r/Awwducational • u/IdyllicSafeguard • 4d ago
Verified The mistletoebird of Australia and Indonesia specializes in feeding on mistletoe berries — digesting the flesh and depositing the sticky seeds onto branches in neat lines, where they quickly germinate and grow. The bird is nomadic, in near-constant search of mistletoe berries.
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u/IdyllicSafeguard 4d ago
Sources:
Australian National Botanic Gardens
Human Ageing Genomic Resources (AnAge)
NSW Government - mistletoe myths
Backyard Buddies - mistletoe in Australia
Botanic Gardens of Sydney - mistletoe
Smithsonian Magazine - biology of mistletoe
Smithsonian Magazine - mistletoe facts
Plantlife - mistletoe
Wisconsin Horticulture: Division of Extension - mistletoe
Texas A&M Forest Service - mistletoe
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u/IdyllicSafeguard 4d ago
The mistletoebird is a specialized mistletoe spreader, in both its anatomy and behaviour. But how exactly is it specialized?
For one, its digestive system is relatively simple — it lacks a muscular gizzard (the part of a bird's stomach that grinds up food) and a berry passes through its system without contacting the stomach's corrosive digestive enzymes. The seed pops out intact, encased within sticky goop.
Up to 85% of a mistletoebird's diet can consist of mistletoe berries, making it among the most specialized of any bird in terms of its diet (i.e. it's a very picky eater).
Its defecating etiquette could almost be called elegant. Compare the specialized mistletoebird to another, more casual, mistletoe enjoyer — like the spiny-cheeked honeyeater, who haphazardly poops out digested seeds, most of which fall to the ground. Meanwhile, the mistletoebird deposits mistletoe seeds in a neat line along a branch so they can infiltrate their host tree.
The mistletoebird ranges across mainland Australia and the eastern Maluku Islands of Indonesia to the north. It goes wherever mistletoe grows. Of the around 90 species of mistletoe in Australia, the mistletoebird is known to eat and disperse at least 21 of them.
The mistletoebird is an elfin ave, barely 10 centimetres (4 in) tall. The female is ashy grey with a light-red undertail, while the male is glossy blue-black from his head and down his back, red and white on his front, with a charcoal line down his belly.
The mistletoebird is a nomad for most of the year, following the most abundant blooms of mistletoe. Only during its breeding season (August to April) does it settle down to build a suspended, pear-shaped nest and raise 3 to 4 chicks. After an initial diet of insects and larvae, the chicks soon transition to a predominantly mistletoe-berry diet.
Delivered onto a branch by a mistletoebird, a mistletoe seed soon germinates and uses a structure called a haustorium (equivalent to a stem or root) to penetrate into the bark of the host tree or shrub, squeezing its way towards the xylem from which it leeches water and nutrients. The Christmas kissing plant is a mooching parasite.
Mistletoe is a plant parasite that weakens, but usually doesn't outright kill its host. All in all, it does more to help than harm its ecosystem. In Australia, mistletoe berries are known to feed 33 species of birds, while the flowers feed at least 41 species, and the leaves feed countless species of invertebrates, as well as mammals like possums and gliders. As many as 245 Australian bird species are known to nest within mistletoe.
Mistletoebirds are like feathery versions of Santa's elves; neatly delivering presents (in the form of goopy parasitic seeds) as they travel across the land. You can learn more about these mistletoe munchers — as well as the biology and history of their favourite parasitic plant — on my website here!