Living on the Edge: Demography of the Slender-Billed Gull in the Western Mediterranean

Sanz‐Aguilar, Ana; Tavecchia, Giacomo; Afán, Isabel; Ramírez, Francisco; Doxa, Aggeliki; Bertolero, Albert; Gutiérrez‐Expósito, Carlos; Forero, Manuela G.; Oro, Daniel

doi:10.1371/journal.pone.0092674

Cited by 12 publications

(8 citation statements)

References 62 publications

(119 reference statements)

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“…a low-quality (in this case, in terms of reproductive output) habitat that individuals prefer according to once reliable cues, which are inducing instead a maladaptive habitat selection due to environmental changes (Hale & Swearer 2016, Sherley et al 2017, Greggor et al 2019. Barren, low-elevated sites, relatively far from the mainland and close to brackish lagoons are usually the preferred nesting habitats for this species due to the low interspecific competition and absence of mammalian predators (Sanz-Aguilar et al 2014). The observed increase in sea level rise and spring or summer storms are nevertheless leading to more and more frequent loss of clutches, as we observed in our study area.…”

Section: Discussionmentioning

confidence: 99%

Do the barrier islands of the Po Delta constitute an ecological trap for colonising Slender-billed Gulls Larus genei?

Valle¹,

Verza²,

Scarton

2023

Ornis Hungarica

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The Slender-billed Gull (Larus genei) breeds with a scattered distribution on an extensive nesting area, ranging from India and Afghanistan in the East to the Iberian Peninsula in the West, including the Mediterranean and the Black Sea. A number of habitats are used for breeding, such as sand-spits and beaches along coasts and islands of land-locked seas, steppe lakes, but also brackish or freshwater lagoons near river deltas. Sea level rise dramatically affects coastal sites, thus being the greatest threat to the survival of many seabird species, including gulls. This note describes habitat selection, breeding success and causes of failure of Slender-billed Gulls during their colonisation of the northern Po Delta (NE Italy) during 2018–2022. Slender-billed Gulls colonised the northern Po Delta in 2018. Six colonies were found during the study period. Birds used both natural barrier islands and artificial dredge islands. Productivity in the first five years after the colonisation event was zero, mostly due to colony sites being flooded by high tides and storms. If Slender-billed Gulls will switch to nest in nearby fish farms, these could provide plenty of suitable breeding sites, safe from tidal flooding and with very low predation pressure, allowing sufficient productivity. At the moment, Slender-billed Gulls are unsuccessful in colonising the barrier islands of the Po Delta.

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Section: Discussionmentioning

confidence: 99%

Do the barrier islands of the Po Delta constitute an ecological trap for colonising Slender-billed Gulls Larus genei?

Valle¹,

Verza²,

Scarton

2023

Ornis Hungarica

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“…Indeed, the Slender‐billed gull present low site tenacity as shown for the population breeding in southern France (Acker et al, ). Its ability to change colony site from one year to another is likely an adaptation to environmental stochasticity (Sanz‐Aguilar et al, ). Yet, the scale at which this colony displacements occur is not clearly described in the literature.…”

Section: Discussionmentioning

confidence: 99%

Foraging niche shift maintains breeding parameters of a colonial waterbird during range expansion

Francesiaz

Yohannes

Besnard

et al. 2020

Ecology and Evolution

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Relating the effects of foraging niche variation to reproductive dynamics is critical to understand species response to environmental change. We examined foraging niche variations of the slender‐billed gull (Chroicocephalus genei), a nomadic colonial waterbird species during its range expansion along the French Mediterranean coast over a 16‐year period (1998–2013). We investigated whether range expansion was associated with a change in chick diet, breeding success, and chicks body condition. We also examined whether breeding success and chicks body condition were explained by diet and colonial characteristics (number of pairs, laying phenology, habitat, and locality). Diet was characterized using dual‐stable isotopic proxies (δ13C and δ15N) of feather keratin from 331 individuals subsampled from a total of 4,154 chicks ringed and measured at 18 different colonies. δ13C decreased and δ15N increased significantly during range expansion suggesting that chicks were fed from preys of increasing trophic level found in the less salty habitat colonized by the end of the study period. Niche shift occurred without significant change of niche width which did not vary among periods, habitats, or localities either. Breeding success and chick body condition showed no consistent trends over years. Breeding success tended to increase with decreasing δ13C at the colony level while there was no relationship between stable isotope signatures and chick body condition. Overall, our results suggest that even if range expansion is associated with foraging niche shift toward the colonization of less salty and more brackish habitats, the shift had marginal effect on the breeding parameters of the Slender‐billed gull. Niche width appears as an asset of this species, which likely explains its ability to rapidly colonize new locations.

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“…Mediterranean and Black-headed Gulls mainly feed on invertebrates, such as mollusks, crustaceans, worms and insects, but also consume plant material (Cramp and Simmons 1983;Goutner 1994). Yellow-legged and Slender-billed Gulls prefer feeding on fish during the breeding season (Skórka and Wójcik 2008;Sanz-Aguilar et al 2014), whereas they take a more varied diet outside the breeding season, also including mollusks, crustaceans, worms, insects and plants (Cramp and Simmons 1983;Gonzáles-Solís et al 1997). At Vourkari, all larid species used mudflat habitats, where they were observed feeding on aquatic plants and exposed invertebrates, crustaceans and small fish.…”

Section: Importance Of Habitats For Waterbirdsmentioning

confidence: 99%

Identifying important habitats for waterbird conservation at a Greek Regional Nature Park

Liordos

Kontsiotis

2020

Avian Res

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Background Small coastal wetlands are vital sites for wintering waterbirds. Identifying important habitats is critical for managing waterbirds effectively. The Vourkari inlet is a small coastal wetland located near the capital Athens, within the most urbanized and industrialized area of Greece. We aimed at identifying the most important habitats for waterbirds at the Vourkari inlet during winter. Methods Data about habitat use and availability were collected for 14 waterbird species and for seven habitat classes. Habitat selection (Manly’s selection ratio), overlap indices (Pianka’s niche overlap index) and null models were calculated. Results All the studied waterbird species selected available habitats nonrandomly. Shallow waters (0–2 m), were used by 13 waterbirds and selected by five waterbirds. Pools and channels were used and selected by 10 species. Mud was used by nine species and selected by six species. Mud with rocky substrate was used by nine species and selected by eight species. Medium (2–4 m) and deep (4–6 m) open water habitats were used by seven species and selected by four species. Halophytic vegetation was used by six species and selected by two species. Several habitats were selected by nationally important populations: mudflat habitats (i.e., mud, mud with rocky substrate and pools and channels) by Common Redshanks (Tringa totanus), halophytic vegetation by Little Egrets (Egretta garzetta), shallow waters by Common Shelducks (Tadorna tadorna) and medium and deep waters by Sandwich Terns (Thalasseus sandvicencis), whilst shallow waters and mudflat habitats were preferred by a possibly internationally important population of Mediterranean Gulls (Ichthyaetus melanocephalus). Although overlap in habitat use between species was generally low, null models indicated habitat sharing and a lack of competition. Conclusions Waterbirds coexisted in the absence of competition for habitats at Vourkari, where they mostly used and preferred shallow water and mudflats. Small coastal wetlands are numerous, both in Greece and worldwide, therefore our findings would be useful as a basis for comparisons, both temporal at the inlet and spatial with other sites, that would help assess the importance of habitats and improve management strategies to benefit waterbirds, especially in areas with similar Mediterranean-type habitats and climate.

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Living on the Edge: Demography of the Slender-Billed Gull in the Western Mediterranean

Cited by 12 publications

References 62 publications

Do the barrier islands of the Po Delta constitute an ecological trap for colonising Slender-billed Gulls Larus genei?

Do the barrier islands of the Po Delta constitute an ecological trap for colonising Slender-billed Gulls Larus genei?

Foraging niche shift maintains breeding parameters of a colonial waterbird during range expansion

Identifying important habitats for waterbird conservation at a Greek Regional Nature Park

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