Scientific Rationale Birds

One of the most pressing issues of our time is the biodiversity crisis, a situation that demands our immediate attention.

Various species' populations are declining, yet the exact reasons for most of these declines remain unknown. For example, European songbirds have declined by approximately 30% over the past 25 years – 600 million birds have been lost! As these birds are highly mobile, any analysis that does not include their movement and migration patterns will not be able to highlight specific causes of death.

Population modeling suggests that approximately 50% of bird fledglings do not survive to maturity. Given that many passerine birds reach maturity in their second year, we can expect that 50% of these birds die within their first year. While models can predict the proportion of first-year fledglings that have most likely perished, it is challenging to determine the specific causes and locations of these deaths under natural conditions. Currently, we can only record isolated instances of mortality that can be assigned to specific causes, such as wind turbines, collisions with glass structures, hunting by house cats, or other reasons. To move from a non-representative assembly of individual cases to population-level insights, we need to tag birds in large quantities to determine their individual fate and relate this to the environmental factors these individuals are exposed to throughout their ontogeny until death.

Understanding the proportion of birds that reach reproductive age, the mortality rates of adult breeding birds, and the proportion of birds that engage in breeding is crucial for comprehending population trends. Currently, these metrics are largely predicted by population models. While these models are generally reliable, they represent theoretical predictions, which may vary in accuracy across different populations. It is crucial to identify where these predictions hold true and where they do not, as this understanding is essential for designing effective strategies to prevent biodiversity loss. With our approach, we now have a tool to measure these vital rates directly in the wild, enabling us to compare real-world data with model predictions.

Given the urgent declarations by nature-protection agencies about the ongoing biodiversity crisis, there is a critical need to understand the causes of species and population declines. Nevertheless, tagging 5,000 birds in five years to evaluate these causes on a continental scale is an ambitious objective. It necessitates advancing beyond current methodologies to develop new technologies, analytical tools, and measurement approaches tailored for examining these phenomena in ecologically relevant settings. This project's high-risk/high-gain goal is to establish large-scale tagging as a primary tool for measuring immigration/emigration and birth/death rates on the pan-European scale. This approach aims to provide comprehensive insights into the causes of species and population declines, with implications for other yet unstudied species and regions globally.

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