Bias Associated with Diet Samples in Audouin's Gulls

Oró, Daniel; Pedrocchi, Vittorio; Jover, Lluís; Ruíz, Xavier

doi:10.2307/1370488

Cited by 74 publications

(5 citation statements)

References 27 publications

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“…Despite this, families with smaller, more fragile hard parts may still be underrepresented in fecal samples as they become more eroded and less identifiable as they pass through the stomach and intestines. (Gonzalez-Solis et al . 1997).…”

Section: Discussionmentioning

confidence: 99%

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Leicht,

Robinette,

Elliott

et al. 2023

Waterbirds

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We evaluated diet and diet assessment methods for the California Least Tern (Sternula antillarum browni) at two nesting sites in California over 12 years (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012). California Least Tern diets at Alameda Point (37° 47ʹ 14ʺ N, 122° 19ʹ 12ʺ W), an estuarine site, and Purisima Point (34° 46ʹ 39ʺ N, 120° 37ʹ 35ʺ W), an open coast site, were compared using dropped fish and hard parts (otoliths and scales) from regurgitated pellets and fecal samples. SIMPER analyses, Kendall's tau, Kruskal-Wallis, Dunn's test, rank-sum tests, and Welch's t-test determined any differences in assessment methods, chick and adult diets, and sizes of prey items. Diet composition differed between sites for both dropped fish (25% similar) and fecal samples (26%). Assessment methods showed similar results at Alameda Point (79%) for dropped fish and fecal samples but not at Purisima Point when comparing dropped fish to fecal samples (12%) and fecal samples to regurgitated pellets (19%). There was no difference in diet composition at either site or between any method using adult-only samples. All differences in diet composition appeared during the rearing/fledging stage. Fish species dropped at both sites were deeper-bodied (17 mm) than those consumed (11.9 mm), with terns at Purisima Point dropping deep-bodied species typically not consumed and those at Alameda Point dropping larger individuals of usually-consumed species. When comparing adult and chick diets at Alameda Point using fecal samples, composition was similar, and chicks ate larger prey. Our results suggest that more than one assessment method is necessary to provide a complete dietary picture.

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Section: Discussionmentioning

confidence: 99%

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Leicht,

Robinette,

Elliott

et al. 2023

Waterbirds

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“…In the eggshells of Audouin’s gulls, Mn concentrations followed a different sequence (first egg < second egg > third egg; Morera et al 1997), and these discrepancies might be the result of different temporal variations in the available Mn for both gull species. Audouin’s gulls are mainly piscivorous (Gonzalez-Solis et al 1997; Morera et al 1997), while black-headed gulls are omnivorous (Cramp and Simmons 1983). Therefore, the main sources of Mn for black-headed gulls are common water macrophytes, which accumulate large amounts of this element (Samecka-Cymerman and Kempers 2000; Demirezen and Aksoy 2006).…”

Section: Discussionmentioning

confidence: 99%

Intra-clutch and inter-colony variability in element concentrations in eggshells of the black-headed gull, Chroicocephalus ridibundus, in northern Poland

Kitowski

Indykiewicz

Wiącek

et al. 2017

Environ Sci Pollut Res

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Eggshells are good bioindicators of environmental contamination, and therefore, the concentrations of 17 trace elements in 87 eggshells of black-headed gulls, Chroicocephalus ridibundus, were determined in five breeding colonies in an area dominated by farmland in northern Poland. The intra-clutch variability in the eggshell concentrations of heavy metals and other elements was also investigated, and the concentrations of the elements showed the following pattern: Ca > Mg > Sr > Fe > Zn > Al > Cr > Se > Mn > Cu > Pb > As > Ni > Mo = V > Sc > Cd. The concentrations of Fe, Al, and Mn decreased with the order in which the eggs were laid, but Sr concentrations increased. In contrast, the concentration of Cu significantly increased with the laying date. The concentrations of all elements significantly differed among the studied colonies; the highest concentration of eight elements was found in the eggshells from the Kusowo colony, which may have resulted from the intensive use of fertilizers, manure, and slurry in the surrounding agricultural region. The concentrations of Mg, Sr, and Zn in the eggshells from Skoki Duże were higher than those of the other studied colonies, which may have occurred because the gulls were nesting in a functioning gravel pit; soil and the parent rock are natural reservoirs of these elements. The observed element levels indicate that the environment where the black-headed gull eggs were formed, i.e., primarily near the breeding colonies, remains in a relatively unpolluted state, which was reflected by the low levels of Cd, Ni, and Pb and the lack of measurable levels of Hg.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-017-8635-z) contains supplementary material, which is available to authorized users.

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“…To evaluate potential differences between reproductive periods (when eggs and chicks of other species are available) and winter periods, pellets were collected during the winter (January and February 2022) and during the spring (May 2022). Given the difficulty of a correct identification of prey at the species level, class level was considered an appropriate identification level for Magpie prey (Oro et al 1997).…”

Section: Diet Datamentioning

confidence: 99%

Analysing citizen science data to address the demographic expansion of the Eurasian Magpie (Pica pica) in southern Spain

De la Cruz,

Morales,

Korneeva

et al. 2024

J Ornithol

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Citizen science platforms such as eBird provide essential spatiotemporal information and big data for the study of birds. The analysis of an extensive 20-year dataset of the distribution of the Eurasian Magpie Pica pica showed that the species is steadily expanding within urbanised areas in the south of the Iberian Peninsula. The occurrence of the species in the eBird checklists in the study area has an average exponential growth rate greater than 20%. The area occupied by the species has multiplied by 40 in the last 20 years, going from 25 to almost 1000 km2. In order to test potential negative impacts of this demographic expansion on potential Magpie prey species, such as other birds, a seasonal study of the Magpie’s diet through pellet analysis showed that its stable diet consists of insects, snails and seeds, while other birds or food from anthropogenic sources does not constitute a significant part of its diet. The combined use of new open-science big data technologies together with classical monitoring and laboratory study offers indispensable tools for the assessment of species distribution and potential spatial management.

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Bias Associated with Diet Samples in Audouin's Gulls

Cited by 74 publications

References 27 publications

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Intra-clutch and inter-colony variability in element concentrations in eggshells of the black-headed gull, Chroicocephalus ridibundus, in northern Poland

Analysing citizen science data to address the demographic expansion of the Eurasian Magpie (Pica pica) in southern Spain

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