Food fights, moonlight, migration decisions, hormones, and house finches have been on researchers’ radar. Here’s a look at recent findings:
Ignoring their parents: A University of Cambridge study found that highly social zebra finches, if exposed to stress hormones just after hatching, will switch to learn foraging techniques only from unrelated adults. The stress may translate into a cue that their parents are doing something wrong. The study was published in Current Biology.
Food fight: Baby starlings that have to compete for food with larger and more aggressive chicks grow up to be fatter and greedier than those who were the winners in the food competition, according to a study published in Animal Behaviour. Apparently the struggle made a lasting impression, and those birds tended to overeat when they were adults.
Small brains, big decisions: Migratory songbirds use two cues, weather and body fat levels, to assess migration risk, according to a National Science Foundation-funded study of three species crossing the Gulf of Mexico, a distance of about 600 miles. Songbirds spend about 30 percent of their lives migrating.
Researchers found that red-eyed vireos, Swainson’s thrushes and wood thrushes would delay starting migration if the humidity was too high. And birds without large amounts of fat often went around the gulf to avoid the overwater crossing.
Avian trade-offs: During migration, birds weigh the risk-reward of stopping to refuel versus threats of predators. After two years of study, researchers from the University of Maine concluded that fruit-eating migratory birds prefer to stop in habitat with plenty of dense vegetation that helps protect them from predators. Published in The Auk, researchers concluded that the longer the migration, the more likely birds are to take risks in more open areas to eat high-energy fruit.
Challenging assumptions: House finches that prefer to eat at bird feeders have an increased risk of acquiring mycoplasmal conjunctivitis, similar to “pink eye” in humans, and also spread the disease to others in the flock more quickly, according to a research team led by Virginia Tech scientists. The disease affects the eyes, which can lead to blindness and death.
For one winter, researchers tracked which feeders that the birds went to and how often, as well as what other birds were there, data that allowed scientists to reconstruct social networks. Scientists expected that the birds with the most connections would be more likely to be exposed to and spread the disease. Instead, it was the birds’ feeding preferences that were most important, according to the study.
Contact Sharon Wootton at www.songandword.com.
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