Urban birds silhouetted against a sunset cityscape, symbolizing conservation.

Urban Birds in Crisis: What Long-Term Studies Reveal About Disappearing Species

Beau Callahan in Climate & Environment December 2025 • 4 min read.

"A 30-year avifaunal survey in Brazil uncovers alarming trends in urban bird populations, highlighting range extensions and the loss of native species."

Urban ecosystems are increasingly becoming the primary landscape for a significant portion of the world's population. As urban areas expand, the impact on local biodiversity, particularly bird populations, becomes a critical concern. Birds play vital roles in maintaining ecosystem health, from pest control and seed dispersal to nutrient cycling and pollination.

Recognizing the importance of understanding these changes, researchers have been conducting avifaunal surveys in urban environments for decades. While these studies provide valuable snapshots of birdlife in specific locations, long-term data is essential for identifying trends in species colonization, range extensions, and, most alarmingly, species decline. Analyzing such data allows for the formulation of actionable strategies to protect urban biodiversity.

A recent study published in the journal Papéis Avulsos de Zoologia provides a unique and detailed look at bird populations in an urban ecosystem in southeastern Brazil. Conducted over 30 years on the campus of the Pontifícia Universidade Católica de Minas Gerais (PUC Minas) in Belo Horizonte, the survey reveals crucial insights into the challenges faced by urban bird communities.

The Alarming Decline: Why Are Bird Species Disappearing From Our Cities?

Urban birds silhouetted against a sunset cityscape, symbolizing conservation.

The Brazilian study, which tracked bird populations on the PUC Minas campus from 1982 to 2013, paints a concerning picture of species loss in urban environments. Researchers documented a total of 134 bird species over the 30-year period. However, the present avifauna, recorded between 2005 and 2013, comprises only 123 species, indicating the disappearance of 11 species over time.

The study identified three primary categories of disappearing species, categorized by habitat:

Forest and Forest Edge Species: Species such as the Swallow-tailed Kite (Elanoides forficatus) and Pauraque (Hydropsalis albicollis) have likely declined due to the reduction of suitable foraging and perching locations, as well as increased ground-nest predation.
Wetland Species: Yellow-chinned Spinetail (Certhiaxis cinnamomeus), White-headed Marsh Tyrant (Arundinicola leucocephala) and Black-capped Donacobius (Donacobius atricapilla) once thrived in wetlands with cattails, but the harvesting of this vegetation led to their disappearance.
Rural Environment Species: Species typical of farms, orchards and plantations, such as Small-billed Tinamou (Crypturellus parvirostris), Rufous-fronted Thornbird (Phacellodomus rufifrons) and Rufous-collared Sparrow (Zonotrichia capensis) have struggled to maintain viable populations in the increasingly urbanized landscape.

This underscores the impact of urbanization on diverse ecosystems and emphasizes the vulnerability of species with specific habitat needs.

Protecting Our Feathered Neighbors: Why Urban Bird Conservation Matters

The 30-year avifaunal survey on the campus of PUC Minas provides critical insights into the challenges faced by bird communities in urban environments. The findings underscore the vulnerability of species with specific habitat requirements and the need for targeted conservation efforts. By understanding the factors that contribute to species decline, we can take proactive steps to create more bird-friendly cities and protect our feathered neighbors for generations to come. Continuing to document the campus avifauna will allow us to document new colonization and future local extinctions, especially in the case of forest-dependent species.

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This article is based on research published under:

DOI-LINK: 10.1590/s0031-10492013002500001, Alternate LINK

Title: Long-Term Avifaunal Survey In An Urban Ecosystem From Southeastern Brazil, With Comments On Range Extensions, New And Disappearing Species

Subject: Animal Science and Zoology

Journal: Papéis Avulsos de Zoologia (São Paulo)

Publisher: Universidade de Sao Paulo, Agencia USP de Gestao da Informacao Academica (AGUIA)

Authors: Marcelo Ferreira De Vasconcelos, Eduardo De Carvalho Dutra, Luiz Gabriel Mazzoni, Letícia Ferreira Pedroso, Alyne Perillo, Fernando Augusto Valério, Tadeu Guerra, Diego Petrocchi, Rodrigo Morais, Lucas Penna Soares Santos, Bruno Garzon, Juan Espanha Moreira Dias, José Enemir Dos Santos, Allan Suhett De Morais, Letícia Souza Lima Guimarães, Frederico Innecco Alves Garcia, Thiago Oliveira E Almeida, Carlos Eduardo Ribas Tameirão Benfica, Helberth José Cardoso Peixoto, Bruno Pardinho Ribeiro

Published: 2013-01-01

Everything You Need To Know

What alarming trend did the 30-year avifaunal survey in southeastern Brazil uncover about urban bird populations?

The 30-year avifaunal survey conducted on the campus of the Pontifícia Universidade Católica de Minas Gerais (PUC Minas) in Belo Horizonte revealed a concerning decline in urban bird populations. Initially recording 134 bird species, the study found that only 123 species were present between 2005 and 2013, indicating the disappearance of 11 species. This highlights the negative impact of urbanization on local bird biodiversity and underscores the urgent need for conservation efforts.

Which types of bird species are most vulnerable to disappearing from urban environments, according to the study?

The study categorizes the disappearing species into three main groups based on their habitat preferences: Forest and Forest Edge Species, Wetland Species, and Rural Environment Species. Forest and Forest Edge Species like the Swallow-tailed Kite (Elanoides forficatus) and Pauraque (Hydropsalis albicollis) suffer from reduced foraging and perching locations. Wetland Species such as the Yellow-chinned Spinetail (Certhiaxis cinnamomeus) disappeared due to habitat destruction, like harvesting of cattails. Rural Environment Species including the Small-billed Tinamou (Crypturellus parvirostris) struggle in increasingly urbanized landscapes, facing challenges in maintaining viable populations.

What specific factors contributed to the decline of Wetland Species, such as the Yellow-chinned Spinetail, in the urban ecosystem studied?

The decline of Wetland Species, including the Yellow-chinned Spinetail (Certhiaxis cinnamomeus), White-headed Marsh Tyrant (Arundinicola leucocephala) and Black-capped Donacobius (Donacobius atricapilla), is primarily attributed to the destruction of their natural habitat. Specifically, the harvesting of cattails from wetlands on the PUC Minas campus eliminated essential vegetation that these birds rely on for shelter, nesting, and foraging. This loss of habitat structure directly impacts their ability to survive and reproduce in the urban environment.

Why is it important to conduct long-term avifaunal surveys in urban environments, like the one at PUC Minas in Brazil?

Long-term avifaunal surveys, such as the 30-year study at PUC Minas, are crucial because they provide insights beyond what short-term studies can offer. They allow researchers to identify trends in species colonization, range extensions, and, most importantly, species decline over extended periods. Analyzing this longitudinal data enables the formulation of effective conservation strategies to protect urban biodiversity. Documenting the campus avifauna helps track new colonizations and future local extinctions, particularly among forest-dependent species. This continuous monitoring is vital for adapting conservation efforts to the evolving urban landscape.

What implications does the disappearance of species like the Rufous-collared Sparrow from urban areas have on the broader ecosystem?

The disappearance of Rural Environment Species like the Rufous-collared Sparrow (Zonotrichia capensis) from urban areas can have significant implications for the broader ecosystem. These species often play crucial roles in seed dispersal and insect control within their habitats. Their decline can disrupt these ecological processes, potentially leading to imbalances in plant populations and increased pest outbreaks. Also the reduction in these species populations are indicators of compromised ecosystem health. This highlights the interconnectedness of species within an ecosystem and the far-reaching consequences of biodiversity loss.