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Mariebirds are a diversified group of insular ducktails, endemic to Marie Byrd. They were able to reach this isolated environment in the middle Lentocene, where a stepping-stones corridor connected Polarica to this island. They are among the largest vertebrates of their territory and despite the Foster's rule some species were able to reach an impressive size.
The most common species is the globose mariebird (Rossornis catenatus), which can be found from coastal woodlands to the small and fragmented mountain tundra of the island, thanks to their great diet versatility.
This species can be rapidly recognized by the large wattle on its head, which is larger in males.
They can also be identified by their low-frequency calls, which are used to communicate with each other over long distances: their hearing is in fact very developed for a bird, capable of listening sounds as low as 10 hz.
This adaptation has proven to be indirectly useful to detect the presence of cervinos, one of their main predators, which often use infrasounds to mark their territories.
Their scientific name ("chained bird of Ross") is referred to their annual migration that they achieve during the breeding season: a multitude of family groups fuse together, forming gigantic herds of thousands of individuals that will move to the temperate coasts of Ross sea, near the Green Channel. For about one month, the global population of globose mariebirds is restricted to just 400 km of coast (250 miles), where they mostly feed on highly energetic food, like fruits, insects and seaweed.
In this area, periodical overgrazing has progressively caused the creation of a linear and contiguous grassland, where highly palatable shrubs and grasses can be found.
Lots of grasslands-adapted bird species can be found only in this coastal corridor, which covers no more than 8.000 km2.
Marie Byrd Island also hosts one of the most primitive-looking bird: the giraffe mariebird (Erbiraptor insularis): this species possesses the proportionally largest pygostile of all ducktails. This, in addition to their long neck, give him an Ornithomimus-like appearance (which is kind of ironic, since Ornithomimus means "bird mimic").
Unlike these long-extinct dinosaurs, the giraffe mariebird is capable of ground food inside its mouth thanks to the presence of small false teeth and a rough tongue, a common characteristic of all ducktails and one of the reasons for the success of this highly-derived duck clade.
The long neck allows these birds to feed on high branches like tower ducktails do on mainland Polarica, a typical example of convergent evolution.
Giraffe mariebirds are stantial herbivores that rarely move outside their territory. Territorial fights can be brutal, often ending with the death of one opponent. To fend off predators, this ducktails use their strong feet as a powerful hammer, that can easily break a geotter head. When facing incubos, giraffe mariebirds aggressively hiss and try to peck the predator. They are surely not an easy prey for anyone.
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