Avian Biology Research

Previous research suggests that environmental and social factors can drive female birds to bias offspring sex ratios. The underlying mechanisms controlling these adjustments remain unclear. Results from experimental and correlative research suggest that maternal corticosterone plays an important role in this process. Since females are the heterogametic sex in birds, corticosterone may potentially bias offspring sex ratios during meiotic segregation, through non-random segregation of sex chromosomes. In a previous study, we showed that pharmacological elevations of corticosterone near the time of meiotic segregation exerted an effect on offspring sex ratio, causing female Zebra Finches (Taeniopygia guttata) to produce significantly more males. Here, we aimed to determine whether endogenous elevations in the physiological range have similar effects on offspring sex. First we examined offspring sex ratio in relation to baseline corticosterone levels to determine if natural variation in circulating corticosterone near the time of meiotic segregation is related to offspring sex ratio. Next, we used a 5-minute bag handling protocol to induce corticosterone elevations 5 hours prior to ovulation. Maternal baseline corticosterone levels did not correlate with average clutch sex ratios. In addition, the sex ratios produced by females exposed to handling stress did not differ from sex ratios produced by unmanipulated females. Together these results suggest that physiological levels of endogenous corticosterone, both baseline and acutely elevated near the time of sex determination may not be involved in the adjustment of primary sex ratios in Zebra Finches.

Tinamous (Tinamidae) represent one of the most ancient living avian lineages but their life history traits are relatively unstudied. Here we identified microsatellite loci for two sympatric tinamou species, the Ornate Tinamou (Nothoprocta ornata) and the Darwin's Nothura (Nothura darwinii) from low coverage Illumina sequencing of genomic DNA. The experiment yielded a large number of candidate loci. We designed primers and tested them for successful amplification in 1 to 2 populations of the target species, tested for deviation from the Hardy–Weinberg equilibrium and the presence of null alleles, the levels of polymorphism and potential cross-amplification. All 30 and 24 loci amplified consistently, in the Ornate Tinamou and in Darwin's Nothura, respectively. In the Ornate Tinamou, 25 loci were polymorphic and in the Darwin's Nothura 12, with 2 to 14 alleles per locus in both species. The expected heterozygosity ranged from 0.054 to 0.917 in the Ornate Tinamou and from 0.044 to 0.908 in the Darwin's Nothura. 23 (40%) of 54 loci were successfully cross-amplified. These newly discovered, polymorphic microsatellite loci represent a valuable tool for future studies on social behaviour, parentage and genetic population structure in tinamous.

The objective of this study was to investigate the effects of the exposure to monochromatic light on growth performance, and on the growth hormone (GH) and insulin-like growth factor 1 (IGF-1) concentrations in growing Pigeons (Columba livia). A total of 144 paired adult White King Pigeons were randomly divided into 12 compartments forming groups of 12 pairs. Then, three compartments were exposed to blue LED (BL), green LED (GL), red LED (RL), and white LED (WL). Allocation of light colours was done within blocks of four compartments. The pigeons were kept under WL for a two week adaptation period before the study began. Body weight (BW) and body weight gain (BWG) were evaluated weekly. Two pigeons from each replicate group were randomly selected for blood collection to determine the hormone concentrations at 1 day, 7 days, 14 days, 21 days, and 28 days of age. The results indicated that there were no between-treatment differences in the final BWs (P = 0.570), but the squabs exposed to RL had greater BWGs between 7 and 14 days of age (P = 0.009, P = 0.049, respectively). The correlation trend lines for the body weight and growth hormone comparisons were inverted U-shaped, which corresponded to the birds’ growth cycle. The results indicated that monochromatic red light had potential effects on growth performance during the early phase of production. Growth performance was closely related to the blood plasma concentrations of GH and IGF-1.

Haematological and blood chemistry variables are widely used in ecophysiological research as physiological indices of body condition in various vertebrate taxa. In this study, we analysed relationships between blood glucose and blood haemoglobin concentrations of adult birds in wild populations of Blue Tits (Cyanistes caeruleus) and Great Tits (Parus major) during the breeding season in central Poland. We found that blood glucose and blood haemoglobin concentrations are negatively correlated. We also show that individual Blue Tits have higher mean haemoglobin levels adjusted for the common value of glucose concentration than individual Great Tits and that females of both species have higher mean haemoglobin concentrations than males. Our results suggest that haematological as well as biochemical variables may be used in tune as complementary indices of body condition in wild bird populations.

Water surfaces are natural barriers for raptors mostly using soaring–gliding flight over land during migration. Among these, the European Honey Buzzard (Pernis apivorus) is a total migrant, breeding in Europe and wintering in central western Africa. Each spring thousands of buzzards undertake long sea crossings between Tunisia and southern Italy, concentrating over small islands en route to central eastern Europe. The aim of this research is to investigate the influence of wind patterns on the flyways used by these raptors during this critical phase of migration through field observations at four small Mediterranean islands (Pantelleria, Marettimo, Ustica and Panarea) and at the Straits of Messina between 20 April and 20 May 2006–2013. In our analyses, peak days were considered for each site. This eight year multisite study allowed the collection of a large data set. While crossing the Channel of Sicily, migrants concentrated over Pantelleria (southern side of the Channel) during moderate NW winds, and over Marettimo (northern side) during weaker southerly winds. Over the island of Ustica (north-western Sicily, Tyrrhenian Sea) raptors were observed mostly with weak southerly winds. Over the island of Panarea (northeastern Sicily) and at the Straits of Messina, European Honey Buzzards passed with weak winds from W and NW, respectively. The average flock size during the peak days was significantly higher over the island of Pantelleria, where birds migrated during the stronger winds. The results of this study show that wind patterns affect both migration pathways and flocking behaviour of this species while crossing large water surfaces.

Understanding the consequences of changing environmental conditions on the demographic parameters of migratory species is key for addressing the widely reported declines for many of these species. We explore the variation in reproductive investment and output of Purple Herons (Ardea purpurea) in two breeding seasons, with very different precipitation levels but similar temperatures. Despite similar investment in egg volume, reproductive output in the drier year was less than half of the wetter year (∼1.9 vs ∼4.1 chicks per pair) due to weather mediated higher predation. The current predictions of erratic precipitation and warming may threaten the breeding output of waterbirds, if water levels are unsuitable during the breeding season.

Some bird species cannot persist during early secondary succession after natural or anthropogenic disturbance of Australian Mountain Ash (Eucalyptus regnans) forest, whilst others remain abundant throughout regeneration. To conserve bird species diversity optimally in such forests, we need to know, inter alia, exactly why the latter species can persist after disturbance. Using a chronosequence approach, we documented four facets of foraging in a suite of these persistent species effectively covering 100 years of succession in E. regnans forest disturbed by wildfire or timber harvesting, namely the foraging strata, locations, substrates and behaviours used. Most species showed plasticity in their use of foraging strata and locations during succession, but four exhibited some limited stereotypy in these facets. In contrast, use of foraging substrates and behaviours was largely invariant within species during secondary succession. We suggest that switching foraging strata and locations was probably critical to persistence of most of these bird species during secondary succession, given the marked variation in structural and floristic variables that characterises this regeneration process. Some plasticity in foraging behaviour repertoire and substrate use was probably possible, but not beneficial. Although some resident bird species’ populations were severely reduced by disturbance in these forests, a substantial subset of species was sufficiently flexible in choosing foraging microhabitats to persist throughout secondary succession at pre-disturbance abundances.

The Northern Goshawk (Accipiter gentilis) is a large forest raptor with a Holarctic distribution and, in some portions of its range, a species of conservation concern. To augment previously reported genetic markers, 13 novel polymorphic microsatellite markers were developed to establish individual identification and familial relationships, to assess levels of genetic diversity, and to identify diagnostic markers. Of the 22 loci tested, 13 were polymorphic, seven were monomorphic, and two failed to amplify. This suite of microsatellite loci yielded a combined probability of parental exclusion of 98%; a single individual sampled from a North American population can be reliably identified using a combination of seven of the 13 polymorphic loci. Cross-species screening in Cooper's Hawks (A. cooperii) and Sharp-shinned Hawks (A. striatus) of the 20 loci that successfully amplified in Northern Goshawks identified 13 loci as polymorphic in each species. Six of these loci (Age1303, Age1308, Age1309, Age1312, and Age1314) appeared to be useful in distinguishing between Accipiter species. These markers will be useful to researchers investigating populations of North American accipiters.

Avian influenza (H9N2) virus infection is an emerging respiratory problem and its prevalence varies significantly among different species of birds. The current knowledge about virus shedding parameters in terrestrial birds is limited. With this in mind, the present study was conducted in different domestic and wild terrestrial birds to investigate species-related differences in infectivity and pattern of viral shedding associated with H9N2 AI virus. Groups of terrestrial birds (domestic Guinea Fowl Numida meleagridis, Japanese Quail Coturnix coturnix japonica, House Sparrows Passer domesticus, House Crows Corvus splendens and Bank Myna Acridotheres ginginianus) were inoculated intra-nasally with A/chicken/Pakistan/10RS3039-284-48/2010 (H9N2) AI virus (10⁶ EID₅₀) and then examined for infectivity and virus shedding patterns. With the exception of House Crows, all infected birds showed clinical signs of different severity, showing the most prominent disease signs in Japanese Quail. All infected birds showed positive results for virus shedding, however, the pattern of virus shedding was different among wild terrestrial birds. Japanese Quail showed the highest levels of virus shedding while samples collected from House Crows revealed only very low levels. Interestingly, virus shedding was observed predominantly via the gastrointestinal tract in House Sparrows and Bank Myna and via the buccal cavity route in Guinea Fowl and Japanese Quail. Here we investigated that the novel genotype of H9N2 AI virus circulating in Pakistan causes clinical disease signs in domestic and wild terrestrial birds. The results of this study suggest that virus shedding varies between different related avian species and highlights the potential role of Guinea Fowl, Japanese Quail, House Sparrows and Bank Myna as mixing bowls for the transmission and maintenance of H9N2 AI viruses between premises.

This study was designed to evaluate a range of avian semen extenders for liquid storage of Indian Red Jungle Fowl (Gallus gallus murghi) spermatozoa at 5 °C. Semen was collected from 8 mature trained cocks and processed in the Beltsville Poultry, Turkey, Lake, EK, Tselutin Poultry and Chicken semen extenders for storage at 5 °C. Semen quality parameters viz, motility (%), plasma membrane integrity (%), livability (%) and acrosomal integrity (%) were assessed at 0, 3, 6, 24 and 48 hours of storage. A time dependent decrease was observed in motility, plasma membrane and acrosomal integrity in all experimental extenders during the storage period. However, the Turkey semen extender was found significantly (P<0.05) superior for protecting all aforementioned semen quality parameters compared to the Beltsville Poultry, Lake, EK, Tselutin Poultry and Chicken semen extenders. It is concluded that the Turkey semen extender can be used efficiently for the liquid storage of Indian Red Jungle Fowl spermatozoa at 5 °C.