Birds Sing to Eggs When Temperature Climbs

Zebra finches are shown to sing to their unhatched chicks particularly when the heat is up.

Much like parents who talk to a pregnant woman's belly, some birds sing to their eggs before they hatch, and the reason may be to prepare them for a warming world, researchers said Thursday.

The study in the journal Science examined a peculiar habit of zebra finches, which sing to their eggs particularly when the weather is hot -- above 78 Fahrenheit (26 Celsius) -- and the end of their incubation period is near.

Eggs are unaffected by outside temperatures and are kept at steady temperature of 98.6 F when the parents are sitting on them.

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What could they be saying? Could it have to do with the temperature outside?

"I would say it translates to: 'it's hot babies, get prepared!'," said lead author Mylene Mariette, in an email to AFP.

"That's what they are effectively telling their embryos."

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To see what impact this chirping chatter might have on eggs, Mariette and Katherine Buchanan of Australia's Deakin University recorded the calls and played them for eggs in an incubator.

Some eggs were played regular contact calls from adult zebra finches, while others were exposed to particular calls made by expectant parents, chirping to their eggs before they hatch in warm weather.

Those who heard these so-called hot calls grew slower and emerged smaller when they hatched than the other birds.

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This compact size would present a survival advantage, because having a small body makes it easier to cool down in hot climes.

As they tracked these hot-call birds over time, researchers found they had more offspring than the other birds that did not hear the preparatory calls during the hot weather.

Researchers believe that the calls somehow affect the babies' growth, since they are delivered in the last one-third of the incubation period when the hatchlings' temperature and regulation system is starting to develop.

"By acoustically signaling high ambient temperatures to their embryos before hatching, zebra finch parents can program the developmental trajectories of their offspring," said the study.

If such a strategy is found to exist in other animals, it would suggest a previously unknown survival mechanism to help creatures adapt to global warming, researchers said.

VIEW PHOTOS: Birds' Nests in Bizarre Urban Places

style="text-align: left;"> Some birds have a flair for the funky when it comes to selecting where to build their nests, finds the Celebrate Urban Birds project at the Cornell Lab of Ornithology. Now that spring nesting season is underway, don't be surprised if you find a nest in old boots left outside, on top of traffic signals, in gutters and downspouts and at many other surprising locations. This osprey, for example, unintentionally gave the female figure depicted by the statue a "hat." Underway right now is Cornell's "Funky Nests in Funky Places" contest, where entrants can submit photos, videos and more documenting oddly placed nests. "Many people, particularly those living in cities, are not aware of all the wild birds living in in their neighborhoods, believing they would only be found in faraway places," Cornell's Marta del Campo told Discovery News. The challenge, held every spring since 2009, was created to encourage people to discover the kinds of birds living and nesting in their neighborhoods, del Campo explained.

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style="text-align: left;">A ladder serves as an avian "condo," since multiple American robins decided to build their nest on it. Del Campo said that American robins, along with mourning doves, house sparrows and certain hummingbird species, commonly build their nests in unexpected urban locations.

Photos: Nests Made Out of Weird Materials

style="text-align: left;">Hopefully the owner of this truck in Pennsylvania did not go for a drive for a while! Presumably, the truck had been stationary for quite some time, catching the eye of an industrious American robin seeking a sheltered space. If you find a nest, del Campo and her team urge that you leave it undisturbed. "Even if a nest has been built in a somewhat inconvenient place (for you), be patient," she said. "In a few weeks the birds will be gone. Meanwhile, you get a front-row seat to a wonder of nature. Do not provide food or get too close to the nest because this can attract predators and stress the bird, which might then abandon the nest."

style="text-align: left;">Birds Build Nests with Camouflage in Mind

style="text-align: left;">Using spider web to affix its nest to a single bulb in a strand of holiday lights, this tiny Anna's hummingbird successfully hatched two chicks last year.

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style="text-align: left;">A goose figurine became home sweet home to a real live bird, a common moorhen. "When birds are looking for a place to nest, they seek specific qualities, depending on the species," del Campo said. "For example, some bird species, such as woodpeckers and chickadees, look for cavities, while hawks like to build on flat surfaces in high places, such as window ledges on tall buildings that must seem like natural cliffs to them." As for the common moorhen, it must have liked its "room" with a view, not to mention the protection provided by the island-like figurine.

style="text-align: left;">The owner of these motorcycle helmets must have been surprised when he found birds nesting in them. "Even in urban areas, we're a lot closer to birds than you might think," Celebrate Urban Birds project leader Karen Purcell said. "This contest is a lot of fun, but it's also about really being aware of what's around you and taking the time to appreciate birds and all of nature."

style="text-align: left;">Neighbors passing by must have given this wreath with an apparent mourning dove "decoration" a second look when the bird actually moved. The dove may have been attracted by the natural materials of the wreath and decided to move in.

style="text-align: left;">Perhaps the nursery rhyme about Old Mother Hubbard was inspired by a sight like this: a Carolina wren's nest in a golf shoe. "All birds are looking for a place where they can be safe from predators and where food and water are handy," del Campo said. "When you look at it that way, some of the 'weird' locations actually make some sense. A bird nesting in an old shoe in your garage will be protected from bad weather and out of view of predators."

style="text-align: left;">By the size of this nest, Big Bird himself could have moved in. Del Campo and Purcell said that BBQ grills actually are fairly common as bird nesting spots. Around houses, birds might also construct their nests in potted plants, on and in light fixtures, on shrubs, atop balconies, under eaves, on doorsills and windowsills.

style="text-align: left;">An American robin selected this urinal in Texas for its nest site. It appears to have been a good decision, based on the many healthy-looking chicks seen in this photo. This location might make Cornell's evolving "funkiest of the funky" list. As of now, the list also includes a great horned owl nest found in a laundry basket on a tree in Toronto, a mourning dove nest on a tombstone in New Orleans, and a European starling nest on retired V1 rockets at the Marshall Space Flight Center in Huntsville, Alabama.

style="text-align: left;">This house sparrow nesting in a dinosaur's mouth seemingly has come full circle, since birds themselves are dinosaurs. (Scientists sometimes refer to dinos as "non-avian dinosaurs" to keep the two groups distinct.) Entries to the Funky Nests in Funky Places challenge are due by June 15, so there is plenty of time to seek out likely subjects. "We are looking for fun and interesting stories about the surprising nests people find in their neighborhoods," del Campo said, "but we do caution people, again, not to get too close to nests. We don't want any harm to come to the birds." Guidelines are at the contest's website.