RT Journal Article T1 Extending Long-Term Avian Studies Alters Temporal and Climate-Driven Trend Conclusions. A1 Zanandrea, Irene A1 Moreno, Juan A1 Cantarero Carmona, Alejandro AB Long-term population studies are crucial for understanding the impacts of climate change on biodiversity; however, predictions based on short-term data may be unreliable. Here, we analyse yearly averages of reproductive parameters (laying date, nestling condition, and female condition) of a Pied Flycatcher () population in central Spain across one, two, and three decades of study to evaluate how study duration affects conclusions about population trends. Our findings reveal that initial trends deduced from studies of shorter duration often weaken, invert, or disappear when extended durations are included. For example, advancements in laying dates only become apparent after more than two decades, while trends in nestling and female condition vanish over time. Additionally, we observed unexpected responses, such as delays in laying during exceptionally hot prelaying periods. These results emphasize the necessity of long-term studies spanning multiple generations to accurately assess the impacts of climate change and inform effective conservation strategies. Our work underscores the risks of relying on short-term data to predict long-term ecological trends. PB Wiley YR 2025 FD 2025 LK https://hdl.handle.net/20.500.14352/123401 UL https://hdl.handle.net/20.500.14352/123401 LA eng NO Zanandrea, I., Moreno, J., & Cantarero, A. (2025). Extending Long-Term Avian Studies Alters Temporal and Climate-Driven Trend Conclusions. Ecology and evolution, 15(8), e71878. https://doi.org/10.1002/ece3.71878 NO Author Contributions:Irene Zanandrea: data curation (equal), formal analysis (equal),methodology (equal). Juan Moreno: conceptualization (equal), projectadministration (equal), resources (equal), writing – review and editing(equal). Alejandro Cantarero: conceptualization (equal), funding ac-quisition (equal), methodology (equal), project administration (equal),supervision (equal), writing – review and editing (equal) NO Ministerio de Ciencia, Innovación y Universidades (España) NO European Commission DS Docta Complutense RD 20 mar 2026