Federico Capelli’s research while affiliated with Museo delle Scienze, Trento, Italy and other places

Microhabitat utilisation holds a pivotal role in shaping a species’ ecological dynamics and stands as a crucial concern for effective conservation strategies. Despite its critical importance, microhabitat use has frequently been addressed as static, centering on microhabitat preference. Yet, a dynamic microhabitat use that allows individuals to adjust to fine-scale spatio-temporal prey fluctuations, becomes imperative for species thriving in challenging environments. High-elevation ecosystems, marked by brief growing seasons and distinct abiotic processes like snowmelt, winds, and solar radiation, feature an ephemeral distribution of key resources. To better understand species’ strategies in coping with these rapidly changing environments, we delved into the foraging behaviour of the white-winged snowfinch Montifringilla nivalis, an emblematic high-elevation passerine. Through studying microhabitat preferences during breeding while assessing invertebrate prey availability, we unveiled a highly flexible microhabitat use process. Notably, snowfinches exhibited specific microhabitat preferences, favoring grass and melting snow margins, while also responding to local invertebrate availability. This behaviour was particularly evident in snow-associated microhabitats and less pronounced amid tall grass. Moreover, our investigation underscored snowfinches’ fidelity to foraging sites, with over half located within 10 m of previous spots. This consistent use prevailed in snow-associated microhabitats and high-prey-density zones. These findings provide the first evidence of dynamic microhabitat use in high-elevation ecosystems and offer further insights into the crucial role of microhabitats for climate-sensitive species. They call for multi-faceted conservation strategies that go beyond identifying and protecting optimal thermal buffering areas in the face of global warming to also encompass locations hosting high invertebrate densities.

During breeding, parents of avian species must increase their foraging efforts to collect food for their offspring, besides themselves. Foraging trips are thus a key aspect of the foraging ecology of central-place foragers when rearing their offspring. However, studies of the foraging ecology of high-elevation specialists inhabiting harsh environments are scarce. Here we report for the first time quantitative information on ecological determinants of foraging trips in the White-winged Snowfinch (Montifringilla nivalis), a high-elevation specialist threatened by climate warming. We focused on seasonal, meteorological , habitat and social factors affecting distance and duration of foraging trips performed during nestling rearing, recorded by visual observations in the Italian Alps. Based on 309 foraging trips from 35 pairs, we found that trips lasted 6.12 min and foraging areas were located at 175 m from the nest site on average. Trip duration was affected by snow cover (longer at intermediate cover), distance travelled and wind, while distance travelled was affected by snow cover (being higher at intermediate cover) and trip duration. Foraging individuals thus travelled farther and spent more time at areas characterized by intermediate snow cover, implying the presence of snow margins. It is likely that at such snow patches/margins snowfinches collected food for self-maintenance, besides that for their offspring, or collected more food items. Any reduction of snow cover during the breeding season, as expected under current climate warming, will severely alter foraging habitat suitability. Conserving suitable foraging habitats in the nest surroundings will be crucial to buffer such negative impacts.

Capsule: Fine-scale use of climate-sensitive habitats by White-winged Snowfinches Montifringilla nivalis is affected by landscape composition, which thus modulates the potential impact of climate change. Aims: To explore the fine-scale habitat use for foraging by breeding White-winged Snowfinches, with the aim of identifying the potential impacts of climate change on their dependence on habitat characteristics in the wider landscape, which could shape the species’ response to climate change. Pairs mostly relying on snow could be at higher risk due to a decrease in spring snow-cover, but the reliance on snow may be mediated by the presence of alternative habitats in the landscape. Methods: The White-winged Snowfinch uses alpine grassland, snowfields and melting snow margins for capturing prey during nestling rearing and is threatened by earlier snowmelt induced by climate change. We investigated habitat use in 17 Snowfinch pairs in relation to landscape composition within a 300 m buffer around their nests. Results: The use of snowfields and snow-bare margins was positively associated with wind intensity (probably due to greater wind-borne arthropod fallout with wind), and negatively associated with grassland cover (i.e. the main alternative habitat) and date within the season. Conclusions: Fine-scale habitat selection was affected by landscape composition: the availability of patches of alternative habitats decreased the reliance on more climate-sensitive resources, modulating the potential impact of climate change. Coupling assessments of fine-scale resource selection with broader habitat descriptors, which are easier to assess over broader scales, may help understand and predict climate change impacts.

The majority of predictions about the impacts of climate change on wildlife have relied either on the study of species' physiological tolerance or on broad-scale distribution models. In comparison, little attention has been paid to species' mechanistic responses to fine-grained, climate-induced modifications of habitat suitability. However, such studies would be pivotal to the understanding of species' ecological requirements (and hence their adaptive potential to environmental change) and the design of management strategies. We investigated foraging microhabitat selection in a potentially climate-change sensitive species, the white-winged snowfinch Montifringilla nivalis, during the breeding season in the Alps. Our microhabitat selection model considered topography, ground-cover variables and sward height within a 5-m radius at foraging and control locations. Habitat selection was positively affected by grassland cover, negatively by sward height and quadratically by snow cover (optimum around 40%); birds avoided anthropized (urban areas, roads) sites. We estimated past (1976) and future (2066) climate-driven changes in foraging microhabitat suitability, assuming a progressively earlier date of snowmelt due to increasing temperatures over this entire time span. We then modelled the potential impact of snowmelt (and related sward height) on habitat suitability under two scenarios: maintaining the current situation (i.e. irregular seasonal grazing) and implementing targeted management in an attempt to mitigate impacts of earlier snowmelt. Predicted foraging habitat suitability (estimated as the fraction of suitable plots) significantly declined over time (−23% between 1976 and 2016, further 32% loss by 2066). However, model outputs demonstrated that maintaining sward height below 6 cm on breeding grounds (e.g. by regular grazing) would significantly decrease the predicted loss of suitable foraging habitat. Detailed information about patterns of resource exploitation allows the identification of mechanistic, functional responses of species to environmental change, and enables an evaluation of habitat management options that can buffer against the detrimental effects of global warming.bi

Sull’arco alpino gli effetti dei cambiamenti climatici hanno già causato importanti alterazioni ad habitat e specie. In Italia specie legate ad ambienti freddi hanno subito contrazioni di areale più forti rispetto a specie legate ad ambienti caldi. Il fringuello alpino Montifringilla nivalis è nidificante su Alpi e Appennini in habitat alpini, sub-nivali e nivali ed è considerato un ottimo indicatore dei cambiamenti climatici. Il progetto Nivalis nasce proprio con lo scopo di studiare gli effetti dei cambiamenti climatici e ambientali usando il fringuello alpino come specie indicatrice. La sensibilità della specie ai cambiamenti climatici è evidenziata nei modelli di idoneità ambientale i quali prevedono un calo fino al 84% (nello scenario climatico peggiore) dei siti idonei alla presenza della specie entro il 2050. Per questo motivo abbiamo studiato l’ecologia di foraggiamento di 18 coppie diverse di fringuello alpino al Parco Nazionale dello Stelvio (PSN) dimostrando come questa specie prediliga siti di foraggiamento freddi, caratterizzati dalla presenza di chiazze di neve ed erba bassa, ma anche roccia e suolo nudo, habitat particolarmente sensibili ai cambiamenti climatici. ll progetto, inoltre, si è occupato di posizionare una quarantina di cassette nido presso il Parco Naturale Paneveggio Pale di San Martino (PNPPSM) e al PSN. Queste cassette hanno un duplice scopo: aumentare i siti di nidificazione favorevoli e facilitare la raccolta di variabili demografiche necessarie per comprendere la dinamica di popolazione. Monitoraggi precedenti all’installazione delle cassette nido hanno evidenziato come nelle due aree studio i fringuelli alpini nidifichino preferibilmente in contesti differenti. Presso PNPPSM i fringuelli alpini nidificano quasi esclusivamente su pareti rocciose verticali alte e inaccessibili. Al PSN la nidificazione avviene più frequentemente su strutture antropiche, come rifugi e impianti di risalita. È forse per questi motivi “abitudinari” che al PNPPSM non ci sono stati tentativi di nidificazione su cassette nido da parte di fringuello alpino (ma di altre specie come il codirosso spazzacamino). Al PNS sono invece state occupate 5 cassette nido, per un totale di 16 pulli inanellati con anello metallico. Nell’autunno 2017 saranno installate 5 cassette nell’area del PNPPSM e 10 nel PNS. In futuro, sarebbe auspicabile l’ampliamento dell’area di studio nelle regioni e province limitrofe.

High-elevation species are expected to be vulnerable to climate warming and to experience dramatic range contractions in the coming decades. Indeed, climate change in high-altitude biota has proceeded at a faster pace compared to lowlands. Understanding basic ecological features of mountain species, such as their foraging ecology, may be useful to further our understanding of the mechanisms dictating species distributions and their responses to global warming, ultimately improving conservation strategies. In this study, we investigated foraging habitat selection of the poorly studied Alpine White-Winged Snowfinch Montifringilla nivalis during the nestling rearing period (June–July) in the Italian Alps. Pair members from 18 different nests were visually followed for 1 day or until we obtained 10 foraging locations. At foraging and control plots (equal numbers per breeding pair; control plots within 300 m of the nest, the average exploited radius according to literature) we recorded habitat variables (habitat types/heterogeneity, sward height, slope, solar radiation). We built models of foraging habitat selection and evaluated whether the selection of climate-related variables varied with temperature and season progression. Snowfinches preferred to forage at colder (low solar radiation) sites, with snow patches and short grasses, some boulders and bare ground, and shifted towards sites with increasingly lower solar radiation after the first week of July. Snow patches are likely to provide both arthropod fallout and suitable sites for invertebrates at their melting margins. Short herbaceous layers likely improved invertebrate detectability in addition to their abundance. These results suggested that climate change may impact on the foraging ecology of this species: warming may reduce the availability of snow patches and favor a denser and taller sward, and may reduce the time frame within which melting snow patches are highly profitable. Hence, the fine-scale habitat requirements of foraging Snowfinches highlight the species’ potential high sensitivity to anthropogenic climate warming.