The population of Europe is expected to fall from ***** million in 2023 to just ***** million people by 2100, in the medium-variant scenario provided in this projection. In the scenario where the population declines even further, the population of Europe may fall to as low as ***** million by 2100, while in the high-variant projection, the population will increase to approximately ***** million.

The population of Europe decreased by approximately 0.09 percent in 2023, falling to an overall total of approximately 743.5 million people. Since 1961, Europe's population growth rate has never exceeded one percent, and was even declining in the late 1990s and between 2020 and 2023.

In 2023, Ukraine had the fastest growing population in Europe. As a result of Ukrainian citizens who had fled Russia's invasion of the eastern European country in 2022 returning to the country in 2023, Ukraine's population grew by 3.68 percent compared to 2022. Excluding this special case, the European countries which saw the greatest population growth in 2023 were Luxembourg, Norway, and Ireland. Overall, Europe's population declined by 0.09 percent in 2022, with this varying by region from a 0.31 percent decline in eastern Europe to an increase of 0.33 percent in northern Europe. All of the countries which saw the largest declines in their population in 2023 were central and eastern European countries which had hosted large numbers of Ukrainian refugees in 2022. Moldova, one of Ukraine's closest neighbours, saw its population decline by 3.6 percent, while Poland's population declined by 2.2 percent, and Slovakia's by 1.8 percent.

In the Cook Islands in 2024, the population decreased by about 2.24 percent compared to the previous year, making it the country with the highest population decline rate in 2024. Of the 20 countries with the highest rate of population decline, the majority are island nations, where emigration rates are high (especially to Australia, New Zealand, and the United States), or they are located in Eastern Europe, which suffers from a combination of high emigration rates and low birth rates.

The population of Europe was estimated to be 742.2 million in 2023, an increase of around 2.2 million when compared with 2013. Over 35 years between 1950 and 1985, the population of Europe grew by approximately 157.8 million. But 35 years after 1985 it was estimated to have only increased by around 38.7 million. Since the 1960s, population growth in Europe has fallen quite significantly and was even negative during the mid-1990s. While population growth has increased slightly since the low of -0.07 percent in 1998, the growth rate for 2020 was just 0.04 percent.

Which European country has the biggest population? As of 2021, the population of Russia was estimated to be approximately 145.9 million and was by far Europe's largest country in terms of population, with Turkey being the second-largest at over 85 million. While these two countries both have territory in Europe, however, they are both only partially in Europe, with the majority of their landmasses being in Asia. In terms of countries wholly located on the European continent, Germany had the highest population at 83.9 million, and was followed by the United Kingdom and France at 68.2 million and 65.4 million respectively.

Characteristics of Europe's population There are approximately 386.5 million females in Europe, compared with 361.2 million males, a difference of around 25 million. In 1950, however, the male population has grown faster than the female one, with the male population growing by 104.7 million, and the female one by 93.6 million. As of 2021, the single year of age with the highest population was 34, at 10.7 million, while in the same year there were estimated to be around 136 thousand people aged 100 or over.

The world population surpassed eight billion people in 2022, having doubled from its figure less than 50 years previously. Looking forward, it is projected that the world population will reach nine billion in 2038, and 10 billion in 2060, but it will peak around 10.3 billion in the 2080s before it then goes into decline. Regional variations The global population has seen rapid growth since the early 1800s, due to advances in areas such as food production, healthcare, water safety, education, and infrastructure, however, these changes did not occur at a uniform time or pace across the world. Broadly speaking, the first regions to undergo their demographic transitions were Europe, North America, and Oceania, followed by Latin America and Asia (although Asia's development saw the greatest variation due to its size), while Africa was the last continent to undergo this transformation. Because of these differences, many so-called "advanced" countries are now experiencing population decline, particularly in Europe and East Asia, while the fastest population growth rates are found in Sub-Saharan Africa. In fact, the roughly two billion difference in population between now and the 2080s' peak will be found in Sub-Saharan Africa, which will rise from 1.2 billion to 3.2 billion in this time (although populations in other continents will also fluctuate). Changing projections The United Nations releases their World Population Prospects report every 1-2 years, and this is widely considered the foremost demographic dataset in the world. However, recent years have seen a notable decline in projections when the global population will peak, and at what number. Previous reports in the 2010s had suggested a peak of over 11 billion people, and that population growth would continue into the 2100s, however a sooner and shorter peak is now projected. Reasons for this include a more rapid population decline in East Asia and Europe, particularly China, as well as a prolongued development arc in Sub-Saharan Africa.

The world's population first reached one billion people in 1803, and reach eight billion in 2023, and will peak at almost 11 billion by the end of the century. Although it took thousands of years to reach one billion people, it did so at the beginning of a phenomenon known as the demographic transition; from this point onwards, population growth has skyrocketed, and since the 1960s the population has increased by one billion people every 12 to 15 years. The demographic transition sees a sharp drop in mortality due to factors such as vaccination, sanitation, and improved food supply; the population boom that follows is due to increased survival rates among children and higher life expectancy among the general population; and fertility then drops in response to this population growth. Regional differences The demographic transition is a global phenomenon, but it has taken place at different times across the world. The industrialized countries of Europe and North America were the first to go through this process, followed by some states in the Western Pacific. Latin America's population then began growing at the turn of the 20th century, but the most significant period of global population growth occurred as Asia progressed in the late-1900s. As of the early 21st century, almost two thirds of the world's population live in Asia, although this is set to change significantly in the coming decades. Future growth The growth of Africa's population, particularly in Sub-Saharan Africa, will have the largest impact on global demographics in this century. From 2000 to 2100, it is expected that Africa's population will have increased by a factor of almost five. It overtook Europe in size in the late 1990s, and overtook the Americas a decade later. In contrast to Africa, Europe's population is now in decline, as birth rates are consistently below death rates in many countries, especially in the south and east, resulting in natural population decline. Similarly, the population of the Americas and Asia are expected to go into decline in the second half of this century, and only Oceania's population will still be growing alongside Africa. By 2100, the world's population will have over three billion more than today, with the vast majority of this concentrated in Africa. Demographers predict that climate change is exacerbating many of the challenges that currently hinder progress in Africa, such as political and food instability; if Africa's transition is prolonged, then it may result in further population growth that would place a strain on the region's resources, however, curbing this growth earlier would alleviate some of the pressure created by climate change.

Over the last decades, the European hare (Lepus europaeus) has become the subject of many interdisciplinary studies due to the sharp Europe-wide population decline. In European hares, the first stage of life until weaning and the subsequent dispersal have been sparsely studied, in particular, habitat selection, movements and survival rate, as juveniles´ precocial lifestyle is dominated by concealment, motionlessness and inconspicuousness. In this study, free-living juvenile European hares (leverets) were detected systematically by thermography (n = 394), radio-tagged or marked (n = 122) from birth until the fifth week of life to research their habitat usage and pre-dispersal movements. The day-resting places and night locations, as well as the distance moved by leverets with aging, were evaluated by generalized linear mixed effect models. In addition, the habitat preference was assessed by a conservative use-availability analysis. Up to the fifth week of life, 30.5% of all leverets used cultivated areas in the daytime. In contrast, the remaining 69.4% animals inhabitated linear or small planar structures in the daytime, with the edges of field tracks, hedges and some ruderal structures clearly being preferred. At nighttime, 93% of all juveniles, which occupied linear structures in the daytime, used the adjoining fields up to 20 m away from the next linear structure. Nocturnal distances of more than 60 m to the next edge rarely occurred before the end of the pre-weaning phase. The time of day and age have a significant influence on the distance moved by juvenile hares. With increasing age, leverets moved less during the day and roamed further at night. The results are largely consistent with the behavioral patterns found in the few previous studies on pre-weaning European hares and show the importance of hiding places for leverets in early life stages. This study should contribute to a better understanding of behavior in juvenile life-history stages of European hares that may help to identify vulnerable phases in their lifecycle. In addition, the findings can refine existing population models and improve conservation efforts.

Globally, about 25 percent of the population is under 15 years of age and 10 percent is over 65 years of age. Africa has the youngest population worldwide. In Sub-Saharan Africa, more than 40 percent of the population is below 15 years, and only three percent are above 65, indicating the low life expectancy in several of the countries. In Europe, on the other hand, a higher share of the population is above 65 years than the population under 15 years. Fertility rates The high share of children and youth in Africa is connected to the high fertility rates on the continent. For instance, South Sudan and Niger have the highest population growth rates globally. However, about 50 percent of the world’s population live in countries with low fertility, where women have less than 2.1 children. Some countries in Europe, like Latvia and Lithuania, have experienced a population decline of one percent, and in the Cook Islands, it is even above two percent. In Europe, the majority of the population was previously working-aged adults with few dependents, but this trend is expected to reverse soon, and it is predicted that by 2050, the older population will outnumber the young in many developed countries. Growing global population As of 2025, there are 8.1 billion people living on the planet, and this is expected to reach more than nine billion before 2040. Moreover, the global population is expected to reach 10 billions around 2060, before slowing and then even falling slightly by 2100. As the population growth rates indicate, a significant share of the population increase will happen in Africa.

This research, designed by the World Bank, and supported by the Department for International Development (DFID), aims to highlight the unprecedented transformation of the urban systems in the ECA region in the last decades, and to look at this shifts from the demographic, economic, and spatial prospectives. Cities in ECA database comprises data from 5,549 cities in 15 countries of the Eastern Europe and Central Asia region, as defined by the World Bank Group, and from the United Kingdom and Germany. Database information for each city is in three dimensions: demographic, spatial, and economic. The starting point to construct the Cities in ECA database was to obtain from each of the countries the list of official cities and these cities' population data. Population data collected for cities falls on or around three years: 1989, 1999, and 2010 (or the latest year available). The official list of "cities" was geo-referenced and overlaid with globally-available spatial data to produce city-level indicators capturing spatial characteristics (e.g., urban footprint) and proxies for economic activity. City-level spatial characteristics, including urban footprints (or extents) for the years 1996, 2000, and 2010 and their temporal evolution, were obtained from the Global Nighttime Lights (NTL) dataset. City-level proxies for economic activity were also estimated based on the NTL dataset. Nighttime Lights (NLS) data is produced by the Defense Meteorological Satellite Program (DMSP) Optical Line Scanner (OLS) database and maintained by the National Oceanic and Atmospheric Administration (NOAA).

Parasites have the capacity to affect animal populations by modifying host survival, and it is increasingly recognized that infectious disease can negatively impact biodiversity. Populations of the house sparrow (Passer domesticus) have declined in many European towns and cities, but the causes of these declines remain unclear. We investigated associations between parasite infection and house sparrow demography across suburban London where sparrow abundance has declined by 71% since 1995. Plasmodium relictum infection was found at higher prevalences (averaging 74%) in suburban London house sparrows than previously recorded in any wild bird population in Northern Europe. Survival rates of juvenile and adult sparrows and population growth rate were negatively related to Plasmodium relictum infection intensity. Other parasites were much less prevalent and exhibited no relationship with sparrow survival and no negative relationship with population growth. Low rates of co-infection suggested sparrows were not immunocompromised. Our findings indicate that P. relictum infection may be influencing house sparrow population dynamics in suburban areas. The demographic sensitivity of the house sparrow to P. relictum infection in London might reflect a recent increase in exposure to this parasite.

• Opinion on the risks of population decline in Europe and Spain.
• Opinion on the effects of the decline in the birth rate in Spain.
• Opinion on the measures to be taken to encourage Spanish families to have more children.
• Opinion on the ideal age of marriage. Attitude to premarital and sexual relations.
• Opinion on cohabitation.
• Reasons that influence a couple to live together without getting married.
• Reasons that influence for a couple to marry.
• Degree of satisfaction with marriage.
• Opinion on factors that influence the success of a marriage. Attitude to divorce.
• Opinion on the grounds for divorce.
• Ideal number of children.
• Opinions about family and children. Attitude to motherhood of single women.
• Opinion on the reasons for not wanting to have children.
• Use of contraceptive methods.
• Reasons for non-use of contraceptives.
• Opinion on the reasons for a married woman to work outside the home.
• Characteristics of the interviewee's home.
• Scale of satisfaction with housing. Attitudes to the ageing of society.
• Opinions before retirement. Attitudes to euthanasia.
• Frequency with which the interviewee deals with the subject of death. Attitude to incineration. Predisposition to emigrate.
• Opinion on immigrants and political refugees.
• Stereotypes of Ibero-Americans, Arabs and Africans.

Bumble bees (Bombus) are vitally important pollinators of wild plants and agricultural crops worldwide. Fragmentary observations, however, have suggested population declines in several North American species. Despite rising concern over these observations in the United States, highlighted in a recent National Academy of Sciences report, a national assessment of the geographic scope and possible causal factors of bumble bee decline is lacking. Here, we report results of a 3-y interdisciplinary study of changing distributions, population genetic structure, and levels of pathogen infection in bumble bee populations across the United States. We compare current and historical distributions of eight species, compiling a database of >73,000 museum records for comparison with data from intensive nationwide surveys of >16,000 specimens. We show that the relative abundances of four species have declined by up to 96% and that their surveyed geographic ranges have contracted by 23–87%, some within the last 20 y. We also show that declining populations have significantly higher infection levels of the microsporidian pathogen Nosema bombi and lower genetic diversity compared with co-occurring populations of the stable (nondeclining) species. Higher pathogen prevalence and reduced genetic diversity are, thus, realistic predictors of these alarming patterns of decline in North America, although cause and effect remain uncertain. Bumble bees (Bombus) are integral wild pollinators within native plant communities throughout temperate ecosystems, and recent domestication has boosted their economic importance in crop pollination to a level surpassed only by the honey bee. Their robust size, long tongues, and buzz-pollination behavior (high-frequency buzzing to release pollen from flowers) significantly increase the efficiency of pollen transfer in multibillion dollar crops such as tomatoes and berries. Disturbing reports of bumble bee population declines in Europe have recently spilled over into North America, fueling environmental and economic concerns of global decline. However, the evidence for large-scale range reductions across North America is lacking. Many reports of decline are unpublished, and the few published studies are limited to independent local surveys in northern California/southern Oregon, Ontario, Canada, and Illinois. Furthermore, causal factors leading to the alleged decline of bumble bee populations in North America remain speculative. One compelling but untested hypothesis for the cause of decline in the United States entails the spread of a putatively introduced pathogen, Nosema bombi, which is an obligate intracellular microsporidian parasite found commonly in bumble bees throughout Europe but largely unstudied in North America. Pathogenic effects of N. bombi may vary depending on the host species and reproductive caste and include reductions in colony growth and individual life span and fitness. Population genetic factors could also play a role in Bombus population decline. For instance, small effective population sizes and reduced gene flow among fragmented habitats can result in losses of genetic diversity with negative consequences, and the detrimental impacts of these genetic factors can be especially intensified in bees. Population genetic studies of Bombus are rare worldwide. A single study in the United States identified lower genetic diversity and elevated genetic differentiation (FST) among Illinois populations of the putatively declining B. pensylvanicus relative to those of a codistributed stable species. Similar patterns have been observed in comparative studies of some European species, but most investigations have been geographically restricted and based on limited sampling within and among populations. Although the investigations to date have provided important information on the increasing rarity of some bumble bee species in local populations, the different survey protocols and limited geographic scope of these studies cannot fully capture the general patterns necessary to evaluate the underlying processes or overall gravity of declines. Furthermore, valid tests of the N. bombi hypothesis and its risk to populations across North America call for data on its geographic distribution and infection prevalence among species. Likewise, testing the general importance of population genetic factors in bumble bee decline requires genetic comparisons derived from sampling of multiple stable and declining populations on a large geographic scale. From such range-wide comparisons, we provide incontrovertible evidence that multiple Bombus species have experienced sharp population declines at the national level. We also show that declining populations are associated with both high N. bombi infection levels and low genetic diversity. This data was used in the paper "Patterns of widespread decline in North American bumble bees" published in the Proceedings of the National Academy of United States of America. For more information about this dataset contact: Sydney A. Cameron: scameron@life.illinois.edu James Strange: James.Strange@ars.usda.gov Resources in this dataset:Resource Title: Data from: Patterns of Widespread Decline in North American Bumble Bees (Data Dictionary). File Name: meta.xmlResource Description: This is an XML data dictionary for Data from: Patterns of Widespread Decline in North American Bumble Bees.Resource Title: Patterns of Widespread Decline in North American Bumble Bees (DWC Archive). File Name: occurrence.csvResource Description: File modified to remove fields with no recorded values.Resource Title: Patterns of Widespread Decline in North American Bumble Bees (DWC Archive). File Name: dwca-usda-ars-patternsofwidespreaddecline-bumblebees-v1.1.zipResource Description: Data from: Patterns of Widespread Decline in North American Bumble Bees -- this is a Darwin Core Archive file. The Darwin Core Archive is a zip file that contains three documents.

The occurrence data is stored in the occurrence.txt file. The metadata that describes the columns of this document is called meta.xml. This document is also the data dictionary for this dataset. The metadata that describes the dataset, including author and contact information for this dataset is called eml.xml.

Find the data files at https://bison.usgs.gov/ipt/resource?r=usda-ars-patternsofwidespreaddecline-bumblebees

Projections estimate that the population in Italy will decrease in the following years. In January 2025, the Italian population added up to 59 million people, but in 2030 Italians will be 58 million individuals. Twenty years later, the population will be around 52 million people. Low birth rate and old population The birth rate in Italy has constantly dropped in the last years. In 2023, 6.4 children were born per 1,000 inhabitants, three babies less than in 2002. Nationwide, the highest number of births was registered in the southern regions, whereas central Italy had the lowest number of children born every 1,000 people. More specifically, the birth rate in the south stood at 7 infants, while in the center it was equal to 5.9 births. Consequently, the population in Italy has aged over the last decade. Between 2002 and 2024, the age distribution of the Italian population showed a growing share of people aged 65 years and older. As a result, the share of young people decreased. The European exception Similarly, the population in Europe is estimated to decrease in the coming years. In 2024, there were 740 million people living in Europe. In 2100, the figure is expected to drop to 586 million inhabitants. However, projections of the world population suggest that Europe might be the only continent experiencing a population decrease. For instance, the population in Africa could grow from 1.41 billion people in 2022 to 3.92 billion individuals in 2100, the fastest population growth worldwide.

Growth rates are highest in the Middle East, Africa, and parts of Latin America. Populations are actually declining in some developed countries, especially in eastern Europe.Source: World Bank

Bird populations are declining globally with losses recorded in many European breeding birds. Habitat management measures have not resulted in a widespread reversal of these declines. We analysed national bird population trends from ten European countries (France, Hungary, Ireland, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland, and the UK) in relation to the species’ nesting strategy (‘ground-nesting' or ‘other’), Annex I designation (‘designated’ or ‘not designated’) and association with agricultural habitats for breeding (‘associated’ or ‘not associated’). For each country in our dataset, we also defined the following factors: farming intensity; predator community complexity; and predator control effort. Our results showed additive effects of nesting strategy, designation, and breeding habitats on the likelihood of population decline. Ground-nesting birds were 86% more likely to decline than birds with other nesting strategies. Annex I designated species of the Birds Directive were 50% less likely to decline than non-designated birds. Birds breeding primarily in agricultural habitats were more likely to decline than birds breeding in other habitats, interactively with farming intensity. Homogenous trends across Europe (i.e., trends in two or more countries that were either not declining in all countries or declining in all countries) indicate that the probability of population decline was related to nesting strategy and breeding habitat, with ground-nesting birds being 15.6 times more likely than other birds to have a declining trend across Europe, and birds nesting in agricultural habitat being 17.8 times more likely than birds nesting in other habitats to have a declining trend across Europe. Our results highlight a widespread challenge, therefore widespread instruments (e.g. legislation, economic policies, agri-environment schemes) will be required to reserve these declines. Ground-nesting species requirements can be complex and multiple strategies will be needed to restore populations including the development of predation management tools. Methods Many countries provide data to the Pan-European Common Bird Monitoring Scheme (PECBMS). We explored the PECBMS web page and the links included therein for each country, to identify if national data on population trends for each species could be obtained. Finally, we obtained national trends data for 10 countries, namely France (FR), Hungary (HU), Ireland (IE), the Netherlands (NL), Poland (PL), Portugal (PT), Spain (ES), Sweden (SE), Switzerland (CH) and the UK (UK). Specifically, common bird species trends in France were obtained from the monitoring programs coordinated by the Natural History Museum (http://www.vigienature.fr/fr/resultats-especes-3367). These data provided a 20-year trend (1998-2018) for each species. Hungary data from the Monitoring Centre of the Hungarian Ornithological and Nature Conservation Association were available at https://mmm.mme.hu/charts/trends and provided species trends for the period 1999-2021. Data from Ireland were available at https://www.npws.ie/sites/default/files/publications/pdf/IWM115.pdf and provided trends for 1998-2016 for each species. Netherlands data were obtained from the monitoring programs carried out by SOVON, the Dutch Centre for Field Ornithology (https://www.vogelwarte.ch/assets/files/publications/upload2019/Zustand%20der%20Vogelwelt%20in%20der%20Schweiz_Bericht%202019_E_low.pdf). These data provided species trends from 1990 to 2016. Polish data were obtained from https://monitoringptakow.gios.gov.pl/database.html, and provided trends for each species for the period 2000-2019. Portuguese data (based on the program organised by the Sociedade Portuguesa para o Estudo das Aves, SPEA) were obtained from https://www.spea.pt/wp-content/uploads/2021/06/relatorio_cac_2021_vf3.pdf, as long-term (2004-2020) trends for each species. Data from Spain were obtained from the monitoring programs conducted by SEO/Birdlife (https://seo.org/boletin/seguimiento/boletin/2018/html5forpc.html?page=0), consisting of long-term trends (1998-2018) for each species. Data from Sweden, showing 1998-2022 trends for each species, were obtained from http://www.fageltaxering.lu.se/resultat/trender. Swiss data were obtained from the monitoring programs carried out by Vogelwarte, the Swiss Ornithological Institute (https://www.vogelwarte.ch/assets/files/projekte/entwicklung/zustandsbericht%202019/Zustandsbericht%202019_e_low.pdf) and consisted of 1990-2018 trends for each species. The UK data were obtained through monitoring programs at the British Trust of Ornithology (https://www.bto.org/our-science/publications/birdtrends/2020/species), providing long-term (1994-2020) trends for each species. In all cases, trends for each species were categorised according to European Bird Census Council (EBCC) definitions (see https://pecbms.info/methods/pecbms-methods/1-national-species-indices-and-trends/1-2-production-of-national-indices-and-trends/trend-interpretation-and-classification) as ‘important decline’, ‘moderate decline’, ‘stable’, ‘moderate increase’, ‘marked increase’ or ‘uncertain. We regrouped the categories as ‘decline’ (either important or moderate) or ‘no decline’, (stability, moderate or important increase, or uncertain trends) to obtain a binomial variable describing the decline probability of a given species in each country.

Regionally distinguished demographic estimates for GS-1 based on dataset A.

Aim: To show how recent declines in populations of long-distance migrant birds are associated with recent increases in human population growth and agricultural intensification on their tropical non-breeding grounds, except for synanthropic species, where we expect the reverse.

Location: Breeding populations throughout Europe and North America spending the non-breeding season throughout Africa, and Central and South America, respectively.

Methods: We mapped 50 species of long-distance migrant birds from published tagging studies of 126 breeding populations and identified their breeding population trends from 2000-2015 from published Country or State census data. We then matched individual bird non-breeding locations, from each population, to local human population change and crop yield data. We used GLMs to predict whether bird population decline was associated with human population change or crop yield and whether this was dependent on if a species was synanthropic or not, controllin...

Detailed information on data sampling and processing can be found in the corresponding article: Laux, A., Gottschalk, E. Local sub-population dynamics of a Central European Grey Partridge meta-population support large-scale conservation approach to halt its ongoing decline. Wildlife Biology. https://doi.org/10.1002/wlb3.01316

Wading birds can be found breeding in a myriad of habitats and ecosystems across Europe that vary widely in their land-use intensity. Over the past few decades, wader breeding populations have declined steeply in habitats ranging from natural undisturbed ecosystems to intensively managed farmland. Most conservation science has focused on factors determining local population size and trends which leave cross-continental patterns and the associated consequences for large-scale conservation strategies unexplored. Here, we review the key factors underlying population decline. We find land-use intensification in western Europe and mostly agricultural extensification and abandonment in northern, central and eastern Europe to be important drivers. Additionally, predation seems to have increased throughout the breeding range and across all habitats. Using collected breeding density data from published and grey literature, we explore habitat specificity of wader species and, of the most widely ..., To examine which habitats waders use for breeding in their main distributional range in Europe, how this differs between species and whether different habitats support different population densities, we searched published papers for quantitative data that could be used to calculate breeding densities. Initially, we performed searches of peer-reviewed scientific articles reporting densities of breeding waders published between 1945 and 2018 using ISI Web of Science Core Collection (WoS) and Elsevier Scopus databases by using a specific combination of related keywords (see Appendix 1 for more detailed information). We only used studies that met the following requirements: (1) the study reported breeding pair density data or gave a number of breeding pairs for a certain specified area from which a breeding density estimation could be calculated; (2) the study described which methodology was used for surveying breeding birds; (3) the study specified the habitat type or vegetation compositio...,