Urbanization, Electromagnetic Radiation and Sparrows: A Case Study from Guwahati, India

The persisting growth of wireless telecommunication technology causes increased electrosmog. Exposure to wide-ranging radiofrequency electromagnetic fields is thought to be a concern for all the living species across the globe. Studies have shown possible effects of electromagnetic radiation on various organisms including electromagnetic radiation risk on birds, but the outcomes were inconsistent. Here, we investigated if there is any impact of electromagnetic radiation on the abundance and habitat use of sympatric House Sparrow and Tree Sparrow in Guwahati City, India. In addition, we did a comparative analysis of previous work that had been conducted on possible effects of EMR on wild birds in field condition. We collected sparrow abundance in selected urbanization gradients temporally over a period of two years in 45 locations and spatially covering 168 locations in the eastern part of Guwahati City. Point counts were carried out, and successively we measured the electromagnetic radiation along with other ecological covariates. It was observed that ecological variables contributed significant variation to explain the habitat use of sparrows in Guwahati City compared to electromagnetic radiation. We observed that House Sparrow had quadratic relationship and Tree sparrow had negative association with increasing urbanization. Studies carried out in the past on the impacts of electromagnetic radiation on birds outside the lab condition had not considered other ecological covariates, which could also influence the life history needs of the bird species. Our study emphasized that the ecological covariates should be taken into consideration while studying the effect of electromagnetic radiation on wild organisms.

Bird visit to Ficus benjamina in two urbanization gradients in the tropics

Fig trees area believed to be important bird habitat in the tropics, including in urban areas. The research objective was to reveal the bird species that visited Ficus benjamina in the low and high urbanization gradients in the tropics. Data were obtained in IPB University Darmaga Campus (low urbanization) and Sentul City (high urbanization) in Bogor (West Java, Indonesia), through direct observations of four trees per site in the morning, midday, late afternoon, and night, totalling 276 observation hours. Total of 29 bird species visited F. benjamina trees (26 species in low urbanization, 12 species in high), mainly insectivores, nectarivores, and frugivores birds. Nine species were common in both sites, i.e., Spotted Dove, Plaintive Cuckoo, Fulvous-breasted Woodpecker, Small Minivet, Common Iora, Sooty-headed Bulbul, Yellow-vented Bulbul, Common Tailorbird, Scarlet-headed Flowerpecker, and Olive-backed Sunbirds. Nocturnal birds (Collared Scops Owl, Large-tailed Nightjar) were present in low urbanization, but absent in high urbanization site, so did kingfishers (White-throated Kingfisher, Collared Kingfisher) and some other urbanization-prone species. The high urbanization site was characterized by the presence of Eurasian Tree Sparrow at the fig tree. This study showed that F. benjamina has an important role for diurnal and nocturnal birds, even in the high urbanization site.

Morphological and Ultrastructural Studies of Pecten in the Eurasian Tree Sparrow

We studied the fine histological structures of pecten oculi of the Eurasian tree sparrow using various microscopy techniques. The pecten of the tree sparrow was found to be of a pleated type comprising of pleats, bridges, and base. The light microscopic study revealed further that the pleats consist of capillaries of varying sizes, blood vessels, and numerous pigmented cells that give them a black color. Histochemical studies of pecten showed a large deposition of lipid droplets, which were more abundant in the basal area. The transmission electron microscopy displayed capillaries and blood vessels that remain surrounded by a thick fibrous basal membrane. They are formed of endothelial cells having a large lumen and abluminal area with microfolds. Interstitial spaces were found filled with rounded melanocytes, electron-dense pigment granules, and mitochondria. Observations under the scanning electron microscope revealed the presence of a dense vascular network of capillaries and vessels. In addition, large hyalocytes were also observed on the surface of the pleats. The above observations suggest that the histological structure of the pecten of the tree sparrow resembles those present in the pecten of other diurnal birds. However, further investigation is required to ascertain its functional role in birds.

Urban landscape for birdwatching activities

Urban landscapes are usually dominated by built spaces and human-made vegetation, which different from natural landscapes. This difference will affect the composition of birds that can be found in the urban landscape. For birdwatchers, birds are the main object in birdwatching activities. The objectives of this paper were to analyze the feasibility of urban landscapes for birdwatching activities and find out the characteristics of urban landscapes favored by birdwatchers in four cities in Java (Bogor, Sukabumi, Bandung, and Surabaya). Birdwatchers’ site preference and perception were surveyed through online questionnaires in February through May 2020 (n=1,247 respondents). Surveyed data revealed that birdwatching sites’ size varied between 0.05 and 76.82 ha, mainly urban forests and city parks. Most of the urban landscape was habitat to various bird species typical of the urban landscape (e.g., Eurasian tree-sparrow, Cave swiftlet, Black-headed Bulbul). Raptors (e.g., Black-thighed Falconet) are found in several locations. Among the respondents, 25 % (n=309) had previously conducted birdwatching activities in urban landscapes, while 72.0% (n=808) expressed their interest in birdwatching in urban landscapes, indicating that urban landscapes was feasible for birdwatching. The most favorite locations were the Bogor Botanical Gardens, Darmaga Research Forest (both in Bogor), Merdeka Field Park, Cikundul Agrotourism Area (Sukabumi), Bandung Zoo, Babakan Siliwangi City Forest (Bandung), Bungkul Park, and Flora Park (Surabaya). Characteristics of sites favored by birdwatchers were a shady area, not noisy location, and any facilities for birdwatching. The diversity of bird species did not became the main reason.

Differential Long-Term Population Responses of Two Closely Related Human-Associated Sparrow Species with Respect to Urbanization

Urban planning and management need long-term population level studies for evaluating how urbanization influences biodiversity. Firstly, we reviewed the current population trends of the House Sparrow (Passer domesticus) and the Eurasian Tree Sparrow (Passer montanus) in Europe, and evaluated the usefulness of citizens’ science projects to monitor these species in Finland. Secondly, we conducted a long-term (1991–2020) winter field study in 31 urban settlements along a 950 km north–south extent in Finland to study how latitude, weather and urbanization influence on sparrow’s growth rates. The House Sparrow is declining in 15 countries, and increasing in 5, whereas the Eurasian Tree Sparrow is declining in 12 and increasing in 9 European countries. The trend of the House Sparrow was significantly negative in continental Europe. However, the trend of the Eurasian Tree Sparrow was not significant. Both species have declined simultaneously in six countries, whereas in four countries, their trends are opposite. Citizen-based, long-term (2006–2020) winter season project data indicated that House Sparrow has decreased, whereas Eurasian Tree Sparrow has increased in Finland. However, the short-term (2013–2020) breeding season citizen-based project data did not indicate significant changes in the occupation rate of sparrows. Our long-term (1991–2020) field study indicated that wintering populations of the House Sparrow have decreased, whereas the Eurasian Tree Sparrows have both expanded their wintering range and increased their population size. Based on our winter count data, latitude and weather did not significantly influence the growth rates of sparrows. When the human population increased within the study plot, House Sparrow populations decreased, and vice versa. There was also a trend that a decreasing number of feeding sites has decreased the House Sparrow numbers. Urban-related factors did not influence the growth rate of the Eurasian Tree Sparrow. Our results indicate that the colonization of a new, even closely related species does not influence negatively on earlier urbanized species. It is probable that the niches of these sparrow species are different enough for allowing them to co-occur. The House Sparrow mainly nests on buildings, whereas the Eurasian Tree Sparrow can easily accept, e.g., nest boxes. Urban planning should take care of both the food availability and nest sites availability for both sparrow species.

Influence of growing up in the city or near an airport on the physiological stress of tree sparrow nestlings (Passer montanus)

Urbanization constitutes one of the major transformations of natural habitats, creating new areas characterized by multiple potential wildlife stressors. Birds that live in highly anthropized zones are confronted with physiological and behavioural challenges caused by these stressors. Here, we investigated if several health parameters differed between three subpopulations of tree sparrow nestlings subjected to different levels of anthropogenic pollution, and particularly noise pollution: a quiet rural area, a noisy rural area adjacent to an airport and a heavily urbanized area. We compared body condition, oxidative stress markers and baseline corticosterone levels, expecting urban nestlings to be in overall worse condition as compared to rural (rural and rural airport) birds. In addition, we expected nestlings exposed to aircraft noise to show intermediate stress levels. We found that rural-airport nestlings had the highest levels of antioxidant capacity of plasma and did not differ from rural counterparts in the rest of the parameters. By contrast, urban nestlings were in slightly worse body condition and had lower antioxidant capacity than rural and rural-airport individuals. Our results suggest that aircraft noise does not constitute a significant stressor for nestlings. In contrast, urban conditions constitute a more challenging situation, negatively impacting different physiological systems. Although nestlings seem able to buffer these challenges in the short-term, further research should explore the long-term potential consequences of early exposure to these conditions.