Amblyornis macgregoriae

Geographic Range

Macgregor’s bowerbirds ( Amblyornis macgregoriae ) are widespread in eastern and central Papua, New Guinea. They range from the eastern Owen Stanley Range to the Adelbert Range in Papua, New Guinea.

• Biogeographic Regions
• australian australian
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Macgregor’s bowerbird primarily spend most of their lives regularly spaced within available habitat in isolated ranges that occur at high elevations (1,200 and 1,400 m) in mountain ranges across central and eastern New Guinea. They live in mixed mid-montane and Nothofagus forests in higher altitudes, along ridges.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest
• mountains mountains

• Aquatic Biomes
• coastal coastal

Physical Description

Macgregor’s bowerbirds are small and stocky with a stout and dark bill. Adult females grow to be about 26 cm and are generally dark brownish with olive coloring and paler faces and necks. Adult males have glossy orange color tipping its feathers that are dark green, black, and brown in coloring. The male has a bright orange head plume, causing them to stand out more so than the females.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful

Reproduction

Bowers are essential to males in mating interactions with females. Male Macgregor’s bowerbirds will not attract a mate without an elaborate and complete bower. The more time and effort the male spends on the bower potentially increases the reproductive success of the male. Macgregor’s bowerbirds are polygamous. The female inspects the male’s bower and if she likes it, she expresses female-choice and mates with the male. After mating, the female leaves the bower and builds her own nest out of plant material and lays one or two eggs. The male continues to work on his bower and attempts to attract as many females as he can.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Male Macgregor's bowerbirds build structures out of sticks called a bower. The female approaches this bower and chooses whether or not she wants to mate with the male who built it. As the female inspects the bower, the male dances and shows off his bright colors. The more intricate bower and the longest dancing male is usually the female's choice, because it represents the fitness of the male. When the female chooses a male, she allows him to copulate. Once copulation has finished, she builds her own nest and parents the offspring alone. The male continues to work on his bower and mate with other females.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

After mating, the female builds her own nest close to the male's bower/territory. The female has access to provisions (fruit) on male's territory. Females raise eggs and young on her own.

• Parental Investment
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Little is known about the Macgregor's bowerbird's life span.

Behavior

Bowerbirds construct a maypole bower on ridgelines with a mean interbower distance of 182.8 m. The males tend to be regularly spaced throughout available habitats on ridgelines and montane forests. A maypole bower consists of twigs piled up around a sapling decorated in fruit, fungus, charcoal and insect frass selected by colors and sizes and is used in courtship. The male Macgregor’s bowerbird aggressively defends this bower and always remains within a 20 m radius of the bower. Bower building reveals a social system consisting of both lek behavior and territoriality. A significant relationship between the bower complexity (amount of decorations, size, color, etc.) and cerebellum size of the male bowerbird was found. This relation is driven by sexual selection; the more elaborate the bower is, the larger the cerebellum and an increase in fitness is a result.

• Key Behaviors
• arboreal arboreal
• terricolous
• flies
• diurnal diurnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• territorial territorial
• dominance hierarchies dominance hierarchies

Communication and Perception

Macgregor’s bowerbirds communicate through visual displays and cues in mating through courtship and the constructing of a bower by the males. They also use vocalizations in courtship signaling to the females. Males use body language through the counter movements around the central bower to communicate with the female on the other side.

• Communication Channels
• visual visual
• acoustic acoustic

• Other Communication Modes
• mimicry mimicry
• duets duets

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Macgregor’s bowerbirds are frugivorous. The males gather fruit for bower decoration, which is a separate behavior than food storing. 95% of the Macgregor’s bowerbird diet consists of medium to large drupes and arillate fruit. Arthropods were found to make up the rest of the diet. The Macgregor bowerbird forages alone or in small groups. Females, juveniles and males all forage in the same areas revealing that the males do not defend any food sources. The males also participate in fruit caching which only takes place during the breeding season. The males who had the most elaborate and complete bowers were found to have the most cache sites.

• Primary Diet
• herbivore herbivore
  • frugivore frugivore

• Plant Foods
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Macgregor’s bowerbirds participate in lek displays and it is thought that this behavior may reduce predation. The bower and the courtship displays distract predators away from nearby nests, but there is no evidence of predation on males or females during these displays. These bowers and nests are made on the ground along ridges where there are not very many predators. Specific predators are unknown to Macgregor’s bowerbirds.

• Anti-predator Adaptations
• aposematic aposematic
• cryptic cryptic

Ecosystem Roles

Macgregor’s bowerbirds are strictly frugivores, therefore are thought to have impacts on the size and structure of fruit growing in their range. The plants have shown an adaptation to Macgregor’s bowerbird feeding habits to enhance certain seed dispersal patterns.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Macgregor’s bowerbirds rarely come in contact with humans except for when they land in the sacred sites and gardens of the indigenous people. Bowerbirds in general provide great research for sexual selection.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

The Macgregor’s bowerbird is not known to have any negative effects on humans.

Conservation Status

The tropical montane climate of the forests Macgregor’s bowerbirds inhabit have effectively confined horticulture by the indigenous people in that area through its high altitudes and rich terrain. There are also sacred sites set aside by the indigenous people that prohibit the killing of birds and mammals. Macgregor’s bowerbirds populations are currently considered least concern by the IUCN but is expected to decrease with the loss and degradation of their habitat.

Additional Links

Encyclopedia of Life

Contributors

Hadley Seniff (author), Hobart & William Smith Colleges, Jim Ryan (editor), Hobart & William Smith Colleges, Laura Podzikowski (editor), Special Projects.

References

Borgia, G. 1997. Biodiversity II: Understanding and Protecting our Biological Resources: Comparative behavioral and biochemical studies of bowerbirds and the evolution of bower-building . Washington, DC: The National Academies Press.

Day, L., D. Westcott, D. Olster. 2005. Brain, Behavior and Ecolution. Brain Behav Evol , 66: 62-72.

Diamond, J. 1986. Biology of Birds of Paradise and Bowerbirds. Ann Rev Ecol Syst , 17: 17-37.

Frith, D., B. Clifford. 2004. The Bowerbirds: Ptilonorhynchidae . Oxford: Oxford UP.

McKean, J., R. Schodde. 1973. Distribution, Taxonomy and Evolution of the Gardener Bowerbirds, Amblyornis spp. in Eastern New Guinea with Descriptions of Two New Subspecies. Emu , 73: 51-60.

Phillips, J. 1990. Lek Behaviour in Birds: Do Displaying Males Reduce Nest Predation?. Animal Behaviour , 39.3: 555-565.

Pratt, T. 1982. Additions to the Avifauna of the Adelbert Range, Papua, New Guinea. Emu , 82: 117-125.

Pruett-Jones, M., S. Pruett-Jones. 1985. Food Caching in the Tropical Frugivore, Macgregor's Bowerbird (Amblyornis macgregoriae). The Auk , 102: 334-341.

Pruett-Jones, M., S. Pruett-Jones. 1982. Spacing and Distribution of Bowers in Macgregor's Bowerbird (Amblyornis macgregoriae). Behavioral Ecology Sociobiology , 11: 25-32.

Stiles, E., T. Pratt. 1985. The Influence of Fruit Size and Structure on Composition of Frugivore Assemblages in New Guinea. Biotropica , 17: 314-321.

Thomas, W. 2009. Landscape, Process and Power: How do they see it? Traditional resource management, disturbance, and biodiversity conservation in Papua, New Guinea. Studies in Environmental Anthropology and Ethnobiology , 10: 140-154.

2007. "Birdlife International" (On-line). Accessed February 14, 2012 at http://www.birdlife.org/datazone/speciesfactsheet.php?id=5172 .