A review and meta-analysis of the effects of climate change on Holarctic mountain and upland bird populations

Mountain regions are globally important areas for biodiversity but are subject to multiple human-induced threats, including climate change, which has been more severe at higher elevations. 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 developed an objective classification of high-elevation, mountain specialist and generalist species, based on the proportion oftheir breeding range occurring in mountain regions. Our review found evidence of responses of mountain bird populations to climate (extreme weather events, temperature, rainfall and snow) and environmental (i.e. land use) change, but we know little about either the underlying mechanisms or the synergistic effects of climate and land use. Long-term studies assessing reproductive success or survival of mountain birds in relation to climate change were rare. Few studies have considered shifts in elevational distribution over time and a meta-analysis did not find a consistent direction in elevation change. A meta-analysis carried out on future projections of distribution shifts suggested that birds whose breeding distributions are largely restricted to mountains are likely to be more negatively impacted than other species. Adaptation responses to climate change rely mostly on managing and extending current protected areas for both species already present, and for expected colonizing species that are losing habitat and climate space at lower elevation. However, developing effective management actions requires an improvement in the current knowledge of mountain species ecology, in the quality of climate data and in understanding the role of interacting factors. Furthermore, the evidence was mostly based on widespread species rather than mountain specialists. Scientists should provide valuable tools to assess the status of mountain birds, for example through the development of a mountain bird population index, and policy-makers should influence legislation to develop efficient agri-environment schemes and forestry practices for mountain birds, as well as to regulate leisure activities at higher elevations.Peer reviewe

Weather, sex and body condition affect post‑fledging migration behaviour of the greater flamingo Phoenicopterus roseus

Abstract Background Understanding which intrinsic and extrinsic factors dictate decision-making processes such as leaving the natal area or not (migratory vs resident strategy), departure time, and non-breeding destination are key-issues in movement ecology. This is particularly relevant for a partially migratory meta-population in which only some individuals migrate. Methods We investigated these decision making-processes for 40 juvenile greater flamingos Phoenicopterus roseus fledged in three Mediterranean colonies and equipped with GPS-GSM devices. Results Contrary to the body size and the dominance hypotheses, juveniles in better body condition were more likely to migrate than those in worse conditions, which opted for a residence strategy. Flamingo probability of departure was not associated with an increase in local wind intensity, but rather with the presence of tailwinds with departure limited to night-time mostly when the wind direction aligned with the migratory destination. Moreover, a positive interaction between tailwind speed and migration distance suggested that juveniles opted for stronger winds when initiating long-distance journeys. In contrast to previous studies, the prevailing seasonal winds were only partially aligned with the migratory destination, suggesting that other factors (e.g., adults experience in mix-aged flocks, availability of suitable foraging areas en route, density-dependence processes) may be responsible for the distribution observed at the end of the first migratory movement. We found potential evidence of sex-biased timing of migration with females departing on average 10 days later and flying ca. 10 km/h faster than males. Female flight speed, but not male one, was positively influenced by tailwinds, a pattern most likely explained by sexual differences in mechanical power requirements for flight (males being ca. 20% larger than females). Furthermore, juveniles considerably reduced their flight speeds after 400 km from departure, highlighting a physiological threshold, potentially linked to mortality risks when performing long-distance non-stop movements. Conclusion These results suggest that not only intrinsic factors such as individual conditions and sex, but also extrinsic factors like weather, play critical roles in triggering migratory behaviour in a partially migratory metapopulation

Spatio-temporal variation in the wintering associations of an alpine bird

Many animals make behavioural changes to cope with winter conditions, being gregariousness a common strategy. Several factors have been invoked to explain why gregariousness may evolve during winter, with individuals coming together and separating as they trade off the different costs and benefits of living in groups. These trade-offs may, however, change over space and time as a response to varying environmental conditions. Despite its importance, little is known about the factors triggering gregarious behaviour during winter and its change in response to variation in weather conditions is poorly documented. Here, we aimed at quantifying large-scale patterns in wintering associations over 23 years of the white-winged snowfinch Montifringilla nivalis nivalis. We found that individuals gather in larger groups at sites with harsh wintering conditions. Individuals at colder sites reunite later and separate earlier in the season than at warmer sites. However, the magnitude and phenology of wintering associations are ruled by changes in weather conditions. When the temperature increased or the levels of precipitation decreased, group size substantially decreased, and individuals stayed united in groups for a shorter time. These results shed light on factors driving gregariousness and points to shifting winter climate as an important factor influencing this behaviour.M.d.M.D. was financially supported by the (i) Spanish Ministry of Sciences, Innovation and Universities (no. CGL2016-79764-P) and (ii) a Spanish Ramon y Cajal grant no. RYC-2014-16263. M.B. was partly supported by the project Mediterranean Mosaics II funded by MAVA to Lipu

GABB : A global dataset of alpine breeding birds and their ecological traits

Alpine ecosystems represent varied climates and vegetation structures globally, with the potential to support rich and functionally diverse avian communities. High mountain habitats and species are under significant threat from climate change and other anthropogenic factors. Yet, no global database of alpine birds exists, with most mountain systems lacking basic information on species breeding in alpine habitats, their status and trends, or potential cryptic diversity (i.e., sub-species distributions). To address these critical knowledge gaps, we combined published literature, regional monitoring schemes, and expert knowledge from often inaccessible, data-deficient mountain ranges to develop a global list of alpine breeding bird species with their associated distributions and select ecological traits. This dataset compiles alpine breeding records for 1,310 birds, representing 12.0% of extant species and covering all major mountain regions across each continent, excluding Antarctica. The Global Alpine Breeding Bird dataset (GABB) is an essential resource for research on the ecological and evolutionary factors shaping alpine communities, as well as documenting the value of these high elevation, climate-sensitive habitats for conserving biodiversity.Peer reviewe

GLI UCCELLI ALPINI E IL CAMBIAMENTO CLIMATICO

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.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

Food supplementation does not increase demographic rates in a passerine species of conservation concern

Numerous studies have examined the effects of the provision of supplementary food on aspects of avian reproductive success, but far fewer have gone on to examine the potential positive effects of food supplementation on the demographic rates which are key for population growth rate. Testing for potential effects of food shortage on vital rates is likely to be particularly important in species of high conservation concern, where populations are particularly small, isolated or decreasing rapidly. Here we test the effects of the provision of supplementary food on reproductive success, body condition at fledging and post-fledging survival of ring ouzels (Turdus torquatus), a species of high conservation concern in the UK. However, food supplementation had no detectable effect on any of these parameters. There was no significant difference in return rates of fed and unfed fledglings in the year following hatching, and most post-fledging mortality was apparently caused by predation by raptors and mustelids. We conclude that the supply of invertebrate food sources for nestlings was not a major limiting factor in our study area, at least during this two-year study. Further studies are required to quantify the precise mix of habitats used by ring ouzels, at the appropriate scale, which provide concealment from predators and access to food supplies throughout the spring and summer months

A spatially explicit definition of conservation priorities according to population resistance and resilience, species importance and level of threat in a changing climate

Aim: Human-induced climate change requires conservation strategies incorporating its potential effects on species and communities. Key components of population persistence can be attributed to resistance (the capacity to remain unaffected) or resilience (capacity to absorb and recover) to climate change. In situ climatic refugia can act as resistant distribution units, and ex situ climatic refugia and the corridors to reach them may enhance resilience. We develop a novel approach selecting conservation priorities, resistant units and resilient areas according to structural connectivity and future distribution, to identify strategies that maximize the chances of species persistence in a changing climate. Location: Italian Alps. Methods: Conservation priorities were defined across species according to the regional conservation status and the level of threat from climate change, and across sites according to their suitability for target species and their related potential for population persistence (in situ climatic refugia, i.e., resistant units) or redistribution (ex situ climatic refugia and main corridors according to current and future connectivity, i.e., resilient units). Results: Models suggested a marked loss of suitable area for all species by 2050 (ranging from ~50% for pygmy owl and water pipit, to 84% for snowfinch in the worst scenario), and a general loss of connectivity, which was particularly marked for pygmy owl and snowfinch. The approach applied to Alpine birds of different habitats led to a spatially explicit definition of conservation priorities. Main conclusions: The spatial definition of conservation priorities according to species (regional importance and level of threat), resistance and resilience refines the definition of management/conservation priorities (including protected area definition), complementing the existing approaches to address climate change-induced threats in planning conservation and ecological networks