In the thorny oak trees of the Kalahari Desert, bird construction workers are hard at work. Brown sparrow weavers, a gregarious bird species, assemble elaborate nests and nests from grasses—many hanging across their small range from one tree to another where. However, not all of these woven, tubular types seem to follow the same pattern. They differ in shape, proportion and size.
“The first thing we noticed when we saw the birds in person is that the groups build differently [from one another],” says Maria Tello-Ramos, a biologist and former researcher at the University of St. Andrews, Scotland. The nests and nests of other groups were short, about the size of balls of burnt vegetation. Other groups assembled tall and boomerang-esque structures, like many horns made of hay. Others were raising nests hanging somewhere in the middle. The architectural features seemed to remain fixed in a certain area.
Tello-Ramos, who was about to start studying at the University of Hull, England, had come to the Tswalu Kalahari Reserve, South Africa to study the sparrows’ unique community building behavior. He wanted to know how many birds coordinate to achieve a common goal, but then a new question arose: Why do groups that live in close proximity (sometimes separated by meters a few) showed different architectural styles. ?
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The answer turned out to be difficult – not readily apparent from the many observations and measurements that Tello-Ramos and his colleagues collected. When you’ve crossed off every obvious possibility on the list, you have to think of something new. In conclusion, in a study published on August 29 in the journal Sciencescientists present their best theory of what happens to desert sparrow weavers. A new study suggests that motley habits are a product of culture, or “the transmission of behavior across generations that is not genetic,” as Tello-Ramos explains. He says: “I really think that social learning and interacting with other people can explain this difference.
Brown-and-white sparrow weavers live in flocks of between two and 14 birds. Each flock is made up of several breeding flocks and the young usually stick around each year to help the parents. see. Sometimes an unrelated person may contact you. Sometimes one bird flies the hook, then goes out to do it away from the family in a different group.
In these stable but flexible colonies, which can last for more than a decade, the birds defend their territory, forage and build together. Each weaver spends the night in a separate, woven nest and hatching sparrow eggs are reared in similarly constructed nests. A group of twelve birds can have 30 to 40 nests built in their territory. Each takes days to complete, many weavers (up to eight) are involved in each project, and new structures are added frequently, especially during the rainy season when the grass is spring is also flexible, says Tello-Ramos.
In ornithology, nest variation is often chalked up to a combination of environmental and genetic factors. Species are limited in what they create by their past and environment. For example, shorebirds that have never had branches and trees in their habitat lay their eggs in the sand, not in elaborate baskets, explains Vanya Rohwer, an expert on birds and keeper of the bird and mammal collection. Cornell University’s Museum of Vertebrates was not involved in sparrow research. “A lot of that is hindered by evolutionary history.” Factors such as temperature are another major factor when it comes to changes in species and species, he adds. Cold-climate birds build larger, denser, water-proof nests than their warm-climate counterparts.
A new study suggests a third potential change: bird culture. Tello-Ramos and his colleagues collected detailed information on 43 different groups of brown sparrows living in an area of about two square kilometers. Each group had an average of about 12 members, and in total these birds built hundreds of structures throughout their territories. The scientists measured 444 of those structures, recording the length of the inlet and outlet pipes, the width of the holes, the total length, and other details.
They found that height and width varied more between groups than within groups—even across two years of observation. The roosts of some groups were 20 inches taller than others. And, most importantly, that difference is “repeatable — they keep doing it,” says Tello-Ramos. “It wasn’t just a one-time thing. It was like, ‘No, this is about us. This is what we do. We build long tubes and they build short ones.’” When a new bird joined a new group, it seemed to quickly adopt the group’s dominant architectural style—congruent. and neighbors.
To try to find out why, the researchers compared temperature, wind speed, distance from neighbors, size of birds, genetic relatedness and tree height between the groups. In total, those models could only account for less than three percent of the patterns they saw — leaving another 97 percent of the mystery unsolved. “I was very impressed with the number of other comments that they reviewed and reviewed,” says Rohwer. Normal Science. He adds: “I can’t argue with their data.
Instead of a clear answer, researchers turned to the scientific literature on social models. Previous research has documented spatial cues in birdsong and socially learned foraging patterns. Some animals, such as whales and monkeys, are known to exhibit behaviors and behaviors learned from their peer groups. And some studies have shown that birds look at each other when building nests. In experiments with nests of captive zebras, researchers have found that individuals choose building materials that match their peers’ nests rather than sticking to their initial preferences.
Tello-Ramos says: “People are not the only ones who build, they are not the only ones who have culture.”
Combining the new measurements and measurements with this prior knowledge, the authors of the study write “cultural transmission appears to be the most likely explanation for our results. The birds will imitate the construction behavior shown by the members that some of the team.”
“It’s a new look at what can influence the behavior of nesting birds and it was exciting to see,” says Rohwer. “They definitely have something.” However, the study also leaves loose threads. He adds: “These findings are really interesting, but they raise a lot of questions.”
For example, Rohwer noted that it is not clear how the construction method will be selected and transferred within the group. (More research is needed to develop a transfer mechanism, agrees Tello-Ramos, and he hopes to start on that soon.) Rohwer also wants to know if the team’s age has anything to do with style changes. , as some species of weaver birds change their strategy as they grow. He’s also curious about how nest designs vary over larger areas in a sparrow’s habitat.
Furthermore, the study has some limitations. Taking accurate measurements of a messy nest is difficult, Rohwer points out. The correlation the researchers found between the group and the different character traits that show similarity “isn’t surprising,” he says. And even if traditional nesting is sustainable for brown sparrows, it may not be a viable design for understanding other bird species. “Most bird nests are built by a single individual,” he says, adding that many species may not exhibit the kind of rigid, hierarchical structures that pass through generations. stated by new research.
However, Rohwer says: “I have this feeling of being very humbled by discoveries like this. “There’s something that’s been sitting in front of us, we’ve always looked at it one way, and maybe there’s more to it than that.”
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