Contrasting impacts of environmental variability on the breeding biology of two sympatric small procellariiform seabirds in south-eastern Australia

Seabirds play a vital role in marine ecosystems and the long-term study of their responses to environmental variations can be used to monitor the effects of climate change on marine fauna. However, slight differences in similar seabird species result in a range of responses which complicates our understanding of the effects of environmental changes to marine ecosystems. The present study investigated inter-annual differences in the breeding biology (breeding phenology, chick growth rates and breeding success) and environmental conditions (seasonal sea surface temperatures) of important foraging areas in two sympatric small Procellariiform species, the fairy prion (Pachyptila turtur) and the common diving petrel (Pelecanoides urinatrix), over four reproductive seasons (2017–2020) in Bass Strait, south-eastern Australia. Marine heatwaves occurred during the years of 2018/19 and 2019/20 and coincided with years of delayed laying dates, slower chick growth and reduced breeding success, in both species. While fairy prions maintained a relatively high breeding success and broadly constant breeding phenology, common diving petrels delayed the start of the breeding season by up to 50 days and experienced dramatic collapses in breeding success in years of high marine heat wave occurrence. The difference in foraging ecology and physiological capacity (largely in the production of stomach oils and fasting abilities of adults and chicks) between both species are likely to influence the variability and phenology in the observed breeding seasons.

Life-history attributes of Arctic-breeding birds drive uneven responses to environmental variability across different phases of the reproductive cycle

1. Animals exhibit varied life-history traits that reflect adaptive responses to their environments. For Arctic-breeding birds, traits like foraging guild, egg nutrient allocation, clutch size, and chick growth are predicted to be under increasing selection pressure due to rapid climate change and increasing environmental variability across high-latitude regions. 2. We compared four migratory birds (black brant [Branta bernicla nigricans], lesser snow geese [Chen caerulescens caerulescens], semipalmated sandpipers [Calidris pusilla], and Lapland longspurs [Calcarius lapponicus]) with varied life histories at an Arctic site in Alaska, USA, to understand how life-history traits help moderate environmental variability across different phases of the reproductive cycle. 3. We monitored aspects of reproductive performance related to the timing of breeding, reproductive investment, and chick growth from 2011–2018. 4. In response to early snow melt and warm temperatures, semipalmated sandpipers advanced their site arrival and bred in higher numbers, while brant and snow geese increased clutch sizes; all four species advanced their nest initiation dates. During chick rearing, longspur chicks were relatively resilient to environmental variation whereas warmer temperatures increased the growth rates of sandpiper chicks but reduced growth rates of snow goose goslings. These responses generally aligned with traits along the capital-income spectrum of nutrient acquisition and altricial-precocial modes of chick growth. Under a warming climate, the ability to mobilize endogenous reserves likely provides geese with relative flexibility to adjust the timing of breeding and the size of clutches. Warmer temperatures, however, may negatively affect the quality of herbaceous foods and slow gosling growth. 5. Species may possess traits that are beneficial during one phase of the reproductive cycle and others that may be detrimental at another phase, uneven responses that may be amplified with future climate warming. These results underscore the need to consider multiple phases of the reproductive cycle when assessing the effects of environmental variability on Arctic-breeding birds.

Breeding Stage and Environmental Factors Affect Prey Selection by Greater Crested Terns Off Southeast Australia

Variation in the diet of marine predators such as seabirds can be used to track environmentally-driven changes in ocean ecosystems. However, studies of predator diet must account for intrinsic influences on prey selection, such as changing nutritional requirements during breeding. Using digital photography, we investigated how the type and size of prey brought back to the colony by greater crested terns (Thalasseus bergii) changed in relation to breeding stage, and to variation in oceanographic conditions around Montague Island, Australia (36°15’S, 150°13’E). 2469 prey items were identified to species or family level over 35 consecutive days of photo-sampling in 2018. Australian anchovy (Engraulis australis), a surface-schooling clupeid fish, was the most abundant prey returned to the colony during all breeding stages (84.5%). The proportion of anchovy increased from 77.0% when birds were provisioning their adult partners during incubation, to 92.4% when they were provisioning chicks, suggesting selective foraging behaviour on this energy-dense species as a means to facilitate rapid chick growth. Anchovy size was largest during incubation (91.1 ± 14.9 mm), smallest during early chick provisioning (71.8 ± 11.0 mm), and increased slightly during mid-provisioning (79.6 ± 11.9 mm), indicating adaptive prey selection that is matched to the physical requirements of different breeding stages. The proportion of anchovy prey was also influenced by extrinsic environmental factors, with anchovy becoming more dominant with increasing local sea surface temperatures, up to ~17.5°C. Our findings highlight the importance of examining both intrinsic and extrinsic determinants of diet composition across breeding stages in seabird populations.

Not so black, not so white: differences in microorganism load of contiguous feathers from white stork chicks

Many organisms are characterized by strikingly contrasting black and white coloration, but the function of such contrasts has been inadequately studied. In this article, we tested the function of black and white contrasting plumage in white stork Ciconia ciconia chicks. We found greater abundance and diversity of microorganisms on black compared with adjacent white feathers. In addition, nest size was positively correlated with the abundance and diversity of microorganisms on white feathers. Flight initiation distance (FID), defined as the distance at which adult white storks took flight when approached by a human, was negatively correlated with most measurements of microorganism abundance. Breeding success was generally positively correlated with the abundance and diversity of microorganisms on black feathers. The feather growth rate was positively correlated with some and negatively correlated with other measurements of microbial abundance and diversity. Finally, chick growth was negatively correlated with the number of microbial species on black feathers and positively with the abundance and diversity of microorganisms on white feathers. These findings are consistent not only with the role of microorganisms in the maintenance of a benign microbial environment which differs between black and white feathers, but also with the hypothesis that several taxa of microorganisms found in black and white plumage are virulent, with negative effects on the fitness of their hosts.

Co-evolved maternal effects selectively eliminate offspring depending on resource availability

Many plants and animals adaptively downsize the number of already-produced propagules if resources become insufficient to raise all of them. In birds, mothers often induce hatching asynchrony by incubating first eggs before last eggs are laid, creating an age/size hierarchy within broods which selectively eliminates the smallest chicks in poor food conditions. However, mothers also deposit more testosterone into late-laid eggs, which boosts competitive abilities of younger chicks, counteracts the competitive hierarchy, and ostensibly creates a paradox. Since testosterone also carries costs, we hypothesized that benefits of maternally deposited testosterone outweigh its costs in good food conditions, but that testosterone has a net detrimental effect in poor food conditions. We found experimental evidence that elevated maternal testosterone in the egg caused higher chick mortality in poor food conditions but better chick growth in good food conditions. These context-dependent effects resolve the paradox, suggesting co-evolution of two maternal effects, and explain inconsistent results of egg hormone manipulations in the literature.

Foraging behavior links sea ice to breeding success in Antarctic penguins

Population trends and breeding success variability of Adélie penguins, a bioindicator of Antarctic environments, have been attributed to changing sea-ice extents; however, causative mechanisms remain unclear. By electronically tagging 175 penguins in four seasons with contrasting sea-ice conditions, we show that ice-free environments enhance, not deteriorate, foraging efficiencies and breeding success. In an ice-free season, penguins traveled by swimming rather than walking, leading to larger foraging areas, shorter trip durations, and lower energy expenditure than three ice-covered seasons. Freed from the need to find cracks for breathing, dive durations decreased, and more krill were captured per unit dive time, which may also be associated with phytoplankton blooms and increased krill density in the sunlit ice-free water. Consequently, adult body mass, chick growth rates, and breeding success increased. Our findings explain the regional population trends and demonstrate a key link among sea ice, foraging behavior, and reproductive success in this iconic species.

Chick growth and nutrient requirement during rearing period on eclectus parrot (Eclectus roratus, Müller 1776)

Nutrition is an important aspect of the successful breeding of wild birds in captivity. This research aims to find out nestling growth of Eclectus parrot (Eclectus roratus, Müller 1776) by parent-reared and nutrient requirement during rearing season. This research used a pair of Eclectus parrot with a male chick at first and fifth clutch, and female chick at the second, third, and fourth clutch. This research was conducted from July 2016 to June 2018. The bodyweight of chick was measured every week and feed intake was observed since the age of one week until the chick can eat independently. Feed was provided ad libitum and cafeteria. The chick was the altricial type. Feathers began to cover all bodies at weeks 9. Fledging time was approximately at weeks 10-11. Chick could be separated from its parents at 20 weeks of age. Feed intake tends to be increased along with the increasing age of chick. Eclectus favorites feed is sunflower seed. Nutrient consumption when rearing male chick is more than rearing the female chick.

PSIII-19 Effects of extrusion on true metabolizable energy, standardized amino acid digestibility, and chick growth assay of red and white sorghum

The aims of this experiment were to determine the energy value of raw grains [corn (CO), red sorghum (RS), white sorghum (WS)], in comparison to the energy values of the same grains post-extrusion. Cecectomized roosters were precision-fed up to 30g of either raw or extruded grains, then placed into individual cages with a collection tray underneath to catch excreta. After 48h, the excreta was collected and analyzed for N, gross energy, amino acids and dry matter. TMEn was highest (P < 0.05) for extruded WS (3.99 kcal/g) and lowest for raw WS (3.79 kcal/g), whereas extruded CO (3.89 kcal/g), and extruded RS (3.89 kcal/g) did not differ from raw RS (3.83 kcal/g) and raw CO (3.82 kcal/g). This indicates that there was greater utilization of the extruded grains compared to the raw, especially for WS. Amino acids were measured in the grains and the excreta to determine the digestibility. In addition to the rooster assay, a chick growth assay was conducted using Ross 308 male broiler chicks. The study lasted 14d, with average initial chick BW being 149.1g ± 0.048. The experimental diets consisted of inclusion of raw and extruded grains, respectively, added at direct substitution of corn. The results of the chick trial appear to be controversial to the rooster assay. The extruded CO and extruded WS diets were similar (P > 0.05) in weight gain compared to raw CO (660.84g, 665.70g, and 690.13g, respectively). Extruded WS had the greatest (P < 0.05) feed intake (973.3g), with raw RS having the lowest (847.44g). Raw CO had the greatest (P < 0.05) G:F, with extruded WS being lowest (P < 0.05); 754.63g and 683.75g, respectively. In conclusion, the chick growth assay showed superior weight gain in the extruded CO and WS diets, however, the extruded diets were least successful in G:F compared to the raw.