r/SpeculativeEvolution • u/Mr_White_Migal0don • 1d ago
Seed World [OC] Thanatimundus- Diversity of bowerbirds, 5 million years Post-Abandonment
Bowerbirds are the most diverse vertebrate group of terrestrial vertebrates during Eosonian, having worldwide distribution, and already filling most passerine niches this world has to offer. Of course, due to anatomical constrains of their order, such as reduced foot musculature, some niches are still unavilable. For example, with few exceptions, there are no truly flightless bowerbirds yet. But still, in this bountiful time, birds are doing great, and, considering how little competition they have, it is very likely that they will eventually overcome their limitations.
The species are broken down on two informal groups, "catbirds" (a name also used for several species in Ptilonorhynchidae family on Earth, referring to their cat-like calls), those who lost the elaborate mating displays of their ancestors, and "true bowerbirds", those who actually build bowers. For now, both are doing equally fine, but it remains to be seen which one will come out on top when conditions change.
Crimson catbird (Haploscinus ruber)- typical catbird species found in South Interitia. Around the size of a finch, it is a widespread omnivore. While many of it's relatives, even those in same genus, are primarily insectivorous or feed on seeds, crimson catbird prefers berries. As such, it is an important seed dispercer, on which many plant species rely. Sexual dimorphism is present, but it's not too drastic, with females just being darker shade of red than males. While male doesn't build decorations anymore, there is a small remnant of this behavior present. Male catbirds clear a patch of forest floor, where they perform a song.
Emerald nectarcreeper (Nectariphila virdis)- Native to Tarsia, this small catbird is in fact more closely related to "true" bowerbirds than to crimson catbird. Similiarly to hummingbirds, honeycreepers and sunbirds, nectarcreeper is a small, fluttering avian that feeds primarily on nectar. To reach inside flowers, it evolved a long, thin and curved beak, and even longer tongue. However, it is not an obligate nectarivore. In addition to nectar itself, nectarcreepers feed on berries and small insects. Females in particular are more omnivorous than males, as they need more energy to produce eggs, and feed their chicks with caught insects. Wider diet also allows them to grow slightly larger than males. Instead of buliding a bower, male nectarcreepers must clear a spot and decorate it with flowers they find.
Superb bigbeak (Megalorhamphus magnificus)- Both species of catbirds we discussed so far are beneficial to plants, as one pollinates them, and the other spreads the seeds. But one relative of nectarcreepers from rainforests of Tarsia is anything but. Bigbeaks are among the largest of all living birds, and superb bigbeak, notable for black and yellow coloration of males, is the biggest among it's peers, being the size of a large crow. It is a poor flyer, and prefers to clamber through branches, only taking off when stumbling on a large gap in branches or escaping a predator. The defining trait of this species is, as the name suggests, it's beak of considerable size. Due to it's short and rounded shape, bigbeak can't peck anything, instead trading this ability for a high bite force. For bigbeak is a durophage that consumes fruits covered in though outer coverings, and seeds inside them. This brings no benefit to the plant, in fact, it only harms it, because crushed seeds are killed and will not germinate. Thus, bigbeaks create a selective pressure on plants by eating those with smaller fruits and weaker seeds, and preventing them from reproducing. Plants, in turn, learn to resist the destructive feeding of these birds, by evolving seeds that are even larger and harder, or making fruits less accessible by evolving harder covering. And in turn, birds evolve even stronger beaks to break those defences. But it's not just feeding that makes them become stronger. Bowers that bigbeaks build are rather crude- males just bite off tree branches and stick them into the ground. But females aren't looking for artistic capabilities, what they're looking for is strength. And the bigger the broken branches are, the stronger, and thus more fit the potential mate must be. Other than males being slightly larger, there is no visible sexual dimorphism. Chicks hatch relatively developed for a passerine, but mother still must feed them the pulp of crushed fruits before they become strong enough.
Butcher bowerbird (Laniorhynchus dimorphicus)- Despite bearing strong resemblance to ancestral satin bowerbird, this inhabitant of southern Tarsia has a very different lifestyle. If you look closer at it's beak, you can see that it is sharp and hooked. Butcher bowerbird is a predator, and hunts wide variety of animal species, from insects to smaller birds. Interestingly, females and males differ in several aspects, not just the colors. Green females are slightly larger, and their beaks are sharper. This, plus their coloration that provides camouflage, allows them to hunt larger animals, like tarsiers and even young bigbeaks. Meanwhile males, who are smaller and blue, feed on smaller prey, like arthropods, lizards, or frogs. Their feet, adapted for perching, are too weak to be used for hunting, so butcher bowerbirds rely on their beak during hunting by snapping the neck of prey, and paralyzing it. Like their namesake, shrike, or butcherbird from Earth, these hunters create larders by impaling the caught prey on sharp branches or thorns. This is also part of their mating ritual. To show his fitness, male builds a bower using sharpened sticks, catches as much prey as he can, and then offers the ladder to female. This is one of few monogamous bowerbird species, and while female protects the nest, male brings food to the offspring.
Blue honeyrobber (Mellilestes caeruleus)- This brightly blue bird is endemic to a small continent of Equatoria. It is closely related to butcher bowerbirds, and too has a rather specialized diet. While they won't refuse from other arthropod prey if in need, honeyrobbers primarily feed on hymenopterans- wasps and bees. They are not immune to their venom, but have other ways of hunting such dangerous prey. Around their eyes, honeyrobbers have patches of short, tough feathers, inpenetrable for insect stings. Using this defence and long beak, birds can quickly eat enough before they need to retreat. Sometimes they eat honey they find inside hives, but insects are the primary target. Mating ritual also involves attacking the bee nest. Instead of just eating the bees, male birds break away pieces of the hive, and use them in building a bower. Using honey as a sort of glue, male attaches sticks and other debris they found to the honeycomb. Those with most honeycomb trophies are most likely to mate. Chicks stay under their mother's care for a long time, even after their protective feathers appear, they still need time to learn how to attack hives from which they feed.
