This is not just a temporary dip \u2013 it\u2019s a long-term, cumulative effect that continues to build as the planet warms.<\/p>\n
Our research helps explain why bird numbers are falling<\/a> even in wild places relatively untouched by humans<\/a>, such as some very remote protected tropical forests<\/a>. It underscores the urgent need to reduce greenhouse gas emissions, to conserve the remaining biodiversity. <\/p>\n The critically endangered Gouldian finch is a colorful tropical bird endemic to the northern Australia. Digging into huge global datasets<\/p>\n We analysed data from long-term monitoring<\/a> of more than 3,000 bird populations worldwide between 1950 and 2020. This dataset captures more than 90,000 scientific observations.<\/p>\n Although there are some gaps, the dataset offers an unmatched view of how bird populations have changed over time. Some parts of the world such as western Europe and North America were better represented than others, but all continents were covered. <\/p>\n We matched this bird data with detailed daily weather records from a global climate database<\/a> that stretches back to 1940. This allowed us to track how bird populations responded to specific changes in daily temperatures and rainfall, including extreme heat.<\/p>\n We also looked at average yearly temperatures, total annual rainfall, and episodes of unusually heavy rainfall. <\/p>\n Using another dataset that reflects human industrial activity over time<\/a>, we accounted for human pressures such as land development and human population density. <\/p>\n By combining all these sources of data, we created computer models to evaluate how climate factors and human impacts influence bird population growth.<\/p>\n Our research confirmed the work of other climate scientists<\/a> showing extreme heat events have increased dramatically over the past 70 years, especially near the equator. <\/p>\n Birds in tropical regions are now experiencing dangerously hot days about ten times more often than they did in the past.<\/p>\n Tropical birds have experienced a 10-fold increase in exposure to extreme heat over the past 60 years. What we found: extreme heat is the biggest climate threat to birds<\/p>\n While changes in average temperature and rainfall do affect birds, we found the increasing number of dangerously hot days had the greatest effect \u2013 especially in tropical regions.<\/p>\n This is a major concern because tropical birds often have small home ranges and are highly specialised in terms of the habitats and climates they persist in. In many cases tropical birds exist within a small range of heat tolerance<\/a>. <\/p>\n At temperatures beyond a bird\u2019s limit of endurance, they go into hyperthermia, where their body temperature rises uncontrollably. In this state, birds may adopt a drooped-wing posture to expose more skin for heat loss, hold their beaks open and pant rapidly<\/a>, spread their feathers, and become lethargic or disoriented. In severe cases, they lose coordination, fall from perches, or even collapse unconscious. <\/p>\n A black-collared barbet (Lybius torquatus) from Botswana. If they survive the experience, they can suffer long-term damage such as heat-induced organ failure and reduced reproductive capacity<\/a>. Heat exposure reduces breeding success by lowering adult body condition and reducing time spent foraging \u2013 because the birds must rest or seek shade during the hottest hours.<\/p>\n It also causes heat stress in eggs and nestlings. In extreme events, nestlings may die from hyperthermia, or parents may abandon nests to save themselves.<\/p>\n Heat also increases a bird\u2019s demand for water \u2014 not because they sweat (birds lack sweat glands) but because they lose water rapidly through evaporative cooling. This happens mainly via panting (respiratory evaporation) and, in some species, gular fluttering (rapid vibration of throat skin to increase airflow), as well as evaporation through the skin. As temperatures climb, these processes accelerate, causing significant dehydration unless birds can drink more frequently or access moister food.<\/p>\n Our study found that across tropical areas, the impact of climate change on birds is perhaps even greater now than the impact of direct human activities such as logging, mining or farming. This is not to say habitat destruction due to these activities is not a serious issue \u2013 it clearly is a major concern to tropical biodiversity<\/a>. But our study highlights the challenges climate change is already bringing to birds in tropical regions. <\/p>\n![\"Two](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2025\/08\/file-20250811-56-knis7u.jpg\")
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\n AAP Image\/Supplied by Bruce Thomson<\/a><\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2025\/08\/file-20250805-56-3pky0.png\")
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\n Kotz, M. et al. (2025) Nature Ecology & Evolution<\/a><\/p>\n![\"Side](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2025\/08\/file-20250805-56-g0yofv.png\")
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\n Sergey Dereliev<\/a><\/p>\n
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