Juan Francisco Masello

Diving seabirds share foraging space and time within and among species

Ecological theory predicts that animals with similar foraging strategies should not be able to co-exist without segregating either in space, time or diet. In communities, intra-specific competition is thought to be more intense than the competition among species, because of the lack of niche partitioning between conspecifics. Hence, while different seabird species can overlap in their foraging distribution, intra-specific competition can drive the neighboring populations of the same species to spatial segregation of foraging areas. To investigate ecological segregation within and among species of diving seabirds, we used a multi-species GPS-tracking approach of seabirds of four species on a small island in the Southwest Atlantic. The present study goes beyond previous work by analyzing simultaneous effects of species and colonies. We observed strikingly strong spatial foraging segregation among birds of the same species, breeding in colonies as close as 2 km from each other. Conspecifics from neighboring colonies used foraging places adjacent to their own colony, and there was little or no overlap with birds from the other colony. A zone with increased predator concentration was completely avoided during foraging trips, likely contributing to the spatial segregation. In addition to spatial segregation, we also observed intra-specific differences in other components of foraging behavior, such as time of day, dive depth and diet. These were most likely caused by optimal foraging of individuals in relation to habitat differences on a local scale, leading to a complex pattern of interactions with environmental covariates, in particular foraging daytime, foraging water layer temperature and depth, distance to coast and bathymetric depth of foraging areas. As mechanisms leading to the spatial segregation we propose a combination of optimal foraging and avoidance of predation.

CHICK GROWTH AND BREEDING SUCCESS OF THE BURROWING PARROT

Abstract We present the first data on the breeding biology of wild Burrowing Parrots (Cyanoliseus patagonus). We studied chick growth and breeding success at the largest colony of the species in the province of Río Negro, Patagonia, Argentina, during the 1999–2000 breeding season. A very high fledging success was observed and related to the absence of nest predation and the colonial breeding system. Safe nest sites were also thought to favor large mass recession of the nestlings before fledging. Mortality during the nestling period tended to be higher for fourth and fifth nestlings of a brood, indicating that brood reduction occurred. Burrowing Parrots in the study colony showed large variability in growth parameters between nestlings, possibly related to the hatching asynchrony observed. Allometric relationships for egg mass, clutch size, relative clutch mass, and nestling period of 29 wild psittaciform species are described and compared with the data from the Burrowing Parrots. Desarrollo de los Pichones y Éxito de Nidificación de Cyanoliseus patagonus Resumen. Presentamos aquí los primeros datos de la biología reproductiva en estado silvestre del loro Cyanoliseus patagonus. Se estudió el crecimiento de los pichones y el éxito de nidificación en la colonia más importante de la especie (provincia de Río Negro, Patagonia, Argentina) durante la temporada de cría 1999–2000. Se observó un alto éxito de emplumamiento de los pichones relacionado a la ausencia de depredación en el nido y al sistema colonial de nidificación que presenta la especie. Los sitios de nidificación seguros habrían favorecido la pronunciada pérdida de masa corporal observada en los pichones antes de abandonar el nido. La mortalidad durante el período de nidificación tendió a ser más alta para el cuarto y quinto pichón de la nidada, indicando la existencia de reducción de la camada. Los loros de la colonia estudiada mostraron gran variabilidad en los parámetros de desarrollo de los distintos pichones, estando ésto posiblemente relacionado con el nacimiento asincrónico de los pichones. Se describen también relaciones alométricas para la masa del huevo, el tamaño de la nidada, la masa relativa de la nidada y el período de permanencia en el nido de 29 psittaciformes silvestres y se comparan con los datos de C. patagonus.

Moving polewards in winter: a recent change in the migratory strategy of a pelagic seabird?

BackgroundDuring the non-breeding period, many birds migrate to milder areas, found closer to the equator than their breeding sites. Opposite movements are very rare. In the Southern Ocean, the abundance of 13C declines markedly with more southern latitude, providing a characteristic 13C isoscape. This can be used as a tracer for the movement of seabirds between breeding and inter-breeding areas, by comparing stable isotope ratios of feathers grown at different times of the year.ResultsWe studied seasonal movements of Thin-billed prions (Aves, Procellariiformes), breeding at the Subantarctic Falkland/Malvinas Islands, compared with those of Wilsons storm-petrels breeding in the Antarctic South Shetland Islands. The two species showed opposite migratory movements. While Wilsons storm-petrels moved to warmer waters north of the Drake Passage in winter, Thin-billed prions showed a reversed movement towards more polar waters. Carbon stable isotope ratios in recent and historical feathers indicated that poleward winter movements of Thin-billed prions were less common historically (45% in 1913-1915), and have only recently become dominant (92% in 2003-2005), apparently in response to warming sea temperatures.ConclusionsThis study shows that pelagic seabirds can rapidly change migration strategies within populations, including migration towards more poleward waters in winter.

Body size, body condition and ornamental feathers of Burrowing Parrots: variation between years and sexes, assortative mating and influences on breeding success

Abstract Individual size and body condition determine the breeding success in many species of birds. We here present morphometric data and describe the relationships between body size, body condition, breeding success and ornaments of genetically sexed Burrowing Parrots (Cyanoliseus patagonus), including data from a year of adverse environmental conditions caused by the strong La Niña phase of the E1 Niño Southern Oscillation phenomenon of 1998–99. During droughts caused by La Niña, adults invested more resources in their own body maintenance and decreased provisioning to nestlings, as shown by higher adult body masses and body conditions, and increased nestling mortality due to starvation. We found slight sexual dimorphism, male Burrowing Parrots being structurally larger (∼5%) than females. Adult Burrowing Parrots mated assortatively with respect to body condition and the size of the red feather patch in the centre of the abdominal region. We identified the red abdominal patch as a signal of individual quality. We also present correlations of adult body mass, body condition, measurements of structural size and ornaments, with parameters of breeding success and nestling growth. Female Burrowing Parrots in better body condition fledged heavier nestlings. Parameters of structural size of male Burrowing Parrots correlated with structural characters of the nestlings such as bill and tarsus length, and wing growth.

Blood chemistry in relation to nutrition and ectoparasite load in Wilson’s storm-petrels Oceanites oceanicus

Haematology and plasma biochemistry values are useful tools for ecological research, providing information on the physiological state and adaptation of individuals to their habitat, changes in nutritional state of birds, body condition, the level of parasite infestation, etc. We studied the effect of stress factors on haematological and plasma biochemistry values in adult and nestling Wilson’s storm petrels Oceanites oceanicus (Aves, Procellariiformes). We measured packed cell volume, triglyceride levels, plasma protein levels, plasma hue and plasma corticosterone of nestlings and breeding adults at King George Island, South Shetland Islands. We used a snow storm as a natural experiment to test what effect starvation has on the stress response of nestlings. In particular, we predicted that: (1) plasma protein concentrations and plasma hue reflect ectoparasite load, (2) triglycerides and hue reflect the nutritional state, and (3) corticosterone levels increase with ectoparasite load and starvation. In line with our predictions, plasma triglycerides were higher in nestlings than adults, indicating a resorptive nutritional state in nestlings, during which dietary fat is deposited in adipose tissues. In adults, plasma triglycerides were positively correlated with body mass. Corticosterone levels increased in response to handling in adults, while we did not find a stress response in nestlings in good condition. However, nestlings sampled after their nests had been blocked by a snow storm showed a stress response in excess of that of adults. In nestlings sampled after the snow storm, corticosterone peak levels were positively correlated with the infestation intensity of the ectoparasite Philoceanus robertsi (Phthiraptera: Ischnocera), suggesting that the stress response is increased when more stressors act at the same time. In adults, plasma hue and proteins decreased with increasing ectoparasite load.

Corticosterone in thin-billed prion Pachyptila belcheri chicks: diel rhythm, timing of fledging and nutritional stress.

Glucocorticosteroids (GCs) of the hypothalam–pituitary–adrenal axis play a role in association with both stressful events and daily life processes. However, relatively little is known about the role of GCs in relation to daily and seasonal life processes in animals in the wild. In this paper, we present data on basal levels of plasma corticosterone CORT in chicks of a pelagic seabird, the thin-billed prion, Pachyptila belcheri, during two predictable changes in demands, the daily activity pattern and the preparation for fledging. By comparing chicks fed recently with unfed chicks, we test how GC levels are modified according to nutritional condition. In accordance with their nocturnal feeding rhythm, chicks had a clear daily rhythm with increased CORT secretion at night, but CORT levels during the active phase were also highly elevated in unfed chicks compared with fed chicks. Close to fledging, chicks rapidly increased basal CORT levels, and again unfed chicks had higher levels than fed chicks, although the age effect here was stronger than the effect of recent feeding. The present data thus support the hypothesis that GC levels are adjusted to life stages with predictable changes in demands, but food availability and/or internal energy stores also affect the level to which GCs increase.

Trophic segregation of Falkland Islands seabirds: insights from stable isotope analysis

Seabird colonies provide rare opportunities to study trophic segregation in an entire bird community. We here present data on nitrogen and carbon isotope ratios of eight species of seabirds from New Island, Falkland Islands, and compare trophic levels (TL) and foraging distributions. We included adult feathers representing the interbreeding season, as well as chick feathers or down representing the breeding season. The stable isotope ratios indicated differences in feeding areas and TLs between species, consistent with the data of previous conventional diet analyses and observations at sea. We further reviewed conventional and stable isotope seabird community studies calculating the means and ranges of TLs observed across these studies. The mean TL (3.7) of the seabird community on New Island was at the lower end of the mean value range (3.5–4.5), but not significantly different, from the reviewed seabird communities. Seabirds on New Island had a range of 1.3 TLs, which is on the upper end of ranges within a community (0.4–1.5), indicating strong trophic structuring.

Prevalence of blood parasites in seabirds - a review

IntroductionWhile blood parasites are common in many birds in the wild, some groups seem to be much less affected. Seabirds, in particular, have often been reported free from blood parasites, even in the presence of potential vectors.ResultsFrom a literature review of hemosporidian prevalence in seabirds, we collated a dataset of 60 species, in which at least 15 individuals had been examined. These data were included in phylogenetically controlled statistical analyses of hemosporidian prevalence in relation to ecological and life-history parameters. Haemoproteus parasites were common in frigatebirds and gulls, while Hepatozoon occurred in albatrosses and storm petrels, and Plasmodium mainly in penguins. The prevalence of Haemoproteus showed a geographical signal, being lower in species with distribution towards polar environments. Interspecific differences in Plasmodium prevalence were explained by variables that relate to the exposure to parasites, suggesting that prevalence is higher in burrow nesters with long fledgling periods. Measures of Plasmodium, but not Haemoproteus prevalences were influenced by the method, with PCR-based data resulting in higher prevalence estimates.ConclusionsOur analyses suggest that, as in other avian taxa, phylogenetic, ecological and life-history parameters determine the prevalence of hemosporidian parasites in seabirds. We discuss how these relationships should be further explored in future studies.

Evaluating the Impact of Handling and Logger Attachment on Foraging Parameters and Physiology in Southern Rockhopper Penguins

Logger technology has revolutionised our knowledge of the behaviour and physiology of free-living animals but handling and logger attachments may have negative effects on the behaviour of the animals and their welfare. We studied southern rockhopper penguin (Eudyptes chrysocome) females during the guard stage in three consecutive breeding seasons (2008/09−2010/11) to evaluate the effects of handling and logger attachment on foraging trip duration, dive behaviour and physiological parameters. Smaller dive loggers (TDRs) were used in 2010/11 for comparison to larger GPS data loggers used in all three seasons and we included two categories of control birds: handled controls and PIT control birds that were previously marked with passive integrative transponders (PITs), but which had not been handled during this study. Increased foraging trip duration was only observed in GPS birds during 2010/11, the breeding season in which we also found GPS birds foraging further away from the colony and travelling longer distances. Compared to previous breeding seasons, 2010/11 may have been a period with less favourable environmental conditions, which would enhance the impact of logger attachments. A comparison between GPS and TDR birds showed a significant difference in dive depth frequencies with birds carrying larger GPS data loggers diving shallower. Mean and maximum dive depths were similar between GPS and TDR birds. We measured little impact of logger attachments on physiological parameters (corticosterone, protein, triglyceride levels and leucocyte counts). Overall, handling and short-term logger attachments (1–3 days) showed limited impact on the behaviour and physiology of the birds but care must be taken with the size of data loggers on diving seabirds. Increased drag may alter their diving behaviour substantially, thus constraining them in their ability to catch prey. Results obtained in this study indicate that data recorded may also not represent their normal dive behaviour.

Do leucocytes reflect condition in nestling burrowing parrots Cyanoliseus patagonus in the wild

The different leucocyte types are an important part of the immune system. Thus, they have been used in ecological studies to assess immune function and physiological stress in wild birds. It is generally assumed that increased stress and decreased condition are associated with an increase in the ratio of heterophils to lymphocytes, the H/L ratio. We studied leucocyte profiles in relation to body condition in nestling Burrowing Parrots (Cyanoliseus patagonus) in North-eastern Patagonia, Argentina. As in other wild parrots, heterophils were the most numerous leucocyte type, suggesting strong investment into innate immunity. Leucocyte profiles did not change with the age, while nestlings in better body condition increased the number of heterophils. Because the number of lymphocytes was independent of body condition, as a result we observed a positive correlation between body condition and the H/L ratio. The total number of leucocytes relative to erythrocytes increased in nestlings in better body condition, indicating a larger overall investment into immune function in well-nourished nestlings. The observed heterophilic profiles of nestling Burrowing Parrots together with the positive relationship between H/L ratio and body condition may indicate a favoured investment in a robust innate immunity that reduces the risk of infection taking hold in these long-lived birds.