COMPARATIVE FEEDING ECOLOGY OF AUDOUIN'S GULL <i>LARUS AUDOUINII</i> AND THE HERRING GULL <i>L. ARGENTATUS</i> IN THE MEDITERRANEAN

Witt, H. -H.; Crespo, J L; Juana, Eduardo de; Varela, Juan Manuel

doi:10.1111/j.1474-919x.1981.tb04058.x

Cited by 40 publications

(14 citation statements)

References 2 publications

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“…Audouin's Gull was previously been described as a specialist in actively catching clupeids (sardines and anchovies), which Proportion of attacks performed by Audouin's Gull deconstitute their main prey. Opportunistic behaviour, such as predation on migrant passerines, temporarily increased the diversity of their diet (Witt et al 1981.…”

Section: Discussionmentioning

confidence: 99%

Interspecific kleptoparasitism in Audouin's Gull Lams audouinii at the Ebro Delta, northeast Spain: a behavioural response to low food availability

Oro¹

1996

Ibis

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Kleptoparasitism of Audouin's Gull Lams audouinii on other seabirds, a foraging behaviour previously unrecorded for the species, was studied in the Ebro Delta, northeast Spain, during 1992. The relationship between kleptoparasitism and trawler activity was assessed through changes in the availability offish discards brought about by a trawling moratorium. When trawlers are not active, Audouin's Gulls use different feeding strategies, such as interspecific kleptoparasitism. Audoin's Gulls appeared to prefer to kleptoparasitize terns rather than gulls, but the success rate on gulls was higher. Most of the attacks rather than gulls, but the success rate on gulls was higher. Most of the attacks were performed by single Audouin's Gulls, although success per attack improved with group size. During the trawling moratorium, the existence of large seabird colonies in the Ebro Delta acted as a buffer for Audouin's Gull through kleptoparasitism, compensating partly for the reduced food supply.

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Section: Discussionmentioning

confidence: 99%

Interspecific kleptoparasitism in Audouin's Gull Lams audouinii at the Ebro Delta, northeast Spain: a behavioural response to low food availability

Oro¹

1996

Ibis

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“…Both methodologies showed that prey related to human activities, such as garbage or fish discards (Witt et al 1981), were the main components of chick diets in the sampled colonies, comprising more than 80% of the total diet biomass in 3 localities, while at the other site (Mazarrón) this value was 60 to 65% (Figs. 2 & 4).…”

Section: Feeding Ecology Of Gullsmentioning

confidence: 99%

Feeding ecology of yellow-legged gulls Larus michahellis in the western Mediterranean: a comparative assessment using conventional and isotopic methods

Ramos¹,

Ramírez²,

Sanpera³

et al. 2009

Mar. Ecol. Prog. Ser.

101

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Accurate determination of feeding habits using only conventional dietary analysis is usually difficult, due to both biases caused by prey digestibility differences and to the discrete aspect of the sampling. However, combining conventional methods with stable isotope analysis provides an integrated view of the assimilated diet. Here, we measured stable isotope ratios of carbon (δ 13 C), nitrogen (δ 15 N) and sulphur (δ 34 S) in feathers of yellow-legged gull Larus michahellis nestlings from 4 colonies along the western Mediterranean coast, where the gulls consume different proportions of marine, terrestrial and garbage resources. We collected and analysed chicks' regurgitates in each colony, thereby determining the isotopic signatures in a significant sample of prey. By applying a mixing model to our isotopic values, we compared the information provided by the 2 methodologies. According to direct prey sampling and the particular conditions of the breeding areas, populations with more enriched δ 34 S values consumed a diet richer in marine prey, with lower δ 15 N signatures indicating garbage consumption. The main pattern resulting from the mixing model agreed with direct diet sampling. However, estimated proportions for small-sized prey were controversial, which indicates that small, soft prey items might be underestimated by regurgitate analysis. We conclude that stable isotope signatures and the use of mixing models are useful tools for the rapid assessment of feeding ecology in certain populations. Solving analytical biases should be considered in future feeding studies, thereby saving time and minimising bird disturbance by using an isotopic methodology.KEY WORDS: Carbon-13 · Mixing models · Nitrogen-15 · Regurgitate · Sulphur-34 Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 377: [289][290][291][292][293][294][295][296][297] 2009 because of the intrinsic characteristics of some food types (e.g. pieces of meat and garbage taken at refuse dumps). These methodologies provide only an episodic view of an individual's diet, since each sample represents only a specific feeding event (Votier et al. 2001). Thus, to obtain reliable information about a population's feeding habits, exhaustive monitoring over time is needed (Jordan 2005). However, conventional approaches are still required when we need to identify the taxonomic group of prey consumed. Regurgitated food appears as the least biased method for describing diet composition (González-Solís et al. 1997).The use of stable isotope analysis (SIA) in animal ecology has increased enormously in recent years and has become an important tool to study trophic ecology (Hodum & Hobson 2000, Post 2002. Although SIA does not provide the taxonomic detail achieved by conventional dietary analysis, it avoids prey digestibility biases because it only takes into account assimilated food. Moreover, it provides a ready-made integrated estimate because the assimilated diet for a certain period of time is summarised, dep...

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“…YLG are known to exploit landfills to varying extents throughout their distribution range (Witt et al 1981, Motis 1989, Bosch et al 1994, Verdu´del Campo et al 1995, Ramos et al 2009). Particularly, Ramos et al (2011) assessed the importance of landfills on YLG in the western Mediterranean basin and demonstrated that landfill waste represents up to 60% of the diet of breeding YLG in our study colony.…”

Section: Introductionmentioning

confidence: 99%

Population control of an overabundant species achieved through consecutive anthropogenic perturbations

Payo‐Payo

Oró

Igual

et al. 2015

Ecological Applications

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Abstract. The control of overabundant vertebrates is often problematic. Much work has focused on population-level responses and overabundance due to anthropogenic subsidies. However, far less work has been directed at investigating responses following the removal of subsidies. We investigate the consequences of two consecutive perturbations, the closure of a landfill and an inadvertent poisoning event, on the trophic ecology (d 13 C, d 15 N, and d 34 S), survival, and population size of an overabundant generalist seabird species, the Yellow-legged Gull (Larus michahellis). We expected that the landfill closure would cause a strong dietary shift and the inadvertent poisoning a decrease in gull population size. As a long-lived species, we also anticipated adult survival to be buffered against the decrease in food availability but not against the inadvertent poisoning event. Stable isotope analysis confirmed the dietary shift towards marine resources after the disappearance of the landfill. Although the survival model was inconclusive, it did suggest that the perturbations had a negative effect on survival, which was followed by a recovery back to average values. Food limitation likely triggered dispersal to other populations, while poisoning may have increased mortality; these two processes were likely responsible for the large fall in population size that occurred after the two consecutive perturbations. Life-history theory suggests that perturbations may encourage species to halt existing breeding investment in order to ensure future survival. However, under strong perturbation pulses the resilience threshold might be surpassed and changes in population density can arise. Consecutive perturbations may effectively manage overabundant species.

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COMPARATIVE FEEDING ECOLOGY OF AUDOUIN'S GULL LARUS AUDOUINII AND THE HERRING GULL L. ARGENTATUS IN THE MEDITERRANEAN

Cited by 40 publications

References 2 publications

Interspecific kleptoparasitism in Audouin's Gull Lams audouinii at the Ebro Delta, northeast Spain: a behavioural response to low food availability

Interspecific kleptoparasitism in Audouin's Gull Lams audouinii at the Ebro Delta, northeast Spain: a behavioural response to low food availability

Feeding ecology of yellow-legged gulls Larus michahellis in the western Mediterranean: a comparative assessment using conventional and isotopic methods

Population control of an overabundant species achieved through consecutive anthropogenic perturbations

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