Nesting Success in Crimson Finches: Chance or Choice?

Abstract

In avian systems, nest predation is one of the most significant influences on reproductive success. Selection for mechanisms and behaviours to minimise predation rates should be favoured. To avoid predation, breeding birds can often deter predators through active nest defence or by modifying behaviours around the nest (e.g. reducing feeding rates and vocalisations). Birds might also benefit from concealing nests or placing them in inaccessible locations. The relative importance of these strategies (behaviour vs. site selection) can be difficult to disentangle and may differ according to life history. Tropical birds are thought to experience higher rates of predation than temperate birds and invest less energy in nest defence. We monitored a population of crimson finches (Neochmia phaeton), in the Australian tropics, over two breeding seasons. We found no relationship between adult nest defence behaviour (towards a model reptile predator) and the likelihood of nest success. However, nest success was strongly related to the visibility of the nest and the structure of the vegetation. We found no evidence that adult nest building decisions were influenced by predation risk; individuals that re-nested after a predation event did not build their nest in a more concealed location. Therefore, predator avoidance, and hence nest success, appears to be largely due to chance rather than due to the behaviour of the birds or their choice of nesting sites. To escape high predation pressures, multiple nesting attempts both within and between seasons may be necessary to increase reproductive success. Alternatively, birds may be limited in their nest-site options; that is, high-quality individuals dominate quality nest sites.

Nest-site fidelity and breeding dispersal by Common Tailorbirds in a tropical forest

“…Although the probability of re-nesting after predation was higher than that of successful breeding, nest predation did not cause Common Tailorbirds to move to a different nest site, and the vast majority of them remained in their initial territory. These results are similar to those found by Young et al (2015) and Beletsky and Orians (1991), in that the nest-site changing frequency and moving distance were independent of nest predation in the previous year. One reason for the birds remaining in a nesting area with predators is that dispersal to other places does not reduce the risk of nest predation.…”

“…Beletsky and Orians (1991) found that nest-site changing frequency of female Red-winged Blackbirds (Agelaius phoeniceus) was independent of nest predation. Young et al (2015) also found that parent Crimson Finches (Neochmia phaeton) did not move farther away after nest predation compared with those that bred successfully. The ability to change nest-sites is evidently an important adaptive strategy for birds, but it may vary between the sexes or among different species.…”

“…Choosing to remain in their territory can also save the time and energy spent finding suitable nest sites (Powell and Frasch 2000;Shutler and Clark 2003). Another possible reason for these birds remaining in their initial territory is that they may be able to reduce nest predation by modifying the characteristics of the nest-site (Young et al 2015). The dense forests in the study area provide many potential nesting sites with different characteristics.…”

Nest reuse by Pale‐breasted Thrushes reduces the chance of cowbird parasitism and allows earlier initiation of breeding

“…Birds use specific features of potential nest sites, such as the degree of concealment and habitat structure, to lower the risk of both nest predation and brood parasitism (Fiorini et al 2009, Young et al 2017). However, selecting safe nest sites is a complex behavioral decision based on multiple microhabitat features because the effectiveness of different nesting strategies in avoiding nest predation depends on the behavior and cognitive abilities of local nest predators, which vary with space and time (Jokimäki et al 2005, Sperry et al 2008).…”

Some important overlooked aspects of odors in avian nesting ecology

“…I used Google Scholar Ô to identify 136 publications that have cited Conover (2007) as of September 2018, and I checked the reference sections of relevant papers in that list. I found only six studies (Conover and Borgo 2009, Conover et al 2010, Soanes 2015, Borgo and Conover 2016, Fogarty et al 2017) that evaluated whether birds chose nest sites that offered olfactory concealment, although several authors have mentioned it as a consideration (Storaas 1988, Webb et al 2012, Young et al 2017). Conover and Borgo (2009) tested if loafing locations of adult sharp-tailed grouse Tympanuchus phasianellus provided optimal olfactory versus optimal visual concealment.…”