Chestnut-Crowned Babblers: Threats to Open Habitats in Australia

In the year 2008, the Chestnut-crowned babblers were studied at the Fowlers Gap Arid Zone research center situated in western New South Wales, Australia. The discovery was that their habitat is open which exposes the birds to aerial threats (Knight, 2016). The birds are in danger while traveling to and from their nests. Chestnut-crowned babblers forage mainly on the ground by just turning over sticks and stones and by digging. Moreover, they hunt for their invertebrate prey from trees and bushes (Russell, 2016). Their brood size and age post-hatching were studied and documented. Nest cameras are used to record the size of their prey fed to the nestlings. Information on the total amount of prey taken to the nestlings recorded.

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2. Introduction

Chestnut-crowned babbler is an Australian bird that is medium-sized. This bird is dark brown-grey with a white throat, and the tip of its tail is white. The Chestnut-crowned babbler is the first non-human species in the world to management to use language as a means for communication. However, their language is simple, and scientists have discovered that the bird uses different sound combinations that are meaningless on their own but convey particular messages when combined. Moreover, this bird is very active and participates in loud social activities. Typically, the birds stay in groups of about four to fifteen. Activities that these birds participate include preening, dust-bathing and group feeding (Crane et al., 2016).

The natural habitat for Chestnut-crowned babbler is arid and semi-arid woodlands, tall shrubs and trees, and shrublands with bare ground. In Australia, the birds are distributed in various regions that include Southwestern Queensland, North-Western Victoria, Eastern South Australia, and Western New South Wales (Crane et al., 2015). The birds feed on reptiles, insects, crustaceans, small amphibians, and spiders. Moreover, they eat seeds and fruits. The breeding habits of the Chestnut-crowned babbler are not known. Their nest is usually dome-shaped, with groups constructing numerous nests, placed in small forks situated in the upper canopy of shrubs or trees. Researchers know little of the Chestnut-crowned babbler's movements; however, they are thought to be sedentary. The following paper evaluates the methods used to study the birds; results obtained, and further discussions concerning the bird (Engesser et al., 2019).

3. Methods

Chestnut-crowned babblers were studied in 2008 at the Fowlers Gap Arid Zone research station in far western New South Wales, Australia. The habitat is open and dominated by low shrubs with occasional linear stands of trees in dry creek zones. The threat of aerial predation is high in the open habitat and traveling to and from the nest is likely to be costly (Lambert & Ford, 2017). Babblers forage primarily on the ground, mainly by digging and turning over stones and sticks, although they also glean their principally invertebrate prey from bushes and trees as well as from on the ground. The climate is arid, with annual rainfall of ca. 200 mm/y.

Brood sizes were counted and the age post-hatching on which they were counted was noted. We also used nest cameras to record the size of prey items brought to the nestlings (based on the size of prey relative to the size of the babbler bill) and noted whether the prey would have required digging or could be gleaned. For example, dug prey includes medium-sized wolf spiders and beetle larvae, while gleaned prey includes caterpillars, adult insects, and small social spiders or large huntsman spiders (Chappell et al., 2016). The total amount of prey brought to the nestlings was also recorded as was the time over which nests were observed. Finally, the number of careers providing food was also noted, as was the habitat characteristics of the territory in terms of shrub and tree cover, which might influence foraging mode, and the threat of predation. We used the R-program to calculate the mean of brood size, chick age, and shrub cover.

4. Results

There is strong evidence for a negative association between the relative shrub cover and the ratio of food gleaned (b SE: -0.88 0.16, F1, 58=30.65, P=7.80x10 -7). This means that when the shrub cover decreases, the ratio of food-gleaned increases, and vice versa (Nomana et al., 2019).

There is strong evidence for a positive association between chick age and the ratio of food gleaned (b SE: 13.29 2.67, F1, 58 = 24.75 P= 6.15 x 10 -6). This means that an increase in click age results to increase in the ratio of food-gleaned, and vice versa (Capp et al., 2018).

5. Discussion

The study evaluates the behavior of the Chestnut-crowned babbler. The results have shown those Chestnut-crowned babblers are exposed to aerial threats while they travel to and from their nests. The birds hunt by turning sticks and stones and by digging. The average size of the prey living on the ground in terms of the size of the babbler bill is 1.071859. This shows that it is the same size. For the preys that live below ground and are extracted by digging, the average size is 0.808856. This is above half the size and below the same size so it is almost three quarters the size. A camera was used during the study to determine the type and size of the prey items. We studied the total number of prey delivered to the brood and recorded the time taken to observe the brood. The average size of the brood was 3.116667. The total amount of prey delivered in the brood varies from six to one hundred and ten. These results show that the average amount of prey taken to the brood is 29.06667. Indeed few studies in the past have concentrated on the evaluation of risk of predators to Chestnut-crowned babbler as they travel to and from their nests. The results of this research shows evidence that the group behavior of the birds is risk-sensitive in an open habitat when they encounter aerial predators. In addition, we found that most attacks of the birds occurred when they were feeding on the ground as compared to when they were near the nest (Liebl et al., 2016).

Various studies identified that the birds had a unique communication method that has never been seen in animals. They use different combinations of sounds when they convey meaning (Chappell et al., 2016). The study illustrated that the birds use similar meaningless sounds in specific arrangements to produce new meaning. Their sounds are described as noisy sharp chattering sounds and are harsher and sharper. Future studies can be conducted to evaluate different calls for different meanings. The results will be used to assess the language used by the birds and help to study their way of life. Furthermore, we have learned of the habitats of Chestnut-crowned babbler. The birds occur in arid and semi-arid woodlands, tall or dense shrubs and trees, and scrublands with bare ground. In the study, the results show that the average shrub cover and tree cover are 1.1 and 1.4 respectively. However, this has provided room for further studies to determine the food distribution of the Chestnut-crowned babbler on their various habitats (Nomana et al., 2019). The results will be used together with preferences of hunting behavior to design management strategies. We have studied that the birds mostly hunt on the ground as compared to tree trunks and branches. The results showed that dug prey for the birds includes medium-sized wolf spiders and beetle larvae, while gleaned prey includes caterpillars, adult insects, and small social spiders or large huntsman spiders (Capp et al., 2018). Future studies can be conducted on the breeding habits of Chestnut-crowned babblers.

References

Capp, E., Liebl, A.L., Cones, A.G. and Russell, A.F., 2018. Advancing breeding phenology does not affect incubation schedules in chestnutcrowned babblers: Opposing effects of temperature and wind. Ecology and evolution, 8(1), pp.696-705.

Chappell, M.A., Buttemer, W.A. and Russell, A.F., 2016. Energetics of communal roosting in chestnut-crowned babblers: implications for group dynamics and breeding phenology. Journal of Experimental Biology, 219(21), pp.3321-3328.

Crane, Jodie MS, Joel L. Pick, Alice J. Tribe, Erno Vincze, Ben J. Hatchwell, and Andrew F. Russell. "Chestnut-crowned babblers show affinity for calls of removed group members: a dual playback without expectancy violation." Animal Behaviors 104 (2015): 51-57.

Crane, J.M., Savage, J.L. and Russell, A.F., 2016. Diversity and function of vocalizations in the cooperatively breeding Chestnut-crowned Babbler. Emu-Austral Ornithology, 116(3), pp.241-253.

Engesser, S., Holub, J.L., O'Neill, L.G., Russell, A.F. and Townsend, S.W., 2019. Chestnutcrowned babbler calls are composed of meaningless shared building blocks. Proceedings of the National Academy of Sciences, 116(39), pp.19579-19584.

Russell, A.F., 2016. Chestnut-crowned babblers: dealing with climatic adversity and uncertainty in the Australian arid zone. Cooperative breeding in vertebrates: studies in ecology, evolution and behavior, pp.150-164.

Lambert, K.T.A. and Ford, H., 2017. Habitat use by grey-crowned babbler, Pomatostomus temporalis, in urban and peri-urban environments. Pacific Conservation Biology, 23(1), pp.88-94.

Liebl, A.L., Nomano, F.Y., Browning, L.E. and Russell, A.F., 2016. Experimental evidence for fully additive care among male careers in the cooperatively breeding chestnut-crowned babbler. Animal Behaviour, 115, pp.47-53.

Knight, K., 2016. Chestnut-crowned babblers huddle for comfort. Journal of Experimental Biology, 219(21), pp.3311-3311.

Nomano, F.Y., Savage, J.L., Browning, L.E., Griffith, S.C. and Russell, A.F., 2019. Breeding phenology and meteorological conditions affect career provisioning rates and group-level coordination in cooperative chestnut-crowned babblers. Frontiers in Ecology and Evolution, 7, p.423.