Browsing by Author "Newsome, Seth D."

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    A multi-isotope approach reveals seasonal variation in the reliance on marine resources, production of metabolic water, and ingestion of seawater by two species of coastal passerine to maintain water balance
    (2023) Navarrete, Lucas; Lubcker, Nico; Alvarez, Felipe; Nespolo, Roberto; Sanchez-Hernandez, Juan Carlos; Maldonado, Karin; Sharp, Zachary D.; Whiteman, John P.; Newsome, Seth D.; Sabat, Pablo
    Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (delta O-16, delta O-17, delta O-18) and bulk tissue carbon (delta C-13) and nitrogen (delta N-15) isotopes of feathers and blood to estimate the proportional contribution of marine resources, seawater, and metabolic water used by two species of unique songbirds (genus Cinclodes) to maintain their water balance in a seasonal coastal environment. We also assessed the physiological adjustments that these birds use to maintain their water balance. In agreement with previous work on these species, delta C-13 and delta N-15 data show that the coastal resident and invertivore C. nigrofumosus consumes a diet rich in marine resources, while the diet of migratory C. oustaleti shifts seasonally between marine (winter) to freshwater aquatic resources (summer). Triple-oxygen isotope analysis (Delta O-17) of blood plasma, basal metabolic rate (BMR), and total evaporative water loss (TEWL) revealed that similar to 25% of the body water pool of both species originated from metabolic water, while the rest originated from a mix of seawater and fresh water. Delta O-17 measurements suggest that the contribution of metabolic water tends to increase in summer in C. nigrofumosus, which is coupled with a significant increase in BMR and TEWL. The two species had similar BMR and TEWL during the austral winter when they occur sympatrically in coastal environments. We also found a positive and significant association between the use of marine resources as measured by delta C-13 and delta N-15 values and the estimated delta O-18 values of ingested (pre-formed) water in both species, which indicates that Cinclodes do not directly drink seawater but rather passively ingest when consuming marine invertebrates. Finally, results obtained from physiological parameters and the isotope-based estimates of marine (food and water) resource use are consistent, supporting the use of the triple-oxygen isotopes to quantify the contribution of water sources to the total water balance of free-ranging birds.
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    Individual diet specialisation in sparrows is driven by phenotypic plasticity in traits related to trade-offs in animal performance
    (2019) Maldonado, Karin; Newsome, Seth D.; Razeto-Barry, Pablo; Manuel Rios, Juan; Piriz, Gabriela; Sabat, Pablo
    Individual diet specialisation (IS) is frequent in many animal taxa and affects population and community dynamics. The niche variation hypothesis (NVH) predicts that broader population niches should exhibit greater IS than populations with narrower niches, and most studies that examine the ecological factors driving IS focus on intraspecific competition. We show that phenotypic plasticity of traits associated with functional trade-offs is an important, but unrecognised mechanism that promotes and maintains IS. We measured nitrogen isotope (delta N-15) and digestive enzyme plasticity in four populations of sparrows (Zonotrichia capensis) to explore the relationship between IS and digestive plasticity. Our results show that phenotypic plasticity associated with functional trade-offs is related in a nonlinear fashion with the degree of IS and positively with population niche width. These findings are opposite to the NVH and suggest that among individual differences in diet can be maintained via acclimatisation and not necessarily require a genetic component.
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    Integrative Physiological Responses to Acute Dehydration in the Rufous-Collared Sparrow: Metabolic, Enzymatic, and Oxidative Traits
    (2021) Navarrete, Lucas; Bozinovic, Francisco; Pena-Villalobos, Isaac; Contreras-Ramos, Carolina; Sanchez-Hernandez, Juan C.; Newsome, Seth D.; Nespolo, Roberto F.; Sabat, Pablo
    Predictions indicate that birds worldwide will be affected by global warming and extreme climatic events which is especially relevant for passerines because the diurnal habits, small body size, and high mass-adjusted metabolic rates of this group make it particularly susceptible to increases in temperature and aridity. Some bird species respond to conditions that stress osmoregulation by increasing their rates of energy expenditure, nevertheless, the effect of dehydration on metabolic rates in birds has produced contrasting results. It also remains unknown whether hydration state may cause shifts in tissue-specific metabolic rates or modify tissue oxidative status. We used the rufous-collared sparrow (Zonotrichia capensis), to experimentally test the effect of dehydration on metabolic enzymes in erythrocytes, tissue oxidative status, basal metabolic rate (BMR), and total evaporative water loss. We found a significant increase in mass-adjusted BMR in water restricted (WR) birds compared to control birds (CT). Activity of cytochrome-c-oxidase (COX) in red blood cells (RBCs) was also significantly higher in the WR group relative to the CT group and this activity was positively correlated with mass-adjusted BMR. We found a moderate effect of water restriction on membrane damage of skeletal muscle. In a second set of individuals subjected to the same experimental conditions, lean mass and total water were tightly correlated and decreased by 10 and 12%, respectively, in birds in the WR group relative to the CT group. Decreases in total water and lean mass leads to an increase in mass-adjusted BMR in WR Z. capensis, suggesting that birds may simultaneously increase protein catabolism and production of metabolic water through oxidation. The significant positive relationship between BMR and COX in RBCs is a finding that requires additional research to determine whether erythrocyte metabolism is affected by dehydration per se and or it more generally reflects rates of energy expenditure in birds.
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    Intraspecific variation in exploratory behavior and elevational affinity in a widely distributed songbird
    (SPRINGER, 2018) Poblete, Yanina; Gutierrez, Victor; Cid, Valeska; Newsome, Seth D.; Sabat, Pablo; Vasquez, Rodrigo A.
    Populations of the same species can vary substantially in their behavioral and morphometric traits when they are subject to different environmental pressures, which may lead to the development of different adaptive strategies. We quantified variation in exploratory behavior and morphometric traits among two rufous-collared sparrow populations that occur at low and high elevations in central Chile. Moreover, we used census and delta H-2 values of feather and blood to evaluate migration. We found that individual sparrows inhabiting high elevations were larger and showed more intense exploratory behavior in comparison with those that were captured at lower elevation. Moreover, we observed a steady decline in sparrow abundance during the winter and similar delta H-2 values for blood collected in the winter and summer at this site, which were significantly lower than blood delta H-2 values observed at low elevation. This pattern suggests that individuals do not move long distances during winter, and likely they remain at similar elevations in refuge habitats. As predicted, our results support the existent of different adaptive strategies among populations of the same species, and suggest that the combination of behavioral, morphometric, and stable isotope data is a novel and robust integrative approach to assess differences in adaptation across environmental gradients.
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    Multi-tissue δ2H analysis reveals altitudinal migration and tissue-specific discrimination patterns in Cinclodes
    (2015) Newsome, Seth D.; Sabat, Pablo; Wolf, Nathan; Rader, Jonathan A.; del Rio, Carlos Martinez
    One of the fastest growing uses of stable isotope analysis in ecology is using hydrogen isotope (delta H-2) values to characterize animal movement and migration strategies. Most studies measure delta H-2 values in metabolically inert tissues such as feathers, which are typically grown during or just after the summer breeding season and provide a limited snapshot of an individual's annual life history. In contrast, isotopic analysis of metabolically active tissues can provide ecological information integrated over weeks to months prior to sampling. Here we characterize delta H-2 patterns among multiple metabolically inert and active tissues in Cinclodes, a genus of South American songbirds noted for variation in altitudinal movement and foraging strategies. We also coupled delta H-2 with carbon (delta C-13) and nitrogen (delta N-15) isotope data to combine information on movement with marine versus terrestrial resource use at the individual level. We find that a combination of physiological and ecological factors control delta H-2 patterns among tissues, which mirrors results of feeding experiments on captive birds. For example, in the coastal resident C. nigrofumosus, metabolically active muscle collected during the winter has higher delta H-2 values than feathers grown the previous summer, a tissue-specific discrimination pattern previously observed in captive birds. This pattern is reversed to various degrees for altitudinal migrants such as C. fuscus and C. oustaleti that spend winters foraging in marine intertidal habitats but migrate to high elevation and forage in stream habitats during the summer. We also find that among altitudinal migrants, individuals that forage sympatrically in intertidal habitats during the winter appeared to summer at a wide range of elevations, as evidenced by large differences of >50 parts per thousand in delta H-2(muscle-feather) offsets. Lastly, a positive correlation between feather delta H-2 and delta N-15 values in Cinclodes that consume a mixed marine-freshwater diet confirms that delta H-2 is a useful proxy for quantifying marine resource use. We anticipate that comparison of delta H-2 values in metabolically active and inert tissues may allow for the reconstruction of animal movement and foraging strategies within the annual life cycle; however, more work is required to better understand the physiological mechanisms responsible for the observed delta H-2 patterns among tissues.
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    Terrestrial birds in coastal environments : metabolic rate and oxidative status varies with the use of marine resources
    (2018) Tapia Monsalve, Romina; Newsome, Seth D.; Sánchez Hernández, Juan C.; Bozinovic Kuscevic, Francisco; Nespolo Rossi, Roberto; Sabat, Pablo
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    Testing the niche variation hypothesis in a community of passerine birds
    (2017) Maldonado, Karin; Bozinovic Kuscevic, Francisco; Newsome, Seth D.; Sabat, Pablo