Avian Biology Research

This study aimed to discover whether the Hill Mynah Gracula religiosa forms pairs for a single breeding season or engages in long-term pair bonding, and to investigate the role of female aggression in maintaining pair bonds. Experiments were conducted on captive birds in Thailand between 2006 and 2013, and pair behaviours such as allopreening and aggression were observed four times every day. In the first experiment, when each breeding pair was preparing to rear a new clutch, pairs were placed in a new aviary with unfamiliar males and females with which they could potentially form relationships. Results indicated that breeding pairs stayed with the same mates over four continuous breeding seasons (2006–2009) without changing partners or taking additional mates. In a second experiment, the role of female aggression in maintaining long-term pair bonding was examined. Each breeding pair, when preparing to rear a new clutch, was placed in a new aviary with three unfamiliar females. The results showed that female breeders displayed vigorous aggression towards the other three females, forcing them to retreat from the pair; this behaviour was sustained over four continuous breeding seasons (2010–2013). Thus, it is suggested that the Hill Mynah engages in long-term pair bonding and that the aggression of the breeding female is an essential component in the maintenance of pair-bonds.

Little is known about the selective pressures driving monogamy in the Hill Mynah (Gracula religiosa). Thus, this study investigated the male's role during reproduction to understand the evolutionary advantages of the monogamous mating system. Experiments were performed on captive birds in Thailand from 2012–2015. In the first experiment, I recorded allopreening and nest-entry frequency/duration from both parents during three periods: nesting, incubation, and feeding of offspring. Females preened their mates significantly more than males did. Moreover, female allopreening was significantly correlated to male parental care (as indicated by nest-entry data), especially when nestlings were 1–20 days old. In the second experiment, males were removed from various nests either when incubation began or when nestlings were 1, 11, or 21 days old. Solitary females were significantly less successful at incubating and raising young, which also weighed less than broods from biparental nests. Therefore, male parental care is likely required for nestling survivability and reinforces monogamy in the Hill Mynah.

In vitro production of germline chimeras and avian cloning may utilise the transfer of avian embryos from their original eggshell to a surrogate eggshell for culture during incubation. Such embryo transfer is valuable for avian cloning as the only alternative would be to transfer the cloned avian embryos into the infundibulum of recipient birds. Given the advances in paleogenomics, synthetic biology, and gene editing, a similar approach might be used to generate extinct species, i.e. de-extinction. One objective of the present research was to examine if ratite eggs could be manipulated via windowing and sham injection, similar to that which could allow for avian genome manipulation and subsequent development. The efficiency of interspecific avian embryo transfer using Chicken (Gallus gallus domesticus) donor eggs and Turkey (Meleagris gallopavo) recipient eggshells was also investigated. Egg windowing and embryo transfer techniques utilised in the present research were adapted from those found in the scientific literature. Presumed fertile eggs from Rhode Island Red (n = 40), Silkie (n = 2), and White Leghorn Chickens (n = 18), Turkey (n = 48), Emu (Dromaius novaehollandiae) (n = 79), and Ostrich (Struthio camelus) (n = 89) were used in this research. Of the 41 Chicken eggs used for transfers into recipient Turkey eggshells, only one (2.4%) produced a chick. Of 31 windowed Emu eggs, one embryo survived for 25 d but no chicks were produced. Of 36 windowed Ostrich eggs, one embryo survived and hatched. The efficiency of the windowing and embryo transfers to produce chicks was low and further refinements are needed. Importantly, the results herein establish that manipulating ratite embryos is possible.

Brain and muscle Arnt-like protein-1 (BMAL1) plays an important role in circadian rhythm, which is involved in daily behaviours and physiological activities. However, little is known about the molecular function of BMAL1 in the Pigeon (Columba livia). In our study, the full-length cDNA of Bmal1 was cloned and sequenced from the Pigeon for the first time, and submitted to the GenBank to obtain the accession number (KF906247). The full-length cDNA of Bmal1 consists of 2,488 nucleotides, and encodes 634 amino acids. Phylogenetic analysis showed that it bore the greatest similarity to Bmal1 from the Chicken (Gallus gallus) and Barn Owl (Tyto alba). The amino acid sequence of the Pigeon BMAL1 contained a HLH domain and two PAS domains, which are involved in forming hetero-homodimers with the CLOCK as the positive element of the circadian rhythm. The results of real-time quantitative PCR of Bmal1 under different light regimes showed that the amplitude and expression pattern of Bmal1 were strongly affected by day length. Bmal1 was most highly expressed in the pancreas. Relative to Bmal1 expression level under 12 h of light exposure, it was increased significantly in the pituitary gland, ovary and uterus under 15 h of light exposure (P < 0.05). However, other tissues, including the hypothalamus, heart, liver, spleen, kidney, intestines, crureus, and pectorals exhibited no significant difference (P < 0.05) under the two light regimes. This is the first study to investigate Bmal1 mRNA levels in various tissues under different light cycles, and thereby provide data for further study of the molecular and regulatory mechanisms of Bmal1 and circadian clock genes of the Pigeon.

Many factors, including nestling age, brood size, and mate quality, can influence the provisioning behaviour of adult birds. Mate quality may affect provisioning behaviour because high-quality individuals may be ‘good parents’ and provision at higher rates. Alternatively, individuals paired to high-quality mates may provision at higher rates because the benefits provided by such mates (e.g. good genes) increase the likelihood of reproductive success. We examined variation in the plumage colour of male and female Eastern Phoebes (Sayornis phoebe) and the possible relationship between such variation and provisioning behaviour. During the 2006–2007 breeding seasons, we captured, banded, and measured adult Eastern Phoebes and collected belly feathers for spectral analyses. We also videotaped nests to quantify provisioning behaviour. Male Eastern Phoebes were larger than females, but the plumage (belly feathers) of males and females did not differ in brightness, hue, and carotenoid chroma (all P ≥ 0.37). Females provisioned nestlings at higher rates than males (P = 0.009), but we found no significant relationship between provisioning rates of males and females and plumage colour. However, relationships between female provisioning rates and the brightness and carotenoid chroma of their mates’ belly feathers approached significance (P ≤ 0.08). The larger size of male Eastern Phoebes suggests there is male–male competition for access to resources (e.g. nest sites and mates), with larger size conferring a selective advantage. However, the absence of intersexual differences in plumage colour suggests limited sexual selection driven by female choice for extra-pair partners. Differences in provisioning rates of males and females may be due to male uncertainty of paternity status or to intersexual differences in foraging behaviour. The relationship between female provisioning rates and male plumage quality suggests that females may invest more in reproduction if male Eastern Phoebes with brighter, carotenoid-rich belly plumage are better able to provide quality nest sites and territories or, perhaps, high-quality genes that can potentially enhance female fitness (differential-allocation hypothesis).

Despite its prevalence across bird taxa, avian vocal mimicry remains a poorly studied field of animal behaviour. In order to advance our understanding of the function of avian vocal mimicry, the field requires that the range of vocal mimicry in birds is described. The Tawny Lark (or Sykes's Lark, Galerida deva) is endemic to central and western India. Recent work on other Galerida larks has found that the mimetic vocalisations match the biodiversity of their acoustic environment, thereby conferring a significant novel function in study of individual mimetic variation linked to biodiversity. Here, we provide a detailed account of the variety of mimetic sounds produced by the Tawny Lark. We also describe acoustic and peer-based analyses that gauge the accuracy of the mimicry. By providing a detailed description of mimicry, we provide a basis for future study of the function of mimicry in this species.

Nest-site selection and breeding success of the Grey Hypocolius (Hypocolius ampelinus) were surveyed in relation to plant structure in 2010 and 2011 in southwestern Iran. Microhabitat parameters such as Ziziphus nummularia as the main shrubs used for nesting, were measured in 20 × 20 m plots around the nest and compared with random plots. There were no best clear model for predicting the nest-site selection, however, plant variables especially the canopy cover and diameter of the Z. nummularia, were the most important determinant for nest-site selection (w_i = 0.5). Grey Hypocolius preferred areas with a higher density of Z. nummularia than other available habitats (28.21 vs 1.2 of cover). There was no strong predictor for breeding success, the best models incorporated either Z. nummularia density or diameter (with model weights of 0.25 and 0.17, respectively). Nests of Grey Hypocolius had a higher chance of success at higher densities of Z. nummularia in nesting plots. We found that a higher density of Z. nummularia improved both the probability of nest-site selection and the breeding success of Grey Hypocolius. Shrubs with greater diameters were more likely to be selected for nesting, but had lower breeding success. To identify the key reasons of nests being successful, more habitat parameters should be monitored. The majority of failure in breeding occurred during the incubation stage (52%).

This study focussed on the microstructure of the digestive canal of the Great Bustard (Otis tarda). Under scanning electron microscopy (SEM), different morphological plicae (rounded protrusions about 10 μm in height) were observed at different locations along the inner surface of the oesophagus. Concentrated microvilli can be seen on the surface of the protrusions in high-power fields. There are papillae in the mucosal fold on the inner surface of the glandular stomach, with openings of about 250 μm in diameter. In high-power fields, the tops of rod cells could be seen in somewhat circular forms with microvilli on them. Inside the muscular stomach, the scraggly- or wavy-formed surface of the cuticle layer could be seen. Stripping off the cuticle layer, at the tops of mucosal folds row- or rope-like forms could be seen. The mucosa of the small intestine is thrown into ridges running longitudinally in a zigzag pattern along the intestine, rather than the finger-like intestinal villi observed in mammals. There are villi on the inner surface of the caecum with impressions on their domes (the troughs between which have diameters of about 200 μm). Villi on the inner surface of the rectum are even thicker, ranging from 200–500 μm in diameter, and could be seen on the inner surface of the caecum and rectum. Outlines of cell domes are clearer on the inner surface of the caecum than those on the rectum. Studies on the fine structures of the inner surface of the Great Bustard digestive canal will enrich the knowledge of the comparative histology of birds, and provide a reference for raising bustards, as well as preventing and curing its diseases.