Project Results

Key Results:

- Radiotransmitters revealed stopovers of up to 2 weeks in lowland tropical dry forest by Yellow-billed Cuckoo

- Two individuals carrying radiotransmitters were later detected by automatic receivers in Panama and Salt Plains, Oklahoma!

- Cuckoos foraging at our study site were largely observed eating small and medium sized caterpillars but also leaves and flowers. The latter may be to aid digestion of toxins in some of the caterpillars.

- Our results highlight the importance of Colombia's Caribbean tropical dry forests for the declining Yellow-billed Cuckoo but time is running out. 92% of Colombia's dry forest have already been cleared, most to make way for cattle pastures.

About This Project

Travelling thousands of kilometers every year, the Yellow-billed Cuckoo is a true globe trotter. Its epic migration takes it from its breeding grounds in North America’s deciduous forest, across the Caribbean and the Amazon basin, and deep into South America – and back again! With your support, in this phase of the Neotropical Flyways Project we will answer the big unanswered question, how?

Ask the Scientists

What is the context of this research?

So how does a Yellow-billed Cuckoo get from Brazil to Tennessee and back again?

Part of the answer may lie in the species' nickname in North America, the “rain crow”, which hints at its association with rainfall and times of plenty. Indeed, the species' presence is somewhat unpredictable throughout the Americas, and it would seem that it seeks out superabundant caterpillars that are there one moment but gone the next. The problem is, we have no idea where Cuckoos find these fleeting bonanzas. More worrying is that we are running out of time, as the species populations are in trouble, having declined 54% since 1970.

What is the significance of this project?

In 2016 we carried out surveys across northern Colombia as part of the Neotropical Flyways Project, uncovering a previously unknown concentration of Yellow-billed Cuckoos. During approximately three weeks of their spring migration, large numbers of cuckoos were found in tropical dry forests. We suspect that these forests provide birds with the huge energy reserves needed for long-haul flights over the Caribbean Sea and the Gulf of Mexico, enabling cuckoos to complete what is probably the most risky stage of their migration.

The problem is that 92% of Colombia’s dry forests have been cleared to make way for cattle pastures, such that the remaining 8% may be critical to migrating cuckoos and the species' survival. That's why we need to find out how they use these forests and soon!

What are the goals of the project?

To solve the Rain Crow Mystery, we will study in minute detail how cuckoos use Colombia's dry forests and biodiversity-friendly farming practices like silvopasture. Through observations, captures and cutting-edge tracking techniques (nano-tag radio-transmitters) we will answer three key questions: How long do cuckoos stay? How much energy do they store? What are they eating and which trees are important? This will allow us to make recommendations to farmers.

Finally, we will track radio-tagged cuckoos as they head north, through an array of automated Motus receivers. Understanding what cuckoos do on leaving Colombia, is central to understanding just how important this stopover is to their overall migration strategy.