Unforeseen effects of ecosystem restoration on yellow-legged gulls in a small western Mediterranean island

Martínez‐Abraín, Alejandro; Sarzo, Blanca; Villuendas, Elena; Bartolomé, Miguel Angel; Mínguez, Eduardo; Oro, Daniel

doi:10.1017/s0376892904001456

Cited by 15 publications

(8 citation statements)

References 21 publications

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“…Unvalidated conservation techniques can cause serious damage (Martínez‐Abraín et al ), especially for threatened species. Nest box supplementation is the most common technique for increasing breeding opportunities of cavity‐nesting organisms.…”

Section: Discussionmentioning

confidence: 99%

Natural cavity restoration as an alternative to nest box supplementation

Valera

Václav

Calero-Torralbo

et al. 2018

Restoration Ecology

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Nest box supplementation is widely used to increase nest‐site availability for cavity nesting animals but the analysis of its effects on individuals breeding in natural cavities is often neglected. This study offers a novel restoration technique to revert abandonment of natural breeding sites by a secondary cavity avian bird, the European roller (Coracias garrulus), and other ecologically similar species. We found that, after a program of nest box supplementation with ensuing monitoring, rollers gradually abandon nesting in natural and seminatural cavities in favor of nest boxes because the latter are of higher quality. We examine whether reducing the entrance size of natural and seminatural cavities improves their suitability for rollers. A 6‐year program reduced the diameter of the entrance of sandstone cavities and cavities in bridges. This led to a high occupancy (59%) of manipulated nest‐sites. Manipulated sites were most frequently occupied by rollers and little owls (Athene noctua) (31 and 18% of sites, respectively). Manipulation did not affect clutch size or fledgling success. We suggest that nest‐site diversity and nesting in natural cavities should be preserved to reduce nest box dependence. Our study illustrates the value of nest boxes when used alongside restoration of natural breeding sites and provides insights for the management of natural cavities.

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Section: Discussionmentioning

confidence: 99%

Natural cavity restoration as an alternative to nest box supplementation

Valera

Václav

Calero-Torralbo

et al. 2018

Restoration Ecology

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“…Importantly, the effects of predatory gulls (e.g. extinction or decline) on their prey should not be assessed at the local population scale but rather at the metapopulation scale, which should be the true unit of management of birds with high dispersal capabilities (such as seabirds and waterbirds in general; see Martínez‐Abraín, Oro & Jimenéz, 2001; Martínez‐Abraín, Sanchez & Oro, 2002; Martínez‐Abraín et al , 2004; Oro, 2003). It is also known that breeding sites at the metapopulation level do not have the same quality, and that habitat heterogeneity (including yellow‐legged gull densities) is essential for metapopulation functioning, the rescue effect or source–sink systems.…”

Section: Discussionmentioning

confidence: 99%

Deconstructing myths on large gulls and their impact on threatened sympatric waterbirds

Oro

Martínez‐Abraín

2006

Animal Conservation

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Owing to increasing population trends and facultative predatory habits, large gulls have been identified as significant agents of change in the alteration of many ecological communities. Often, they are perceived as negatively impacting the population trends of most sympatric waterbirds. Consequently, culling programs have been implemented to remove adults, chicks and eggs intensively. Here, we review the interactions recorded in the literature between the yellow-legged gull Larus michahellis and 10 sympatric waterbirds in the Mediterranean region, all threatened and classified as species of conservation concern. We also used 177 long-term population trends derived from previous studies to study the population dynamics of these species and the culling effort performed. We show that gulls negatively affected survival, fecundity, foraging ecology and nesting habitat availability for many species. However, the annual population growth rates of most sympatric waterbirds showed positive values, even at sites where culling has yet to be initiated and local yellow-legged gull populations are large and increasing. Our results suggest clearly that population increase has not been exclusive of yellow-legged gulls, especially at the regional level. Yet, growth rates of both yellow-legged gulls and sympatric waterbirds were positively associated. Strikingly, the population extinction rate was similar between colonies of yellowlegged gulls and those of sympatric species. Thus, evidence exists to state that the success of gull control programs is relatively low in the long term. We recommend that conservation agencies heed several basic principles of population and community ecology before initiating control, for instance that (1) yellow-legged gulls have bred historically with other bird species and have likely developed defensive mechanisms against this predator and (2) populations of large gulls are regulated by density-dependent mechanisms in both space and time. Incoming European environmental policies on fishing discards and rubbish management should control more naturally and efficiently the density of large gulls and the composition of seabird communities in the long term.

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“…Pod Mrčaru has long been known as a brooding place for yellow‐legged seagulls (Radovanović 1956) and also during our visits, we found many more occupied nests on this island (n=38, 29.23 nest hect −1 ) than on Pod Kopište (n=8, 1.6 nest hect −1 ). Sea gulls may prefer Pod Mrčaru as a brooding place because its vegetation offers more protection to their eggs and young (Martinez‐Abrain et al 2004), or conversely, their presence may have changed the aboveground biomass of plants and community composition (Ellis 2005). The presence of gulls may relax predation pressure on lizards because gulls tend to chase away other, perhaps more dangerous bird predators (such as crows and falcons), and this benefit may outweigh the putative greater risk of predation by the gulls themselves (Wheelwright et al 1997).…”

Section: Discussionmentioning

confidence: 99%

Differences in morphology, performance and behaviour between recently diverged populations of Podarcis sicula mirror differences in predation pressure

Vervust¹,

Grbac²,

Damme³

2007

Oikos

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We investigated the possible role of variation in predation pressure in the phenotypic divergence of two island populations of the Italian wall lizard, Podarcis sicula . In 1971, ten adult specimens from the island of Pod Kopište (Adriatic Sea, Croatia) were transported to the island of Pod Mrčaru, 3.5 km east, where they founded a new population. Although the two islands resemble each other in general physiognomy (size, elevation, microclimate) and in the absence of terrestrial predators, lizards from the newly established population are now on average larger and have shorter hind limbs. They also exhibit lower maximal sprint speed as measured on a racetrack, and fatigue faster when chased in a torus track. In the field, lizards from the original population of Pod Kopište respond to a simulated predatory attack by fleeing at larger approach distances and by running further from the predator than lizards from Pod Mrčaru. These changes in morphology, behaviour and performance may result from the relaxed predation intensity on the latter island. Our analysis of the structural features of the microhabitats suggests that the vegetation on Pod Mrčaru offers more protection to lizards. Also, plasticine models of lizards, laid out on the islands, less often exhibited signs of being attacked by birds on Pod Mrčaru than on Pod Kopište. Our findings provide an example of how changes in (possibly a single) environmental factor may simultaneously produce responses in behaviour, morphology and whole-animal physiology, and this on a surprisingly small spatial and temporal scale.

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Unforeseen effects of ecosystem restoration on yellow-legged gulls in a small western Mediterranean island

Cited by 15 publications

References 21 publications

Natural cavity restoration as an alternative to nest box supplementation

Natural cavity restoration as an alternative to nest box supplementation

Deconstructing myths on large gulls and their impact on threatened sympatric waterbirds

Differences in morphology, performance and behaviour between recently diverged populations of Podarcis sicula mirror differences in predation pressure

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