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Spatial structure of fruit abundance and frugivore abundance at the bird assemblage level. (a) Maps showing the spatial distribution of total fruit abundance (estimated as the pulp dry mass in grams) and abundance of frugivores recorded in the 6-ha study plot during 2 years. (b) Correlograms of fruit abundance (circles) and total abundance of fruit-eating birds (diamonds) recorded during 2 years in 20 × 20 m cells; filled symbols show lag distances with a significant (P < 0·05) Moran's I value. (c) Scatter plot of frugivore and fruit abundances by cell and their relationship estimated with a spatial autoregressive model (SAR).

Spatial structure of fruit abundance and frugivore abundance at the bird assemblage level. (a) Maps showing the spatial distribution of total fruit abundance (estimated as the pulp dry mass in grams) and abundance of frugivores recorded in the 6-ha study plot during 2 years. (b) Correlograms of fruit abundance (circles) and total abundance of fruit-eating birds (diamonds) recorded during 2 years in 20 × 20 m cells; filled symbols show lag distances with a significant (P < 0·05) Moran's I value. (c) Scatter plot of frugivore and fruit abundances by cell and their relationship estimated with a spatial autoregressive model (SAR).

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1. The fruit-tracking hypothesis predicts spatiotemporal links between changes in the abundance of fruit-eating birds and the abundance of their fleshy-fruit resources. 2. While the spatial scale of plant–frugivore interactions has been explored to understand mismatches between observed and expected fruit–frugivore patterns, methodological issues s...

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... total abundance of fruit-eating birds recorded per cell along the study period varied between 12 and 58 (n = 4949) and tended to be distributed in small patches, as displayed in the plot map (Fig. 4a). This is also sug- gested by a positive and significant spatial autocorrelation found at short distances (Fig. 4b). The total abundance of fruits for the assemblage showed a marked spatial structure through the gradient of distances in the plot (Fig. 4a-b). The SAR model of the relationship between fruit and frugivore abundance was not ...
Context 2
... total abundance of fruit-eating birds recorded per cell along the study period varied between 12 and 58 (n = 4949) and tended to be distributed in small patches, as displayed in the plot map (Fig. 4a). This is also sug- gested by a positive and significant spatial autocorrelation found at short distances (Fig. 4b). The total abundance of fruits for the assemblage showed a marked spatial structure through the gradient of distances in the plot (Fig. 4a-b). The SAR model of the relationship between fruit and frugivore abundance was not significant (R 2 = 0·11, F 1,150 = 3·15, P = 0·08; Fig. 4c) and had a lower AICc (Akaike Information Criterion ...
Context 3
... and 58 (n = 4949) and tended to be distributed in small patches, as displayed in the plot map (Fig. 4a). This is also sug- gested by a positive and significant spatial autocorrelation found at short distances (Fig. 4b). The total abundance of fruits for the assemblage showed a marked spatial structure through the gradient of distances in the plot (Fig. 4a-b). The SAR model of the relationship between fruit and frugivore abundance was not significant (R 2 = 0·11, F 1,150 = 3·15, P = 0·08; Fig. 4c) and had a lower AICc (Akaike Information Criterion corrected for sample size) value than a OLS model (R 2 = 0·03, F 1,150 = 3·88, P = 0·05). The total fruit availability for the fruit-eating ...
Context 4
... and significant spatial autocorrelation found at short distances (Fig. 4b). The total abundance of fruits for the assemblage showed a marked spatial structure through the gradient of distances in the plot (Fig. 4a-b). The SAR model of the relationship between fruit and frugivore abundance was not significant (R 2 = 0·11, F 1,150 = 3·15, P = 0·08; Fig. 4c) and had a lower AICc (Akaike Information Criterion corrected for sample size) value than a OLS model (R 2 = 0·03, F 1,150 = 3·88, P = 0·05). The total fruit availability for the fruit-eating assemblage also showed a strong spatial gradient (Fig. 5a), but the frequency of frugivory per cell (range, 0-29; n = 1272) had a very weak ...

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... Changes in propagule pressure due to changes in human activities have led to an increase of invasive woody species in mountainous areas across central and northern Argentina (Giorgis et al. 2011), and some of these species are having increasing impacts on native ecosystems. Many of these invasive species are bird-dispersed and their success is likely due to the attractiveness of the fleshy fruits to frugivorous birds facilitating dispersal (Gosper et al. 2005), which is enhanced by the availability of the fruit of some non-native species during seasons when the fruits of native species are scarce (Rouges and Blake 2001;Blendinger et al. 2012). Pyracantha is one such species, and it should be a major cause for concern, because it is currently in the early stages of invasion in some mountainous areas of northwestern Argentina. ...
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... Birds are considered the main frugivores and dispersers in the Cerrado biome (Kuhlmann & Ribeiro 2016), and their abundance and the variety of their diets are directly related to the richness and abundance of the available fruits (Darosci et al. 2017). Some of these frugivores may to forage in numerous gallery forests to exploit the diversity of fruits (Blendinger et al. 2012) to supplement their diet (Whelan et al. 1998), thus increasing the range of seed dispersal within a region, as was found by Morales et al. (2013). Although fleshy-fruited tree species communities in tropical forests can be limited to just a few hyper-abundant species, these locally abundant species may play an important role as food for frugivores Staggemeier et al. 2017). ...
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Thesis
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... Interestingly, within the same area, foraging habitat selection may be predicted by food abundance for species exploiting easily assessable resources (i.e. fruits), and by proximate cues, such as vegetation structure, in species relying on less assessable resources like insects (Martin 1998, Wolfe et al. 2014), but drivers may be species-specific (Blendinger et al. 2012) and even individual-specific (i.e. conspecific attraction, site familiarity, age, sex; Piper 2011, Spiegel et al. 2017). ...
Thesis
Abstract (ENG) Although considered globally important areas for birds and biodiversity in general, mountain regions remain poorly studied despite their renowned susceptibility to climatic alterations. Basic knowledge of bird species inhabiting these regions is scarce, and even a univocal definition of mountain regions lacks, as interpretations vary across countries and institutions. These ambiguities may prevent the definition of effective large-scale conservation strategies, and it is urgent to define “mountain birds” and investigate the potential impact of climate change on such species. In this thesis, we reviewed evidence for impacts of climate change on Holarctic mountain bird populations in terms of physiology, phenology, trophic interactions, demography and observed and projected distribution shifts, including effects of other factors that interact with climate change. We introduced for the first time an objective classification of mountain bird specialists and generalists, presented the results of a systematic review and meta-analysis of the effects of climate change on Holarctic mountain and upland birds, quantifying the general responses to climate change including altitudinal shifts, changes in life history traits and assessment of mitigation actions. Using Italy as a case-study, we demonstrated a relationship between climate and changes in bird distribution in the last 30-years, by comparing net range variation in cold-adapted and closely related control species. In addition, using the white-winged snowfinch Montifringilla nivalis (a mountain indicator species sensitive to climate change) as a model species, we aimed at improving the knowledge on biology, ecology and demographic aspects of this species to better elucidate the mechanisms driving declines of mountain birds. Finally, we developed adaptation frameworks for climate change at both large and small scale. For the first case, we established a novel approach for selecting conservation priorities, resistant units and resilient areas in the Italian Alps according to structural connectivity and future distribution for a range of mountain bird species to identify strategies that maximize the chances of species persistence in a changing climate. At a finer scale, we evaluated the role of microhabitats as refugia for climate-threatened species, and developed a theoretical approach based on human-mediated actions (i.e. grazing, mowing) to contain the detrimental effects of climate change on our study species, the white winged-snowfinch. We identified 2316 bird species breeding in the Holarctic realm, 818 (35.3%) of which were defined as either high-elevation mountain specialists (n = 324 species) or mountain generalists (n = 494 species). We found evidence of biological and ecological responses of mountain birds to climate and environmental change, but little is known about underlying mechanisms or synergistic effects. Meta-analyses did not find a consistent direction in elevation change to track suitable climate but suggested that in the future mountain birds will be significantly more impacted than non-mountain species. In Italy, we found a strong positive correlation between change in range size and species thermal index (STI: average temperature of a species’ European range), confirming that recent climatic warming has favoured species of warmer climates and adversely affected species occupying colder areas. A model including STI and birds’ associated habitats was not so strongly supported but further suggested that forest species performed better than alpine open habitat and agricultural ones. Regarding our indicator/model species, we found that the white-winged snowfinch selected specific and climate sensitive microhabitat during the nestling rearing period: cool sites with short grass cover, melting snow margins adjacent to grassland and snow patches. These microhabitats harboured high quality and quantities of invertebrates and snowfinches were able to efficiently tune their microhabitat selection in relation to prey abundance and type, suggesting a high adaptability to resource variation in specie and time, a typical characteristic of high elevation sites. When hindcasting (1976) and forecasting (2066) the suitability of such microhabitats in relation to the observed changes associated to climate change, we found higher suitability in the past and a predicted decline in the future. Grazing activities, which can keep the sward height suitable for snowfinches, could improve the suitability in the present and in the future, but only for population that can have access to extensive grassland areas. For populations confined to more rocky habitats (i.e. subnival and nival), where grassland cover is generally low or even absent, this mitigation may not be applicable and snowfinches living in these habitats could be more at risk from climate change, as they largely rely on snow patches. Measures for adaptation to climate change mostly relied on broad-scale management and extension of protected areas for species already present and for future colonizers from lower elevations. We suggested the development of management/restoration plans in mountain areas that consider threats and opportunities resulting from interactions of climate and land-use changes and encompass different spatial scales, from landscape to microhabitats. Riassunto (ITA) Le regioni montane, sebbene considerate aree globalmente importanti per gli uccelli e la biodiversità in generale, rimangono scarsamente studiate, nonostante la loro ben nota suscettibilità alle alterazioni climatiche. La conoscenza di base delle specie di uccelli che popolano queste regioni è scarsa, e manca persino una definizione condivisa di “regioni montane”, in quanto le interpretazioni variano in base a paesi e istituzioni. Queste ambiguità possono potenzialmente precludere la delineazione di efficaci strategie di conservazione su larga scala, ed è quindi urgente dare una definizione univoca di “avifauna di montagna” per poter indagare il potenziale impatto dei cambiamenti climatici su queste comunità di specie. In questa tesi abbiamo esaminato le evidenze degli impatti dei cambiamenti climatici sulle popolazioni di avifauna di montagna su scala olartica, riguardo a fisiologia, fenologia, interazioni trofiche, demografia e spostamenti di distribuzione osservati e previsti, considerando anche gli effetti di ulteriori fattori che interagiscono con i cambiamenti climatici, esacerbandone o attenuandone gli effetti. Per la prima volta abbiamo formulato una classificazione oggettiva dell’avifauna di montagna “specialista” e “generalista” e presentato i risultati di una revisione sistematica e di una meta-analisi riguardanti gli effetti dei cambiamenti climatici sugli uccelli montani, quantificando le conseguenze di tali alterazioni, come gli spostamenti altitudinali o i cambiamenti nei tratti biologici, e la valutazione di potenziali azioni mitigatrici e di compensazione degli impatti dovuti alle variazioni nel clima. Utilizzando l'Italia come caso-studio, abbiamo dimostrato l’esistenza di una relazione tra il clima e i cambiamenti nella distribuzione degli uccelli negli ultimi 30 anni, confrontando gli andamenti di occupazione ed abbandono di aree riproduttive da parte di specie legate ad ambienti freddi e di specie-controllo tassonomicamente vicine ma presenti in climi più miti. Inoltre, abbiamo utilizzato il fringuello alpino Montifringilla nivalis come specie modello (in quanto particolarmente sensibile ai cambiamenti climatici), al fine di migliorare le attuali conoscenze su biologia, ecologia e aspetti demografici delle specie d’alta quota, e chiarire meglio così i meccanismi che determinano il declino dell’avifauna di montagna. Infine, abbiamo sviluppato degli approcci conservazionistici innovativi per far fronte agli impatti del cambiamento climatico, su larga scala e poi su piccola scala. Nel primo caso, per identificare strategie che massimizzino le possibilità di persistenza delle specie in un clima che cambia, abbiamo stabilito nuove metodologie che hanno consentito di identificare nelle Alpi italiane le specie e le aree prioritarie per la conservazione (unità geografiche resistenti e resilienti ai mutamenti climatici), basandoci su connettività strutturale e previsioni di distribuzione futura di varie specie di avifauna di montagna. A scala più piccola invece abbiamo valutato il ruolo dei microhabitat come siti di rifugio per le specie minacciate dal clima, e sviluppato un approccio teorico basato sulla capacità di alcune attività umane (attività di pascolo e sfalcio) di contenere gli effetti dannosi del cambiamento climatico, con particolare riferimento alla nostra specie studio, il fringuello alpino, e alla struttura del suo habitat di foraggiamento. Abbiamo identificato 2316 specie avifaunistiche che si riproducono nell’Olartico, 818 (35,3%) delle quali sono state divise secondo le nostre definizioni in specialiste d’alta quota (n = 324 specie) o generaliste di montagna (n = 494 specie). Abbiamo poi riscontrato evidenze di reazioni biologiche ed ecologiche degli uccelli di montagna al cambiamento climatico ed ambientale, ma l’influenza di meccanismi ed effetti sinergici di altre variabili sono ancora poco conosciuti. Una meta-analisi svolta per valutare gli spostamenti altitudinali degli uccelli di montagna in risposta alle anomalie termali, non ha trovato una direttrice costante nel cambiamento di quota, ma una seconda meta-analisi riguardante le previsioni future ha suggerito che proprio le specie montane saranno significativamente più impattate dai cambiamenti climatici rispetto a specie non-montane. In Italia, abbiamo trovato una forte correlazione positiva tra variazione delle dimensioni degli areali riproduttivi e l’indice termale delle specie (STI: temperatura media di presenza di una specie a scala europea), a conferma del fatto che il recente riscaldamento climatico ha favorito specie di climi più caldi e sfavorito quelle legate ad ambienti più freddi. Un modello che includeva STI e habitat associati agli uccelli è risultato poco supportato, ma ha anche suggerito che le specie forestali hanno avuto variazioni più positive rispetto a specie legate agli habitat aperti alpini o agricoli. Per quanto riguarda la nostra specie modello, abbiamo scoperto che il fringuello alpino durante il periodo riproduttivo, seleziona per il foraggiamento luoghi freddi, caratterizzati da copertura erbosa bassa, margini di neve in scioglimento adiacenti al prato e macchie di neve: microhabitat sensibili al cambiamento climatico e che ospitano un’alta qualità e quantità di invertebrati. I fringuelli alpini sono in grado di selezionare con grande efficienza questi microhabitat in relazione all'abbondanza e al tipo di prede, dimostrando un'alta adattabilità alla variabilità delle risorse trofiche nello spazio e nel tempo, caratteristica tipica delle specie proprie di ambienti d’alta quota. Modellizzando l’idoneità di foraggiamento di questi microhabitat rispetto ai cambiamenti climatici osservati rispetto al passato (1976) e previsti per il futuro (2066), abbiamo riscontrato un’idoneità maggiore di tali siti nel passato e un previsto calo della stessa per il futuro. Le attività di pascolo, in grado di mantenere il manto erboso ad un’altezza adatta ai fringuelli alpini, potrebbero migliorare l'idoneità strutturale attuale e futura di tali microhabitat di foraggiamento, almeno per le popolazioni presenti in habitat adiacenti a prati alpini adibiti a pascolo. Per le popolazioni confinate invece in habitat rocciosi (ad esempio sub-nivali e nivali), dove la copertura erbosa è generalmente bassa o addirittura assente, questa mitigazione non potrà essere applicata, ed i fringuelli alpini di questi habitat, dipendendo principalmente dalla presenza di macchie di neve, potrebbero essere più colpiti/minacciati dai cambiamenti climatici. Le misure per mitigare e compensare gli effetti dei cambiamenti climatici si basano principalmente su una gestione a vasta scala che dovrebbe estendere le attuali aree protette per favorire le specie già presenti ed anche quelle future colonizzatrici provenienti da quote più basse. Abbiamo dunque suggerito lo sviluppo di piani di gestione delle aree montuose che considerino le minacce e le opportunità derivanti dalle interazioni fra cambiamenti climatici, uso del suolo a diverse scale spaziali e conservazione di ambienti chiave dal macro al micro habitat.