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.

Sex-specific signalling of individual personality by a mutual plumage ornament in a passerine

The significance of colour signals in species with strong sexual dimorphism and/or elaborated visual ornaments is rather well-understood. Less attention has, however, been devoted to study colour signals in species with weak or no apparent sexual dimorphism. In such species, an interesting possibility arises as both sexes can bear the same colour ornament(s) (i.e. sexes are mutually ornamented), but their signalling value might differ in males and females. We aimed to explore this possibility by investigating the phenotypic correlates of the black bib, a melanin-based plumage ornament, in the Eurasian tree sparrow (Passer montanus). More specifically, we studied the sex-dependent relationships between bib size and three aspects of individuals’ phenotype: body condition (i.e. size-corrected body mass), physiology (i.e. cellular innate immunity/inflammation status, expressed through total leucocyte counts, and chronic physiological stress, expressed through the ratio of heterophils to lymphocytes) and individual personality (i.e. activity in a novel environment). We found that bib size was not associated with body condition and cellular innate immunity/inflammation status, but was positively related to physiological stress levels independent of sex. Furthermore, bib size was negatively associated with activity in males but positively in females. Our findings bring important correlative evidence that mutual ornamental traits may have sex-specific signalling value. Significance statement The signalling role of elaborated colourful ornaments, that are usually possessed only by males in sexually dimorphic species, is well-established. The function of various colour traits which are borne by both sexes (i.e. mutual ornaments), however, is less obvious. Do they have a signalling value in both sexes? If yes, do they signal the same information in males and females? Or, most intriguingly, can they convey different information in the two sexes? To test these alternatives, we studied the signalling value of the black bib, a melanin-based mutual plumage ornament, in Eurasian tree sparrows (Passer montanus). Apart from being correlated with chronic stress in both sexes, bib size was positively related to activity in females but negatively in males. Our results suggest that the information content of the same colour trait in males and females can be different in mutually ornamented species.

Thermogenic responses in Eurasian Tree Sparrow (Passer montanus) to seasonal acclimatization and temperature-photoperiod acclimation

Background Small birds in temperate habitats must either migrate, or adjust aspects of their morphology, physiology and behavior to cope with seasonal change in temperature and photoperiod. It is, however, difficult to accurately measure how seasonal changes in temperature and photoperiod affect physiological processes such as basal metabolic rate (BMR) and metabolic activity. To address this problem, we collected data in each month of the year on body mass (Mb) and BMR, and conducted a series of experiments to determine the effect of temperature and photoperiod on Mb, BMR and physiological markers of metabolic activity, in the Eurasian Tree Sparrow (Passer montanus). Methods In one experiment, we measured monthly change in Mb and BMR in a captive group of birds over a year. In another experiment, we examined the effects of acclimating birds to two different temperatures, 10 and 30 °C, and a long and a short photoperiod (16 h light:8 h dark and 8 h light:16 h dark, respectively) for 4 weeks. Results We found that these treatments induced sparrows to adjust their Mb and metabolic rate processes. Acclimation to 30 °C for 4 weeks significantly decreased sparrows’ Mb, BMR, and energy intake, including both gross energy intake and digestible energy intake, compared to birds acclimated to 10 °C. The dry mass of the liver, kidneys and digestive tract of birds acclimated to 30 °C also significantly decreased, although their heart and skeletal muscle mass did not change significantly relative to those acclimated to 10 °C. Birds acclimated to 30 °C also had lower mitochondrial state-4 respiration (S4R) and cytochrome c oxidase (COX) activity in their liver and skeletal muscle, compared to those acclimated to 10 °C. Birds acclimated to the long photoperiod also had lower mitochondrial S4R and COX activity in their liver, compared to those acclimated to the short photoperiod. Conclusions These results illustrate the changes in morphology, physiology, and enzyme activity induced by seasonal change in temperature and photoperiod in a small temperate passerine. Both temperature and photoperiod probably have a strong effect on seasonal variation in metabolic heat production in small birds in temperate regions. The effect of temperature is, however, stronger than that of photoperiod.