Golden-crowned sparrows leave their favored sites when they lose close flockmates

Upon first glance, golden-crowned sparrows may seem like any other bird. However, a recent study has explored the subtle social dynamics of these birds, revealing that the bonds formed among these sparrows hold deep implications for their spatial patterns.

Researchers from the University of Nebraska–Lincoln discovered that the absence of close flockmates causes these sparrows to drift away from their favored overwintering sites. This implies that the familiar faces of their bird buddies are key anchors to familiar territories.

Grueling migration

The typical golden-crowned sparrow, after a grueling winter migration that could cover up to 3,000 miles, returns to California and resettles merely 90 feet from its last year’s home base. Yet, the study revealed that those appearing for their third consecutive winter or more had a tendency to stray from their chosen sites if their cherished flockmates did not join them.

“The fact that they come back to this winter site and then hang out with the same individuals – and it’s important for them to be with the same individuals – is kind of a crazy thing that we’re still wrapping our heads around,” said study lead author Annie Madsen.

Focus of the study

The motivation behind this study was to solve the “chicken-and-egg question” of social behavior in animals. While many species, including the golden-crowned sparrow, share spaces and form communities, it’s a puzzle for ecologists to distinguish whether these animals prioritize territories rich in resources or if they value the social ties formed within these communities.

Madsen asked: “Are they coming together because of a resource? Or is it their friends, their flockmates, that they’re coming back to spend time with?”

How the research was conducted 

Santa Cruz’s University of California arboretum is a popular overwintering spot for sparrows fleeing the chilly conditions of Alaska and western Canada. This became the researchers’ observatory. 

Over a decade, from 2009 to 2019, they used multi-colored leg bands combined with meticulous observations to chart the geographical and social habits of these sparrows.

The data compiled over this period suggested that the longer a sparrow spent winters in Santa Cruz, the less they deviated from their chosen locale. This observation might indicate that certain areas hold specific appeal. 

Significance of social bonds

However, a deeper look the data uncovered a more sentimental picture. Sparrows, upon losing their close contacts or “favored flockmates,” seemed to exhibit a shift in their territorial preferences, opting to stray farther from their previous centers.

This drift, according to Madsen and her team, highlights the significance of social bonds in a sparrow’s life. The ties formed with their flockmates may be just as vital as the resources their territories provide.

Madsen remarked on the intriguing nature of their return to such specific wintering spots, where resources are abundant: “Whether it’s more this social cohesion – individuals staying together because they prefer to be together – or maybe partially that they’re trying to avoid dominance interactions with other individuals, it does seem like there’s something to having familiar flockmates that is important.”

The study revealed an interesting pattern: sparrows returning for only their second winter in Santa Cruz did not display significant shifts in their home ranges despite losing flockmates. This led Madsen to hypothesize that these birds might not have forged as many close-knit bonds compared to those returning for several consecutive winters.

“Some of these relationships are being built up over multiple years… they’re building lots of social capital,” said Madsen.

The research is published in the journal Proceedings of the National Academy of Sciences. 

More about golden-crowned sparrows 

The golden-crowned sparrow (Zonotrichia atricapilla) is a fascinating bird primarily known for its distinctive yellow crown. Here’s an overview of some of its key characteristics and behaviors:

Physical description

Golden-crowned sparrows are medium-sized birds. The most distinguishing feature is their bright yellow crown, which is bordered by black stripes. 

Adults have a gray face, brown streaked underparts, and a clear, gray breast. Immature birds have brown streaks on the crown, giving them a more muted appearance compared to the adults.

Habitat

They typically breed in Alaska and the western Yukon, and during winter, they migrate to the west coast of North America, ranging from British Columbia to Baja California. 

The sparrows prefer shrubby habitats and can often be found in open areas, edges of forests, and even in gardens and urban settings during their wintering period.

Song

Their song is quite distinctive. It’s often described as a series of clear whistles followed by a trill. The song can be represented phonetically as “oh-dear-me.” 

The interesting aspect of their song is the regional variation. Birds from different geographical areas might have slightly different tunes.

Diet

The golden-crowned sparrow primarily feeds on seeds, but they will also consume insects, especially during the breeding season. They forage on the ground, often in flocks.

Breeding

Their nests are typically built on the ground, concealed by shrubs or grass. The female lays 3-5 eggs, which she incubates for about 12-14 days. Once hatched, both parents take turns feeding the chicks.

The golden-crowned sparrow is not just visually distinctive but also an interesting species in terms of behavior and adaptability. If you’re on the west coast during the winter months, keep an ear out for their unique song and you might just spot one!

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