Climate forcing on avian life history

In the 21st century, human-induced global climate change has been highlighted as one of the most serious threats to ecosystems worldwide. According to global climate scenarios, the mean temperature in Finland is expected to increase by 1.8 4.0°C by the end of the century. The regional and seasonal change in temperature has predicted to be spatially and temporally asymmetric, where the High-Arctic and Antarctic areas and winter and spring seasons have been projected to face the highest temperature increase. To understand how species respond to the ongoing climate change, we need to study how climate affects species in different phases of their life cycle. The impact of climate on breeding and migration of eight large-sized bird species was studied in this thesis, taking food availability into account. The findings show that climatic variables have considerable impact on the life-history traits of large-sized birds in northern Europe. The magnitude of climatic effects on migration and breeding was comparable with that of food supply, conventionally regarded as the main factor affecting these life-history traits. Based on the results of this thesis and the current climate scenarios, the following not mutually exclusive responses are possible in the near future. Firstly, asymmetric climate change may result in a mistiming of breeding because mild winters and early spring may lead to earlier breeding, whereas offspring are hatching into colder conditions which elevate mortality. Secondly, climate induced responses can differ between species with different breeding tactics (income vs. capital breeding), so that especially capital breeders can gain advantage on global warming as they can sustain higher energy resources. Thirdly, increasing precipitation has the potential to reduce the breeding success of many species by exposing nestlings to more severe post-hatching conditions and hampering the hunting conditions of parents. Fourthly, decreasing ice cover and earlier ice-break in the Baltic Sea will allow earlier spring migration in waterfowl. In eiders, this can potentially lead to more productive breeding. Fifthly, warming temperatures can favour parents preparing for breeding and increase nestling survival. Lastly, the climate-induced phenological changes in life history events will likely continue. Furthermore, interactions between climate and food resources can be complex and interact with each other. Eiders provide an illustrative example of this complexity, being caught in the crossfire between more benign ice conditions and lower salinity negatively affecting their prime food resource. The general conclusion is that climate is controlling not only the phenology of the species but also their reproductive output, thus affecting the entire population dynamics.Globaali ilmastonmuutos on nostettu 2000-luvulla yhdeksi suurimmista uhkista maailman ekosysteemeille. Ilmastoennusteiden perusteella maapallon keskilämpötilan on ennustettu nousevan 1.8 4.0 astetta kuluvan vuosisadan loppuun mennessä. Muutosten on esitetty olevan ajallisesti ja paikallisesti epäsymmetristä: lämpötilan nousu on voimakkainta napa-alueilla sekä talvi- ja kevätkuukausina. Ymmärtääksemme, miten lajit pystyvät vastaamaan muuttuviin ilmasto-oloihin, on tutkittava miten ilmastotekijät vaikuttavat lajeihin eri elinkierron vaiheissa. Tässä tutkimuksessa selvitettiin, miten ilmasto vaikutti muuton ajoittumiseen ja pesintään kahdeksalla suurikokoisella lintulajilla ottaen ravinto-olosuhteet huomioon. Tulokset osoittavat, että ilmastomuuttujilla on useilla lajeilla yhtä suuri merkitys pesintään kuin ravinnolla, jota on perinteisesti pidetty keskeisenä lisääntymiseen vaikuttavana tekijänä. Tulosten ja vallitsevien ilmastoskenaarioiden perusteella muuttuvan ilmaston on ennustettavissa vaikuttaa Pohjois-Euroopan lintulajeihin seuraavilla tavoilla. Lämpenevä lopputalvi ja alkukevät aikaistavat kevätmuuttoa ja pesintää. Toiseksi, lämpimämpi alkukesä parantaa ja sateisempi alkukesä heikentää pesimämenestystä. Kolmanneksi, voimakkaasti lämmennyt alkukevät voi johtaa yhä aikaisempaan pesimäkauden aloitukseen. Koska epäsymmetrisen ilmastonmuutoksen myötä loppukevät ja alkukesä eivät kuitenkaan ole lämmenneet yhtä voimakkaasti kuin alkukevät, saattavat jälkeläiset kuoriutua aikaistuneen pesinnän takia yhä kylmempiin olosuhteisiin, mikä voi heikentää pesimämenestystä. Neljänneksi, lajit, jotka kartuttavat lisääntymistä varten tarvitsemansa vararavintonsa pitkällä aikavälillä ennen pesintää (ns. capital breeder lajit, kuten haahka, viirupöllö), saattavat hyötyä lämpenemisestä, koska lämpimän talven ja kevään aikana vararavinnon kartuttaminen ja ylläpitäminen on helpompaa kuin kylminä kausina. Viidenneksi, vähenevä jääpeite ja aikaisempi jäänlähtö mahdollistaa aikaisemman vesilintujen kevätmuuton, mikä haahkalla voi johtaa parantuneeseen pesimämenestykseen. Ilmaston ja ravinto-olosuhteiden väliset yhteisvaikutukset ovat kuitenkin usein monimutkaisia. Tästä erinomainen esimerkki on Itämeren haahkakanta, joka saattaa hyötyä leudommista jääoloista. Toisaalta lisääntyvän talvisateisuuden takia Itämeren suolapitoisuuden on ennustettu laskevan heikentäen haahkan pääravintokohteen sinisimpukan elinolosuhteita, mikä voi supistaa haahkan levinneisyysaluetta. Johtopäätöksenä voidaan todeta, että ilmasto säätelee niin lajien fenologiaa kuin myös lisääntymismenestystä vaikuttaen siten lajien kannankehitykseen

What do birds tell us about recent changes in the environment?

The loss of biodiversity has become an increasingly important topic of societal discussions. However, measuring biodiversity loss is not easy compared to for instance documenting the other environmental crisis, the climate change. Therefore, different tools are needed to measure whether biodiversity has changed, and how it reflects known habitat changes and possible conservation actions. Birds have been used in many countries as indicators of environmental status. There are several reasons for this. There is a large number of bird enthusiasts around the world who collect data on species. This has led to the accumulation of a considerable amount of long-term data on birds, and the amount of data is increasing every year. Because birds are at the top of the food chain, which means that their numbers are likely to reflect changes at lower trophic levels. Birds are also ubiquitous in a variety of environments and every human knows something about birds, which greatly facilitates the popularisation of science and communication of the impacts of habitat change

Role of forest ditching and agriculture on water quality: connecting the long-term physico-chemical subsurface state of lakes with landscape and habitat structure information.

Increasing anthropogenic pressures have affected the status of surface freshwater ecosystems. Eutrophication, water browning, acidification, and several other processes may be channelled through the food web. In this study, we evaluate the role of hydrology impacting anthropogenic pressures, flows from urban, farmland and ditched forest areas, and how they explain the physico-chemical quality of lakes and ponds in the boreal biome of Finland. We study the long-term effect around 445 waterfowl survey sites that had physico-chemical measurements (total phosphorus, total nitrogen, pH, water clarity and colour) produced by Finnish environmental authorities done in years 1986-2020. Furthermore, we investigate whether a long-term national-level citizen science study focusing on rather robust visible habitat structures measured by the volunteers can reveal physicochemical water quality using data from >270 lakes where the waterfowl habitat survey and physico-chemical measurements could be spatio-temporally matched. Farmland occurrence around the lakes was positively associated with pH, colour and nutrient concentrations but negatively associated with water clarity. Furthermore, ditch length was positively associated with nitrogen concentration and water colour, while being negatively associated with pH and water clarity. Overall, the studied lakes showed a negative trend in nutrients and clarity but a positive trend in pH and colour. As expected, nutrient concentration increased and clarity decreased along the gradient from oligotrophic to eutrophic lake habitat classifications, which suggests that the citizen science classification seem to reflect the subsurface physico-chemical status of the lakes. We conclude that farming and forest ditching practices in particular seem to associate with the state of the study lakes and that the ecological impacts of intensified turbidity and brownification in wetland ecosystems should be studied further in the future. Sustainable improvement of water quality rests upon scientific understanding of biogeochemical processes in lake ecosystems and the primary sources of the nutrient and sediment loading. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Snow depth drives habitat selection by overwintering birds in built-up areas, farmlands and forests

Aim Abundances of animals vary according to species-specific habitat selection, but habitats are undergoing rapid change in response to anthropogenic alterations of land use and climate. The long-term decline of snowfall is one of the most dramatic abiotic changes in boreal regions, with potential to alter species communities and shape future ecosystems. However, the effects of snow cover on habitat-specific abundances remain unclear for many taxa. Here we explore whether long-term declines in snow cover affect the abundances of overwintering birds. Taxon Fifty bird species. Location Finland, Northern Europe. Methods We used generalized linear mixed models to analyse citizen-led monitoring data from 196 transects over a 32-year period to assess whether abundances of birds have changed in built-up areas, farmlands and forests, and whether these covary with warming temperatures and decreasing snow. We then explored if changes in abundance can be explained by body mass, migration strategy or feeding guilds of the species. Results Over the study period, the abundance of overwintering birds increased. This increase was most pronounced in farmlands (69.6%), where abundances were positively associated with decreasing snow depth. On the other hand, while abundances in built-up habitats (19.5%) decreased over the study period, they increased in periods of high snow depths. Finally, we found that the short-distance migration strategy explains changes in bird abundances with snow. In farmlands, ground feeding birds and heavier birds also show a positive trends in abundance with decreasing snow depths. Main conclusions Local snow conditions are driving habitat selection of birds in the winter; birds in farmlands were most responsive to a decrease in snow depth. Changing snow depths can affect bird movements across habitats in the winter, but also influence migratory patterns and range shifts of species.Peer reviewe

Counteracting wetland overgrowth increases breeding and staging bird abundances

Human actions have led to loss and degradation of wetlands, impairing their suitability as habitat especially for waterbirds. Such negative effects may be mitigated through habitat management. To date scientific evidence regarding the impacts of these actions remains scarce. We studied guild specific abundances of breeding and staging birds in response to habitat management on 15 Finnish wetlands. In this study management actions comprised several means of vegetation removal to thwart overgrowth. Management cost efficiency was assessed by examining the association between site-specific costs and bird abundances. Several bird guilds exhibited positive connections with both habitat management as well as with invested funds. Most importantly, however, red-listed species and species with special conservation concern as outlined by the EU showed positive correlations with management actions, underlining the conservation value of wetland management. The results suggest that grazing was especially efficient in restoring overgrown wetlands. As a whole this study makes it clear that wetland habitat management constitutes a feasible conservation tool. The marked association between invested funds and bird abundance may prove to be a valuable tool for decision makers when balancing costs and impact of conservation measures against one another.Peer reviewe

Advanced Autumn Migration of Sparrowhawk Has Increased the Predation Risk of Long-Distance Migrants in Finland

Predation affects life history traits of nearly all organisms and the population consequences of predator avoidance are often larger than predation itself. Climate change has been shown to cause phenological changes. These changes are not necessarily similar between species and may cause mismatches between prey and predator. Eurasian sparrowhawk Accipiter nisus, the main predator of passerines, has advanced its autumn phenology by about ten days in 30 years due to climate change. However, we do not know if sparrowhawk migrate earlier in response to earlier migration by its prey or if earlier sparrowhawk migration results in changes to predation risk on its prey. By using the median departure date of 41 passerine species I was able to show that early migrating passerines tend to advance, and late migrating species delay their departure, but none of the species have advanced their departure times as much as the sparrowhawk. This has lead to a situation of increased predation risk on early migrating long-distance migrants (LDM) and decreased the overlap of migration season with later departing short-distance migrants (SDM). Findings highlight the growing list of problems of declining LDM populations caused by climate change. On the other hand it seems that the autumn migration may become safer for SDM whose populations are growing. Results demonstrate that passerines show very conservative response in autumn phenology to climate change, and thus phenological mismatches caused by global warming are not necessarily increasing towards the higher trophic levels.Peer reviewe

Protected areas act as a buffer against detrimental effects of climate change-Evidence from large-scale, long-term abundance data

Climate change is driving species to shift their distributions toward high altitudes and latitudes, while habitat loss and fragmentation may hamper species ability to follow their climatic envelope. These two drivers of change may act in synergy, with particularly disastrous impacts on biodiversity. Protected areas, PAs, may thus represent crucial buffers against the compounded effects of climate change and habitat loss. However, large-scale studies assessing the performance of PAs as such buffers remain scarce and are largely based on species occurrence data. Conversely, abundance data have proven to be more reliable for addressing changes in wildlife populations under climate change. We evaluated changes in bird abundance from the 1970s-80s to the 2000s inside and outside PAs at the trailing range edge of 30 northern bird species and at the leading range edge of 70 southern species. Abundances of retracting northern species were higher and declined less inside PAs at their trailing range edge. The positive effect of PAs on bird abundances was particularly marked in northern species that rely strongly on PAs, that is, their density distribution is largely confined within PAs. These species were nearly absent outside PAs in the 2000s. The abundances of southern species were in general lower inside PAs and increased less from the 70s-80s to 2000s. Nonetheless, species with high reliance on PAs had much higher abundances inside than outside PAs in the 2000s. These results show that PAs are essential in mitigating the retraction of northern species, but also facilitate northward expansions of southern species highly reliant on PAs. Our study provides empirical evidence documenting the role of PAs in facilitating species to adjust to rapidly changing climatic conditions, thereby contributing to the mitigation of impending biodiversity loss. PAs may thus allow time for initiating wider conservation programs on currently unprotected land.Peer reviewe