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"In a tree by the brook, there's a songbird who sings": Woodlands in an agricultural mateix maintain functionality of a wintering bird community.
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Goswami V R

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Nam Sylem B L

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Vsudev D

2018
The agricultural matrix has increasingly been recognized for its potential to supplement Pro-tected Areas (PAs) in biodiversity conservation. This potential is highly contextual, depending on composition and spatial configuration of matrix elements and their mechanistic relationship with biological communities. We investigate the effects of local vegetation structure, and proximity to a PA on the site-use of different guilds in a wintering bird community within the PA, and in wooded land-use types in the surrounding matrix. We used occupancy models to estimate covariate–guild relationships and predict site-use. We also compared species richness (estimated through capture–recapture models) and species naïve site-use between the PA and the matrix to evaluate taxonomic changes. We found that tree cover did not limit the site- use of most guilds of the community, probably due to high canopy cover across all chosen sites. Exceptions to this were guilds comprising generalist species. Shrub cover and bamboo cover had important effects on some woodland-ass ociated guilds, suggesting a change in limiting factors for site-use under adequate tree cover. Site-use across the matrix was high for all analyzed guilds. This was found to be due to three non-exclusive reasons: (i) presence of one or more ubiquitous species (found all across the landscape) within some guilds, (ii)redun-dancy of species within guilds that buffered against a decrease in site-use, and (iii) turn over in guild composition/abundances to more generalist species from PA to matrix. Estimated species richness was higher in the matrix (107 11; mean SE) than in the PA (90±7), which may have been in part due to the addition of generalist species in the matrix. Understanding factors that limit biological communities is crucial to better managing the ever-increasing matrix for biodiversity conservation. Our study provides insights into the effects of different components of vegetation structure on the bird community in wooded land-use types in the matrix. We highlight the value of woodlands surrounding PAs in maintaining multiple guilds, and hence, the functionality of a wintering bird community. However, we caution that the matrix may fall short in retaining some specialized species of the community.
Seabirds enhance coral reef productivity and functioning in the absence of invasive rats
BRB
Available Online

Carr, Peter.

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Graham, Nicholas A. J.

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Hoey, Andrew S.

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Jennings, Simon.

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MacNeil, M. Aaron

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Wilson, Shaun K.

2018
Biotic connectivity between ecosystems can provide major transport of organic matter and nutrients, influencing ecosystem structure and productivity, yet the implications are poorly understood owing to human disruptions of natural flows. When abundant, seabirds feeding in the open ocean transport large quantities of nutrients onto islands, enhancing the productivity of island fauna and flora. Whether leaching of these nutrients back into the sea influences the productivity, structure and functioning of adjacent coral reef ecosystems is not known. Here we address this question using a rare natural experiment in the Chagos Archipelago, in which some islands are rat-infested and others are rat-free. We found that seabird densities and nitrogen deposition rates are 760 and 251 times higher, respectively, on islands where humans have not introduced rats. Consequently, rat-free islands had substantially higher nitrogen stable isotope (?15N) values in soils and shrubs, reflecting pelagic nutrient sources. These higher values of ?15N were also apparent in macroalgae, filter-feeding sponges, turf algae and fish on adjacent coral reefs. Herbivorous damselfish on reefs adjacent to the rat-free islands grew faster, and fish communities had higher biomass across trophic feeding groups, with 48% greater overall biomass. Rates of two critical ecosystem functions, grazing and bioerosion, were 3.2 and 3.8 times higher, respectively, adjacent to rat-free islands. Collectively, these results reveal how rat introductions disrupt nutrient flows among pelagic, island and coral reef ecosystems. Thus, rat eradication on oceanic islands should be a high conservation priority as it is likely to benefit terrestrial ecosystems and enhance coral reef productivity and functioning by restoring seabird-derived nutrient subsidies from large areas of ocean.