Assessing bias in diet methods for the Long-legged Buzzard Buteo rufinus

Bakaloudis, Dimitrios E.; Iezekiel, S.; Vlachos, Christos; Bontzorlos, Vasileios; Papakosta, Malamati A.; Birrer, Simon

doi:10.1016/j.jaridenv.2011.10.004

Cited by 22 publications

(17 citation statements)

References 13 publications

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“…Although the present study included only 3 nests, which may jeopardize the scientific accuracy of the conclusions drawn, the results are largely in accordance with previous studies conducted, where reptiles and mammals (especially rodents) have been the main food items and birds have been the most important alternative prey (Cramp and Simmons, 1979;Spidsø and Selås, 1988;Alivizatos and Goutner, 1997;Forsman, 1998;Snow and Perrins, 1998;Reif et al, 2001;Selås, 2001;Khaleghizadeh et al, 2005;Selås et al, 2007;Hosseini-Zavarei et al, 2008;Bakaloudis et al, 2012).…”

Section: Discussionsupporting

confidence: 89%

Breeding Long-legged Buzzard Buteo rufinus in forests of southwestern Iran:feeding habits and reproductive performance

Shafaeipour¹

2015

Turk J Zool

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The breeding biology, behavior, and diet of Long-legged Buzzard Buteo rufinus were studied during 2 breeding seasons in forests in southwestern Iran (n = 3 nests) from April to June in 2012 and 2013. All nests faced west to east on the upper edges of cliffs. Eggs were laid during 7-11 March. The clutch size was 3 eggs and incubation period was 31 ± 1 days. Brood reduction was observed in one of the nests (in the first year), and mortality of the smallest chicks occurred during the second week after hatching. The young fledged successfully at 49.5 ± 0.5 days of age and left the nest at approximately 52 ± 2 days. Information about diet during the breeding season was obtained by collecting pellets, prey remains, and video recordings. Mammalian prey, especially Persian squirrel (Sciurus anomalus), and lizards and snakes made up most of the diet of Long-legged Buzzards.

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Section: Discussionsupporting

confidence: 89%

Breeding Long-legged Buzzard Buteo rufinus in forests of southwestern Iran:feeding habits and reproductive performance

Shafaeipour¹

2015

Turk J Zool

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“…There are no “universal methods” allowing the reliable determination of the diet composition of predators. In the case of vertebrate, diet composition can rarely be determined through the direct observation of prey consumption [2,3]. Ecologists must then employ several indirect methods to determine diet composition.…”

Section: Introductionmentioning

confidence: 99%

“…Ecologists must then employ several indirect methods to determine diet composition. These methods include the analyses of stomach contents [3,4], scats [5–7], regurgitations [8] and pellets [9,10]. Nevertheless, all these indirect methods rely on the recovery and identification of hard items (e.g.…”

Section: Introductionmentioning

confidence: 99%

Bias in Diet Determination: Incorporating Traditional Methods in Bayesian Mixing Models

et al. 2013

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There are not “universal methods” to determine diet composition of predators. Most traditional methods are biased because of their reliance on differential digestibility and the recovery of hard items. By relying on assimilated food, stable isotope and Bayesian mixing models (SIMMs) resolve many biases of traditional methods. SIMMs can incorporate prior information (i.e. proportional diet composition) that may improve the precision in the estimated dietary composition. However few studies have assessed the performance of traditional methods and SIMMs with and without informative priors to study the predators’ diets. Here we compare the diet compositions of the South American fur seal and sea lions obtained by scats analysis and by SIMMs-UP (uninformative priors) and assess whether informative priors (SIMMs-IP) from the scat analysis improved the estimated diet composition compared to SIMMs-UP. According to the SIMM-UP, while pelagic species dominated the fur seal’s diet the sea lion’s did not have a clear dominance of any prey. In contrast, SIMM-IP’s diets compositions were dominated by the same preys as in scat analyses. When prior information influenced SIMMs’ estimates, incorporating informative priors improved the precision in the estimated diet composition at the risk of inducing biases in the estimates. If preys isotopic data allow discriminating preys’ contributions to diets, informative priors should lead to more precise but unbiased estimated diet composition. Just as estimates of diet composition obtained from traditional methods are critically interpreted because of their biases, care must be exercised when interpreting diet composition obtained by SIMMs-IP. The best approach to obtain a near-complete view of predators’ diet composition should involve the simultaneous consideration of different sources of partial evidence (traditional methods, SIMM-UP and SIMM-IP) in the light of natural history of the predator species so as to reliably ascertain and weight the information yielded by each method.

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“…, Bakaloudis et al . ), to date few isotopic studies have focused on assessing the diets of avian terrestrial predators, including most raptor species (but see Roemer et al . , Caut et al .…”

mentioning

confidence: 99%

“…Despite the applicability of both conventional diet analyses and isotopic mixing models to determine avian diets, and the caveats and potential biases associated with each, few studies have compared these methods (but see Doucette et al 2011, Steenweg et al 2011, Weiser & Powell 2011. Moreover, although conventional methods have been used traditionally to assess raptor food habits (Real 1996, Marti et al 2007, S anchez et al 2008, Bakaloudis et al 2012, to date few isotopic studies have focused on assessing the diets of avian terrestrial predators, including most raptor species (but see Roemer et al 2002, Caut et al 2006. Consequently, the potential applicability of isotopic mixing models to assess raptor foraging ecology is still poorly understood.…”

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confidence: 99%

Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet

Resano‐Mayor

Hernández‐Matías

Real

et al. 2013

Ibis

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Diet analyses are central to the study of avian trophic ecology, and stable isotope analyses have made an increasing contribution in the last two decades. Few isotopic studies have assessed the diet of raptor species, which are more frequently analysed by conventional diet methods such as pellet analysis. In this study, we compare prey consumption estimates of nestling Bonelli's Eagles Aquila fasciata from conventional pellet analysis (in terms of items and biomass) and stable isotopic mixing models (SIAR) using δ13C, δ15N and δ34S of feathers. The pellet analysis showed that European Rabbits Oryctolagus cuniculus, pigeons (mainly Common Wood Pigeons Columba palumbus and Domestic Pigeons Columba livia dom.), Red‐legged Partridges Alectoris rufa, passerines, Yellow‐legged Gulls Larus michahellis and Eurasian Red Squirrels Sciurus vulgaris were the main prey, so they were selected for diet reconstructions in SIAR. At the population level, mean prey consumption estimates were similar for pellets (both items and biomass) and SIAR. At the territory level, the weighted kappa statistic showed good ordinal scale agreement in main prey consumption between items or biomass and SIAR. Although the intraclass correlation coefficient showed poor method agreement when considering all prey in the same analysis, the intraclass correlation coefficients for each prey category showed significant agreement between pellets and SIAR when estimating the consumption of Rabbits, pigeons and Gulls, with lower agreement for passerines and Squirrels. Lastly, there was poor method agreement for estimates of Partridges. Our results suggest an overall agreement between the pellet analysis and SIAR when estimating nestling Bonelli's Eagle diet at both the population and, to a lesser extent, the territory level, supporting the usefulness of isotopic mixing models when identifying the terrestrial and marine components of raptor diets.

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Assessing bias in diet methods for the Long-legged Buzzard Buteo rufinus

Cited by 22 publications

References 13 publications

Breeding Long-legged Buzzard Buteo rufinus in forests of southwestern Iran:feeding habits and reproductive performance

Breeding Long-legged Buzzard Buteo rufinus in forests of southwestern Iran:feeding habits and reproductive performance

Bias in Diet Determination: Incorporating Traditional Methods in Bayesian Mixing Models

Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet

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