Sturnus Vulgaris Research Articles

Effects of habitat heterogeneity on bird communities in the forests of northeastern Germany

Habitat heterogeneity is a key factor for regulating biodiversity in temperate lowland forests. Specifically, stands associated with late forest development phases provide important habitat structures for many rare and threatened forest bird species. However, how forest stands that differ in their structural complexity, canopy conditions and tree species composition affect forest bird assemblages both at the local and landscape scale remains largely unclear. In a young moraine lake landscape of northeastern Germany, we assessed correlations of bird diversity and bird composition with stand properties. We used data from 48 transects (400 m) established in (1) unmanaged, closed-canopy, mature stands that were dominated by Fagus sylvatica (UDS), and (2) diverse managed, mixed coniferous stands with a mosaic of open and closed canopy patches (MCS). We found that bird communities of the UDS strongly differed from those in the MCS, with open habitat species being more frequent in the MCS. By contrast, differences in diversity measures were less distinct. Moreover, we identified nine indicator species for the UDS (Columba oenas, Cyanistes caeruleus, Muscicapa striata, Leiopicus medius, Certhia brachydactyla, Ficedula parva, Dryobates minor, Sturnus vulgaris, Ficedula hypoleuca) and seven indicator species for the MCS (Periparus ater, Pyrrhula pyrrhula, Regulus regulus, Prunella modularis, Lophophanus cristatus, Emberiza citronella, Anthus trivialis). Several famous ancient beech forest patches in Müritz National Park and the UNESCO Biosphere Reserve “Schorfheide-Chorin” were found to harbour the set of the UDS indicator species. The UDS support of bird coenosis is typical for old mature broadleaved forests and can be considered as an effective tool for bird conservation. Our results further indicate that the combination of unmanaged and managed stands associated with different habitat complexities would benefit forest bird assemblages at the landscape scale. Key words: forest specialist birds, bird conservation, non-managed forests, old-growth patches, Ficedula parva, Leiopicus medius, coniferous forest

Ecological value of wood energy plantations in the support of some animal groups

Today, some environmental problems have reached such severe proportions that it is no longer enough to recognise them, but environmentally friendly solutions must be used to reduce them. The reduction in the area of natural forests of native species is causing problems in several ways. This research aimed to highlight how environmental, conservation and economic interests can be reconciled. In addition to natural forests, wood energy plantations are becoming increasingly important. Energy import dependency is a problem for most countries, for which wood energy plantations can partly offer an alternative. Native forests can be protected, and their area increased where possible. Meanwhile, energy plantations can be established in areas with low agricultural productivity. In this experiment, I studied a plantation of Pedunculate Oak (Quercus robur), a Black Locust (Robinia pseudoacacia) and a Paulownia (Paulownia Shan Tong). I selected burrowing birds and ground-dwelling arthropods as indicator groups. I did this by establishing a nesting colony and soil trapping. I wanted to demonstrate that, in addition to natural forests, wood energy plantations have a role not only in economic terms but also in maintaining certain animal groups. Soil trapping tests were carried out in all three tree plantations. The obtained results showed that in the Paulownia plantation, the occupancy rate of nest boxes was almost 100%, while in the Black Locust plantation it was around 30%. Among the species that occupied the nesting sites, the Common Starling (Sturnus vulgaris) and the Eurasian Tree Sparrow (Passer montanus) were more abundant, while Great Tit (Parus major) was present in the Black Locust plantation. These are opportunistic species for which nesting opportunity is the most important factor, since their feeding area (in the case of the Common Starling and the Eurasian Tree Sparrow) is not typical of the nesting area. The soil trap investigations show that there are no significant differences in the composition of the arthropod group (beetles, spiders) in the study areas.

Experimental assessment of laser scarecrows for reducing avian damage to sweet corn.

Birds damage crops, costing millions of dollars annually, and growers utilize a variety of lethal and nonlethal deterrents in an attempt to reduce crop damage by birds. We experimentally tested laser scarecrows for their effectiveness at reducing sweet corn (Zea mays) damage. We presented 18 captive flocks of free-flying European starlings (Sturnus vulgaris) with fresh sweet corn ears distributed on two plots where laser and control treatments were alternated each day and allowed each flock to forage over 5 days. In 16 trials, fresh sweet corn ears were mounted on wooden sticks distributed from 0 to 32 m from laser units (Stick Trials), and in two trials birds foraged on ripe corn grown from seed in the flight pen (Natural Trials). We aimed to determine if laser-treated plots had significantly less damage overall and closer to the laser unit, and whether birds became more or less likely to forage in laser-treated plots over time. Lasers reduced damage overall, marginally in Stick Trials and dramatically in Natural Trials. Damage increased during each week in both trial types. Damage increased significantly with distance from lasers, and significant treatment effects occurred up to ~20 m from lasers. Our results concur with recent field trials demonstrating strong reductions in sweet corn damage when lasers are deployed. This study provides a first look at how birds respond to repeated laser exposure and whether damage increases with distance from lasers. Key differences between pen and field trials are discussed. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Decoupling of body size, physiological state and subsequent performance in a developmentally manipulated songbird

Abstract It is generally assumed that larger juveniles are more physiologically mature, hence their overall condition and subsequent performance are higher. Some taxa face extreme workload transitions during development (e.g. nest departure in birds), which may select for non‐linear growth profiles that decouple relationships between body size and physiological state, making the links between metrics of development (e.g. body mass) and juvenile performance uncertain. We manipulated perceived mass in European starlings approaching fledging using 4.0 g weighted backpacks, measuring subsequent growth trajectories (mass, wing length) and physiological state (aerobic capacity, energy state, oxidative status) to test whether body size and physiology are coupled during a non‐linear developmental phase (pre‐fledging mass recession). Nanotag radio transmitters were then used to track post‐fledging performance (activity, activity‐slope, dispersal). Weighted nestlings had greater pre‐fledging mass recession and marginally reduced wing growth when compared to controls. Consequently, weighted birds had lower body mass at fledging, while also displaying markers of oxidative stress (increased reactive oxygen metabolites), yet aerobic capacity and energy state were equal between treatment groups. Previously weighted birds showed no correlation between fledgling state (body size, physiology) and subsequent performance. However, control fledglings that had decreased mass recession and greater wing growth prior to fledging dispersed earlier, while longer wings at fledging were associated with more rapid increases in post‐fledging activity (activity‐slope). In addition, control fledglings with lower haemoglobin also dispersed earlier, while increased reactive oxygen metabolites were associated with decreased activity levels. Body mass and energy state were unrelated to any metric of post‐fledging performance. Our data suggest mass‐independent development of some physiological traits in species with non‐linear growth profiles, potentially with a context‐dependent oxidative cost, and that physiology may predict some measures of post‐fledging performance not captured by body size. Read the free Plain Language Summary for this article on the Journal blog.

Concurrent invasions of European starlings in Australia and North America reveal population‐specific differentiation in shared genomic regions

AbstractA species' success during the invasion of new areas hinges on an interplay between the demographic processes common to invasions and the specific ecological context of the novel environment. Evolutionary genetic studies of invasive species can investigate how genetic bottlenecks and ecological conditions shape genetic variation in invasions, and our study pairs two invasive populations that are hypothesized to be from the same source population to compare how each population evolved during and after introduction. Invasive European starlings (Sturnus vulgaris) established populations in both Australia and North America in the 19th century. Here, we compare whole‐genome sequences among native and independently introduced European starling populations to determine how demographic processes interact with rapid evolution to generate similar genetic patterns in these recent and replicated invasions. Demographic models indicate that both invasive populations experienced genetic bottlenecks as expected based on invasion history, and we find that specific genomic regions have differentiated even on this short evolutionary timescale. Despite genetic bottlenecks, we suggest that genetic drift alone cannot explain differentiation in at least two of these regions. The demographic boom intrinsic to many invasions as well as potential inversions may have led to high population‐specific differentiation, although the patterns of genetic variation are also consistent with the hypothesis that this infamous and highly mobile invader adapted to novel selection (e.g., extrinsic factors). We use targeted sampling of replicated invasions to identify and evaluate support for multiple, interacting evolutionary mechanisms that lead to differentiation during the invasion process.

Mitochondrial metabolism in blood more reliably predicts whole-animal energy needs compared to other tissues

Understanding energy metabolism in free-ranging animals is crucial for ecological studies. In birds, red blood cells (RBCs) offer a minimally invasive method to estimate metabolic rate (MR). In this study with European starlings Sturnus vulgaris, we examined how RBC oxygen consumption relates to oxygen use in key tissues (brain, liver, heart, and pectoral muscle) and versus the whole organism measured at basal levels. The pectoral muscle accounted for 34%-42% of organismal MR, while the heart and liver, despite their high mass-specific metabolic rate, each contributed 2.5%-3.0% to organismal MR. Despite its low contribution to organismal MR (0.03%-0.04%), RBC MR best predicted organismal MR (r= 0.70). Oxygen consumption of the brain and pectoralis was also associated with whole-organism MR, unlike that of heart and liver. Overall, our findings demonstrate that the metabolism of a systemic tissue like blood is a superior proxy for organismal energy metabolism than that of other tissues.

Distinct patterns of activity within columns of the periaqueductal gray are associated with functionally distinct birdsongs.

Male songbirds produce female-directed songs in spring that convey a state of sexual motivation. Many songbirds also sing in fall flocks in affiliative/gregarious contexts in which song is linked to an intrinsic positive affective state. The periaqueductal gray (PAG) in mammals, which is organized into functional columns, integrates information from multiple brain regions and relays this information to vocal motor areas so that an animal emits a vocal signal reflective of its affective state. Here, we test the hypothesis that distinct columns in the songbird PAG play roles in the distinct affective states communicated by sexually motivated and gregarious song. We quantified the numbers of immediate early gene ZENK-positive cells in 16 PAG subregions in male European starlings (Sturnus vulgaris) after singing gregarious or sexually motivated song. Results suggest that distinct PAG columns in songbirds context-specifically regulate song, agonistic, and courtship behaviors. A second exploratory, functional tract-tracing study also demonstrated that inputs to the PAG from specific subregions of the medial preoptic nucleus may contribute to gregarious song and behaviors indicative of social dominance. Together, findings suggest that conserved PAG columns and inputs from the preoptic nucleus may play a role in context-specific vocal and other social behaviors.

COMPARISON OF HEMATOLOGIC DIFFERENCES WITH LITHIUM HEPARIN AND DIPOTASSIUM ETHYLENEDIAMINETETRAACETIC ACID IN EUROPEAN STARLINGS (STURNUS VULGARIS).

Preservation of blood through use of anticoagulants allows delayed assessment of hematologic health and is commonly employed in veterinary health assessments. The two most common anticoagulants are lithium heparin (LH) and dipotassium ethylenediaminetetraacetic acid (EDTA), and their effects can vary widely between species. The hematologic effects of these anticoagulants on blood from European starlings (Sturnus vulgaris) have not been established, and these birds could serve as models for passerine species both in managed collections and in the wild. Blood was drawn from 45 European starlings and immediately divided into either LH or EDTA microtainers. For each sample, packed cell volume (PCV), total solids (TS), and complete blood counts were performed. There were no significant differences between EDTA and LH anticoagulated blood for PCV, white blood cell count (WBC) slide estimates, WBC determined by Leukopet, absolute heterophils, absolute lymphocytes, absolute monocytes, absolute eosinophils, or absolute basophils. Blood anticoagulated with EDTA had higher total solids than blood mixed with LH. For both anticoagulants, Leukopet-measured total WBC were consistently higher than blood film estimates. There were no subjective morphologic differences for WBC and no hemolysis observed in the samples. Thrombocyte clumping was prominent for LH blood samples and minimal for EDTA samples. These results reveal that LH and EDTA are both suitable anticoagulants for use in European starlings, and EDTA may be superior for diagnostic purposes or for qualitative evaluation of thrombocyte quantity.

THE PHARMACOKINETICS AND PHARMACODYNAMICS OF ORAL PONAZURIL IN THE TREATMENT OF SYSTEMIC ISOSPOROSIS IN PASSERINE BIRDS.

Systemic isosporosis, previously atoxoplasmosis, is a significant cause of mortality in juvenile passerine birds. Recommended treatment regimens are empiric and vary in efficacy. The goal of this study was to determine the pharmacokinetics and pharmacodynamics of ponazuril for treatment of systemic isosporosis. Ponazuril, diluted with water to create an oral suspension (50 mg/ml), was administered (100 mg/kg) to 72 European starlings (Sturnus vulgaris) by a single dose via direct oral gavage (n = 24), a single dose injected into superworm larvae (Zophobas morio; n = 24), or a daily dose mixed with commercial dog food to top-dress feed for 5 d (n = 24). Peak plasma concentrations were 5.84, 2.46, and 9.13 µg/ml for the direct gavage, injected larvae, and top-dressed feed groups, respectively. With repeated dosing, mean plasma concentrations from the top-dressed feed group were maintained between 8.12 to 13.11 µg/ml. Results suggested ponazuril at a dosage of 100 mg/kg administered via direct gavage or top-dressed feed, but not via injected larvae, would exceed the concentrations needed to inhibit merogony of other apicomplexan parasites in cell culture (5 µg/ml). To assess the pharmacodynamics of this dose, seven passerine birds, red-vented bulbuls (Pycnonotus cafer; n = 2), blue-grey tanager (Thraupis episcopus; n = 1), and red-capped cardinals (Paroaria gularis; n = 4), were identified as shedders of systemic Isospora spp. via fecal qPCR. Birds were then treated with ponazuril (100 mg/kg) daily on top-dressed feed for 14 d. Fecal shedding was assessed via qPCR for 6 wk from the initiation of treatment. Treatment was associated with reduction in proportions of fecal shedding during the treatment period and the week following treatment, but shedding resumed in all birds by the end of sampling. Results support that treatment of breeding birds with 100 mg/kg ponazuril could reduce the shedding of active oocysts and decrease risk of clinical infection in susceptible juveniles.

Observations of avifauna on Rēkohu / Wharekauri / Chatham Island, Chatham Islands group, in February 2023

Rēkohu / Wharekauri / Chatham Island (hereafter Rēkohu) is the largest island in the Chatham Islands group, 800 km east of the Te Wai Pounamu / South Island, Aotearoa / New Zealand. This island has an avifauna of 170 taxa. Here, we present a list of bird species encountered during an eight-day undergraduate field trip in February 2023. Based on visual encounters or via calls heard, we encountered 38 species of bird (two seabirds, eight coastal birds, six freshwater birds and 22 terrestrial birds) across 13 locations over six days. The most common species sighted were common starlings (Sturnus vulgaris vulgaris), followed by white-fronted terns (Sterna striata) and black swans (Cygnus atratus). We encountered a Chatham Island tūī (Prosthemadera novaeseelandiae chathamensis) in Nikau Bush Reserve, c.35 km north of the translocated population in Awatotara Valley. We also present the first list of bird species for Motuhinahina and a nearby limestone rock stack in Te Whanga Lagoon. Birds encountered there included Chatham Island shag (Leucocarbo onslowi), Pitt Island shag (Phalacrocorax featherstoni), Buff weka (Gallirallus australis hectori) and New Zealand little penguin (Eudyptula minor minor). We formally report the presence of feral emu (Dromaius novaehollandiae), including chicks, at Te Matarae, where there is self-sustaining population following their release to the wild years ago. In previous observations, feral chicken (Gallus gallus gallus) and turkey (Meleagris gallopavo) were ‘semi-wild’ on the basis that observations made of these species were well outside sites of human habitation. In the case of turkey, they are in the process of self-establishing. We suggest a full census is required to determine the status of these populations, particularly emu. As the emu population is self-sustaining, they should be considered as a new addition not only to the avifauna of the Chatham Islands group but to Aotearoa / New Zealand.

Molecular characterization of highly prevalent Escherichia coli and Escherichia marmotae resistant to extended-spectrum cephalosporins in European starlings (Sturnus vulgaris) in Tunisia.

European starlings are widespread migratory birds that have already been described as carrying bacteria resistant to extended-spectrum cephalosporins (ESC-R). These birds are well known in Tunisia because they spend the wintertime in this country and are hunted for human consumption. The goal of our study was to estimate the proportion of ESC-R in these birds and to characterize the collected isolates using whole-genome sequencing. Results showed that 21.5% (42/200) of the birds carried either an extended-spectrum beta-lactamase (ESBL) or an acquired AmpC gene. Diverse bla CTX-M genes were responsible for the ESBL phenotype, bla CTX-M-14 being the most prevalent, while only bla CMY-2 and one bla CMY-62 were found in AmpC-positive isolates. Likewise, different genetic determinants carried these resistance genes, including IncHI2, and IncF plasmids for bla CTX-M genes and IncI1 plasmids for bla CMY-2 genes. Three chromosomally encoded bla CTX-M-15 genes were also identified. Surprisingly, species identification revealed a large proportion (32.7%) of Escherichia marmotae isolates. This species is phenotypically indistinguishable from Escherichia coli and has obviously the same capacity to acquire ESC-R genes. Our data also strongly suggest that at least the IncHI2/pST3 plasmid can spread equally between E. coli and E. marmotae. Given the potential transmission routes between humans and animals, either by direct contact with dejections or through meat preparation, it is important to closely monitor antimicrobial resistance in European starlings in Tunisia and to set up further studies to identify the sources of contamination of these birds. IMPORTANCE The One Health concept highlighted knowledge gaps in the understanding of the transmission routes of resistant bacteria. A major interest was shown in wild migratory birds since they might spread resistant bacteria over long distances. Our study brings further evidence that wild birds, even though they are not directly submitted to antibiotic treatments, can be heavily contaminated by resistant bacteria. Our results identified numerous combinations of resistance genes, genetic supports, and bacterial clones that can spread vertically or horizontally and maintain a high level of resistance in the bird population. Some of these determinants are widespread in humans or animals (IncHI2/pST3 plasmids and pandemic clones), while some others are less frequent (atypical IncI1 plasmid and minor clones). Consequently, it is essential to be aware of the risks of transmission and to take all necessary measures to prevent the proportions of resistant isolates from increasing uncontrollably.

American Kestrels Compete with European Starlings over Nest Boxes in Eastern Pennsylvania

ABSTRACT The American Kestrel (Falco sparverius) has been steadily declining throughout most of its eastern North American range, and the cause of this decline is still relatively unknown. As a cavity nesting species, the American Kestrel often competes with other cavity nesters such as the invasive and abundant European Starling (Sturnus vulgaris) over nest boxes. The relationship between European Starling presence at nesting sites and American Kestrel occupancy and nesting success is understudied. We analyzed data from nest boxes monitored in eastern Pennsylvania, USA, from 1992 to 2021 to identify changes in occupancy of American Kestrels and competitors, and to examine the relationship between competition at nest boxes and American Kestrel nesting parameters. We found that American Kestrel occupancy decreased while European Starling occupancy increased over the study period. All other species occupying nest boxes (small mammals, passerines, owls, and snakes) showed no significant occupancy trends. On average 21% of nest boxes remained unoccupied annually, and 7% of occupied nest boxes were used by both American Kestrels and competitors in the same breeding season. The presence of these competitors had negative associations with American Kestrel occupancy, clutch size, number of fledglings produced, and overall nesting success. Specifically, the rate of nesting success decreased by 26% when European Starlings used the same nest box within the same breeding season. In recent years, nesting productivity of American Kestrels has decreased, with the average number of nestlings, fledglings, and nesting success rate all declining, while the average clutch size remained constant. Our results suggest that American Kestrel nesting parameters in eastern Pennsylvania are negatively associated with competition for nest boxes during the breeding season. The opposing trends in occupancy for the European Starling and the American Kestrel in this study area coupled with the declining productivity of American Kestrel nests raise concerns over the future of this raptor species in eastern Pennsylvania.

Distinct patterns of gene expression in the medial preoptic area are related to gregarious singing behavior in European starlings (Sturnus vulgaris)

BackgroundSong performed in flocks by European starlings (Sturnus vulgaris), referred to here as gregarious song, is a non-sexual, social behavior performed by adult birds. Gregarious song is thought to be an intrinsically reinforced behavior facilitated by a low-stress, positive affective state that increases social cohesion within a flock. The medial preoptic area (mPOA) is a region known to have a role in the production of gregarious song. However, the neurochemical systems that potentially act within this region to regulate song remain largely unexplored. In this study, we used RNA sequencing to characterize patterns of gene expression in the mPOA of male and female starlings singing gregarious song to identify possibly novel neurotransmitter, neuromodulator, and hormonal pathways that may be involved in the production of gregarious song.ResultsDifferential gene expression analysis and rank rank hypergeometric analysis indicated that dopaminergic, cholinergic, and GABAergic systems were associated with the production of gregarious song, with multiple receptor genes (e.g., DRD2, DRD5, CHRM4, GABRD) upregulated in the mPOA of starlings who sang at high rates. Additionally, co-expression network analyses identified co-expressing gene clusters of glutamate signaling-related genes associated with song. One of these clusters contained five glutamate receptor genes and two glutamate scaffolding genes and was significantly enriched for genetic pathways involved in neurodevelopmental disorders associated with social deficits in humans. Two of these genes, GRIN1 and SHANK2, were positively correlated with performance of gregarious song.ConclusionsThis work provides new insights into the role of the mPOA in non-sexual, gregarious song in starlings and highlights candidate genes that may play a role in gregarious social interactions across vertebrates. The provided data will also allow other researchers to compare across species to identify conserved systems that regulate social behavior.

Variation in oxidative status, but not structural and physiological development, associated with changing ontogenetic environments.

Despite the potential for temporally-dependent relationships between trait values and fitness (e.g., as juveniles approach life-stage transitions such as fledging), how developmental stage affects canalization (a measure of robustness to environmental variation) of morphological and physiological traits is rarely considered. To test the sensitivity of morphological and physiological traits to environmental variation in two developmental stages, we manipulated brood size at hatch in European starlings (Sturnus vulgaris) and cross-fostered chicks between enlarged and reduced broods approaching fledging. We measured body size (mass, tarsus, wing length) and physiological state (aerobic capacity, oxidative status) at asymptotic mass on day 15, then cross-fostered chicks between 'high' and 'low' quality environments and assessed the same traits again on day 20, after five days of pre-fledging mass recession. Chicks in reduced broods were heavier at asymptotic mass and had lower reactive oxygen metabolites than enlarged broods, while structural size, aerobic capacity, and antioxidant capacity were unaffected by experimental brood size. The observed canalization of structural and physiological traits during early development was maintained after cross-fostering, during late development. However, in contrast to early development, antioxidant capacity approaching fledging appeared sensitive to environmental conditions, as trajectories varied by cross-fostering treatment. Elevated reactive oxygen metabolites observed after early development in enlarged brood chicks were maintained after cross-fostering, suggesting canalized development in low-quality environments could produce oxidative costs that carry over between life-stages, even when conditions improve. These data reveal trait-specific relationships between environmental conditions and development and highlight how natal environment effects may vary by developmental stage.

Long term stability of corticosterone in feathers

Measuring corticosterone in feathers allows researchers to make long-term, retrospective assessments of physiology with non-invasive sampling. To date, there is little evidence that steroids degrade within the feather matrix, however this has yet to be determined from the same sample over many years. In 2009, we made a pool of European starling (Sturnus vulgaris) feathers that had been ground to a homogenous powder using a ball mill and stored on a laboratory bench. Over the past 14 years, a subset of this pooled sample has been assayed via radioimmunoassay (RIA) 19 times to quantify corticosterone. Despite high variability across time (though low variability within assays), there was no effect of time on measured feather corticosterone concentration. In contrast, two enzyme immunoassays (EIA) produced higher concentrations than the samples assayed with RIA, though this difference is likely due to different binding affinities of the antibodies used. The present study provides further support for researchers to use specimens stored long-term and from museums for feather corticosterone quantification, and likely applies to corticosteroid measurements in other keratinized tissues.

The motivation to flock correlates with vocal-social behaviors and dopamine-related gene expression in male European starlings

It is proposed that songbird flocks are partly reinforced by positive social interactions, however not all flock mate interactions are positive. The combination of both positive and negative social interactions with flock mates may play a role in the motivation for birds to flock. The nucleus accumbens (NAc), medial preoptic area (POM), and ventral tegmental area (VTA) are implicated in vocal-social behaviors in flocks, including singing. Dopamine (DA) within these regions modifies motivated, reward-directed behaviors. Here, we begin to test the hypothesis that individual social interactions and DA within these regions are involved in the motivation to flock. Vocal-social behaviors were recorded in eighteen male European starlings in mixed-sex flocks in fall, when starlings are highly social and form large flocks. Males were then singly removed from their flock and the motivation to flock was quantified as the amount of time spent attempting to join a flock following separation. We used quantitative real-time polymerase chain reaction to measure expression of DA-related genes in the NAc, POM, and VTA. Birds producing high levels of vocal behaviors were more highly motivated to flock and had higher tyrosine hydroxylase (the rate-limiting enzyme in DA synthesis) expression in the NAc and VTA. Birds that received high levels of agonistic behaviors were less motivated to flock and had higher DA receptor subtype 1 expression in the POM. Overall, our findings suggest that interplay between social experience and DA activity in NAc, POM, and VTA plays a key role in social motivation in flocking songbirds.

Dehydroepiandrosterone (DHEA) increases undirected singing behavior and alters dopaminergic regulation of undirected song in non-breeding male European starlings (Sturnus vulgaris).

It has been proposed that in species that defend territories across multiple life history stages, brain metabolism of adrenal dehydroepiandrosterone (DHEA) regulates aggressive behavior at times when gonadal androgen synthesis is low (i.e. the non-breeding season). To date, a role for DHEA in the regulation of other forms of social behavior that are expressed outside of the context of breeding remains unknown. In this experiment, we used the European starling (Sturnus vulgaris) model system to investigate a role for DHEA in the neuroendocrine regulation of singing behavior by males in non-breeding condition. Starling song in a non-breeding context is spontaneous, not directed towards conspecifics, and functions to maintain cohesion of overwintering flocks. Using within-subjects design, we found that DHEA implants significantly increase undirected singing behavior by non-breeding condition male starlings. Given that DHEA is known to modulate multiple neurotransmitter systems including dopamine (DA) and DA regulates undirected song, we subsequently used immunohistochemistry for phosphorylated tyrosine hydroxylase (pTH, the active form of the rate-limiting enzyme in DA synthesis) to investigate the effect of DHEA on dopaminergic regulation of singing behavior in a non-breeding context. Pearson correlation analysis revealed a positive linear association between undirected singing behavior and pTH immunoreactivity in the ventral tegmental area and midbrain central gray of DHEA-implanted, but not control-implanted, males. Taken together, these data suggest that undirected singing behavior by non-breeding starlings is modulated by effects of DHEA on dopaminergic neurotransmission. More broadly, these data expand the social behavior functions of DHEA beyond territorial aggression to include undirected, affiliative social communication.

Seasonal Use of Dairies as Overnight Roosts by Common Starlings (Sturnus vulgaris)

The Common Starling (Sturnus vulgaris) is an invasive bird species in North America that can cause damage to dairies. Starlings roost in structures on dairies overnight, defecating on cows, feed, and supplies. To target roosts for effective deterrence, farmers must know what times of the year starling populations are greatest. To test seasonality, two data sets were analyzed. First, birds were counted for 20–30 min at sunrise and sunset on 10 Whatcom County, Washington dairies over four weeks in September and October of 2016. Starling counts were greater in the last week of observations than in weeks one, two, and three. Second, birds were counted at sunset for four weeks during winter 2021 and spring and summer 2022 at two dairies in the Palouse region of Washington State and Idaho. As temperature and minutes of daylight decreased, bird abundance increased. There was also an effect of season, with more birds counted in winter and spring than in summer. These data sets combined suggest a seasonal use of dairies as night roosts by starlings. With this information, farmers in the United States will know to contact wildlife managers in the summer, so a starling deterrence strategy can be developed before roosts are established in the fall.

Analysis of Association of Ultradian Body Temperature Rhythms in Animals with Intensity of Fluctuations of Radioactive Decay of Natural 40K Isotope.

The study monitored the long-term body temperature (BT) oscillations of C57BL/6 mice and outbred starlings (Sturnus vulgaris) to compare them with fluctuation in decay rate of radioactive natural 40K isotope. The spectrum analysis revealed simultaneous changes of the predominant periods in BT spectra of the animals and those in fluctuation in 40K decay rate. A positive correlation was established between BT dynamics and fluctuation in decay rate. The superposed epoch analysis revealed predominant coincidence of the moments of BT and fluctuation in 40K decay rate. The novel data indicate association between BT ultradian rhythms with quasirhythmic variations of fluctuation in 40K decay rate.

Long-term, not short-term, temperatures predict timing of egg laying in European Starling

Abstract Temperature, particularly within ~1 month of egg laying, is thought to be an important, short-term cue used by female birds to calibrate timing of breeding to local conditions. Here, we show that a relatively broad, long-term, temperature window (January 2 to April 4, 92 days; r2 = 0.73) best predicted timing of egg laying in European Starlings (Sturnus vulgaris). A “mid-winter” temperature window was also strongly correlated with laying date (r2 = 0.58), but we found no support for an influence of short-term temperatures immediately before egg laying. We assessed the relationship between ambient temperature and timing of egg laying using three complimentary approaches: (1) an “unconstrained,” exploratory analysis; (2) a traditional sliding window approach; and (3) specific, biologically informed temperature windows. Our results contrast with the widely held view that short-term, prebreeding temperatures best predict variation in laying because they allow birds to adjust timing of breeding to local conditions around the time of egg laying. This means that mechanisms that allow integration of long-term temperature information must exist in birds—perhaps most parsimoniously involving indirect effects of temperature on growth of the bird’s ectothermic insect prey—even though these are currently poorly characterized.