Novel natural history notes from three nests of the vulnerable Tawny-chested Flycatcher (Aphanotriccus capitalis)

In the dense, humid forests of Central America, the survival of many bird species depends on a delicate balance between finding food and raising young in a rapidly changing world. When forests are cut down or broken into small, isolated patches, birds that rely on specific trees or quiet places to build their homes often struggle to reproduce. For scientists, understanding exactly how these birds live—their breeding habits, the materials they use for nests, and how they care for their babies—is not just a matter of curiosity. It is a necessary step to protect them. Without knowing the specific needs of a species, conservation efforts can miss the mark, leaving vulnerable populations without the habitat they require to continue. The Tawny-chested Flycatcher is one such bird, a small insect-eater with a distinctive chest patch, currently facing a decline in numbers across its range.

A team of researchers recently set out to fill in the missing pages of this bird's life story. By observing three different nests in Costa Rica during 2025 and 2026, they uncovered new details about how these birds raise their families. The scientists, working along quiet, unpaved roads that cut through mature forests, watched adult birds as they hunted for insects and returned to their homes. They found that these birds do not build elaborate structures on the ground or in open branches. Instead, they seek out hidden spots, such as deep cracks in tree trunks or hollows where moss grows thick. In one instance, a nest was tucked into a crevice about three meters above the ground, lined with plant fibers that hung over the edge like a curtain. In another, a nest sat just two meters up, nestled in a moss-covered hollow. These locations are often found near the edges of forests, where the trees are old and the canopy is thick, providing the cover these birds seem to prefer.

The researchers were able to watch the birds through different stages of their breeding cycle, from the moment eggs were laid to the time the babies left the nest. They observed that the female lays eggs with a pink base color covered in reddish-brown spots, usually laying two or three at a time. Once the eggs hatch, the parents work tirelessly to feed the growing chicks. The adults catch insects like small green caterpillars and beetles, carrying them back to the nest. When they arrive, they do not rush in immediately. Instead, they often pause, hovering or perching nearby to watch the nestlings before flying in to feed them. The babies, covered in feathers except for their ears and eyes, open their mouths wide and beg for food the moment their parents appear. The parents are attentive, feeding the young and then carefully picking up the waste produced by the chicks, carrying it away in their beaks to keep the nest clean.

One of the most striking discoveries was the behavior of the parents and the condition of the nestlings. In one nest, the researchers noticed a parasite, a botfly larva, attached to the throat of a chick, a reminder of the constant challenges these birds face. Despite such threats, the parents continued their routine, feeding the young even during light rain. The team measured how often the birds returned with food, finding that in a forty-five-minute period, they fed the chicks eleven times, which means a new meal arrived roughly every three minutes. This high level of activity shows just how much energy is required to raise a family in the wild. The study also noted that one of the nests, after a heavy rain, quickly fell apart and washed away, suggesting that these birds may not reuse their nests from year to year, but rather build new ones each season.

These observations add crucial pieces to the puzzle of the Tawny-chested Flycatcher's life. Before this work, very little was known about how many chicks a pair raises, how the parents behave, or what the babies look like. Now, we know that they rely on specific types of trees and crevices, that they build their homes with plant fibers and moss, and that they are dedicated parents who work hard to keep their young safe and fed. The findings also highlight a potential threat: the birds were found nesting near quiet, gravel roads. If these roads are paved, the noise and disturbance could disrupt the birds' ability to breed successfully. By documenting these natural history details, the researchers provide a clearer picture of what the Tawny-chested Flycatcher needs to survive, offering a guide for those working to protect this vulnerable species and the forests it calls home.