Bird O'clock

Discover the Fascinating World of Brown Nunlets in Central and South America

The Brown Nunlet, scientifically named Nonnula brunnea, is a small bird species that belongs to the Bucerotidae family. These birds can be found in Central and South America, particularly in countries such as Brazil, Ecuador, Peru, and Venezuela.

Brown Nunlets are often spotted in the understory of humid tropical forests, and they are known for their unique appearance and vocalizations.


When identifying the Brown Nunlet in the field, it is important to note that these birds have a distinct, round head that is often compared to a tomato or a ping-pong ball. They have a dark brown or black beak that is slightly curved downward, which distinguishes them from other bird species in their habitat.

Brown Nunlets have a brownish-gray plumage, with a white throat and chest. The wings and back have black and white spots, and the tail is slightly rounded.

Similar Species

Though Brown Nunlets have a unique appearance, they still share similarities with other bird species in their habitat. Green-fronted Nunlets, for example, have a similar body shape and feather pattern to Brown Nunlets.

However, the former species have a white forehead and a green crown, which differentiates them from the latter. Another species that may be mistaken for Brown Nunlets is the Semicollared Nunlet, which has a similar color scheme but has a white band on the neck, unlike the Brown Nunlet.


Brown Nunlets have four different plumages throughout their lifespan, namely the juvenile, immature, sub-adult, and adult. Juvenile Brown Nunlets have a grayish-brown plumage, with a feather pattern that is more subtle compared to adults.

Immature Brown Nunlets have a more pronounced feather pattern, but their plumage still contains some grayish-brown spots. Sub-adult Brown Nunlets resemble the adult plumage pattern, but their feathers are less bright and less defined.

Finally, adult Brown Nunlets have a distinct, brownish-gray plumage, with a more pronounced feather pattern on the wings and back.


Brown Nunlets undergo two molts throughout their life, the pre-basic and pre-alternate molts. Pre-basic molts occur after breeding season, and it results in the growth of new feathers to replace the old ones that were damaged or worn out.

Pre-alternate molts, on the other hand, occur before the breeding season, and it allows Brown Nunlets to grow more vibrant feathers that are essential for attracting mates. During the molting period, Brown Nunlets may look scruffy or unkempt, and they may also have a decreased appetite due to the energy required in growing new feathers.

In conclusion, Brown Nunlets are unique bird species that are distinguishable through their brownish-gray plumage, round head, and black beak. They can be found in Central and South America, and are often identified by their vocalizations.

Though they have a unique appearance, they share some similarities with other bird species in their habitat. Brown Nunlets have four different plumages, beginning with the juvenile stage and followed by the immature, sub-adult, and adult stages.

They also undergo two molts throughout their life, which growth new feathers and allow them to have more vibrant plumage during the breeding season.

Systematics History

The Brown Nunlet (Nonnula brunnea) belongs to the Bucerotidae family, which comprises hornbills and hoopoes. It was first described in 1858 by French zoologist Charles Lucien Bonaparte.

In the early 20th century, the taxonomy of the Brown Nunlet was reorganized based on the variation in its physical characteristics.

Geographic Variation

The Brown Nunlet can be found in Central and South America, where it inhabits humid tropical forests. There is a variation in the physical characteristics exhibited by the bird depending on where it is located.

The northern population has more black feathering, while the southern population has more bluish-gray feathering.


The Brown Nunlet has five recognized subspecies, based on its physical characteristics and geographic range:

1. Nonnula brunnea brunnea – This subspecies is found in eastern Ecuador, northern and eastern Peru, adjacent Brazil, and western Venezuela.

It is characterized by its black head, underparts, and back. 2.

Nonnula brunnea maxima – This subspecies is found in western Amazonian Brazil, eastern Peru, and southeastern Colombia. It has a more brownish-black plumage and is larger than the other subspecies.

3. Nonnula brunnea cinerascens – This subspecies is found in southeastern Brazil and northeastern Argentina.

It has a bluish-gray head, underparts, and back, and less black feathering than the other subspecies. 4.

Nonnula brunnea frantzii – This subspecies is found in Costa Rica and western Panama. It has a less distinct plumage pattern, with more gray feathering on the back and wings.

5. Nonnula brunnea salvini – This subspecies is found in southeastern Mexico, Guatemala, Honduras, and Belize.

It has a more reddish-brown head and back than the other subspecies.

Related Species

The Brown Nunlet is related to other hornbill and hoopoe species within the Bucerotidae family. The Green-fronted Nunlet (Nonnula rubscens) is a close relative of the Brown Nunlet, with a similar body shape and feather pattern.

However, it has a white forehead and greenish coloring on its head, which differentiates it from the Brown Nunlet. The Speckled Chachalaca (Ortalis guttata), a member of the Cracidae family, is often mistaken for the Brown Nunlet due to their similar appearance.

However, Chachalacas are larger birds with longer tails and necks.

Historical Changes to Distribution

The distribution of the Brown Nunlet has changed over time due to natural and human-driven factors. In the past, the Brown Nunlet colony was widespread across the Amazon basin of South America.

However, the fragmentation of their habitat due to deforestation and mining activity has led to a decline in their population in certain areas. Additionally, the alteration of the natural landscape by human activity has affected the distribution of the Brown Nunlet.

Some populations have suffered from the changes in riparian zones and river basin habitats, which have shifted the birds to move higher up in the forest canopy. In contrast, other populations have benefited from agriculture activities that create new habitats, such as coffee plantations and banana farms.

In conclusion, the Brown Nunlet is a bird species found in Central and South America. The Brown Nunlet exhibits variation in its physical characteristics based on its geographic location and has five recognized subspecies.

The Brown Nunlet is related to other hornbill and hoopoe species and has been affected by historical changes to its distribution due to human and natural factors.


The Brown Nunlet (Nonnula brunnea) inhabits humid tropical forests throughout Central and South America, including countries like Brazil, Ecuador, Peru, and Venezuela. They are often found in the understory layer of the forest, where they nest and forage for food.

Brown Nunlets tend to prefer primary forests, which are considered more intact and undisturbed by human activity.

In primary forests, Brown Nunlets can be found in riverine forests, gallery forests, and terra firme forests.

In some cases, Brown Nunlets can also be found in secondary forests that have regrown after being cleared for agriculture or other human activities. They may also occur in forest fragments that have arose due to habitat fragmentation.

The Brown Nunlet habitat is characterized by dense tree cover and a high level of humidity. In riverine forests and gallery forests, they can be found alongside waterways, while in terra firme forests, they are found in areas with a high canopy cover.

The dense vegetation provides nest sites and shelter from predators, and the high humidity ensures that the bird has enough moisture to continue to survive.

Movements and Migration

Brown Nunlets are non-migratory birds and are likely to be sedentary in their habitat range. They are generally thought to be resident within their geographic range throughout the year, with little movement taking place.

However, there have been a few instances where Brown Nunlets have been observed outside of their range, but these occurrences are rare. One such report came from the Santa Elena Province of Ecuador, where a Brown Nunlet was sighted outside of its typical range.

The sighting was thought to be due to the bird’s dispersal from its home range.

Brown Nunlets may also exhibit local migratory movements within their habitat range, depending on the availability of food.

During the dry season, food availability may be limited in some areas, leading Brown Nunlets to move to other areas where food is more abundant. This is not considered a true migratory movement, as it does not involve a seasonal change in location.

In conclusion, Brown Nunlets are non-migratory birds and are likely residents within their geographic range throughout the year. However, they may exhibit movement within their habitat range depending on food availability.

The habitat of the Brown Nunlet is characterized by dense tree cover and high humidity, and they generally prefer primary forests that are undisturbed by human activity.

Diet and Foraging


The Brown Nunlet (Nonnula brunnea) is a frugivorous species, which means that it feeds primarily on fruit. Its diet also includes other insects and invertebrates that it may come across while foraging.

Brown Nunlets forage in the understory layer of the forest, primarily feeding on fruit that has fallen from the canopy. Insects and invertebrates provide a supplementary source of food for the Brown Nunlet, making up only a small percentage of its diet.

These may include beetles, ants, caterpillars, and spiders, among others. Brown Nunlets use their beak to probe into the crevices of the bark and leaves to find insects and other invertebrates.


The diet of the Brown Nunlet varies depending on the availability of fruit in its habitat range. It has been observed that different populations of Brown Nunlets may have slightly different diets, based on the fruits available in the region.

In general, Brown Nunlets feed on a variety of fruits, such as figs, guava, and plums. In some instances, they have also been observed feeding on the fruits of palm trees.

The amount of fruit in the diet of the Brown Nunlet varies from population to population, with some populations consuming a larger amount of fruit than others. This variation is thought to be due to the availability of fruit in the region.

Metabolism and Temperature Regulation

The Brown Nunlet is an endothermic species, which means that it can control its body temperature internally. This is important for regulating its metabolic rate and ensuring that it has enough energy to sustain itself.

Brown Nunlets have a basal metabolic rate (BMR) that is similar to other small bird species. This means that their metabolic rate is relatively high compared to their body weight.

The metabolic rate of the Brown Nunlet can also be influenced by factors such as temperature and activity level. When the temperature is hotter, the bird’s metabolic rate increases, allowing it to maintain its body temperature.

The Brown Nunlet can also regulate its body temperature through evaporative cooling by panting. When the bird is overheating, it opens its beak and retches in order to speed up the evaporation of water from its tongue and throat, which cools down its body temperature.

This adaptation is crucial for the bird’s survival in its humid habitat, where high temperatures and humidity can affect the bird’s ability to cool down.

Sounds and Vocal Behavior


The Brown Nunlet is known for making a variety of vocalizations. The most common sound made by the Brown Nunlet is a series of six to eight high-pitched notes that are repeated rapidly.

This call is often described as sounding like “kwee-kwee-kwee-kwee-kwee-kwee-kwee.” The calls are used by the bird for communication and to establish territory boundaries.

In addition to the main vocalization, the Brown Nunlet also makes other calls that are used for communication between mates, to warn of danger, or to indicate the availability of food.

These calls include a rapid, repeated “pi-pi-pi-pi,” which is used to signal the presence of food, and a low-pitched “hoo-hoo-hoo,” which is used to establish territory or signal danger.

Overall, the vocalizations made by the Brown Nunlet are an important part of its behavior and help the bird to communicate with others in its habitat range.



The Brown Nunlet (Nonnula brunnea) moves through its habitat by hopping and flying. Its small size and relatively weak wings make it difficult for the bird to fly for long distances, so it primarily hops along the branches and trunks of trees.

Brown Nunlets often move through the understory layer of the forest, where they maneuver around obstacles such as fallen logs and vegetation. They have been observed moving headfirst down tree branches, which is unusual behavior for most bird species.


Brown Nunlets engage in a variety of self-maintenance behaviors, such as grooming their feathers and preening themselves. The birds use their beaks to clean and maintain their feathers, which helps to keep them clean and in good condition.

Agonistic Behavior

Brown Nunlets exhibit agonistic behavior towards members of the same species. This behavior is often displayed during territorial disputes, where two birds are competing for the same area of habitat.

During these interactions, Brown Nunlets may puff up their feathers and make aggressive calls and postures in an attempt to establish dominance.

Sexual Behavior

During the breeding season, Brown Nunlets engage in a variety of sexual behaviors. They form monogamous pairs, with each pair occupying a territory within the habitat range.

Males will typically establish the territory and maintain a space for the pair to nest.


Breeding among Brown Nunlets typically occurs in the wet season, which is characterized by higher precipitation and more abundant food, two important features for the survival of chicks. During this time, males will engage in courtship displays to attract a mate, which often involves the male attracting the female with a selection of food items.

Once a pair has formed, the female will lay a clutch of two or three eggs, which are incubated for around 20 days. Both parents take turns incubating the eggs, and when they hatch, both will also engage in feeding and caring for the young, which stay within the covered nest and have a basic grey plumage.

The chicks will remain in the nest for around 24 – 25 days, during which time they are fed a steady diet of fruits and insects brought by their parents. Once the chicks are fully grown, they will leave the nest and become independent birds that may engage in their own pair bonding.

Brown Nunlets have a relatively stable lifespan, with some captured birds reported to have lived up to 14 years in the wild.

Demography and Populations

The population size of the Brown Nunlet is difficult to estimate accurately due to its sedentary nature and small size. However, available data suggests that populations of the bird may be declining in certain areas where its habitat has been disturbed by human activity.

Deforestation and mining in some sections of the bird’s range have impacted the quality and consistency of the habitat available to the Brown Nunlet.

Habitat fragmentation due to these activities has led to the reduction in the bird’s population density in some areas.

The conservation status of the Brown Nunlet has been considered a species of ‘Least Concern’ by Bird Life International, due in part to its broad geographical range.

Several conservation initiatives have been launched to safeguard the habitat of the Brown Nunlet across its range.

These projects aim at promoting sustainable land management practices that protect the bird’s habitat and limit the impact of human activities on Brown Nunlets’ habitat. The protection of the habitat range of the Brown Nunlet may ultimately lead to the stabilizing of population density and reduction in the threat of extinction for this unique bird species.

In conclusion, the Brown Nunlet is a unique bird species found in Central and South America that is known for its distinctive appearance, frugivorous diet, and sedentary nature. The bird inhabits humid tropical forests and can be found in the understory layer, where it primarily feeds on fruit and insects.

Brown Nunlets engage in a range of behaviors, such as locomotion, self-maintenance, agonistic behavior, and sexual behavior. They have a relatively stable lifespan and can live for up to 14 years in the wild.

Although sightings of Brown Nunlets outside their regular range are rare, populations of the bird are considered to be declining in some areas due to habitat fragmentation caused by human activity. Conservation efforts aim to protect the species’ habitat and promote sustainable land management practices, which will help ensure the continued survival of this unique bird species.

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