Chick Survival Research Articles

Effects of Diet and Provisioning Behavior on Chick Growth in Adélie Penguins (Pygoscelis adeliae)

When provisioning chicks, parents trade-off their time, energy, and other resources to maximize reproductive success. As parents adjust investment to maximize their fitness, impacts on offspring growth can occur. We investigated provisioning and chick growth of Adélie Penguins (Pygoscelis adeliae) at one of the largest colonies (∼175,000 pairs), during one year of normal chick growth and survival and in a year which, by chance, was characterized by low chick growth and survival (“difficult” year). We measured daily average amount and quality of food delivered, as well as foraging-trip duration, and compared them to chick mass and skeletal growth during two years of contrasting conditions. We used mixed-effects models to test the prediction that increased parental investment would lead to increased growth rates, while accounting for confounding effects. There was no evidence of an effect of parent age. All provisioning measures predicted growth of at least one morphological character but, especially during the year of normal reproductive success, no provisioning measure strongly predicted growth across most morphological characters. However, during the difficult year parental investment positively affected growth rates, especially for males that were fed relatively more fish. The observed variation in growth rates between males and females, and between years of contrasting apparent resource availability, was large enough to lead to size differences that may subsequently affect post-fledging survival and ultimately population processes.

Correction to 'Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics'.

Correction to 'Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics'.

Chick survival and hunting are important drivers for the dynamics of two Alpine black grouse Lyrurus tetrix populations

Alpine black grouse populations are generally declining, but the underlying demographic drivers are largely unknown. We studied the dynamics of two adjacent black grouse populations over a 20 years period in the Italian Alps that differ in hunting pressure to identify the main demographic process affecting these populations and to study the impact of hunting on males. We collected radio-tracking data and conducted population surveys in spring to count displaying cocks and in late summer to determine the breeding success by means of pointing dogs. These different data sets were jointly analysed using a seasonal integrated population model to estimate population sizes and various demographic rates. The two populations fluctuated in size and the number of males from one population increased after hunting intensity was reduced. The main demographic rates did not differ between the populations. Adult survival was relatively low and productivity was high, so the life history shows the feature of a fast turnover species. In both populations, the variability of survival from hatching to the age of five weeks (chick survival) contributed more to the variation of the population growth rates than the variability of survival in later life-history stages, and the former was positively affected by ambient temperatures in July, favouring chick survival. The adult sex ratio of the population where males hunting occurred was shifted towards females, but it evened over time with the reduction of hunting pressure. The adult sex ratio in the population without hunting and the chick sex ratios in both populations were even, suggesting that hunting acted as a mostly additive source of mortality.

Chick survival and hunting are important drivers for the dynamics of two Alpine black grouse Lyrurus tetrix populations

Chick survival and hunting are important drivers for the dynamics of two Alpine black grouse Lyrurus tetrix populations

Habitat‐specific behavior, growth rate, and survival of piping plover chicks in New Jersey, USA

AbstractAnthropogenic disturbance has been demonstrated to affect the behavior of beach‐nesting birds, yet the energetic consequences of recreational activities have received less attention. Because precocial chicks are often displaced as a result of disturbance events, lower access to food may lead to lower fitness. We studied the influence of site characteristics and human disturbance on behavior, habitat use, growth rate, and survival of piping plover chicks in New Jersey, a portion of the Atlantic Coast population that continues to demonstrate poor demographic output. Sites varied in levels of human disturbance and access to high‐quality foraging habitat, which are two critical components of fledging success. We found that compared to chicks with access to bayside foraging habitat, chicks at sites without such access experienced higher rates of anthropogenic disturbance, spent less time in moist‐substrate habitats, and spent more time in upland dunes. Foraging rates were greatest for chicks in moist‐substrate habitat with bayside access and for chicks in the oceanside intertidal zone without bayside access. Further, overall chick growth rates were higher for chicks reared at sites with bayside access. Chick survival increased with age, decreased with increasing precipitation, and increased with bayside foraging habitat availability. Human disturbance was likely limiting chick access to foraging opportunities at sites open to the public, with an apparent effect on growth rate. Maintaining access to high‐quality foraging habitat that is free of human activity through habitat restoration, supplementary food, or beach closures could help to increase reproductive success in New Jersey.

Does Reproductive Status Influence Habitat Selection by Female Greater Sage-grouse in a Sagebrush-Juniper Landscape?

Greater sage-grouse (Centrocercus urophasianus, hereafter, sage-grouse) have experienced habitat loss from expansion of juniper (Juniperus spp.) woodlands into sagebrush steppe. Sage-grouse avoid high levels of juniper cover (> 10% cover) but can vary in response to cover > 0–10%. Selection patterns by hens may be affected by differences in resource needs or predation risk between brooding (i.e., hens with chicks) and nonbrooding hens (i.e., hens without chicks). We investigated whether reproductive status influenced habitat selection at multiple spatial scales among hens in a landscape undergoing juniper expansion. We conducted our study during the 2017–2018 breeding seasons in southwestern Idaho. We collected habitat data at broad spatial extents (hereafter, macroscales) using remotely sensed layers and at a fine spatial extent (hereafter, microscale) with field-based surveys. We collected data at used and available locations for 11 brooding and 19 nonbrooding hens at macroscales (n = 2 059 locations) and microscales (n = 181 locations). At the macroscales, both reproductive groups avoided cover class II (> 10–20% juniper cover) and III (> 20% juniper cover) but nonbrooding hens were 2.8 × more likely to select cover class I (> 0–10% juniper cover) than brooding hens. In addition, nonbrooding hens selected wetlands dominated by woody vegetation (e.g., willows), whereas brooding hens selected wetlands dominated by herbaceous vegetation. At the microscale, brooding hens were 22.1 × more likely to select taller nonsagebrush shrubs than nonbrooding hens. Our results support our prediction that nonbrooding hens were more likely to select cover class I juniper than brooding hens. Our results help inform more targeted treatment whereby removal of juniper around wetlands and mesic habitats with taller nonsagebrush shrubs may be the most beneficial because increasing the availability of these habitats could positively influence survival of chicks and adults.

Population, Breeding Phenology, and Factors Affecting Breeding Success of River Tern (Sterna aurantia) in Eastern India

Although the River Tern (Sterna aurantia) has been widely distributed across south and southeast Asia, its population is declining and was classified as Vulnerable in the 2020 IUCN Red List of Threatened Species. Insufficient information is available on its breeding ecology. This study reports the breeding ecology and factors affecting breeding of the River Tern over three years (2017-2019) along the Mahanadi River in Odisha, eastern India. Breeding was observed between February and May, with peak activity in April. The mean clutch size was 2.4 ± 0.06 SE and incubation period was 22.1 ± 0.06 days. Out of 163 nests, 68 nests succeeded in hatching at least one egg and apparent nesting success rate varied between 2.6% (2018) and 62.3% (2017). Factors affecting nesting success (95 nests) were predation (37.9%), flooding (32.6%), a cyclone (28.4%) and nest desertion (1.1%). Overall, of 124 chicks hatched, 58 were estimated to have fledged. Factors affecting chick survival were a cyclone (43.9%), predation (39.4%), and unknown causes (16.7%). A cyclone in May 2019 wiped out all eggs and chicks. Development and implementation of an evidence-based multi-species conservation action plan to protect River Tern and other globally threatened riverine ground nesters is urgently required.

​Physical and Biochemical Characterization of Eggs of Chicken Crossbreed and Its Comparison with Dahlem Red for Rural Poultry Development

Background: Crossbreeds of indigenous chicken are suitable for sustainable rural farming practices in developing countries as they are better adapted to local environment than pure breeds. Study was conducted to compare physical and biochemical parameters of egg between indigenous crossbreed of chicken (DND) locally called Himsamridhi and exotic chicken breed Dahlem Red (DR) under similar rearing conditions. Methods: 45 egg samples were collected from DND and 45 from DR. Physical characteristics and biochemical parameters of eggs were determined. Further, effect of these egg characteristics on hatching and progeny health were investigated. Result: External physical characteristics viz. weight, length, breadth, shell weight and total egg surface were significantly (P less than 0.05) higher in DR whereas shape index and shell ratio were significantly (P less than 0.05) higher in DND. Internal physical characteristics viz. yolk, albumen weights and albumen volume were significantly (P less than 0.05) higher in DR whereas Haugh unit was significantly (P less than 0.05) higher in DND. Biochemical parameters viz. total proteins significantly (P less than 0.05) higher in DND and total cholesterol significantly (P less than 0.05) higher in DR. Egg hatchability on fertile egg set basis (FES) and total egg set basis (TES) was higher in DND. Thus, some parameters were better in indigenous crossbreed, such as low cholesterol, higher total proteins, higher hatchability and chick survivability

Warming Arctic summers unlikely to increase productivity of shorebirds through renesting

Climate change in the Arctic is leading to earlier summers, creating a phenological mismatch between the hatching of insectivorous birds and the availability of their invertebrate prey. While phenological mismatch would presumably lower the survival of chicks, climate change is also leading to longer, warmer summers that may increase the annual productivity of birds by allowing adults to lay nests over a longer period of time, replace more nests that fail, and provide physiological relief to chicks (i.e., warmer temperatures that reduce thermoregulatory costs). However, there is little information on how these competing ecological processes will ultimately impact the demography of bird populations. In 2008 and 2009, we investigated the survival of chicks from initial and experimentally-induced replacement nests of arcticola Dunlin (Calidris alpina) breeding near Utqiaġvik, Alaska. We monitored survival of 66 broods from 41 initial and 25 replacement nests. Based on the average hatch date of each group, chick survival (up to age 15 days) from replacement nests (Ŝi = 0.10; 95% CI = 0.02–0.22) was substantially lower than initial nests (Ŝi = 0.67; 95% CI = 0.48–0.81). Daily survival rates were greater for older chicks, chicks from earlier-laid clutches, and during periods of greater invertebrate availability. As temperature was less important to daily survival rates of shorebird chicks than invertebrate availability, our results indicate that any physiological relief experienced by chicks will likely be overshadowed by the need for adequate food. Furthermore, the processes creating a phenological mismatch between hatching of shorebird young and invertebrate emergence ensures that warmer, longer breeding seasons will not translate into abundant food throughout the longer summers. Thus, despite having a greater opportunity to nest later (and potentially replace nests), young from these late-hatching broods will likely not have sufficient food to survive. Collectively, these results indicate that warmer, longer summers in the Arctic are unlikely to increase annual recruitment rates, and thus unable to compensate for low adult survival, which is typically limited by factors away from the Arctic-breeding grounds.

Dietary Exposure of Japanese Quail (Coturnix japonica) to Perfluorooctane Sulfonate (PFOS) and a Legacy Aqueous Film-Forming Foam (AFFF) Containing PFOS: Effects on Reproduction and Chick Survivability and Growth.

Effects of perfluorooctane sulfonate (PFOS) and a legacy aqueous film-forming foam (AFFF) containing 91% PFOS (AFFF PFOS) on reproduction, chick survivability, and growth of Japanese quail (Coturnix japonica) were determined. Day-old Japanese quail were administered PFOS or AFFF PFOS at 6 dietary concentrations ranging from 0 to 21 mg kg-1 feed for a total of 20 wk. At the age of 4 wk, 16 male/female pairs per treatment were assigned to cages, and egg laying was induced by the age of 10 wk. Eggs were collected daily, set weekly, and incubated for 18 d for the following 10 wk. Hatchlings were fed uncontaminated feed for 2 wk and euthanized to collect blood and liver. After 10 wk of egg collection, adults were euthanized to collect blood, liver, and kidneys. Significantly increased myofiber numbers in the liver and glomerular sclerosis in the kidneys of adults indicated damage at greater doses. Perfluorooctane sulfonate or AFFF PFOS did not significantly affect egg production; however, hatchability was decreased at the highest PFOS dose. The no-observed-adverse-effect levels for chick survivability, considered the critical effect, were 4.1 mg PFOS kg feed-1 (0.55 mg kg body wt-1 d-1 ) and 5.0 mg AFFF PFOS kg feed-1 (0.66 mg kg body wt-1 d-1 ), resulting in calculated average toxicity reference values of 0.25 mg kg feed-1 and 0.034 mg kg body weight-1 d-1 . Environ Toxicol Chem 2021;40:2521-2537. © 2020 SETAC.

Coexistence without conflict, the recovery of Ireland\u2019s endangered wild grey partridge Perdix perdix

By 1995, Ireland’s wild grey partridge (Perdix perdix) was extinct nationally as a breeding species on farmland. The two populations remaining were confined to Ireland’s industrial cutaway peat bogs. One of these populations was deemed viable. In 1996, the National Parks and Wildlife Service of Ireland and the Irish Grey Partridge Conservation Trust established a conservation project to prevent the extirpation of this population. In this paper, we explore the impact of each management factor on two key demographic response variables: chick survival rates and the number of breeding pairs. The numbers of linear metres of nesting strips had the most significantly positive effect on spring pairs, followed by the total number of supplementary food hoppers and the total hectares of brood-rearing and over-winter cover. Counterintuitively, encounters with Hen Harriers (Circus cyaneus) did not negatively affect chick survival or the number of spring pairs. While we cannot rule out the contribution of each explanatory variable, none had a statistically significant effect on chick survival, suggesting there may be locally confounding factors that our model could not capture. The weather conditions during the peak hatching period had a significant influence on chick survival, with the average maximum temperature observed in June having the strongest positive association with an increase of 1 °C in the average maximum temperature in June associated with an increase in chick survival of 9.4% on average. Conversely, for every additional 1 mm of rain in June, there was a 0.23% drop in chick survival on average.

Preparing for translocations of a Critically Endangered petrel through targeted monitoring of nest survival and breeding biology

Abstract The population of the recently-described Whenua Hou diving petrel Pelecanoides whenuahouensis comprises c. 200 adults that all breed in a single 0.018 km2 colony in a dune system vulnerable to erosion. The species would therefore benefit from the establishment of a second breeding population through a translocation. However, given the small size of the source population, it is essential that translocations are informed by carefully targeted monitoring data. We therefore modelled nest survival at the remaining population in relation to potential drivers (distance to sea and burrow density of conspecifics and a competitor) across three breeding seasons with varying climatic conditions as a result of the southern oscillation cycle. We also documented breeding phenology and burrow attendance, and measured chicks, to generate growth curves. We estimated egg survival at 0.686, chick survival at 0.890, overall nest survival at 0.612, and found no indication that nest survival was affected by distance to sea or burrow density. Whenua Hou diving petrels laid eggs in mid October, eggs hatched in late November, and chicks fledged in mid January at c. 86% of adult weight. Burrow attendance (i.e. feeds) decreased from 0.94 to 0.65 visits per night as chicks approached fledging. Nest survival and breeding biology were largely consistent among years despite variation in climate. Nest survival estimates will facilitate predictions about future population trends and suitability of prospective translocation sites. Knowledge of breeding phenology will inform the timing of collection of live chicks for translocation, and patterns of burrow attendance combined with growth curves will structure hand-rearing protocols. A tuhinga whakarāpopoto (te reo Māori abstract) can be found in the Supplementary material.

Manipulating parental condition affects brood sex ratio, immunocompetence, and early chick mortality in two gull species differing in sexual size dimorphism

AbstractSex allocation theory predicts that parents should adjust their brood sex ratio to maximize fitness returns in relation to parental investment. Adaptive adjustment of sex ratio may be driven by differential costs of rearing sons and daughters or differential benefits of investing limited resources into offspring of different sex. In both cases, possible sex ratio bias should depend on parental condition. For sexually dimorphic birds with males larger than females, sons may be less likely to fledge since they are more vulnerable to food shortages or because they have impaired immunocompetence due to higher testosterone levels. Poor condition females should thus overproduce daughters to minimize possible reproductive failure. We manipulated the number of eggs laid and the amount of food available to laying females to induce differences in the condition in 2 gull species differing in sexual size dimorphism. In the Black-headed Gull (Chroicocephalus ridibundus), sexual size differences are marginal; but in the Mew Gull (Larus canus), males are 11% larger. In both species, females forced to lay an additional egg (presumed in worse condition) overproduced daughters, whereas females receiving supplemental food before laying (presumed improved condition) overproduced sons. This sex ratio skew was larger in Mew Gull, a species with larger size dimorphism. Chick immunocompetence at hatching was unrelated to sex, being higher in broods of fed mothers and lower for chicks hatched from last-laid eggs. Chick survival between hatching and day 5 post-hatch was positively related to their immunocompetence, but chicks from last-laid eggs and males of Mew Gull, the more dimorphic species, survived less well. Results indicate that costs of raising larger sex offspring coupled with parental condition shape brood sex ratio in populations studied. Adaptive brood sex ratio adjustment occurs mostly before egg laying and includes differential sex allocation in eggs depending on the probability of producing a fledged chick.

Does the Breeding Biology of the Eurasian Stone-Curlew Burhinus oedicnemus in South-Western Morocco Differ between Grazed Steppe and Irrigated Farmland?

Birds associated with steppe and pseudosteppe habitats are one of the most threatened avian communities in Europe, given their recent decline due to agriculture intensification and land abandonment. Large-scale conversion of natural and rural areas into irrigated farmlands is ongoing in North Africa, but the effects of this habitat modification on steppe bird species are not investigated. In this study, we investigated the breeding biology of the Eurasian Stone-curlew nesting in grazed steppes and irrigated farmlands in south-western Morocco. Breeding data were collected during 2017 and 2018 breeding seasons on 59 nests. Egg volume was significantly higher in grazed steppes than in irrigated farmlands (37.3 ± 2.30 cm3 vs 35.1 ± 2.11 cm3, average ± SD), possibly due to greater food availability in the former habitat. On the other hand, daily nest survival over the incubation period did not differ between habitats and it was quite high (0.85 [95% CI: 0.71–0.93]) also when compared to the data available for other regions. These results suggest that birds nesting in protected areas characterized by traditional pastoralism might find better conditions for reproduction which allow them to lay larger eggs. In addition, the ongoing process of agricultural intensification in the area does not seem to affect the likelihood of nest failure. Our data add to the few available pieces of evidence regarding the effect of breeding habitat on the reproductive biology of the Stone-curlew in the southern range of its distribution. Further data are needed in order to understand the conservation implication of our findings and, in particular, how the observed variability of egg size might affect chick quality and survival.

Increasing Survival of Wild Macaw Chicks Using Foster Parents and Supplemental Feeding

The use of foster parents has great potential to help the recovery of highly endangered bird species. However, few studies have shown how to successfully use these techniques in wild populations. Scarlet Macaws (Ara macao macao) in Perú hatch 2–4 chicks per nest but about 24% of all chicks die of starvation and on average just 1.4 of them fledge per successful nest. In this study we develop and test new techniques to increase survival of wild Scarlet Macaw chicks by reducing chick starvation. We hypothesized that using foster parents would increase the survival of chicks at risk of starvation and increase overall reproductive success. Our results show that all relocated macaw chicks were successfully accepted by their foster parents (n = 28 chicks over 3 consecutive breeding seasons) and 89% of the relocated chicks fledged. Overall, we increased fledging success per available nest from 17% (2000 to 2016 average) to 25% (2017 to 2019) and decreased chick death by starvation from 19% to 4%. These findings show that the macaw foster parents technique and post relocation supplemental feeding provide a promising management tool to aid wild parrot population recovery in areas with low reproductive success.

Offspring desertion with care? Chick mortality and plastic female desertion in Snowy Plovers

Abstract Offspring desertion is often a plastic behavioral strategy that requires precise timing as the termination of parental care may have profound consequences for the fitness of parents and offspring. However, the decision process involved with termination of care is still poorly understood. Snowy Plovers Charadrius nivosus show highly flexible brood care with some females deserting the brood early and re-mate, whereas others provide extended care until the young are independent. Using a dynamic modeling framework, we investigated the effect of multiple factors on the decision-making process of female brood care in Ceuta, Mexico over a 7-year period. Females were more likely to stay with larger broods, while their probability of care was lower at the beginning of the season, when re-mating opportunities are higher than later in the season. Offspring condition at hatching did not influence the length of female care. Chick death and offspring desertion frequently coincided, suggesting that deteriorating offspring condition may trigger female desertion. Females deserted broods with high survival prospects when their absence did not impact negatively chick survival. Conversely, females deserted broods with low survival prospects when chick mortality despite female care reduced the value of the brood and re-mating was still possible. This suggests that female Snowy Plovers are sensitive to the needs and the value of their broods and adjust their parental care strategy accordingly. Taken together, we conclude that offspring desertion is a highly plastic behavior that allows females to maximize their reproductive success in a stochastic environment.

Sensitivity of multiple vital rates for Ruffed Grouse in the Upper Great Lakes Region

AbstractEffective management of wildlife requires a full understanding of population dynamics and knowledge of potential drivers that influence population growth. The Ruffed Grouse (Bonasa umbellus) is a popular upland game bird widely distributed across the northern United States and Canada that has experienced population declines within portions of its range in response to forest maturation and habitat loss. Although the species has been extensively studied, few efforts have been made to synthesize demographic data into a sensitivity analysis to guide management actions. We reviewed the literature and compiled Ruffed Grouse vital rates from 14 field studies conducted across four decades (1982−2018) within the Upper Great Lakes region of Michigan, Minnesota, and Wisconsin, USA. We parameterized a deterministic matrix model to evaluate population dynamics and conducted sensitivity analyses to identify vital rates projected to have the greatest influence on the finite rate of population change (λ). Our modeling effort projected a stable but highly variable annual rate of population change (λ = 1.01; 95% CI = 0.88–1.14) for Ruffed Grouse in the Upper Great Lakes region. Stochastic rates of population change derived from spring drumming surveys (λ = 1.01; 95% CI = 0.61–1.45) and Christmas Bird Count surveys (λ = 0.99; 95% CI = 0.62–1.76) of the corresponding regional population provided validation of stable trends over the same time period as our demographic model. Prospective elasticities and variance-scaled sensitivities suggested λ would be greatly influenced by components of reproductive performance: nesting success, chick survival, and post-fledging juvenile survival. Retrospective analysis indicated that much of the overall variability in λ and annual productivity was also attributed to annual variation in nesting success. Management of this species has often focused on fall and overwinter survival, but population projection models provided little evidence that survival was the predominant factor affecting population growth of Ruffed Grouse in this region. A suite of confounding factors and demographic processes that drive population trends can differ significantly across a species’ range. In the Upper Great Lakes region, management efforts aimed at maximizing reproductive success would likely have the greatest potential influence on Ruffed Grouse population growth. Other types of systematic, regional survey data can also be useful for validating population trends derived from demographic modeling studies.

Predictors of invertebrate biomass and rate of advancement of invertebrate phenology across eight sites in the North American Arctic

Average annual temperatures in the Arctic increased by 2–3 °C during the second half of the twentieth century. Because shorebirds initiate northward migration to Arctic nesting sites based on cues at distant wintering grounds, climate-driven changes in the phenology of Arctic invertebrates may lead to a mismatch between the nutritional demands of shorebirds and the invertebrate prey essential for egg formation and subsequent chick survival. To explore the environmental drivers affecting invertebrate availability, we modeled the biomass of invertebrates captured in modified Malaise-pitfall traps over three summers at eight Arctic Shorebird Demographics Network sites as a function of accumulated degree-days and other weather variables. To assess climate-driven changes in invertebrate phenology, we used data from the nearest long-term weather stations to hindcast invertebrate availability over 63 summers, 1950–2012. Our results confirmed the importance of both accumulated and daily temperatures as predictors of invertebrate availability while also showing that wind speed negatively affected invertebrate availability at the majority of sites. Additionally, our results suggest that seasonal prey availability for Arctic shorebirds is occurring earlier and that the potential for trophic mismatch is greatest at the northernmost sites, where hindcast invertebrate phenology advanced by approximately 1–2.5 days per decade. Phenological mismatch could have long-term population-level effects on shorebird species that are unable to adjust their breeding schedules to the increasingly earlier invertebrate phenologies.

SURVIVAL POTENTIAL OF STRESSED CHICKS

Two hundred and forty broiler, cockerel and pullet chicks were deprived feeds, water brooder heat or combination of these to stimulate similar careless or accidental farm situations so as to find their effect on the chicks survival.The type of bird as well as brooder heat had no significant effect (P>0.05) respectively on survival of chicks exposed to starvation stress, Age of chicks and nature of starvation significantly affected chicks survival. condition. A significant (P<0.05) mortality rate was recorded at ages 4 and 5 days. The maximum and evening to monitor the room temperature survival duration was 8 days for all stress chicks. Those deprived of only water survived significantly (P <0.05) longer than others. either feed, drinking water or both.

Seabird reproductive responses to changing climate and prey communities are mediated by prey packaging

Climatic factors drive changes in forage fish communities and may influence the productivity of piscivorous predators, but specific mechanisms of response remain poorly known. Between 1984 and 2020, we studied the rhinoceros auklet Cerorhinca monocerata, a seabird breeding in the western North Pacific at Teuri Island, Japan. We tested the hypothesis that climate-mediated prey-switching affects ‘food packaging’ (i.e. the way energy is brought to dependent offspring) and breeding success by quantifying relationships between climate, prey energy density, amount of food delivered, and the growth and survival of chicks. Prey composition switched 4 times: 1988-1992, 1997-1998, 2013-2014, and 2017-2018. All but the last of these switches were associated with (lagged) shifts in seawater temperature/Pacific Decadal Oscillation. Rhinoceros auklets brought multiple fish in each meal-load to chicks, and numbers were inversely correlated with the size of the fish. These relationships varied between fish species. The heaviest meal-loads were achieved when diets were dominated by anchovy Engraulis japonicas, which occurred during warm phases (1992-2013). Chick production, growth rates, and mass at fledgling were also highest during the warm phases. This study shows that climate affects seabird reproduction by shifting the manner in which food is selected relative to changes in forage fish community structure and abundance.