Amblyornis macgregoriaeMacGregor's bowerbird

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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. (McKean and Schodde, 1973; Pruett-Jones and Pruett-Jones, 1982; Stiles and Pratt, 1985)

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. (Borgia, 1997; McKean and Schodde, 1973; Pruett-Jones and Pruett-Jones, 1982; Stiles and Pratt, 1985)

  • Range elevation
    1,200 to 1,400 m
    to ft

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. (Borgia, 1997; Frith and Clifford, 2004)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Average length
    26 cm
    10.24 in

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. (Diamond, 1986; Pruett-Jones and Pruett-Jones, 1985)

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. (Diamond, 1986; Pruett-Jones and Pruett-Jones, 1985)

  • Breeding interval
    The frequency of mating is unknown.
  • Breeding season
    Macgregor's bowerbirds breed between September and February.
  • Average eggs per season
    1 to 2
  • Range time to hatching
    19 to 24 days

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. (Diamond, 1986; Pruett-Jones and Pruett-Jones, 1985)

  • Parental Investment
  • 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. (Day, et al., 2005; Pruett-Jones and Pruett-Jones, 1985)

  • Average territory size
    20 m^2

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. (Borgia, 1997)

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. (Pruett-Jones and Pruett-Jones, 1985)

  • Plant Foods
  • fruit

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. (Borgia, 1997; Phillips, 1990)

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. (Stiles and Pratt, 1985)

  • 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. (Thomas, 2009)

  • 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. ("Birdlife International", 2007; Thomas, 2009)

Contributors

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

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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acoustic

uses sound to communicate

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

mimicry

imitates a communication signal or appearance of another kind of organism

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

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

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.