Rapid urban expansion across Africa is altering ecological systems in ways that are still being documented. Two interconnected lines of research in Nigeria and other Afrotropical regions now point to a consistent pattern: as cities grow, bird communities are changing in composition, function, and health.

A recent synthesis of field studies from Nigeria and Kenya, alongside new parasite screening work in Southwest Nigeria, shows that urban landscapes are not only reducing bird diversity but are also reshaping host–parasite dynamics in ways that differ by parasite type, habitat, and season.

The findings come at a time when urban land cover in Africa is projected to triple by 2030, according to research cited in a commentary published by Mongabay, a researcher at the A.P. Leventis Ornithological Research Institute and coordinator of the IUCN Species Survival Commission Center for Species Survival Nigeria.

Mongabay wrote that urban growth is producing “more uniform communities with generalist species” while reducing ecological functions performed by birds such as seed dispersal, pollination, and pest control.

These ecological shifts now appear to extend beyond species counts into the microscopic world of parasites that circulate within bird populations.

Urban growth

The Mongabay commentary draws from a study co-authored by Danmallam, Peggy Ngila, and Iniunam Iniunam, which used citizen science bird data from Nigeria and Kenya to examine how urbanization affects avian diversity and ecological roles.

The study found that urban environments tend to support fewer specialized bird species while favoring generalists that can tolerate human disturbance. According to Iniunam Iniunam, reduced diversity has functional consequences.

“When urbanization erodes functional richness, it not only disrupts essential ecosystem services like pest control, seed dispersal, and nutrient cycling but also weakens species’ ability to adapt and persist in changing environments,” Iniunam said. “As specialized species disappear, ecosystems become dominated by generalists, reducing ecological resilience and increasing the risk of biodiversity collapse.”

Peggy Ngila noted that urban transformation is often underestimated in ecological planning. She said, “Our research sheds light on how this process is changing the composition of bird communities and their vital ecosystem services.”

The broader concern raised by the authors is that Africa’s rapid urban expansion is occurring alongside some of the continent’s richest concentrations of biodiversity, creating conditions where ecological disruption may be especially pronounced.

Parasite dynamics

Against this broader backdrop, a detailed field study conducted in Southwest Nigeria provides new insight into how urbanization is influencing avian health at the parasite level.

The study, led by Adewale G. Awoyemi, Jorge Garrido-Bautista, Yahkat Barshep, and Juan Diego Ibáñez-Álamo, examined haemosporidian parasites in birds across urban and non-urban habitats in Ado, Ibadan, and Lagos.

Published research data show that haemosporidian parasites, which include Plasmodium, Haemoproteus, and Leucocytozoon, are widespread in bird populations globally. Their impacts range from negligible to severe, depending on host species and ecological conditions.

The Nigeria study screened 95 birds across 31 species and found an overall infection prevalence of 36.8 percent.

However, the distribution of infections was not uniform across parasite genera or habitats.

The study reports that Haemoproteus infection was significantly more likely in urban environments, while Plasmodium and Leucocytozoon showed no significant difference between urban and non-urban habitats.

According to the results, “The probability of Haemoproteus infection was higher in urban than non-urban habitats,” while Plasmodium and Leucocytozoon infections remained statistically similar across both habitat types.

This pattern suggests that urban environments may selectively favor certain parasite lineages while limiting or not affecting others.

Across habitats

The research identified 12 Haemoproteus lineages and 7 Plasmodium lineages. Some were widely distributed, while others were restricted to specific habitats.

Notably, Haemoproteus lineages were found primarily in urban areas, while most Plasmodium lineages were associated with non-urban environments.

The study also recorded first detections of certain parasite lineages in the Afrotropical region, including hPYNJOC1 and pLUME2.

The lineage hPYNJOC1 was detected in a Common Bulbul in Nigeria and had previously been recorded only once in India. The authors describe this as the first record of the lineage in the Afrotropics.

Similarly, pLUME2, previously documented in a single European Robin in Germany, was identified in both Common Bulbul and African Thrush in Nigeria.

The authors note that these findings “suggest that these lineages are rare, or at least not sufficiently explored in the Afrotropics,” pointing to persistent gaps in regional surveillance.

In addition, several new host associations were recorded, including Village Weaver, Blue-spotted Wood Dove, African Thrush, and Green Hylia.

Parasite transmission

The study links observed differences in parasite distribution to changes in vector ecology. Haemosporidian parasites are transmitted by blood-feeding insects such as mosquitoes and biting midges.

Urbanization can alter breeding sites, temperature, vegetation structure, and water availability, all of which influence vector abundance.

The authors cite earlier work indicating that urban areas may reduce suitable habitats for insect vectors, potentially altering transmission dynamics.

However, the Nigerian findings suggest a more complex picture. While some parasite groups appear constrained, Haemoproteus was more prevalent in urban habitats, indicating that certain vectors or host interactions may persist or even intensify in cities.

The authors state that “urbanization is associated with changes in the prevalence and richness of lineages” and emphasize the need for more detailed ecological work on vector populations in African cities.

Seasonal variation

Contrary to expectations, the study found no significant seasonal effect on infection probability for any of the parasite genera.

This suggests that, in the sampled regions, habitat type may be a stronger determinant of infection patterns than seasonal rainfall variation.

However, the authors caution that limited sample size may have constrained detection of finer-scale seasonal differences.

Methods and sampling

Birds were sampled using mist nets across paired urban and non-urban sites in Lagos, Ibadan, and Ado during both dry and wet seasons between 2023 and 2024.

Blood samples were collected via brachial venipuncture and preserved for molecular analysis using nested PCR protocols commonly applied in haemosporidian detection studies.

The authors note that while widely used, these methods have limitations, including reduced sensitivity for co-infections and potential biases against certain parasite genera such as Leucocytozoon.

A total of 95 individuals were included in the final dataset, representing a cross-section of urban and rural bird communities.

Ecological implications 

The convergence of findings from parasite ecology and broader avian diversity studies points toward a shared conclusion: urbanization is reshaping ecological networks at multiple levels.

Changes in bird community structure documented in Nigeria and Kenya suggest a reduction in functional diversity, while parasite data indicate shifts in infection patterns that may reflect altered vector ecology and host availability.

Danmallam’s commentary highlights this linkage, noting that without strategic planning, “urban expansion will continue to erode biodiversity, altering species interactions, ecosystem functions, and threatening species survival.”

The study co-authors also emphasize that Africa remains understudied in this field compared with Europe and North America, limiting understanding of how tropical urban systems respond to rapid environmental change.

Emerging pressures

Beyond parasites and habitat loss, urban landscapes are also facilitating the spread of invasive species.

One example highlighted in the broader literature is the Indian house crow, now established in parts of East Africa. The species has expanded rapidly along transport corridors, particularly highways connecting major cities.

According to Anthony Kuria of the Tropical Biology Association, the species has “firmly established itself in Mombasa and other coastal towns,” and its expansion is linked to urban food waste, warming conditions, and transport networks.

Such invasive species can increase pressure on native birds through nest predation and competition, adding another layer of ecological stress to already fragmented systems.

Health and ecosystem

Researchers interviewed in the Mongabay commentary link these ecological shifts to broader environmental and public health considerations.

Pantong Mark, a medical doctor and citizen scientist at Jos University Teaching Hospital, stated that “by decreasing the diversity of birds, we are undermining the very systems that help regulate diseases, control pests, and promote overall ecosystem health.”

The combined evidence suggests that bird diversity loss, parasite redistribution, and vector ecology changes may interact in ways that affect ecosystem stability.

Evidence gaps 

The combined findings from Nigerian field studies and broader Afrotropical research highlight a consistent pattern of ecological restructuring linked to urban expansion.

In Southwest Nigeria, Haemoproteus parasites appear more prevalent in urban environments, while Plasmodium lineages are more associated with non-urban habitats. At the same time, overall bird diversity is declining in urban settings, with functional consequences for ecosystem processes.

Researchers involved in the study recommend expanded surveillance using larger sample sizes, improved molecular tools for detecting co-infections, and targeted studies on vector populations across urban gradients.

They also emphasize the need for more systematic monitoring in Afrotropical cities, where rapid urban growth is occurring alongside high levels of biodiversity.

From a policy perspective, the evidence points to the importance of integrating biodiversity monitoring into urban planning frameworks, strengthening green space protection, and supporting long-term ecological research in rapidly expanding cities.

The data from Nigeria adds to a growing body of evidence that urban expansion is not only reshaping landscapes above ground but also altering biological interactions at microscopic levels that sustain bird populations across the region.