Housing Shortages in Urban Regions: Aggressive Interactions at Tree Hollows in Forest Remnants

Abstract

Urbanisation typically results in a reduction of hollow-bearing trees and an increase in the density of particularly species, potentially resulting in an increased level of competition as cavity-nesting species compete for a limited resource. To improve understanding of hollow usage between urban cavity-nesting species in Australia, particularly parrots, we investigated how the hollow-using assemblage, visitation rate, diversity and number of interactions varied between hollows within urban remnant forest and continuous forest. Motion-activated video cameras were installed, via roped access to the canopy, and hollow usage was monitored at 61 hollows over a two-year period. Tree hollows within urban remnants had a significantly different assemblage of visitors to those in continuous forest as well as a higher rate of visitation than hollows within continuous forest, with the rainbow lorikeet making significantly more visitations than any other taxa. Hollows within urban remnants were characterised by significantly higher usage rates and significantly more aggressive interactions than hollows within continuous forest, with parrots responsible for almost all interactions. Within urban remnants, high rates of hollow visitation and both interspecific and intraspecific interactions observed at tree hollows suggest the number of available optimal hollows may be limiting. Understanding the usage of urban remnant hollows by wildlife, as well as the role of parrots as a potential flagship for the conservation of tree-hollows, is vital to prevent a decrease in the diversity of urban fauna, particularly as other less competitive species risk being outcompeted by abundant native species.

Two speed invasion: assisted and intrinsic dispersal of common mynas over 150 years of colonization

“…The species inhabits urbanized areas, open agricultural land, and forest edges in its introduced range (Long, 1981). Mynas have the potential to spread disease (Baker, Harvey, & French, 2014), and in some parts of their geographical range mynas can compete with native species for tree hollows and other resources (Pell & Tidemann, 1997;Harper, McCarthy, & van der Ree, 2005;Tindall, Ralph, & Clout, 2007;Grarock, Tidemann, Wood, & Lindenmayer, 2012;Orchan, Chiron, Shwartz, & Kark, 2013; but see Crisp & Lill, 2006;Parsons, Major, & French, 2006;Lowe, Taylor, & Major, 2011;Davis, Major, & Taylor, 2013). They roost in large congregations in cities (Martin, 1996;Old, Spencer, & Wolfenden, 2014), which may cause disturbance to humans, and are considered one of the most unpopular feral animals in some areas of their introduced range (e.g., Thompson, Arthur, & Gilmour, 2005).…”

Distribution and abundance of hollow-bearing trees in urban forest fragments

“…landscapes (Harper et al, 2005a;Durant et al, 2009;Davis et al, 2013;Treby, 2013). This highlights the pivotal importance of HBTs in urban forest patches for the maintaining urban biodiversity.…”

“…Nestboxes are used by fauna in a range of environments and occupancy may be affected by a number of factors including the density of natural tree hollows, the age of the forest habitat, the time since establishment of the boxes, the size of wildlife populations, the presence of competing species, and nest-box design (Durant et al, 2009;Goldingay and Stevens, 2009;Lindenmayer et al, 2009;Ball et al, 2011). While nest-boxes are known to be used in urban remnants (Harper et al, 2005b;Davis et al, 2013) these authors also called for a greater understanding of HBT resource availability, the presence of species that require tree-hollows, as well as speciesspecific hollow requirements prior to introducing nest-boxes into any environment. The current study therefore provides essential data about the HBT resource to inform future management practices aimed at providing a wider range of hollow options for urban wildlife.…”

Behavioural and Ecological Keys to Urban Colonization by Little Ravens ()

“…Another facilitating factor may be social foraging, given the proven benefits of flocking in detecting predators, locating food and particularly learning about novel food sources [18]. In contrast, nest sites may be fewer in cities for many bird species because of the reduction and fragmentation of natural vegetation [19], although hole-nesters that can exploit the many cavities in city buildings may be an exception [14].…”