Field Abundance—Museum Abundance (FAMA)

 Why in the News ? 

The collapse of grassland bird communities in the Nilgiri hills of India’s Western Ghats, as revealed by a 2025 study, underscores a significant ecological crisis driven by historical landscape changes. Researchers from institutions like Columbia University and the Cornell Lab of Ornithology analyzed bird specimens from the early and late 1800s alongside modern field surveys, using a novel Bayesian statistical method called Field Abundance—Museum Abundance (FAMA).

Key Points of the Study

• Sharp Drop in Grassland Birds: Since the 1850s, eight out of nine bird species native to the Nilgiris’ grasslands have experienced a 90% decline in their populations. Birds such as the Nilgiri pipit and Malabar lark, which depend heavily on grassland habitats, have been particularly affected.
• Stable Forest Bird Populations: About 53% of forest bird species have remained stable, as they adapted to timber plantations, unlike grassland birds, which lack alternative habitats.
• Habitat Loss: Grassland area in the Nilgiris shrank by 80%, from 993 sq. km in 1848 to 201 sq. km in 2018, due to conversions to tea, eucalyptus, and pine plantations during colonial times.
• Data Integration: The study combined 19th-century museum specimens, historical maps, and records with modern field surveys and satellite imagery to reconstruct and compare bird populations across time.
• Conservation Call: It urges prioritizing grassland restoration and policy focus on open ecosystems to support the recovery of declining bird species.

About the Field Abundance—Museum Abundance (FAMA) Method:

The FAMA method is a Bayesian statistical tool designed to estimate species abundance across historical and modern periods by integrating museum and field data. Here’s a detailed overview:

• Purpose: FAMA enables accurate comparisons of species abundance despite biases in historical museum collections, such as uneven sampling or collector preferences.
• Data Sources: It uses historical museum specimens (including species, collection date, and location) and modern field surveys from the same sites, supplemented by land-cover analysis from historical maps and satellite imagery.
• Bayesian Modeling: The method employs Bayesian statistics to handle uncertainties in historical data, modeling the probability of species presence based on specimen counts and modern observations. This produces reliable abundance estimates over time.
• Key Strength: FAMA overcomes limitations of traditional methods by standardizing disparate datasets, enabling researchers to quantify long-term population trends, such as the severe decline of Nilgiri grassland birds.
• Broader Utility: The method’s flexibility makes it applicable to other regions and species, leveraging museum collections to study biodiversity changes globally.

Conclusion

The study reveals a catastrophic decline in Nilgiri grassland bird communities, driven by colonial-era habitat loss, and underscores the stability of forest birds in contrast. The innovative FAMA method provides a robust tool to quantify these changes, highlighting the urgent need for grassland conservation. Its newsworthiness stems from its alarming findings, novel methodology, and call for action, making it a pivotal contribution to understanding and addressing biodiversity loss.