Diet to tissue discrimination factors for the blood and feathers of the monk parakeet (Myiopsitta monachus) and the ring–necked parakeet (Psittacula krameri)

J. González–Solís,J. C. Senar,D. Mazzoni,L. Arroyo,A. Ortega–Segalerva,N. A. Borray-Escalante

doi:10.32800/abc.2019.42.0389

J. González–Solís, J. C. Senar + Show 4 more

Open Access

https://doi.org/10.32800/abc.2019.42.0389

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Abstract

Stable isotope analyses (SIAs) have been widely used in recent years to infer the diet of many species. This isotopic approach requires using diet to tissue discrimination factors (DTDFs) for each prey type and predator tissue, i.e., to determine the difference between the isotopic composition of the predator tissues and the different prey that conform its diet. Information on DTDF values in Psittaciformes is scarce. The aim of this study was to assess DTDF values for the carbon and nitrogen isotopes of the monk parakeet (Myiopsitta monachus) and the ring–necked parakeet (Psittacula krameri), two invasive alien species of concern. We fed captive birds of the two parakeet species on a single–species diet based on sunflower seeds to establish the DTDFs for the blood and feathers. In the monk parakeet (N = 9) DTDFs were Δδ13C 2.14 ‰ ± 0.90 and Δδ15N 3.21 ‰ ± 0.75 for the blood, and Δδ13C 3.97 ‰ ± 0.90 and Δδ15N 3.67 ‰ ± 0.74 for the feathers. In the ring–necked parakeet (N = 9), the DTDFs were Δδ13C (‰) 2.58 ± 0.90 and Δδ15N (‰) 2.35 ± 0.78 for the blood, and Δδ13C 3.64 ‰ ± 0.98 and Δδ15N 4.10 ‰ ± 1.84 for the feathers. DTDF values for the ring–necked parakeet blood were significantly higher than those for the monk parakeet blood. No difference was found between the two species in the DTDF for feathers. Our findings provide the first values of DTDFs for blood and feathers in these parakeets, factors that are key to infer the diet of these species based on SIA.

Highlights

Diet is a key aspect in ecological studies (Newton and Brockie, 1998)
The two species differed in blood diet to tissue discrimination factors (DTDFs) values for both isotopes (Kruskal–Wallis test: δ13C x2(1) = 12.79, p < 0.001; δ15N x2(1) = 12.79, p < 0.001)
The comparison of DTDF values between the two tissues within the same species resulted in statistically significant differences for both isotopes (monk parakeet blood vs. feathers: δ13C x2(1) = 12.79, p < 0.001; δ15N x2(1) = 12.79, p < 0.001; rose–ringed parakeet blood vs. feathers: δ13C x2(1) = 12.79, p < 0.001; δ15N x2(1) = 5.48, p = 0.02)

Summary

Introduction

In the last few decades, analyses of stable isotopes of carbon and nitrogen have been widely used as ecological tracers to assess the diet of several species (Tieszen et al, 1983; Hobson and Clark, 1992b; Becker et al, 2007; Bearhop and Inger, 2008). Deriving quantitative estimates of dietary contributions needs precise estimates of the difference in isotopic composition between predator tissues and preys (diet to tissue discrimination factor, DTDF) (Bond and Diamond, 2011; Parnell et al, 2013). Researchers have documented considerable variation in DTDF computations. Some reviews and meta–analyses summarized this variation as a function of a number of environmental and physiological factors that included environment (terrestrial, freshwater, marine), trophic level, taxon, tissue, metabolic rate (poikilotherm, homeotherm), nitrogenous excretion (ammonia, urea, uric acid), and sample treatment procedures (Dalerum and Angerbjörn, 2005; Caut et al, 2008; Phillips et al, 2014). There is a lack of information for the Psittaciformes order, to date computed only for the kea Nestor notabilis (Greer et al, 2015)

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