Eusocial birds

I found a fasinating webpage. An evolutionary AH where the dinosaurs never died and continued to adapt. Any way, I found a very interesting article about a group of Eusocial birds that live in that world's Africa. I think "hey now! that would be great for green antarctica!"

(6 photos)

The site's detailed article on these bird's social structure:

Although the basic allospizian form has come down through the ages with very little modification, and the more basal cityfinch species are little different from their ancestors of 20 million years ago, the city-building behavior seems to be a very new phenomenon. Based upon fossil evidence, cityfinches as social birds evolved in the Pliocene, the earliest undisputed city remains coming from 5 million year old strata in Ethiopia, and many paleontologists theorize that, like our own ancestors, these birds were driven to explore new modes of life as the African forests shrank and disappeared. The question as to why such birds never evolved in our own time-line is more difficult to answer. Perhaps neornithian birds are somehow unsuited for the social life-style, or perhaps the presence of hominids on our Africa's grasslands precluded other species from evolving into the grain-eating niche. The most likely explanation, however, is that the finches of our home timeline never stumbled upon the cityfinches' primary mutation, the crucial piece of genetic machinery necessary for their social lifestyle. The birds of our Earth never made use of haplodiploidy. Like the social insects, cityfinches are haplodiploid, with male body cells containing half the chromosomes of female cells. For this reason, potentially destructive recessive genes may lurk unexpressed in the genomes of the females, but the males with their unpaired alleles are 'cleaner' genetically. Female cityfinches may thus safely mate with close kin, confident that this inbreeding will not result in the expression of detrimental recessive alleles, as their mates have none. Haplodiploidy has evolved a few times among birds and many times among arthropods in both timelines, and may be an adaptive strategy for keeping a population genetically stable in an unchanging environment. Some species, however, also use the closely inbred families allowed by haplodiploid breeding for another purpose, kin selection. Because evolution is based upon the selection and proliferation through breeding of specific genes, organisms are, by and large, selfish. Natural selection favors those individuals that take all the resources they can and use them to breed profusely, regardless of the cost to other members of the same species. Lions of our own timeline and false-panhas of Spec kill offspring of other males to increase their own relative success in the gene pool, and there are many more examples of such selfishness among organisms of all kinds in both universes. How then, can altruistic behavior, behavior that favors another individual at the expense of the altruist, ever evolve? The key to this problem is kin selection, where the altruist and the recipient of the favor are kin and so both share a large number of genes. If an individual helps a sibling to collect food, for example, the individual will be aiding its own genes. Siblings share at least half of their genes, so even if an altruist cannot breed itself, if its siblings breed twice as much as they would have without help, the altruist's genes are transmitted just as they would have been had the altruist itself bred normally. For the city-finches, these bonds of kin selection form the essential glue that hold a colony together. A cityfinch colony begins when a group of brother and sister cityfinches leave their old home and stake out a new nest site. The exact construction and placement of these cities changes depending on species, but most cityfinches take the same factors into account as human engineers, placing their homes in areas of high grain productivity to feed their populous, near running water to carry away waste, and in an area far from the territorial patrols of other cities. The birds construct their nests out of a mixture of woven grass-stems, mud, and saliva, and many species make use of trees for structural support. The exact composition, size, and general shape of these cities is highly variable, dependant both upon species, local conditions, and the lineage of its builders, allowing naturalists to accurately map cityfinch lines of descent by comparative architecture. Once the city begins to take shape, the females lay their eggs. The eggs hatch quickly and soon the social hierarchy of a typical cityfinch colony beings to manifest itself. At birth, the chicks come in the normal vertebrate compliment of two sexes, male and female, but as the chicks age, they being to specialize upon purely cityfinch reproductive lines. From very early, the individuals bully their weaker siblings, pecking them mercilessly and almost ceaselessly. This pecking may result in bald patches around the head and tail, but almost never causes permanent physical harm. Those birds most often bullied, however, grow more slowly than their siblings, and most of them fail to go through puberty, maturing as small, sexless 'serfs'. With very few exceptions, serfs do not exhibit any mature adult specialisations, and seem to be completely infertile. Rather than furthering the transmission of their genes through breeding, serfs help their siblings to thrive, collecting food, performing domestic chores including egg and chick-rearing, cleaning and structural maintenance. The serfs and young males of very large cities may also act as "air conditioners", beating their wings at the entrance of special "ventilation tunnels" to maintain air circulation in the deeper parts of the colony. The childhood tormenters of the serfs, those chicks that were slightly larger and stronger than their sisters, mature normally, and a few months have fledged as mature, fertile castemembers. The colony generally maintains roughly equal proportions of adult serfs, females, and males, and while this mechanism remains poorly understood, the frequent bullying and pecks that the other castes inflict on the serfbirds may keep them in this undifferentiated, non-reproductive state. When the "bullying" falls below a certain level due to the reduction the number of mature adults, this inhibitor is removed and the strongest, most aggressive serfs change into mature castemembers. Conversely, when the number of serfs reaches over one half of the total adult population, the sexual adults turn on these birds and either kill or drive away some fraction of their number. In most cases, these 'proletariat flocks' die, but in some cases enough of the serfs metamorphose into sexual adults that they are able to form a new colony, usually with the cooperation of other exiled serfs. Proletariat colonies are usually smaller than their equivalents, and their members, which are of mixed genetic stock are less eager to cooperate than the citizens of a normal cityfinch colony. These colonies often fail in times of strife, but one persists long enough to build up a kin-bound population, then it may last for hundreds of generation. Naturalists believe that several of the oldest and most successful hitchcock cites in the Rift Valley are the fruits of several long-ago proletariat colonies. Serfs make up a third of the population of a healthy colony and do much of the day-to-day work, but the key task of reproduction they must leave to their siblings. Spared from the bullying that stunted the serfs, female chicks grow enormously in their first few weeks of life, and after three moults have matured as adult, fertile 'warbirds'. Warbirds are the colony's defence force and are larger and more robustly built than other cityfinch castes. They can be fanatical in the defence of their homes; even sauropods are not immune from their ferocious pecking beaks and sharp claws. In basal cityfinch species like the hitchcock, warbirds are only slightly larger, sharper-beaked versions of the serfs, but the warbirds of some species grow bizarre hornlike structures from their beaks which act as weapons and display structures. Except in certain circumstances, warbirds mate with their brothers, depositing their singleegg into a communal nestchamber. The eggs are tended to by serfs and "off-duty" warbirds who bring food from storage chambers replenished by the male scouts. Mature male cityfinches, or 'scouts' are the food-gatherers and early-warning sentries of the colony. These birds tend to have large crops for storing seeds and longer wing feathers than their siblings, in order to help them fly long distances. Parties of scouts will often travel for days on foraging missions, but these males almost always return home to their mates and children. Unmated males, however, with fewer of their genes invested in the colony, are less reliable as scouts, and sometimes wander off into the grassland to fend for themselves. These wanderers, called 'ronin', can feed themselves adequately on the savanna, but when they try to extend their genetic line, they run into problems. Warbirds attack ronin and scouts with untempered ferocity when the males are foolish enough to enter their territory. A ronin is more likely to be killed than mate successfully with an alien warbird, and so most ronin die without having passed their genes to the next generation. One would think that, given the abysmally low incidence of mating among ronin, such behavior would soon be weeded out of the cityfinch gene pool. The selective pressures usually in operation on cityfinches, would favor the scouts, who mate with their sisters to produce colonies of kin-bound workers. Indeed, such seems to be the general way of life for cityfinches, but behaviors that are usefull in one season might kill a colony in another, and the cityfinch behavior must allow for accommodation to change. During seasons of dearth, when the grasslands are especially unproductive, roninism increases until half or more of every colony's young male population is gone. This increased wanderlust is accompanied by a shift in warbird behavior, as these females begin to mate with any foreign males they can find. The resultant increase in genetic diversity in the cityfinch colony increases the spread of possibly beneficial mutations in a time of stress, but it also completely destroys the intricate kinship-altruism bonds that hold the colony together. In the generation after such free-mating, roninism spreads to nearly all nest-members and most of the colony's population departs, driven out by the strongest and most aggressive of the warbirds, who then mate with their brothers to being the rebuilding of the colony. Of the birds that leave the colony, few survive to mate, but a few band together into kinship groups and work together to build a new nest. Of these new nests, a few will survive the harsh savanna climate and become true cityfinch cities.

Cool. Tell ya what, for a real life example of bird eusociality and hoarding behaviour check out Acorn Woodpeckers. Very cool stuff there. It's difficult to speculate, but forms of bird eusociality may have potential as a future evolutionary adaptation.

I do tend to agree that Social or Eusocial behaviour may be a key survival trait, particularly for small animals.