Ahmad Barati

Context While habitat fragmentation negatively impacts native biodiversity, this ecological process can be beneficial for edge-specialist species that preferentially occupy remnant patches. In the eastern woodlands of Australia, this process leads to the despotic Noisy Miner (Manorina melanocephala) dominating remnant patches and aggressively excluding other avifauna. Culling has been trialled in attempt to alleviate the impacts of Noisy Miners, however has yielded mixed success in the short-term as recolonising miners from the surrounding areas rapidly occupy newly culled sites. Objectives We tested if ongoing, continuous removal of Noisy Miners from one site could create an artificial ‘sink’ habitat that would allow more efficient management of recolonisation reduction and allow native woodland bird recovery in other areas. Methods Over 18 months, Noisy Miners were removed from two sites on a regular basis and the changes in the miner density and avian diversity were assessed. Results At one site, birds routinely recolonised newly created vacant ‘sink’ areas following a culling round, therfore miner density at this site was not impacted long-term. In contrast, a nearby area was not effectively recolonised and was kept miner-free for more than one year, concurrently experiencing a rebound in avian diversity. Conclusions Together, these results suggest that as well as being more feasible logistically, conducting ongoing longer-term culling at highly favoured sites is likely to be a more effective and logistically simpler management strategy than repeated, separate short-term culling events at a range of habitats, offering an additional model for the management of overabundant, despotic species.

From an evolutionary perspective, the ability to recognize individuals provides great selective advantages, such as avoiding inbreeding depression during breeding. Whilst the capacity to recognize individuals for these types of benefits is well established in social contexts, why this recognition might arise in a potentially deadly alarm-calling context following predator encounters is less obvious. For example, in most avian systems, alarm signals directed toward aerial predators represent higher predation risk and vulnerability than when individuals vocalize toward a terrestrial-based predator. Although selection should favor simple, more effective alarm calls to these dangerous aerial predators, the potential of these signals to nonetheless encode additional information such as caller identity has not received a great deal of attention. We tested for individual discrimination capacity in the aerial alarm vocalizations of the noisy miner (Manorina melanocephala), a highly social honeyeater that has been previously shown to be able to discriminate between the terrestrial alarm signals of individuals. Utilizing habituation–discrimination paradigm testing, we found conclusive evidence of individual discrimination in the aerial alarm calls of noisy miners, which was surprisingly of similar efficiency to their ability to discriminate between less urgent terrestrial alarm signals. Although the mechanism(s) driving this behavior is currently unclear, it most likely occurs as a result of selection favoring individualism among other social calls in the repertoire of this cooperative species. This raises the intriguing possibility that individualistic signatures in vocalizations of social animals might be more widespread than currently appreciated, opening new areas of bioacoustics research.

In many socially monogamous bird species, both sexes regularly engage in mating outside their pair bond. Although the benefits of extra-pair (EP) mating behavior are clear and well established for males, such as an increase in the number of sired offspring, the benefits of EP mating behavior to females are less clear. A dominant theory for the incidence of EP mating is that socially monogamous females can improve the genetic quality of their offspring and avoid the costs of inbreeding through EP mating. In addition, in cooperatively breeding species, the theory of “parental care” predicts that females obtain additional help for their offspring through EP matings. Here, we examined evidence for both the inbreeding avoidance and parental care hypotheses in the cooperatively breeding noisy miner (Manorina melanocephala). Overall, EP mating occurred in 27% of broods, with 14% of offspring sired by males other than the identified pair-bonded male. There was a strong tendency to avoid pairing with genetically related individuals, with 86% of breeding pairs being significantly less related to each other than the general population. The occurrence of EP paternity was independent of the degree of relatedness between the pair. Provisioning patterns in relation to EP mating was not consistent with the “parental care” hypothesis and EP males did not contribute to the care of broods. These results demonstrate that in this system, there is no evidence that EP mating might function as a mechanism to reduce the costs of inbreeding depression or to gain benefits of extra helpers.

Predation is one of the main threats to altricial nestlings, with predators often locating nests via eavesdropping on begging signals. Nestlings may be able to adjust their begging based on the current level of risk by monitoring both intra- and interspecific alarm calls near the nest. We show that noisy miner (Manorina melanocephala) nestlings can differentiate between terrestrial and aerial alarm calls of their own species, as they suppressed begging behaviour for longer in response to terrestrial rather than aerial alarm calls. This differential response is potentially due to greater danger that terrestrial calls encode. In contrast, nestlings ignored alarm calls of the sympatric grey butcherbird (Cracticus torquatus) and continued to beg but reduced begging intensity in response to the non-alarm calls of a sympatric eastern rosella (Platycercus eximius), suggesting nestlings were likely responding based upon similarity to a known signal as opposed to expressing a learnt behaviour. Results show that nestlings respond adaptively to two different intraspecific alarm signals but have not learnt to respond to the alarm calls of sympatric species. These suggest that nestlings are able to take advantage of the complex vocal repertoire that adults produce, although discernment is an issue when filtering out irrelevant stimuli.

The effects of habitat fragmentation as a threat to biodiversity are well known; decreased connectivity can potentially influence population processes and dynamics, resulting in smaller, isolated populations that may not function optimally. However, fragmentation may also increase the amount of edge or ecotone habitat available to open country species, benefiting their populations and enabling them to dominate remnant habitats. Noisy miners (Manorina melanocephala) are one such species, occupying eastern‐Australian eucalypt woodlands. They are considered a ‘despotic’ species, in that their presence negatively impacts woodland avifauna biodiversity due to their aggressive exclusion of other taxa from occupied areas. Despite this well‐known impact, little information exists on the patterns of nest‐tree occupancy by noisy miners within eucalypt woodlands. In the current study, we explored the patterns of nest‐tree occupancy by noisy miners across two successive years, aiming to identify preferences for breeding areas relative to vegetation structure. Our results show that both habitat fragmentation and the characteristics of individual eucalypt trees in an area influenced nest‐tree occupancy. Noisy miners constructed nests in trees near the edge of woodland patches more often than expected. Moreover, the nest tree chosen was a eucalypt that was significantly smaller than randomly selected trees from the surrounding area. The results highlight the importance of habitat management measures that may reduce the suitability of woodland patches as nesting sites for this species, in order to mitigate the severe effects of this despotic edge specialist.

Summary: The current distribution and recent population trends of the Great Bustard (Otis tarda) in Iran were investigated based on a literature review and unpublished data (1995–2008) followed by three years of census (2009–2011) in areas where the species is still breeding. Results suggest that Great Bustards have disappeared from a large part of their former distribution in the country, including East Azarbayjan, Hamedan and Kurdistan provinces. The surviving groups are concentrated in West Azarbayjan where numbers are rapidly declining. The present population is estimated at about 43–48 birds in 2011, confirming a marked decline compared to the 200–300 birds estimated in the early 1990s. About 80–90% of the extant birds are concentrated in the plains of Boukan. Strict conservation measures are urgently needed to prevent the extinction of this species in Iran.

The nesting success and nestling growth were studied in a Gull-billed Tern Gelochelidon nilotica Gmelin, 1789 colony located in western Iran, during the 2008 breeding season. The nesting success was modelled in order to assess the effects of various nest-site parameters and nest initiation date. Nestling growth rate, described as body mass, head-bill and tarsus growth per day during the first 10 days of age, was analyzed in relation to brood size and the hatching position of nestlings. Mean daily growth rate of nestlings’ mass (7.82 ± 0.35 g/day) varied in broods of different size but remained independent of nestlings’ hatch order within the brood. Similarly, the growth rate of head-bill length was influenced only by brood size while neither brood size nor hatching position had a significant effect on the wing length growth rate. Nest initiation dates and plant cover around the nests were the most important factors predicting nesting success. As time of breeding period progressed, the rate of nesting success increased. Higher plant cover around the nest also increased the nesting success, probably by hiding the eggs and providing shelter for nestlings thus decreasing predation and mortality rate.