Baby birds vomit in response to predators

Anyone on the Hopkins Emergency Response Unit - or at a college party, for that matter - has probably seen their fair share of drunk kids puking their guts out. People vomit for a wide variety of reasons; maybe they have the flu, maybe the biochemistry test was upsetting to the stomach, or perhaps riding a roller-coaster gave their stomach the flip-flops. While highly unpleasant, vomiting is actually quite an important adaptation. Ever wonder why rats take tiny bites all the time? That's because rats lack the ability to vomit, so they have to take extra care to not swallow any toxins.
Surprisingly, humans are not the only organisms that unload their stomachs as a result of environmental stimuli. Researchers at the Estaci??n Experimental de Zonas ??ridas, CSIC, recently found that baby Eurasian rollers (a bird species) spew a smelly orange liquid when scared by predators, an adaptive signal that warns parents to stay away from the nest. At a glance, the behaviors of these self-sacrificing babies seem to be evolutionarily counterproductive. After all, isn't survival of the youngsters critical to perpetuating the species? Not, as behavioral research indicates, if the birds are long-lived.
According to researcher Deseada Parejo, parental birds must weigh the benefits of their own survival against those of defending their nestlings. In the animal world, parental love is truly conditional - virtually every parenting decision is made in an attempt to improve the individual's net reproductive success.
The algorithm is quite simple: when you are a short-lived bird, such as the quail, you have few opportunities to mate and produce viable offspring. Given the threat of many predators, such as hawks, snakes and foxes, the quails are more likely to prioritize the safety of their young above your own survival. By contrast, Eurasian rollers have a longer life span, so they have multiple opportunities to mate and do not have to prioritize the safety of their young.
These parenting behaviors may seem heartless and brutal to us, but that's just how the animal world works - survival of the fittest. When it comes to sex, birds are no less ambitious. The image of the monogamous bird is mostly just an illusion. Most, if not all, songbirds would start an affair with a handsome stranger if their current mate is, genetically speaking, a loser.
Known scientifically as Coracias garrulous, Eurasian rollers are beautiful birds, with violet and turquoise plumage and chestnut-brown backs. They are solitary outside the mating season and prevail in many parts of the world, including Europe, Asia, the Middle East and Africa.
See BIRDS, Page B9
BIRDS, From B7
In attempt to better understand their unique vomiting adaptation, the researchers recruited rollers from nests in breeding boxes in southeastern Spain. The subjects, 15 nests of baby birds no older than 10 days old, were observed for half a day. Then, the researchers applied either baby bird vomit or lemon scent to the bird nests and continued their observation for another 100 minutes. A researcher under the single-blind condition counted how quickly and often parents returned to the nest boxes.
As you might expect, vomit-coated birds do not make a tasty snack, and predators and bird parents alike are not very willing to get near the odorous hatchlings. When vomit was applied to the nests, the parents delayed their visit to the nest for about 27 minutes and skipped two regular feeding visits during the first 20 minutes of observation. It took almost 100 minutes for the birds to fully conquer their "vomit-smell" fear. Conversely, the lemon scent caused the opposite effect, increasing the frequency of nest visits.
For the rollers, bird vomit signals fear and alerts the parents of a disturbance at the nest. To us, this would be equivalent to seeing our apartment door open when we come home from class, suggesting that a stranger has been in our house.
According to Parejo, birds use olfactory cues in several biologically relevant contexts, including orientation, navigation, prey detection and recognition of conspecifics. As rollers tend to dwell in dark places, they may be more likely than other birds to utilize scented cues.
The researchers must have had a hard time working with the birds because they vomit when handled by humans, a sign that vomiting may also have a defensive function. Interestingly, Eurasian rollers are not the only birds who regurgitate their lunches under pressure. Study leader Parejo says that the phenomenon is not common in birds, but the adult Northern Fulmars, Fulmaris glacialis, has been known to use its digestive enzymes against intruders. The behavior is actually more common in other animals - many arthropods lose their lunches when disturbed.
Even in humans, vomit has its use as a defensive mechanism. Scientists believe that incredibly nauseating phenomenon of chain-vomiting is an evolved trait in primates. The reason behind this is quite clear: if a member in your early human hunting party consumes a toxic animal or plant, it would do well for other party members to not befall the same fate. While the unfortunate taster may not live to pass on his or her genes, the people around him or her get the benefit of blacklisting whatever morsel that person swallowed.
Just because vomiting useful, though, does not mean that it is particularly pleasant. According to an online survey conducted by the University of Salford's Acoustic Research Centre, most people find the sound of vomiting "the most disgusting."
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