Movement, habitat requirements, nesting and foraging site selection: a case study of an endangered granivorous bird, the Black-throated finch Poephila cincta cincta in north-eastern Australia

Rechetelo, Juliana (2015) Movement, habitat requirements, nesting and foraging site selection: a case study of an endangered granivorous bird, the Black-throated finch Poephila cincta cincta in north-eastern Australia. PhD thesis, James Cook University.

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Species all over the world are declining to unsustainable population levels due to habitat destruction, introduced species and pollution. Susceptible species begin to decline prior to noticeable degradation of the environments in which they live. Savannas are the dominant vegetation type in northern Australia and, although considered relatively unmodified, have experienced severe faunal decline, particularly among granivores. Granivorous birds represent 20% of Australian land birds and range-scale declines have been documented for several species. Declines of the granivorous birds of Australian tropical savannas are associated with land use change resulting from European settlement, such as land clearance, changes in fire regime, pastoralism, introduced species and shrub proliferation.

Although it is generally recognized that granivorous birds have declined, there are still many gaps in our understanding of the underlying causes. The Black-throated finch southern subspecies (Poephila cincta cincta, herein referred to as BTF) is an endangered, endemic granivore of eastern Australia. BTF have had an estimated range contraction of 80% since the late 1970s. Little is known about BTF ecological requirements, home range size or movement patterns. Increased knowledge of these will greatly assist with management and conservation actions. In this thesis, I investigate the ecology of BTF in north-eastern Australia. I examine (a) home range sizes, movement patterns and habitat use, and (b) habitat requirements, nesting and foraging site selection.

Understanding how animals move in the landscape to meet their demands – food, water, and shelter - is a prerequisite for successful conservation outcomes. To acquire more information about BTF movements, I mist netted in eight sites on the Townsville Coastal Plain (TCP) and radio-tracked in two of these sites. I color-banded 102 BTF and estimated the home ranges of 15. More than half of all resightings occurred within 200m of the banding site and within 100 days of capture. Long distance movements (up to 17 km) were recorded for only three individuals. Home range size differed between sites but not between seasons (early dry season and late dry season). BTF home ranges encompassed four broad vegetation types among eight available (Regional Ecosystems), with habitat selection significantly different from random. BTF showed a distinct local daily movement pattern at one site (roosting to feeding area). In this study, BTF maintained home ranges ranging from 25.2 to 120.9 ha over short time scales (e.g. within seasons).

Vegetation structure and composition greatly influence the way animals use habitat. Determining key habitat features for a threatened species is paramount for identifying appropriate management actions. To understand these for BTF, vegetation surveys were undertaken at 10 sites on TCP. BTF flocks were most closely associated with higher cover of native grasses, low shrub cover, with the presence of dead trees and high cover of certain grass species, e.g. Eragrostis spp. Small flocks were associated with low percentages of native grasses, high shrub cover and low grass richness. BTF showed a preference for nesting at sites with lower tree and grass diversity, but no preferences for ground cover structural features. Other environmental structural features in the nesting habitat might be more important to the birds.

I explored BTF nesting habitat selection by comparing areas around nests (used) with that in the surrounding area (available). Individual nests were used for breeding and/or roosting. Fifty active BTF nests were found during this study. BTF nested in four tree species, preferentially using Eucalyptus platyphylla and Melaleuca viridiflora in areas of low tree density. BTF showed a preference for nesting in sites with lower tree and grass diversity, but no preference for ground cover structural parameters. Other environmental features in the nesting habitat might be more important to the birds as structural features.

Specific patches where animals are exploiting resources differ in nature and appearance from the matrix in which they are embedded. Being ground-foragers, BTF are likely to be specific in the micro-structure preferences of foraging patches, such as the presence of bare ground patches. To understand the BTF needs, foraging patches – specific areas where animals were exploiting resources – were examined. Vegetation structure and composition were compared between foraging patches (used) and surrounding (neighboring) and general areas (available). Of the ground cover structural characteristics, nearly all variables were significantly different between used, neighbouring and available areas. BTF foraged preferentially in areas with lower diversity of grasses but nearby areas with high diversity (neighbouring areas). BTF selected specific structural vegetation features for foraging patches, compared with neighboring and available areas, particularly the ground cover features. Foraging patches were less densely vegetated than neighboring and available areas; however, they adjoined areas with high grass structural complexity (higher visual obstruction, higher vegetation density in almost all levels measured, higher vegetation cover, particularly grass cover, and higher number of species per hectare). In summary, foraging BTF require open areas finely interspersed with to grassy areas.

In this study, I found that BTF habitat must encompass patches with suitable grasses (e.g. Eragrostis spp.), and patches with bare ground or low vegetation density (ground cover) to allow BTF access to the seed bank. BTF prefer a general absence of shrubs but the scattered presence of a medium strata. Therefore, large homogeneous areas will not usually meet the requirements of BTF populations. Extensive woody thickening could disadvantage BTF, as has been found for other granivorous birds such as the Golden-shouldered parrot (Psephotus chrysopterygius). Instead, they require a mosaic of vegetation within their daily home range: areas with bare ground finely interspersed with areas of suitable grass species, low shrub density, presence of suitable woody plant cover and the presence of species such as Eucalyptus platyphylla and Melaleuca spp.

Item ID: 46293
Item Type: Thesis (PhD)
Keywords: Australian finches; Black-throated finch; foraging; granivores; granivorous birds; habitat modification; habitat; home range; nesting; nests; Poephila cincta cincta
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Appendix E: Vanderduys, Eric Peter, Reside, April E., Grice, Anthony, and Rechetelo, Juliana (2016) Addressing potential cumulative impacts of development on threatened species: the case of the endangered black-throated finch. PLoS ONE, 11 (3). pp. 1-19.

Date Deposited: 09 Nov 2016 23:11
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 25%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060201 Behavioural Ecology @ 50%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 25%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960510 Ecosystem Assessment and Management of Sparseland, Permanent Grassland and Arid Zone Environments @ 25%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960811 Sparseland, Permanent Grassland and Arid Zone Flora, Fauna and Biodiversity @ 25%
96 ENVIRONMENT > 9699 Other Environment > 969999 Environment not elsewhere classified @ 50%
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