The functional significance of multiple nest‐building in the Australian Reed Warbler Acrocephalus australis

Abstract

The vast majority of bird species build a nest in which to breed. Some species build more than one nest, but the function of most multiple nest‐building remains unclear. Here we describe the unusual nest‐building behaviour of the Australian Reed Warbler Acrocephalus australis, and test experimentally the hypotheses that multiple nest‐building is related to individual condition or territory quality, and plays a role in mate assessment. Australian Reed Warblers built two types of nest structures: ‘type I’ nests, which were used for eggs and nestlings, and ‘type II’ nests, which were structurally distinct from type I nests, did not support eggs, nestlings or adults and were not essential for successful breeding. The number of type II nests built in each territory varied. Type II nests were only built before breeding had commenced in a territory and females were not observed participating in their construction, supporting a role in female mate choice. Birds provided with supplementary food built significantly more type II nests than control birds. However, supplementary‐fed birds did not have greater pairing success, and the addition of further type II nests to territories did not increase the pairing rate or type II nest construction in those territories. There was no relationship between the presence of type II nests and either reproductive success or likelihood of nest predation. We discuss the implications of these results in light of previous suggestions regarding the function of multiple nest‐building in birds.

The Energetic Costs of Nest Building in Birds

“…Supplemented males built significantly more type 2 nests than control males, but did not have greater pairing success in terms of having more breeding attempts by area or per male. Further, the experimental addition of further type 2 nests to territories did not increase the pairing rate of those males or their construction of further type 2 nests in their territories (Berg et al, 2006).…”

“…In Australian Reed Warblers (Acrocephalus australis), food supplementation resulted in more nest building by territorial males, but this species is unusual in that individual males build multiple nests within their territories (Berg et al, 2006). Australian reed warblers build both 'type 1' nests which are used for reproduction and 'type 2' nests which are structurally different and do not support eggs, nestlings or adults.…”

“…Three studies have provided supplementary food during the nest building period and examined the nest building behaviour of birds (Berg et al, 2006;Mainwaring and Hartley, 2009;Smith et al, 2013). In Australian Reed Warblers (Acrocephalus australis), food supplementation resulted in more nest building by territorial males, but this species is unusual in that individual males build multiple nests within their territories (Berg et al, 2006).…”

Opportunistic Use of a Wool-like Artificial Material as Lining of Tit (Paridae) Nests

“…detailed descriptions of some passerines' nests are available (kern and van riper 1984, Blem and Blem 1994, Elts 2005, Crossman et al 2011, and nests of the great and Blue Tits differ (Britt and deeming 2011). use of artificial nest materials in nests has been reported (Hansell 2000, Berg et al 2006 but not systematically reviewed. There is anecdotal evidence of rapid use of novel artificial material; for instance, during the Second world war, within two weeks of its first deployment, aluminium foil dropped over Jersey from bombers to confuse figurE 2. frequency of nests incorporating artificial nest material as a function of distance from dispenser (all species, colors, and locations of dispensers combined).…”

“…food availability may be a limiting factor in nest-construction behavior in general because supplementary feeding of Blue Tits increased nest mass (Mainwaring and Hartley 2009). in the australian reed warbler (Acrocephalus australis) supplementary feeding increased the number of "type ii" nests a male built in his territory; these nests are not used for reproduction and are considered to be a sexual signal (Berg et al 2006).…”