Post-natal corticosterone exposure affects ornaments in adult male house sparrows (Passer domesticus).

In vertebrates, the ontogeny of several crucial organismal systems is known to occur early in life. Developmental conditions can ultimately have important consequences on adult fitness by affecting individual phenotype. These developmental effects are thought to be primarily mediated by endocrine systems, and especially by glucocorticoids. In this study, we tested how post-natal exposure to corticosterone (the primary avian glucocorticoid) may subsequently affect the expression of ornaments in adult male house sparrows (Passer domesticus). Specifically, we investigated the long-term consequences of this manipulation on the size and color of several visual signals: badge, wing bar, tarsus and beak. Post-natal corticosterone exposure had a strong negative impact on the size, but not the color, of some male ornaments (badge and wing bar surface area). Because wing bar and badge surface area are used as sexual and/or hierarchical signals in house sparrow, we showed that early life stress can affect some aspect of attractiveness and social status in this species with potentially important fitness consequences (e.g. sexual selection and reproductive performance). Future studies need now to explore the costs and benefits of this developmental plasticity for individuals (i.e. fitness).

Neuropeptide Y and orexin immunoreactivity in the sparrow brain coincide with seasonal changes in energy balance and steroids.

The transition between the breeding and nonbreeding states is often marked by a shift in energy balance. Despite this well-known shift in energy balance, little work has explored seasonal differences in the orexigenic neuropeptides that regulate food intake in wild animals. Here we tested the hypothesis that free-living male song sparrows (Melospiza melodia) show seasonal changes in energetic state, circulating steroids, and both neuropeptide Y (NPY) and orexin (OX) immunoreactivity. Nonbreeding song sparrows had more fat and muscle, as well as a ketone and triglyceride profile suggesting a greater reliance on lipid reserves. Breeding birds had higher plasma androgens; however, nonbreeding birds did maintain androgen precursors in circulation. Nonbreeding birds had more NPY immunoreactivity, specifically in three brain regions: lateral septum, bed nucleus of the stria terminalis, and ventral tegmental area. Furthermore, nonbreeding birds had more OX immunoreactivity in multiple brain regions. Taken together, the data indicate that a natural shift in energy balance is associated with changes in NPY and OX in a region-specific manner.

Characterizing morphological (co)variation using structural equation models: Body size, allometric relationships and evolvability in a house sparrow metapopulation.

Body size plays a key role in the ecology and evolution of all organisms. Therefore, quantifying the sources of morphological (co)variation, dependent and independent of body size, is of key importance when trying to understand and predict responses to selection. We combine structural equation modeling with quantitative genetics analyses to study morphological (co)variation in a meta-population of house sparrows (Passer domesticus). As expected, we found evidence of a latent variable "body size," causing genetic and environmental covariation between morphological traits. Estimates of conditional evolvability show that allometric relationships constrain the independent evolution of house sparrow morphology. We also found spatial differences in general body size and its allometric relationships. On islands where birds are more dispersive and mobile, individuals were smaller and had proportionally longer wings for their body size. Although on islands where sparrows are more sedentary and nest in dense colonies, individuals were larger and had proportionally longer tarsi for their body size. We corroborated these results using simulations and show that our analyses produce unbiased allometric slope estimates. This study highlights that in the short term allometric relationships may constrain phenotypic evolution, but that in the long term selection pressures can also shape allometric relationships.

Actuarial senescence in a dimorphic bird: different rates of ageing in morphs with discrete reproductive strategies.

It is often hypothesized that intra-sexual competition accelerates actuarial senescence, or the increase in mortality rates with age. However, an alternative hypothesis is that parental investment is more important to determining senescence rates. We used a unique model system, the white-throated sparrow (Zonotrichia albicollis), to study variation in actuarial senescence. In this species, genetically determined morphs display discrete mating strategies and disassortative pairing, providing an excellent opportunity to test the predictions of the above hypotheses. Compared to tan-striped males, white-striped males are more polygynous and aggressive, and less parental. Tan-striped females receive less parental support, and invest more into parental care than white-striped females, which are also more aggressive. Thus, higher senescence rates in males and white-striped birds would support the intra-sexual competition hypothesis, whereas higher senescence rates in females and tan-striped birds would support the parental investment hypothesis. White-striped males showed the lowest rate of actuarial senescence. Tan-striped females had the highest senescence rate, and tan-striped males and white-striped females showed intermediate, relatively equal rates. Thus, results were inconsistent with sexual selection and competitive strategies increasing senescence rates, and instead indicate that senescence may be accelerated by female-biased parental care, and lessened by sharing of parental duties.

Meta-analysis challenges a textbook example of status signalling and demonstrates publication bias.

The status signalling hypothesis aims to explain within-species variation in ornamentation by suggesting that some ornaments signal dominance status. Here, we use multilevel meta-analytic models to challenge the textbook example of this hypothesis, the black bib of male house sparrows (Passer domesticus). We conducted a systematic review, and obtained primary data from published and unpublished studies to test whether dominance rank is positively associated with bib size across studies. Contrary to previous studies, the overall effect size (i.e. meta-analytic mean) was small and uncertain. Furthermore, we found several biases in the literature that further question the support available for the status signalling hypothesis. We discuss several explanations including pleiotropic, population- and context-dependent effects. Our findings call for reconsidering this established textbook example in evolutionary and behavioural ecology, and should stimulate renewed interest in understanding within-species variation in ornamental traits.

Inferences of genetic architecture of bill morphology in house sparrow using a high-density SNP array point to a polygenic basis.

Understanding the genetic architecture of quantitative traits can provide insights into the mechanisms driving phenotypic evolution. Bill morphology is an ecologically important and phenotypically variable trait, which is highly heritable and closely linked to individual fitness. Thus, bill morphology traits are suitable candidates for gene mapping analyses. Previous studies have revealed several genes that may influence bill morphology, but the similarity of gene and allele effects between species and populations is unknown. Here, we develop a custom 200K SNP array and use it to examine the genetic basis of bill morphology in 1857 house sparrow individuals from a large-scale, island metapopulation off the coast of Northern Norway. We found high genomic heritabilities for bill depth and length, which were comparable with previous pedigree estimates. Candidate gene and genomewide association analyses yielded six significant loci, four of which have previously been associated with craniofacial development. Three of these loci are involved in bone morphogenic protein (BMP) signalling, suggesting a role for BMP genes in regulating bill morphology. However, these loci individually explain a small amount of variance. In combination with results from genome partitioning analyses, this indicates that bill morphology is a polygenic trait. Any studies of eco-evolutionary processes in bill morphology are therefore dependent on methods that can accommodate polygenic inheritance of the phenotype and molecular-scale evolution of genetic architecture.

Genomic Contingencies and the Potential for Local Adaptation in a Hybrid Species.

Hybridization is increasingly recognized as a potent evolutionary force. Although additive genetic variation and novel combinations of parental genes theoretically increase the potential for hybrid species to adapt, few empirical studies have investigated the adaptive potential within a hybrid species. Here, we address whether genomic contingencies, adaptation to climate, or diet best explain divergence in beak morphology using genomically diverged island populations of the homoploid hybrid Italian sparrow Passer italiae from Crete, Corsica, and Sicily. Populations vary significantly in beak morphology both between and within islands of origin. Temperature seasonality best explains population divergence in beak size. Interestingly, beak shape along all significant dimensions of variation was best explained by annual precipitation, genomic composition, and their interaction, suggesting a role for contingencies. Moreover, beak shape similarity to a parent species correlates with proportion of the genome inherited from that species, consistent with the presence of contingencies. In conclusion, adaptation to local conditions and genomic contingencies arising from putatively independent hybridization events jointly explain beak morphology in the Italian sparrow. Hence, hybridization may induce contingencies and restrict evolution in certain directions dependent on the genetic background.

Temperature modulates photoperiodic seasonal responses in the subtropical tree sparrow, Passer montanus.

We studied the effects of temperature on the photoperiodic regulation of seasonal reproduction and related events in the subtropical tree sparrow at Shillong, India. In the first experiment, one group of birds was maintained in an outdoor open aviary receiving natural photoperiod and temperature conditions, while the other group was exposed to natural photoperiod and constant temperature of 17 ± 2 °C in an outdoor closed aviary for 12 months. Although both sexes achieved peak gonadal growth at the same time (May) under the two conditions, gonadal regression and feathers molt were delayed under the temperature controlled condition. In the second experiment, the groups of birds were exposed to three different temperatures (17, 25 and 30 °C) under both long (LD-14L:10D) and short (SD-9L:15D) day lengths for 7 months. Birds showed relatively small but significant gonadal growth, darkening of bill color and feathers molt only at 30 °C under SD. However, they behaved as though they were under natural conditions and exhibited the above responses significantly at all temperatures under LD. There was delayed gonadal regression at the lower temperature (17 °C), while feathers molt delayed with increasing temperature (25, 30 °C) under LD. These results clearly indicate that temperature modulates photoperiodic seasonal responses in the tree sparrow.

Phenotypic divergence despite low genetic differentiation in house sparrow populations.

Studying patterns of phenotypic variation among populations can shed light on the drivers of evolutionary processes. The house sparrow (Passer domesticus) is one of the world's most ubiquitous bird species, as well as a successful invader. We investigated phenotypic variation in house sparrow populations across a climatic gradient and in relation to a possible scenario of an invasion. We measured variation in morphological, coloration, and behavioral traits (exploratory behavior and neophobia) and compared it to the neutral genetic variation. We found that sparrows were larger and darker in northern latitudes, in accordance with Bergmann's and Gloger's biogeographic rules. Morphology and behavior mostly differed between the southernmost populations and the other regions, supporting the possibility of an invasion. Genetic differentiation was low and diversity levels were similar across populations, indicating high gene flow. Nevertheless, the southernmost and northern populations differed genetically to some extent. Furthermore, genetic differentiation (F ST) was lower in comparison to phenotypic variation (P ST), indicating that the phenotypic variation is shaped by directional selection or by phenotypic plasticity. This study expands our knowledge on evolutionary mechanisms and biological invasions.

Surface ultrastructural (SEM) characteristics of oropharyngeal cavity of house sparrow (Passer domesticus).

The focus of the present study is to provide a full morphological description of the oropharyngeal cavity of the house sparrow. The head of six birds was prepared for gross examination and by stereo and electron microscopy. The bifid lingual apex has multiple long, rostrally directed needle-like processes. The lateral border of the apex carries rostromedially directed needle-like processes. The dorsal lingual surface of the apex and body carries numerous caudomedially directed filiform papillae and many orifices of lingual salivary glands. The lingual body is divided into two parts: rostral and caudal. The caudal part is divided into two laterally elevated regions by a median groove, while the rostral part is bounded laterally by a rostrodorsally directed papillary row, which on SEM is formed from two rows. On SEM, the lingual root has many orifices of posterior salivary glands. The pharyngeal papillary row is located at the caudal border of the laryngeal mound, but this single papillary row is formed from two rows at SEM magnification. The laryngeal cleft continues caudally as a laryngeal fissure bounded by two longitudinal rows of caudally directed papillae; at high SEM magnification, this fissure is divided into two halves by a median ridge which carries caudally directed papillae on its posterior part. The choanal cleft proceeds rostrally by the median tubercle. There are a small number of orifices of palatine salivary glands. The morphological characters of the oropharyngeal cavity of the sparrow confirm its adaptation to surrounding environmental conditions and available food particles.

A 3D-printed modular device for imaging the brain of small birds.

BACKGROUND: One potential barrier to using in vivo imaging in any new animal species is solving the basic problem of how to hold animals safely and securely during scans. NEW METHOD: In this paper, we describe the design, fabrication, use, and positional reproducibility of a 3D-printed plastic device (the Avian Imaging Device, or AID) for imaging the brain of 1 or 2 small songbirds. We designed two different types of head cones to use with this device: one that was not contoured and designed for anesthesia induction, and one contoured to the shape of a house sparrow head, designed to be used with a pre-anesthetized animal. RESULTS: Compared to no holder, using the AID with both contoured and non-contoured head cones significantly reduced the amount of translation necessary to align the head in pairs of CT scans (by 78% and 90%, respectively); using the contoured head cone also significantly reduced the amount of rotation necessary for head alignment in registering pairs of scans (by 90%). COMPARISON WITH EXISTING METHOD(S): Using an animal holder that can not only securely hold animals but which has high positional reproducibility is essential to take advantage of the maximum resolution possible with small animal imaging. 3D-printed materials are also compatible with PET and CT, environmentally stable, and fast and inexpensive to make. CONCLUSIONS: Researchers can learn from the design of the AID and use our CAD models as a starting point for fabricating devices for multiple small-animal imaging needs.

A species dependent response to the pro-epileptic drug pentylentetrazole in birds.

Epilepsy is common disorder that affects over 50 million people worldwide. Birds remain a promising yet largely under-explored model of epilepsy. This study reports the comparison of the response of two species of birds, Australian Parrots (APs) and Sparrows (SPs), to a pro-epileptic drug, Pentylenetetrazole (PTZ). PTZ injections caused myoclonic jerks (MCJs) and tonic clonic seizures (TCSs) in both species. The frequency of MCJs in APs was greater at the dose of 75mg/kg compared to both 50mg/kg and 25mg/kg while it was not significantly different in SPs. The comparison of APs and SPs showed that the frequency of MCJs was greater in APs compared to SPs at 25mg/kg and 75mg/kg while its latency was reduced at 25mg/kg and 50mg/kg. Interestingly SPs had a reduced latency of TCSs compared to APs at 75mg/kg. Glutamatergic and Gabaergic cell count was conducted to determine an association with the epileptic response to PTZ. The Glutamatergic cell counts for SPs was significantly greater than APs and conversely the Gabaergic cell counts in APs was higher compared to SPs. The reason for this difference in findings needs to be further investigated. This study shows that birds, and APs and SPs in particular, are a valid, interesting and under-explored model of epilepsy that should be further explored in order to understand the mysteries of epilepsy.

Major histocompatibility complex genes partly explain early survival in house sparrows.

Environmental factors and genetic incompatibilities between parents have been suggested as important determinants for embryonic mortality and survival. The genetic set-up of the immune system, specifically the highly polymorphic major histocompatibility complex (MHC) may also influence individual resistance to infections. MHC proteins are important for an appropriate adaptive immune response and enable T-cells to separate 'self' from 'non-self'. Here we investigate the importance of MHC functional diversity for early development in birds, more specifically, if offspring survival and body mass or size depends on number of different functional MHC alleles, specific functional MHC alleles or similarity of MHC alleles in the parents. Unhatched eggs are common in clutches of many bird species. In house sparrows (Passer domesticus), embryo and nestling mortality can exceed 50%. To control for environmental factors, our study was carried out on an aviary population. We found that one specific functional MHC allele was associated with reduced nestling survival, which was additionally supported by lower body mass and a smaller tarsus when nestlings have been 6 days old. Another allele was positively associated with tarsus length at a later nestling stage (nestlings 12 days old). These results indicate that MHC alleles might influence pathogen resistance or susceptibility.

Captivity influences immune responses, stress endocrinology, and organ size in house sparrows (Passer domesticus).

Studies using wild animals in laboratory-based research require bringing wild-captured organisms into a novel setting, which can have long-lasting impacts on physiology and behavior. In several species, captivity stimulates stress hormone production and can alter immune function. Despite this, there is little consensus on how captivity influences stress hormone regulation, or if captivity-induced changes in stress hormone production and regulation mediate changes in immune function. In this study, we investigate the influence of captivity on the physiology of a wild bird commonly-used in laboratory-based research, the house sparrow (Passer domesticus). We tested how captivity influences stress endocrinology, immune responses, and organ mass, and also investigated if the production or regulation of corticosterone, the main stress hormone in birds, correlated with changes in immunity. We found that baseline corticosterone concentrations and maximum capacity of the adrenals to secrete corticosterone increase following captivity and remain elevated after 9weeks of captivity. A measure of innate immune function, the bactericidal ability of plasma, also increased with time spent in captivity. Wound healing was also influenced by time spent in captivity, with birds taking almost 2days longer to heal if they were wounded after 3weeks in captivity when compared with birds that were wounded immediately upon capture. Additionally, captivity caused notable reductions in spleen and liver mass. Together, these results imply that captivity can have long-lasting effects on house sparrow corticosterone release and immune function, and suggest that even after 9weeks house sparrows do not acclimate physiologically to life in captivity.

Corticosterone regulation in house sparrows invading Senegal.

What traits help organisms expand their ranges? Several behavioral and life history traits have been identified, but physiological and especially endocrinological factors have been minimally considered. Here, we asked whether steroid hormonal responses to stressors might be important. Previously, we found that corticosterone (CORT) responses to a standard restraint stressor were stronger at a range edge than at the core of the recent house sparrow (Passer domesticus) invasion of Kenya. In related work in the same system, we found that various behaviors (exploratory activity, responses to novelty, etc.) that are affected by CORT in other systems varied among sparrow populations in a manner that would suggest that CORT regulation directly influenced colonization success; birds at the range edge were less averse to novelty and more exploratory than birds from the core. Here, we asked whether the pattern in CORT regulation we observed in Kenya was also detectable in the more recent (∼1970) and independent invasion of Senegal. We found, as in Kenya, that Senegalese range-edge birds mounted stronger CORT responses to restraint than core birds. We also found lower baseline CORT in range-edge than core Senegalese birds, but little evidence for effects of individual sex, body mass or body size on CORT. Follow-up work will be necessary to resolve whether CORT regulation in Senegal (and Kenya) actively facilitated colonization success, but our work implicates glucocorticoids as a mediator of range expansion success, making stress responses potentially useful biomarkers of invasion risk.

Morphological changes in hippocampal cytoarchitecture as a function of spatial treatment in birds.

Maintaining cognitive processes comes with neurological costs. Thus, enhanced cognition and its underlying neural mechanisms should change in response to environmental pressures. Indeed, recent evidence suggests that variation in spatially based cognitive abilities is reflected in the morphology of the hippocampus (Hp), the region of the brain involved in spatial memory. Moreover, recent work on this region establishes a dynamic link between brain plasticity and cognitive experiences both across populations and within individuals. However, the mechanisms involved in neurological changes as a result of differential space use and the reversibility of such effects are unknown. Using a house sparrow (Passer domesticus) model, we experimentally manipulated the space available to birds, testing the hypothesis that reductions in dendritic branching is associated with reduced Hp volume and that such reductions in volume are reversible. We found that reduced spatial availability associated with captivity had a profound and significant reduction in sparrow hippocampal volumes, which was highly correlated with the total length of dendrites in the region. This result suggests that changes to the dendritic structure of neurons may, in part, explain volumetric reductions in region size associated with captivity. In addition, small changes in available space even within captivity produced significant changes in the spine structure on Hp dendrites. These reductions were reversible following increased spatial opportunities. Overall, these results are consistent with the hypothesis that reductions to the Hp in captivity, often assumed to reflect a deleterious process, may be adaptive and a consequence of the trade-off between cognitive and energetic demands. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 93-101, 2017.

Taxonomic revision of Saffron-billed Sparrow Arremon flavirostris Swainson, 1838 (Aves: Passerellidae) with comments on its holotype and type locality.

The Saffron-billed Sparrow (Arremon flavirostris) complex occurs in the undergrowth of deciduous woodlands and forests from the Andes of Bolivia and northern Argentina to Paraguay and southern, mid-western and interior eastern Brazil. Currently four subspecies are recognized: A. f. flavirostris, A. f. polionotus, A. f. devillii and A. f. dorbignii. We review the taxonomy of this complex by analyzing coloration and morphometrics of a series of 234 skins, and by comparing 101 sound recordings. Our results suggest that under both the Phylogenetic and Biological Species Concept, three species should be recognized in this complex: A. flavirostris, A. polionotus and A. dorbignii. On the other hand, A. devillii should be considered a junior synonym of A. polionotus since these two have no constant differences in morphology and vocalization. These species are diagnosable by their coloration characters, but not by morphometrics. Vocalizations are useful in diagnosing A. flavirostris from A. dorbignii, but do not diagnose A. polionotus from the others. We show that part of the previous taxonomic confusion can be attributed to variation in back color of adult and immature A. polionotus. Finally, we comment on the recently located holotype of A. flavirostris, which was believed to be lost, and its type locality.

Flying high: limits to flight performance by sparrows on the Qinghai-Tibet Plateau.

Limits to flight performance at high altitude potentially reflect variable constraints deriving from the simultaneous challenges of hypobaric, hypodense and cold air. Differences in flight-related morphology and maximum lifting capacity have been well characterized for different hummingbird species across elevational gradients, but relevant within-species variation has not yet been identified in any bird species. Here we evaluate load-lifting capacity for Eurasian tree sparrow (Passer montanus) populations at three different elevations in China, and correlate maximum lifted loads with relevant anatomical features including wing shape, wing size, and heart and lung masses. Sparrows were heavier and possessed more rounded and longer wings at higher elevations; relative heart and lung masses were also greater with altitude, although relative flight muscle mass remained constant. By contrast, maximum lifting capacity relative to body weight declined over the same elevational range, while the effective wing loading in flight (i.e. the ratio of body weight and maximum lifted weight to total wing area) remained constant, suggesting aerodynamic constraints on performance in parallel with enhanced heart and lung masses to offset hypoxic challenge. Mechanical limits to take-off performance may thus be exacerbated at higher elevations, which may in turn result in behavioral differences in escape responses among populations.

Energetic costs and implications of the intake of plant secondary metabolites on digestive and renal morphology in two austral passerines.

Seed-eating birds have a diet of high nutritional value; however, they must cope with plant secondary metabolites (PSM). We postulated that the detoxification capacity of birds is associated with a metabolic cost, given that the organs responsible for detoxification significantly contribute to energetic metabolism. We used an experimental approach to assess the effects of phenol-enriched diets on two passerines with different feeding habits: the omnivorous rufous-collared sparrow (Zonotrichia capensis) and the granivorous common diuca-finch (Diuca diuca). The birds were fed with one of three diets: control diet, supplemented with tannic acid, or supplemented with Opuntia ficus-indica phenolic extract (a common food of the sparrow but not the finch). After 5 weeks of exposure to the diets, we measured basal metabolic rates (BMR), energy intake, glucuronic acid output and digestive and kidney structure. In both species, detoxification capacity expressed as glucuronic acid output was higher in individuals consuming phenol-enriched diets compared to the control diet. However, whereas sparrows increase energy intake and intestinal mass when feeding on phenol-enriched diets, finches had lower intestinal mass and energy intake remains stable. Furthermore, sparrows had higher BMR on phenol-enriched diets compared to the control group, whereas in the finches BMR remains unchanged. Interspecific differences in response to phenols intake may be determined by the dietary habits of these species. While both species can feed on moderate phenolic diets for 5 weeks, energy costs may differ due to different responses in food intake and organ structure to counteract the effects of PSM intake.

Steroids in house sparrows (Passer domesticus): Effects of POPs and male quality signalling.

At high trophic levels, environmental contaminants have been found to affect endocrinological processes. Less attention has been paid to species at lower trophic levels. The house sparrow (Passer domesticus) may be a useful model for investigating effects of POPs in mid-range trophic level species. In male house sparrows, ornamental traits involved in male quality signalling are important for female selection. These traits are governed by endocrinological systems, and POPs may therefore interfere with male quality signalling. The aim of the present study was to use the house sparrow as a mid-range trophic level model species to study the effects of environmental contaminants on endocrinology and male quality signalling. We analysed the levels of selected PCBs, PBDEs and OCPs and investigated the possible effects of these contaminants on circulating levels of steroid hormones (4 progestagens, 4 androgens and 3 estrogens) in male and female adult house sparrows from a population on the island Leka, Norway. Plasma samples were analysed for steroid hormones by GC-MS and liver samples were analysed for environmental contaminants by GC-ECD and GC-MS. In males, we also quantified ornament traits. It was hypothesised that POPs may have endocrine disrupting effects on the local house sparrow population and can thus interfere with the steroid hormone homeostasis. Among female house sparrows, bivariate correlations revealed negative relationships between POPs and estrogens. Among male sparrows, positive relationships between dihydrotestosterone levels and PCBs were observed. In males, positive relationships were also found between steroids and beak length, and between steroids and ornamental traits such as total badge size. This was confirmed by a significant OPLS model between beak length and steroids. Although sparrows are in the mid-range trophic levels, the present study indicates that POPs may affect steroid homeostasis in house sparrows, in particular for females. For males, circulating steroid levels appears to be more associated with biometric parameters related to ornamental traits.