Asities: The Unique Endemic Birds of Madagascar
The asities are a specialized family of birds, known scientifically as Philepittidae, found exclusively on the island of Madagascar. Comprising four distinct species divided into two genera, these small forest dwellers are a testament to the island's extraordinary biodiversity. While some species were previously referred to as false sunbirds, they are now recognized as a distinct lineage within the infraorder Eurylaimides.
Key Facts
- Endemism: Found only in Madagascar.
- Unique Biology: Males possess eye wattles colored by collagen fiber arrays, a trait unique in the animal kingdom.
- Diet: Primarily frugivorous (fruit-eating), playing a critical role in seed dispersal.
- Classification: Divided into two genera: Philepitta and Neodrepanis.
- Conservation: The yellow-bellied sunbird-asity is listed as vulnerable.
Physical Characteristics and Anatomy
Asities are small birds characterized by sexually dichromic plumage, meaning males and females exhibit different colors. One of their most striking features is the brightly colored wattles around the eyes of the males. These wattles become most prominent during the breeding season and derive their color from ordered arrays of collagen fibers, a method of pigmentation not found in any other animal.
Anatomically, asities differ from their relatives, the broadbills, in several ways. They possess twelve tail feathers on extremely short tails—which are nearly non-existent in the Philepitta genus. Their syrinx (the vocal organ of birds) is encased in a large bronchial ring. Additionally, they have forked tongues specifically adapted for nectivory (the consumption of nectar). A long outer primary feather creates a buzzing sound during flight, which is believed to be used for courtship signaling.
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Behavior and Ecology
Diet and Feeding
Fruit is the primary component of the asity diet. Because there are very few other frugivorous birds in Madagascar's forests, asities serve as some of the most important avian dispersers of seeds. While they also consume insects, the Neodrepanis (sunbird-asities) specifically supplement their diet with nectar, using their long tongues rather than inserting their curved bills deep into flowers.
Breeding Habits
Breeding typically occurs during the Malagasy rainy season, from September to November, though the velvet asity in the north may begin slightly earlier. The velvet asity employs a polygynous breeding system, where males maintain small territories or leks to display for females. In this species, females handle all nest building, incubation, and chick rearing.
However, breeding strategies vary across the family; for instance, male yellow-bellied sunbird-asities have been reported feeding their young. Their nests are elaborate, pear-shaped woven structures that hang from branches. Uniquely, the entrance to these nests is created by pushing through the wall after construction, rather than being woven into the structure from the start.
Taxonomy and Conservation Status
Historically, asities were thought to be related to pittas, which influenced their family name. However, research in 1993 suggested they might be a subfamily of the broadbills (Eurylaimidae) due to similarities in the syrinx. Currently, they are traditionally treated as a separate family, Philepittidae.
Conservation efforts are focused on the more threatened species. The yellow-bellied sunbird-asity is listed as vulnerable by the IUCN and BirdLife International. While once feared extinct due to a lack of surveys in high-altitude regions, subsequent research confirmed its presence, though habitat fragmentation remains a threat. Schlegel's asity is categorized as near threatened, surviving in fragmented distributions within inaccessible ravines.
| Genus | Species | Conservation Status |
|---|---|---|
| Philepitta | Velvet asity (P. castanea) | Not specified |
| Philepitta | Schlegel's asity (P. schlegeli) | Near Threatened |
| Neodrepanis | Common sunbird-asity (N. coruscans) | Not specified |
| Neodrepanis | Yellow-bellied sunbird-asity (N. hypoxanthus) | Vulnerable |
Frequently Asked Questions
What makes the asity's eye wattles unique?
The wattles of male asities are unique in the animal kingdom because they obtain their bright colors from arrays of collagen fibers rather than standard pigments.
Why are asities important to the Madagascar ecosystem?
Asities are among the most critical avian seed dispersers in Madagascar's forests because there are very few other bird species that primarily eat fruit.
How do asity nests differ from other woven nests?
Unlike most birds that weave an entrance into the nest during construction, asities create the entrance by pushing through the wall of the completed pear-shaped structure.
Are all asity species endangered?
Not all, but some are threatened. The yellow-bellied sunbird-asity is listed as vulnerable, and Schlegel's asity is considered near threatened due to habitat loss and fragmentation.