Immunolabeling provides evidence for subregions in the songbird nucleus accumbens and suggests a context-dependent role in song in male European starlings (Sturnus vulgaris)

Birdsong is well known for its role in mate attraction during the breeding season. However, many birds, including European starlings (Sturnus vulgaris), also sing outside the breeding season as part of large flocks. Song in a breeding context can be extrinsically rewarded by mate attraction; however, song in non-breeding flocks, referred to here as gregarious song, results in no obvious extrinsic reward and is proposed to be intrinsically rewarded. The nucleus accumbens (NAc) is a brain region well-known to mediate reward and motivation, which suggests it is an ideal candidate to regulate reward associated with gregarious song. The goal of this study was to provide new histochemical information on the songbird NAc and its subregions (rostral pole, core, and shell), and to begin to determine subregion-specific contributions to gregarious song in male starlings. We examined immunolabeling for tyrosine hydroxylase (TH), neurotensin, and enkephalin (ENK) in NAc. We then examined the extent to which gregarious and sexually-motivated song differentially correlated with immunolabeling for the immediate early genes FOS and ZENK in each subdivision of NAc. We found that TH and ENK labeling within subregions of the starling NAc was generally similar to patterns seen in the core and shell of NAc in mammals and birds. Additionally, we found that gregarious song, but not sexually-motivated song, positively correlated with FOS in all NAc subregions. Our observations provide further evidence for distinct subregions within the songbird NAc and suggest the NAc may play an important role in regulating gregarious song in songbirds.

First Report of Haemoproteus (Haemosporida, Haemoproteidae) Megalomeronts in the Brain of an Avian Host, with Description of Megalomerogony of Haemoproteus Pastoris, the Blood Parasite of the Common Starling

Species of Haemoproteus (Haemoproteidae, Haemosporida) are common bird pathogens. Recent molecular studies combined with histopathology research have reported development of megalomeronts of these parasites in various organs, sometimes resulting in the death of the avian host. Five Common starlings (Sturnus vulgaris) were found naturally infected with Haemoproteus pastoris lineage hLAMPUR01. The parasite was identified using microscopic examination of blood films and DNA sequences. Infected bird organs were investigated histologically for (i) the presence of exo-erythrocytic stages and (ii) the patterns of development (morphology and localization) in different host individuals. For the first time, megalomeronts of Haemoproteus parasites were seen developing in the brain, while numerous others at different stages of maturation were found in the intestine, pancreas, kidneys, lungs, esophagus, spleen, gizzard, and trachea. Megalomeronts were predominantly roundish or oval, up to 800 μm, they were surrounded by a capsular-like wall and developed asynchronously in the same bird individual. After megalomeront maturation and rupture, a massive infiltration of blood cells occurred, indicating the hemorrhagic processes. Review of available data showed that different Haemoproteus species produce markedly different megalomeronts, morphology of which can probably be predicted using phylogenetic analysis based on partial sequences of cytochrome b gene.

Exposure to food insecurity increases energy storage and reduces somatic maintenance in European starlings ( Sturnus vulgaris )

Birds exposed to food insecurity—defined as temporally variable access to food—respond adaptively by storing more energy. To do this, they may reduce energy allocation to other functions such as somatic maintenance and repair. To investigate this trade-off, we exposed juvenile European starlings ( Sturnus vulgaris , n = 69) to 19 weeks of either uninterrupted food availability or a regime where food was unpredictably unavailable for a 5-h period on 5 days each week. Our measures of energy storage were mass and fat scores. Our measures of somatic maintenance were the growth rate of a plucked feather, and erythrocyte telomere length (TL), measured by analysis of the terminal restriction fragment. The insecure birds were heavier than the controls, by an amount that varied over time. They also had higher fat scores. We found no evidence that they consumed more food overall, though our food consumption data were incomplete. Plucked feathers regrew more slowly in the insecure birds. TL was reduced in the insecure birds, specifically, in the longer percentiles of the within-individual TL distribution. We conclude that increased energy storage in response to food insecurity is achieved at the expense of investment in somatic maintenance and repair.

Global change affects differently at local scales animal populations: why Starlings still expands to the south while other temperate species go to the north?

Global change, which regroups global warming, landscape transformations and other anthropic modifications of ecosystems, has effects on populations and communities and produces modifications in the expansion area of species. While some species disappear, other ones are beneficiated by the new conditions and some of them evolve in new adapted forms or leave their ancient distribution area. As climate change tends to increase the temperature in several regions of the world, some species have been seen to leave areas in equatorial regions in order to join colder areas either towards the north of the northern hemisphere or towards the south of the southern one. Many birds as have moved geographically in direction to the poles and in many cases they have anticipated their laying dates. Actually, two tit species that use to lay their eggs in a period that their fledging dates synchronize with the emerging dates of caterpillars are now evolving to reproductive in periods earlier than before the climate change. Several species are reacting like that and other ones are moving to the north in Europe for example. Nevertheless, and very curiously, European starling, Sturnus vulgaris, populations are behaving on the contrary: their laying dates are moving towards later spring and their distribution area is moving towards the south. In this study we explore and discuss about different factors that may explain this difference from other birds.

Habituation, task solving and memorization may facilitate biological invasions: the Starling example

Invasions ecology deals more and more with behavioural characteristics of invasive species. Particularly, research have focused on the personality of invaders and on their way of coping with novelty in new habitats. Traits of neophobia may limit individuals in their exploration of novel objects or the consumption of novel foods, they may stop the access to valuable ressources. Actually, in novel environments like cities, food can be unreachable in throwaway dishes with lids or hidden in the garbage or even close to frightening objects. Animals may either left the place and waste these resources, or they can express low neophobia from the beginning and manipulate the objects to reach food. They may also habituate progressively to the context and use the ressources. Here we analyzed the behavioural responses of individuals from three populations of European starling Sturnus vulgaris: a population anciently settled in a rural region, a population that has recently colonized a urban area and a population of wintering migrant birds. We used a series of tests in order to explore if individuals would habituate to a novel object and if they could remember it eight months later. We explored if individuals would be less neophobic when confronted to two novel objects successively and we tested them in a learning task involving a novel object and an attractive food. Our results show that Sturnus vulgaris habituates rapidly to novel objects and that categorization facilitates neophobia lost when confronted to two different novel objects. Initially young birds appeared to be more skilled than adults in the learning task. Individuals from this species seem to be able to remember an object durably. We suggest that habituation, task solving and memorization are three mechanisms enhancing biological invasions.

Detection of a novel enterotropic Mycoplasma gallisepticum-like in European Starling (Sturnus vulgaris) around poultry farms in France

Recent outbreaks of highly pathogenic avian influenza in southwest France have raised questions regarding the role of commensal wild birds in the introduction and dissemination of pathogens between poultry farms. To assess possible infectious contacts at the wild-domestic bird interface, the presence of Mycoplasma gallisepticum (MG) was studied in the two sympatric compartments in southwest France. Among various peridomestic wild birds (n=385), standard PCR primers targeting the 16S rRNA of MG showed a high apparent prevalence (up to 45%) in cloacal swabs of European starlings (Sturnus vulgaris, n=108), while the MG-specific mgc2 gene was not detected. No tracheal swab of these birds tested positive, and no clinical sign was observed in positive birds, suggesting commensalism in the digestive tract of starlings. A mycoplasma strain was then isolated from a starling swab and its whole genome was sequenced using both Illumina and Nanopore technologies. Phylogenetic analysis showed that it was closely related to MG and M. tullyi, although it was a distinct species. A pair of specific PCR primers targeting the mgc2-like gene of this MG-like strain was designed and used to screen again the same avian populations and a wintering urban population of starlings (n=50). Previous PCR results obtained in starlings were confirmed to be mostly due to this strain (20/22 positive pools). In contrast, the strain was not detected in fresh faeces of urban starlings. Furthermore, it was detected in one tracheal pool of cattle egrets and one cloacal pool of white wagtails, suggesting infectious transmissions between synanthropic birds with similar feeding behaviour. As the new starling mycoplasma was not detected in free-range ducks (n=80) in close contact with positive starlings, nor in backyard (n=320) and free-range commercial (n=720) chickens of the area, it might not infect poultry. However, it could be involved in mycoplasma gene transfer in such multi-species contexts.