published in the journal Deep Sea Research Part II: Topical Studies in Oceanography on at-sea sightings of the Near threatened Black-footed Albatross Phoebastria nigripes.

The paper’s abstract follows:

“A serious threat to pelagic seabird populations today is interactions with longline fisheries. While current seabird mitigation efforts have proven successful in substantially reducing seabird interactions in the Hawai‘i-based longline fishery, black-footed albatross (Phoebastria nigripes) interactions have increased. In an effort to better understand when and where these interactions take place, we explore the relationship between black-footed albatross sightings in the Hawai‘i-based deep-set longline fishery and fleet dynamics and environmental variables. Environmental drivers include both large-scale climate variability due to the Pacific Decadal Oscillation (PDO) and El Niño – Southern Oscillation, as well as local oceanographic and atmospheric drivers, such as wind patterns, sea surface temperature, and surface chlorophyll. Using generalized linear models, we found that while season, latitude, and longitude of fishing explained much of the variation throughout the time series, both large scale and local climate variables – positive PDO, strong westerly winds, and cooler sea surface temperatures – explained the increase in black-footed albatross sightings in recent years. Black-footed albatross nest in the Northwestern Hawaiian Islands, and their main foraging habitat while nesting are the productive fronts to the north and east of the Hawaiian Islands. During a positive PDO, a more intense and expanded Aleutian Low shifts westerly winds southward, replacing trade winds in the northern region of the longline fishing grounds. The expanded westerly winds may have two impacts. Firstly, they drive productive surface waters to the south, increasing the overlap of the albatross foraging grounds and the deep-set fishing grounds. Secondly, when westerlies move south, more birds transit through the fishing grounds to the east rather than traveling north to reach the westerlies before traveling eastward north of the fishing grounds. Because the PDO operates on decadal timescales, the high levels of sightings and interactions may persist for many years.”

Black-footed Albatross at sea, photograph by Aleks Terauds

Reference:

Wren, J.L.K., Shaffer, S.A. & Polovin, J.J. 2019.  Variations in black-footed albatross sightings in a North Pacific transitional area due to changes in fleet dynamics and oceanography 2006–2017.  Deep Sea Research Part II: Topical Studies in Oceanography doi.org/10.1016/j.dsr2.2019.06.013.

John Cooper, ACAP Information Officer, 29 July 2019

Raül Ramos (Departament de Biologia Evolutiva, Universitat de Barcelona, Spain) has published in the open-access journal Ecology and Evolution on migration strategies of four different populations of Scopoli's Shearwaters Calonectris diomedea.

The paper’s abstract follows:

“Variability in long‐distance migration strategies is still poorly understood due to the fact that individuals are often tracked from a single colony/population. Transoceanic migrations of Scopoli's shearwaters (Calonectris diomedea) across the Strait of Gibraltar (SoG) have been tracked from several breeding colonies isolatedly, and factors related to the variability in phenological schedules among different populations remain, therefore, not well‐understood. Using light‐level geolocator data, I examined the autumn (postbreeding) and spring (prebreeding) migratory passage dates through SoG of four populations of Scopoli's shearwater spread along the longitudinal breeding range of the species. Additionally, I also estimated the at‐sea activity patterns (from immersion data) during both migratory passages, as well as the body size (from morphometric data) of the individuals of these populations. On average, Scopoli's shearwaters leave the Mediterranean (cross SoG) on 31 October ± 1.8 days on their autumn migrations and return on 03 March ± 1.6 days on their spring migrations. At the population level, there was a clear gradient in the timing of crossing SoG: birds from the westernmost populations (Murcia, SE Spain) were the first ones in leaving the Mediterranean while easternmost breeders (Paximada, Crete) were the last ones. In spring, only birds from the largest breeding population (Zembra, Tunisia) seemed to advance their return and crossed SoG significantly earlier than birds tracked at the remaining populations. In both passages, shearwaters from central and eastern populations spent more time flying than their conspecifics from the western Mediterranean. Scopoli's shearwater populations display a differential phenology and behavior in their migratory passages through SoG. The longitudinal gradient in body size already reported for the species could be an evolutionary response to an obvious trade‐off between sharing common wintering grounds in the Atlantic Ocean and the temporal constraints of restoring physiological condition in those grounds.”

Scopoli's Shearwater at sea, photograph by 'Pep' Arcos

Reference:

Ramos, R. 2019.  Crossing the Pillars of Hercules: understanding transoceanic migrations of seabirds throughout their breeding range.  Ecology and Evolution doi.org/10.1002/ece3.5079.

John Cooper, ACAP Information Officer, 28 July 2019