Green Woodhoopoe (Phoeniculus purpureus)
Green woodhoopoes are a medium sized bird averaging 12 inches long with an equivalent wingspan. Their weight averages between 60 - 70 grams depending on gender. Adult plumage is overall dark green with glossy reflections of purple, black, and green. Wings are rounded with white bars crossing mainly the primary feathers. Tail is graduated with white spots and is generally longer than the body. Adults have a distinctive long, red, decurved bill, which is longer in males than females. Bill color varies from bright red to dull black depending on age and sub-species. Their short red legs are a bright contrast to the dark plumage. Immature birds are generally much duller in color and instead have straight, black bills and black legs.
DISTRIBUTION AND HABITAT
Woodhoopoes are one of the few bird families that are found exclusively in Africa. They dwell in savannah, open woodland, palm groves, acacia thornvelds and wooded garden areas. They are absent from arid zones and forest.
HABITS AND SOCIAL STRUCTURE
Green woodhoopoes are highly sociable, chattering birds usually seen in small flocks of 4-15 individuals. Groups are often seen following each other from tree to tree while foraging in cracks and crevices. During the dry season they also forage on the ground. The sex ratio in flocks is about 1:1 but as a rule only includes one breeding pair. They climb trees in a jerky fashion similar to woodpeckers; often dropping perpendicularly along the trunk and then clinging to the bark with their sharp, curved claws and using their tail as a prop.
They are generally known as one of the noisiest birds of the bush, with their old African regional name 'Kakelaar' being derived from its voice. Their displays include a loud 'kuk-uk-uk-uk' cackling call; starting off slowly then with a crescendo as a group as the birds rock back and forth with their heads lowered. They also have a distinct musky scent they produce from their uropygial gland that is often used for defense from predators. A nestling's defense consists of squirting large quantities of smelly excrement when taken from the nest.
These birds are highly territorial with each flock usually defending the same large area throughout the year. Territorial defense is through group displays with birds often passing lichens or bark between themselves to increase group cohesion. Sexes generally roost separately. When vacancies in flocks occur through predation, they are usually filled by birds of the same sex from nearby territories. Members of flocks tend to be very closely related. Unrelated females sometimes break off to form new flocks.
REPRODUCTION IN WILD POPULATIONS
In any given territory there is generally one monogamous breeding pair, usually the oldest birds. Prior to breeding, the pair leaves the group to forage and allopreen quietly on their own with the male frequently offering food to the female. During this time, the non-breeding members of the flock are scouting for nesting sites while foraging. Nest sites chosen are usually closest to the most concentrated food source in the territory. The unlined nest of choice usually consists of a natural live tree cavity or an old nest hold from a woodpecker or barbet.
The average clutch size is 3-5 blue-green eggs about 25x18mm. Pairs can produce two clutches per year in a bountiful season. Breeding usually occurs during the rainy season (July through October depending on the geographical area). Incubation by the female starts with the complete clutch and lasts for 17-18 days.
These birds use a cooperative breeding system in which the breeding pair will have help feeding their young from typically 1-10 non-breeding birds, including their offspring from previous clutches. The male and helper birds will forage for food and bring it to the female who relays it to the altricial chicks. Just prior to fledging, all of the members of the flock call extensively to the young and preen them. This appears to prepare them for integration into the group. Fledging occurs at 28-30 days. The young are protected and fed by all members of the flock for several weeks after fledging. A few months later the fledglings will, in turn, contribute food to the next group of hatchlings. They will remain with the parents for 1-5 years as non-breeding helpers.
DIET AND STATUS OF WILD POPULATIONS
Their natural diet consists of arthropods, insects, and occasionally lizards and vertebrates probed out of crevices and fissures in bark, wood and grasses. They have also been shown to drink nectar of Erythrina flowers and eat small fruits. Diet for the young can include: caterpillars, grubs, insect egg masses, beetles, termites, ants, and moths. For adults, prey is either swallowed directly or first beaten against a branch.
Studies have shown their lifespan to be around 8 years due to heavy predation. Breeding success and life expectancy are affected by several factors including predation and competition. Driver ants have shown to be nocturnal predators of nestling woodhoopoes in nest holes. Predators to fledglings and adults include Gabar goshawks, Harrier hawks, Pearl-spotted owls, genets and mite infestations. There is often intense competition for proper nesting sites between woodhoopoes and other bird species, mammals, and honeybees. Green woodhoopoe annual numbers are further affected by parasitation by Greater Honeyguides in Nigeria. According to Urban et al., their overall mean annual survival is low. Currently they are not listed as a threatened species.