Decoding Forest Changes through Birdsongs: A Study Spanning Decades

Mapping Songbird Territories: Insights into Evolving Ecosystems

At Dartmouth College, Miranda Zammarelli and Dick Holmes pour over old territory maps which reveal the longstanding presence of songbirds in a forest patch in central New Hampshire.

When out in the field, Zammarelli, who is a PhD candidate specializing in behavioral ecology, identifies trees tagged with pink ribbons marking territory boundaries set in 1969.

Her main task at this point is to wander through the woods, listening attentively.

On a crisp June morning, a gentle song floats down from the treetops. "That’s the black-throated blue warbler," notes Zammarelli, her voice tinged with admiration.

Using a smartphone app, she records the bird's location, tracking its seasonal territory during breeding times.

"During this time, the bird asserts its claim over a patch of land," she explains. "It's essentially a musical battle for territorial dominance, with each song staking a claim."

For the male bird, securing his space is critical to attract a mate and ensure a safe environment for raising his offspring.

Zammarelli and her colleagues have meticulously mapped where dozens of songbird species establish their territories. These birds play a crucial role in the ecosystem by aiding seed dispersal and controlling insect populations, often migrating between North America and the tropics.

Monitoring these territories grants valuable insights into the forest's health. As Zammarelli puts it, "If we find less occupancy, it raises questions about habitat quality and forest wellbeing."

Bird Territories as Indicators of Forest Health and Change

Holmes, who began this ambitious project as a young biologist, is now an emeritus professor at almost 89 years old.

He mentions, "Throughout 57 years, we’ve compiled extensive maps noting bird territories, reflecting seasonal changes backed by daily observations."

These maps, filled with symbols and lines, represent the territories of various species, illustrating space usage over the years.

Initially, Holmes aimed to understand the energy dynamics within the forest ecosystem, focusing on songbirds' roles within the food web.

As data accumulated, their research questions expanded—wondering about bird population trends and the factors affecting these shifts.

Notably, by the mid-1990s, the least flycatcher disappeared from their records, as did the American redstart during the early 2000s.

This change aligns with natural forest maturation, after being clearcut in the 1920s and left to regrow, evolving over time.

Different species flourish in younger forests, but as the environment matures, they may relocate, a phenomenon documented by the study.

Supporting countless research endeavors, this site has produced an extensive array of publications, owing to the meticulous data collection tradition continued by Zammarelli through digitalization.

Digitization Breaths New Life into Historical Data

Digitizing the vast archive has enabled Zammarelli to pose new questions about territory use and size among birds.

A recent study revealed equitable territory division among bird species, ensuring healthy reproduction rates and population stability.

Reflecting on the legacy of these maps, Zammarelli feels privileged to contribute to a research tradition that predates her lifetime.

Holmes regards this dataset as one of the most comprehensive records of breeding birds, offering crucial insights amidst escalating environmental changes.

However, the project faces challenges due to financial constraints, threatening its future under shifting political climates.

Yet, for now, the team continues to monitor these birds as they sing their songs, offering a glimpse into the forest's evolutionary tale.