Similar to the carrier pigeon of many Prime worlds, the astral streaker is a creature with a long history of messenger service across the Outer Planes. The great distinction between the two, however, is that in the case of the streaker, the messenger is intelligent.
Being such a minor creature, there is no record of the origin of the astral streaker. It seems to have been present on the Astral Plane for some millennia in much the same form, but unfortunately, the streakers themselves have no clue as to their origins, having little in the way of care for the past. Most sages assume that they are a transplant species, given their avian form; a form quite unsuited to the Astral. The most popular theory associates the astral streaker to the possibly-extinct krandohl, a similar species of bird once known on the Beastlands that was known for being the subject of intelligence-boosting experiments in the distant past.
It was the githyanki to first realize the potential of streakers as messengers within the Astral some millennia hence, given their great ability to navigate the plane with an ease far outpacing their natural intelligence. Still, it took some centuries for use of the bird to spread beyond the Astral, due to both the natural reluctance of the githyanki to spread use of any possible advantage, and the common belief among those aware of them that the streaker's natural predilection for navigation was restricted solely to the Astral. Eventually, though, the bird spread beyond that plane; first to Sigil, and from there to some of the more hospitable Outer Planes.
Though slight in intelligence compared to most humanoid species, astral streakers do have their own culture of a kind. They lack in any sort of social structure larger than a clan, and have no sense of leaders, elders, or anyone with authority greater than any other. However, their clans and their families tend to be quite close indeed. Unlike many avian species, a family of streakers remains as a unit throughout their lives, with every living generation passing along to each new one the knowledge needed to navigate appropriately.
It is important to note that their innate talent at navigation is not in itself a natural gift, but rather their gift is the ability to memorize in great detail large swathes of terrain and layout. Not just in three dimensions, but seemingly the true underlying multidimensional structure of planar space. A newborn streaker takes but weeks of study from its kin to learn the full street layout of a metropolis like Sigil, months for a region or realm, and years for a full layer. This innate facility for memorization is considered by streakers to be the center of their being, though with no central authority each family of streakers tends to interpret this slightly differently. Some see themselves as nothing but their knowledge, growing as it does; others see great hidden meanings in the arrangement of paths, trails, and routes, meanings beyond their facility to understand; and still others believe each street is its own living being, and mourn every washed-out forest trail or bit of urban redevelopment. And of course, as can be expected from a concept so central, there are a number of rituals built up around the passing of this knowledge to each new generation — though much as the beliefs themselves, these rituals tend to be different for every family group.
Outside the Astral, astral streakers are insectivorous, each requiring close to twice the food a bird their size would normally require. This is thanks both to their (for an animal) prodigious minds, and their extreme longevity. Even without the timeless properties of their homeland, an astral streaker can live for hundreds of years. Also as a result, they go quite long between clutches, with a single generation usually around 100 years and averaging a mere 1-2 young. It's this fact that largely contributes to them not overwhelming a region with their population; were it not for this, they would likely exhaust any realm's supply of edible insects within mere decades.
Strangely, though, wild young astral streakers do appear on the Astral, and wild streakers are seen to age. The mechanism of this isn't yet understood, as it never seems to function for streakers held in captivity. Some sages believe that streakers have regular migrations to the Prime, unseen by mortals, while others believe wild streakers exploit the anti-timeless properties of certain godcorpses and keep their colonies there. The high speeds and excellent multidimensional instincts of streakers, however, have made tracking streakers back to their local Astral homes too difficult for any to have bothered trying.
Close to the size of a sparrow, streakers' plumage is quite glossy, varying in shade from dark grey to near-white; the better to camouflage themselves from predators. Males tend to be slightly smaller than females on average, with more elaborate feather patterns. The female's plumage, on the other hand, is usually quite flat, with little variation across the body.
- In the Cage, pg.70
- A Guide to the Astral Plane, pp.72-73