ProtectFish project partner Czech Academy of Sciences has published a new research paper on the ecology on the common kingfisher (Alcedo atthis). This study aimed at exploring more details on the long-term impact of this fish micropredator’s behaviour and ecology on fish populations in European rivers and streams.
The paper, recently accepted in Acta Ornithologica (January 2025) and published in late spring 2025, investigates how nest temperature affects kingfisher breeding success. The study found that nest temperature, although highly variable, has no significant impact on reproductive outcomes. This discovery offers valuable new insights into the breeding ecology of the species.
The Common Kingfisher : A specialist fish predator
99% of the common kingfisher’s diet is made up of fish across rivers, streams, and reservoirs (Čech & Čech, 2015 – Bird study). Despite its small size (around 50 g), it can catch prey up to 13 cm long, with an optimum between 6–8 cm.
Earlier research has shown that an adult kingfisher consumes around 60% of its body weight in fish every day, while nestlings require nearly 40% of their weight in daily fish intake. With the potential to breed up to three or four times in one season (each nest producing an average of seven chicks) kingfishers can exert significant predation pressure on local fish populations, particularly targeting young-of-the-year (0+) and one-year-old (1+) fish.
Common Kingfisher’s conservation status
The common kingfisher is protected both nationally in the Czech Republic (Act No. 114/1992 on Nature and Landscape Conservation) and at the European level under the EU Birds Directive (2009/147/EC) and the Bern Convention. Despite this protection, populations remain vulnerable to threats such as predation of nests by otters, foxes or invasive mink, flooding, entanglement in fishing lines, and harsh winters that freeze fishing grounds.
This makes understanding breeding success and ecological impacts all the more critical. The new findings reinforce that while kingfishers are a flagship conservation species, there are also other efficient predators – e.g. cormorants – whose role in fish population dynamics must be considered in fisheries management.
Why Kingfisher research matters for ProtectFish
For more than 25 years, the research team of our ProtectFish partner – Czech Academy of Sciences – has been studying the feeding ecology of fish-eating predators such as cormorants, otters, herons, and kingfishers in the Czech Republic. One of its key findings has been that fish predation involves multiple species, including kingfishers.
Some river stretches may never host a single cormorant, yet they are subject to intense predation pressure from kingfishers for most of the year. This particularly during the breeding season, when adults feed their growing chicks. For this reason, the ProtectFish project focuses on cormorants in winter and kingfishers in summer, maximizing knowledge on how different predators impact fish populations throughout the year. As the common kingfisher is an almost entirely a fish-dependent predator. It forms an integral part of the ProtectFish research activities. Until now, it was unclear whether nest temperature or surrounding environmental conditions influenced these feeding needs, breeding success, or fledging rates. Understanding this is vital, as it directly affects population size and, consequently, the overall predation pressure exerted on fish communities. In other words, it helps the experts determine how many fish-eating birds will ultimately be present in a given ecosystem.
A steep bank wall with the nests of common kingfisher indicated by arrows
Young kingfishers almost ready to leave the nest
ProtectFish leads the way with innovative research methods
Studying kingfisher nests presents major challenges, as they are dug into steep riverbanks and can be easily disturbed by predators—or even human presence. For the first time, our research team used temperature data loggers inside nest chambers to non-invasively monitor breeding events.
By placing sensors in both active nests and control burrows, researchers were able to detect egg-laying, incubation, chick-rearing, fledging, and even cases of nest failure. Combined with camera recordings, this method provided a detailed picture of kingfisher breeding dynamics without disturbing the birds.
The results confirmed that temperature monitoring is a promising tool for studying burrow-nesting bird species and could be widely applied in ornithological research.
A kingfisher chick swallowing a large fish
Conclusion – limited role for nest temperature in reproductive outcomes
This study highlights that understanding the ecology of the common kingfisher is essential for studying the broader picture of fish predation in European freshwater systems. As exclusive fish-eaters, kingfishers contribute significantly to predation pressure, complementing the impact of cormorants and other predators.
Through the ProtectFish project, we are committed to advancing knowledge on all major fish-eating species to better inform fish protection strategies and conservation efforts across Europe.
You can access the full article using this link: Temperatures in Common Kingfisher Alcedo atthis Nesting Holes Indicate the Timing of Breeding Phases
for any further information – Aliénor: protectfish@alienor.eu
