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199 results for “Nestling”

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Data from: Are brood sex ratios adaptive? The effect of experimentally altered brood sex ratio on nestling growth, mortality, and recruitment

Brood sex ratios (BSRs) have often been found to be non-random in respect of parental and environmental quality, and many hypotheses suggest that non-random sex ratios can be adaptive. To specifically test the adaptive value of biased BSRs, it is crucial to disentangle the consequences of BSR and maternal effects. In multiparous species, this requires cross-fostering experiments where foster parents rear offspring originating from multiple broods, and where the interactive effect of original and manipulated BSR on fitness components are tested. To our knowledge, our study on collared flycatchers (Ficedula albicollis) is the first that meets these requirements. In this species, where BSRs had previously been shown to be related to parental characteristics, we altered the original BSR of the parents shortly after hatching by cross-fostering nestlings among trios of broods, and examined the effects on growth, mortality, and recruitment of the nestlings. We found that original and experimental BSR, as well as the interaction of the two were unrelated to the fitness components considered. Nestling growth was related only to background variables, namely brood size and hatching rank. Nestling mortality was related only to hatching asynchrony. Our results therefore do not support that the observed BSRs are adaptive in our study population. However, we cannot exclude the possibility of direct effects of experimentally altered BSRs on parental fitness, which should be evaluated in the future. In addition, studies similar to ours are required on various species to get a clearer picture of the adaptive value of non-random BSRs.

opencc-zeroOct 2022View details →

dryad36/100

Data for: Innate immune function and antioxidant capacity of nestlings of an African raptor co-vary with the level of urbanization around breeding territories

Urban areas provide breeding habitats for many species. However, animals raised in urban environments face challenges such as altered food availability and quality, pollution, and pathogens assemblages. These challenges can affect physiological processes like immune function and antioxidant defences which are important for fitness. Here, we explore how levels of urbanisation influence innate immune function, immune response to a mimicked bacterial infection and antioxidant capacity of nestling Black Sparrowhawks Accipiter melanoleucus in South Africa. We also explore the effect of timing of breeding and rainfall on physiology since both can influence the environmental condition under which nestlings are raised. Finally, because urbanisation can influence immune function indirectly, we use path analyses to explore direct and indirect associations between urbanisation, immune function, and oxidative stress. We obtained measures of innate immunity (haptoglobin, lysis, agglutination and bactericidal capacity), indices of antioxidant capacity (total non-enzymatic antioxidant capacity (tAOX), and total glutathione from nestlings from 2015 - 2019. In addition, in 2018 and 2019, we mimicked a bacterial infection by injecting nestlings with lipopolysaccharide and quantified their immune response. Increased urban cover was associated with an increase in lysis and a decrease in tAOX, but not with any of the other physiological parameters. Furthermore, except for agglutination, no physiological parameters were associated with the timing of breeding. Lysis and bactericidal capacity, however, varied consistently with the annual rainfall pattern. Immune response to a mimicked a bacterial infection decreased with urban cover but not with the timing of breeding nor rainfall. Our path analyses suggested indirect associations between urban cover and some immune indices via tAOX but not via the timing of breeding. Our results show that early-life development in an urban environment is associated with variation in immune and antioxidant functions. The direct association between urbanisation and antioxidant capacity and their impact on immune function is likely an important factor mediating the impact of urbanisation on urban-dwelling animals. Future studies should explore how these results are linked to fitness and whether the responses are adaptive for urban-dwelling species.

opencc-zeroNov 2022View details →

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Data for: Polymorphism at the nestling stage and host-specific mimicry in an Australasian cuckoo-host arms race

Decades of research have shown that the coevolutionary arms race between avian brood parasites and their hosts can promote phenotypic diversification in hosts and brood parasites. However, relatively little is known about the role of brood parasitism in promoting phenotypic diversification of nestlings. We review field data collected over four decades in Australia, New Caledonia and New Zealand to assess potential for coevolutionary interactions between the shining bronze-cuckoo (Chalcites lucidus) and its hosts, and how diversification at the nestling stage may be generating different subspecies. The shining bronze-cuckoo is a specialist parasite of a few hosts in the family Acanthizidae. It has diversified into subspecies, of which the nestlings closely mimic the respective host nestlings in each region. Additionally, some cuckoo subspecies have polymorphic nestlings. The Acanthizidae hosts have similar breeding and nesting habits and only moderately effective frontline defences against parasitism at cuckoo egg laying or at the egg stages. However, some hosts have developed highly effective defences at the nestling stage by recognising and ejecting cuckoo nestlings from the nest. As with the cuckoo nestlings, some hosts have polymorphic nestlings. The coevolutionary interactions in each region suggest different evolutionary stages of the arms race in which either the parasite or the host is currently in the lead. The presence of moderately effective defences at the egg laying and egg stages might explain why some hosts do not have defences at the nestling stage. The south-Pacific cuckoo – host systems are excellent models to explore the evolutionary mechanisms driving the diversification at the nestling stage in the coevolutionary arms race between avian brood parasites and their hosts.

opencc-zeroNov 2022View details →

dryad36/100

Nestling growth rate and food consumption increases under experimentally prolonged day length in a New World Sparrow

When evaluating avian reproduction, life history theory examines the trade-offs between parental effort, the number and size of offspring, and the rate of nestling development. The growth rates and body sizes of developing birds vary geographically and can diverge with both latitude and migratory strategies. In terms of offspring size, growth rate can deviate in nestlings of the same or similar species due to the correlated influences of weather events, predation pressure, food availability, number of nestmates, and parental provisioning. Furthermore, a longer photoperiod for species nesting at higher latitudes increases the duration over which a nestling can be fed each day, and increased nestling provisioning has been positively correlated with growth rate. Whether the amount of time in which a bird is fed during development drives this variation in growth rate and morphology is unknown. By removing supplemental environmental stressors (e.g., food availability, weather, predation pressure) and standardizing feeding rate and environment, we explored the influence of daily duration of nestling provisioning on dark-eyed junco (Junco hyemalis) nestlings. We hand-reared 65 chicks of a sedentary junco subspecies (J. h. carolinensis) under both their natural photoperiod and the longer photoperiod of a closely related migratory subspecies (J. h. hyemalis) and compared growth rate, mass, morphology, and the amount of food consumed. Average growth rate, fasted mass, wing length, and total daily food consumption were all greater in birds hand-reared under the longer, more northern photoperiod treatment. These findings suggest that increased daily photoperiod at higher latitudes may allow for greater total food provisioning and thus may play a role in the ability of parents in compressed breeding seasons to produce high-quality offspring. This points to a trade-off between provisioning effort and nestling growth rate in lower latitude (shorter photoperiod) populations and points to an important role of developmental plasticity on growth rate and morphology.

opencc-zeroMay 2023View details →

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Data from: Predator-prey interactions in the Arctic: DNA-metabarcoding reveals that nestling diet of snow buntings reflects arthropod seasonality

Tundra arthropods are of considerable ecological importance as a seasonal food source for many arctic-breeding birds. Dietary composition and food preferences are rarely known, complicating assessments of ecological interactions in a changing environment. In our field study, we investigated nestling diet of snow buntings (Plectrophenax nivalis (L., 1758)) breeding in Svalbard. We collected faecal samples from 8-day-old nestlings and assessed dietary composition by DNA-metabarcoding. Simultaneously, the availability of potential prey arthropods was measured by pitfall-trapping. Molecular analyses of nestling faeces identified 31 arthropod taxa in the diet, whose proportions changed throughout the brood-rearing period. Changes in nestling diet matched varying abundances and emergence patterns of the tundra arthropod community. Snow buntings provisioned their offspring mainly with Diptera (true flies) based on both presence/absence and relative read abundance of diet items. At the beginning of the season in June, Chironomidae (non-biting midges) and the scathophagid fly Scathophaga furcata (Say, 1823) dominated the diet, whereas the muscid fly Spilogona dorsata (Zetterstedt, 1845) dominated the diet later in July. When accounted for availability, muscid flies were selected positively amongst the most often provisioned food taxa. Our study demonstrates the ecological role of the snow bunting as a generalist arthropod predator and highlights DNA-metabarcoding as a non-invasive technique for diet analyses with high taxonomical precision if sufficient DNA-sequence libraries are available.

opencc-zeroJun 2023View details →

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Nestling begging calls resemble maternal vocal signatures when mothers call slowly to embryos

Vocal production learning (the capacity to learn to produce vocalizations) is a multi-dimensional trait that involves different learning mechanisms during different temporal and socio-ecological contexts. A key outstanding question is whether vocal production learning begins during the embryonic stage and whether mothers play an active role in this through pupil-directed vocalization behaviors. We examined variation in vocal copy similarity (an indicator of learning) in eight species from the songbird family Maluridae, using comparative and experimental approaches. We found that: (1) incubating females from all species vocalized inside the nest and produced call types including a signature 'B element' that was structurally similar to their nestlings' begging call; (2) in a prenatal playback experiment using superb fairywrens (Malurus cyaneus), embryos showed a stronger heart rate response to playbacks of the B element than to another call element (A); and (3) mothers that produced slower calls had offspring with greater similarity between their begging call and the mother's B element vocalization. We conclude that malurid mothers display behaviors concordant with pupil-directed vocalizations and may actively influence their offspring's early-life through sound learning shaped by maternal call tempo.

opencc-zeroJul 2023View details →

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Data for: Cool, dry nights and short heatwaves during growth result in longer telomeres in temperate songbird nestlings

Exposure to rising sublethal temperatures can affect development and somatic condition, and thereby Darwinian fitness. In the context of climate warming, these changes could have implications for population viability, but they can be subtle and consequently difficult to quantify. Using telomere length (TL) as a known biomarker of somatic condition in early life, we investigated the impact of pre-hatching and nestling climate on six cohorts of wild nestling superb fairy-wrens (Malurus cyaneus) in temperate south-eastern Australia. Models incorporating only climate information from the nestling phase were best supported compared to those including the (pre-)laying to incubation phase (previously shown to affect mass) or both phases combined. This implies that nestling TL is most sensitive to ambient climate in the nestling phase. The top model showed a negative relationship between early-life TL and nestling mean daily minimum temperature when rainfall was low which gradually became positive with increasing rainfall. In addition, there was a positive relationship between TL and the frequency of hot days (daily maximum temperature ≥ 35°C), although these temperatures were rare and short-term. Including other pre-hatching and nestling period climate variables (e.g., mean daily maximum temperature and mean diurnal temperature variability) did not improve the prediction of nestling TL. Overall, our results suggest that cooler nights when conditions are dry, and short-term temperature spikes above 35°C during development are conducive for somatic maintenance. While these findings indicate a potential pathway for climate warming to impact wildlife fitness, they emphasise the need to elucidate the mechanisms underlying these complex associations.

opencc-zeroAug 2023View details →

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