Are birds more afraid in urban parks or cemeteries? A Latin American study contrasts with results from Europe

The escape behaviour, measured as flight initiation distance (FID; the distance at which individuals take flight when approached by a potential predator, usually a human in the study systems), is a measure widely used to study fearfulness and risk-taking in animals. Previous studies have shown significant differences in the escape behaviour of birds inhabiting cemeteries and urban parks in European cities, where birds seem to be shyer in the latter. We collected a regional dataset of the FID of birds inhabiting cemeteries and parks across Latin America in peri-urban, suburban and urban parks and cemeteries. FIDs were recorded for eighty-one bird species. Mean species-specific FIDs ranged from 1.9 to 19.7 m for species with at least two observations (fifty-seven species). Using Bayesian regression modelling and controlling for the phylogenetic relatedness of the FID among bird species and city and country, we found that, in contrast to a recent publication from Europe, birds escape earlier in cemeteries than parks in the studied Latin American cities. FIDs were also significantly shorter in urban areas than in peri-urban areas and in areas with higher human density. Our results indicate that some idiosyncratic patterns in animal fearfulness towards humans may emerge among different geographic regions, highlighting difficulties with scaling up and application of regional findings to other ecosystems and world regions. Such differences could be associated with intrinsic differences between the pool of bird species from temperate European and mostly tropical Latin American cities, characterized by different evolutionary histories, but also with differences in the historical process of urbanization.

Bird diversity-environment relationships in urban parks and cemeteries of the Neotropics during breeding and non-breeding seasons

Background

Urbanization will increase in the next decades, causing the loss of green areas and bird diversity within cities. There is a lack of studies at a continental scale analyzing the relationship between urban green areas, such as parks and cemeteries, and bird species richness in the Neotropical region. Bird diversity-environment relationships in urban parks and cemeteries may be influenced by latitudinal gradients or species-area relationships. However, the seasonal variation of species diversity- environment has not been analyzed at a continental scale in the Neotropics.

Methods

Bird surveys were conducted in 36 cemeteries and 37 parks within 18 Neotropical cities during non-breeding and breeding seasons. Bird diversity was assessed through Hill numbers, focusing on species richness, the effective number of species derived from Shannon index and the Simpson index. Environmental variables included latitude, altitude, and local scale variables such as area size, habitat diversity and pedestrian traffic.

Results

Species richness and Shannon diversity were higher during the breeding season, whereas Simpson diversity did not vary between seasons. During both seasons, species richness increased with area size, was negatively related to altitude, and was the highest at 20° latitude. Species richness was also positively related to habitat diversity, pedestrian traffic, and was highest in suburban areas during the non-breeding season. Shannon and Simpson diversity showed significant relationships with habitat diversity and area size during the breeding season. Bird diversity was similar between parks and cemeteries.

Discussion

Our results showed that urban parks and cemeteries have similar roles in conserving urban bird diversity in Neotropical cities. However, species diversity-environment relations at the continental scale varied between seasons, highlighting the importance of conducting annual studies.

Avirulence and immunogenicity in mice of a bovine mastitis Staphylococcus aureus mutant

An avirulent mutant, designated RC122, was derived from Staphylococcus aureus bovine mastitis strain RC108 after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Mutant RC122, which was isolated on the basis of reduced colony size, showed diminished virulence in mice (LD50 of RC122: 3.1 x 10(10) cfu vs LD50 of RC108: 2.3 x 10(7) cfu). Mutant RC122 grew more slowly than its parental strain and showed decreased production of several exoproteins, such as alpha- and beta-hemolysin, DNAse and coagulase. The production of its capsule was induced only under in vivo growth conditions. Clearance studies performed in the mouse kidney revealed that the kinetics of disappearance of the mutant was similar to that of its parental strain. Protection experiments carried out by intraperitoneal administration in mice showed that mutant RC122 conferred a good degree of protection from challenge with homologous and heterologous strains.

[Resistance to antibiotics in strains of Azospirillum sp]

A total of 32 strains of Azospirillum mainly isolated from rhizosphere of grasses and soils of Argentina were examined for susceptibility to 9 antimicrobial agents (trimethoprim, ampicillin, carbenicillin, streptomycin, spectinomycin, chloramphenicol, kanamycin, nalidixic acid and tetracycline). Many of the strains were sensitive to tetracycline, kanamycin, chloramphenicol and nalidixic acid, and resistant to ampicillin (more than 50 mg/l) and carbenicillin (more than 200 mg/l). In spite of this general pattern, for most of the strains it was possible to obtain an antibiotype. Such antibiotype could be useful for identification of the strains in field experiments or in genetic transfer experiments.