http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:23419 The Zebra Finch Taeniopygia guttata is a model bird species for the experimental study of behavioural and evolutionary concepts in captivity and especially sexual selection. The validity of sexual selection studies of domesticated birds is of long-standing concern as little is known about the influence of domestication on sexually selected traits. Most domesticated Zebra Finch populations are maintained under a strict breeding regime to avoid potential inbreeding. However these breeding regimes may interfere with the processes of sexual selection and influence the evolution of sexually selected traits because they may limit or prohibit active mate choice. Here we investigated the potential impact of a monogamous breeding scheme in a domesticated population in which active mate choice is largely inhibited, on the evolution of sperm morphometry as a sexually selected trait. We compared sperm morphometric traits (total sperm length and length of sperm head, midpiece and flagellum), and the variance thereof, between a domesticated and two wild Zebra Finch populations. Although we found significant differences between the three populations for certain sperm traits (head length, midpiece length), which may be of importance in postcopulatory sexual selection, overall, variance in sperm morphometry did not differ between the domesticated and the wild Zebra Finch populations. Our results validate the use of domesticated Zebra Finches for further studies of postcopulatory sexual selection and sperm competition. 2012-12-17T10:00:27.321Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:19964 The zebra finch is the model species for the study of the evolution of birdsong, female song preferences, song learning and the neural processes underlying song learning and production. Despite this, almost all work to date in these fields has focused on domesticated zebra finches in captivity and remarkably little is known about song preferences, or the reproductive success of males with different songs, in wild populations. In this study we tested, for the first time in a wild zebra finch population, whether a male's song structure predicts his reproductive success. We recorded male songs in a nestbox population. Males from this wild population sang longer songs, with a higher peak frequency, than domesticated males. The number of each male's offspring that survived until day 12 posthatching (a proxy for fledging success) was used as a measure of reproductive success. Nestlings were partially cross-fostered, allowing us to disentangle the indirect effects of male genetic quality or maternal effects from those of direct benefits such as parental care. Male song structure predicted the number of genetic offspring surviving, as well as hatching success, but not the number or size of eggs in a clutch. Song structure did not predict the number of unrelated foster-offspring that survived. These results provide the first evidence that differences in male song can predict differences in reproductive success in the zebra finch, and suggest that differences in genetic quality are responsible, rather than differences in parental care or maternal investment in the eggs. 2012-06-19T06:40:06.638Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18098 The evolutionary consequences of parent-offspring conflict have received considerable attention, yet the extent to which parent-offspring conflict influences life history traits remains uncertain. In particular, it is unclear whether hatching patterns are parental strategies to manipulate competitive dynamics among offspring, or whether they are instead consequences of physiological or ecological variables affecting the payoffs of adjusting the onset of incubation. Here we describe an experiment in which we manipulated the hatching pattern of wild free-living zebra finches. We examined the consequences of hatching pattern on parental feeding behaviour and sibling competition, with the aim of identifying selective pressures that underlie differing hatching patterns. Increasing hatching asynchrony reduced the overall quantity of food that parents delivered and the equitability of its distribution among nestlings compared with synchronous broods. However, for each unit of food received, the begging intensity of nestlings from asynchronous broods was lower. As a consequence, the growth rate of first-hatched nestlings in asynchronous broods was significantly greater than those in synchronous broods, and there was no significant difference in growth rate between last-hatched nestlings in asynchronous broods and nestlings from synchronous broods, even though they received less food overall. The reduced scramble competition and energy wasted on begging behaviour in asynchronous broods supports the sibling rivalry hypothesis, suggesting an adaptive function for hatching asynchrony in wild zebra finches. 2012-03-14T15:00:11.795Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:15857 Although the costs of parental care are at the foundations of optimal-parental-investment theory, our understanding of the nature of the underlying costs is limited by the difficulty of measuring variation in foraging effort. We simultaneously measured parental provisioning and foraging behavior in a free-living population of Zebra Finches (Taeniopygia guttata) using an electronic monitoring system. We fitted 145 adults with a passive transponder tag and remotely recorded their visits to nest boxes and feeders continuously over a 2-month period. After validating the accuracy of this monitoring system, we studied how provisioning and foraging activities varied through time (day and breeding cycle) and influenced the benefits (food received by the offspring) and costs (interclutch interval) of parental care. The provisioning rates of wild Zebra Finches were surprisingly low, with an average of only one visit per hour throughout the day. This was significantly lower than those reported for this model species in captivity and for most other passerines in the wild. Nest visitation rate only partially explained the amount of food received by the young, with parental foraging activity, including the minimum distance covered on foraging trips, being better predictors. Parents that sustained higher foraging activity and covered more distance during the first breeding attempt took longer to renest. These results demonstrate that in some species matching foraging activity with offspring provisioning may provide a better estimate of the true investment that individuals commit to a reproductive attempt. 2011-11-09T03:16:14.149Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:14603 Although the zebra finch, Taeniopygia guttata, has been a very important model system for the study of intrafamilial conflict and parental strategies, a detailed understanding of the variation in parental effort that can occur both within and between pairs is lacking. In part this is because many different methods have been used by individual studies to quantify parental care (i.e. nest visit rate, time in the nest and number of feeds per visit), but these have not directly been compared. We used nestbox cameras to monitor parental visit rate and the distribution of food among the nestlings in domestic, captive wild and wild free-living zebra finches. The percentage of nest visits by parents in which they fed the nestlings was consistent, with multiple feeds to different nestlings occurring within a single visit. The quantity of food delivered and its distribution among the nestlings, however, varied greatly both within and between broods. The number of regurgitations a brood received correlated significantly with the number of individual feeds when accounting for environment, but not with nest visit rate or the duration of time parents spent in the nestbox. In captive conditions, parents visited the nest at twice the rate of wild free-living birds, overall providing nestlings with twice the amount of food. Captive conditions also led to food distribution becoming less equitable among t he brood, owing to changes in the number of regurgitations per individual feed and the number of overall feeds per nest visit. 2011-08-23T08:00:22.231Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11123 The captive zebra finch, Taeniopygia guttata, has become one of the key vertebrate model systems for studying a range of behavioural, physiological and neurological phenomena. In particular, this species has played a key role in developing our understanding of sexual selection and sperm competition. In contrast with the large number of studies using domesticated zebra finches, relatively few studies have focused on free-living populations of wild zebra finches. Investigating the incidence of extrapair paternity in zebra finches in the Australian desert, we found a very low level; 1.7% of 316 offspring from four of 80 broods fathered outside the pair bond. These numbers contrast with the high levels of extrapair paternity observed in domesticated aviary populations, and suggest a low level of sperm competition and sexual selection in natural populations. Our finding of such a low rate of extrapair paternity in the wild zebra finch suggests that it is one of the most genetically monogamous of all passerine species and that has important implications for future studies of this model organism in studies of sexual selection and reproductive biology. In addition, we found that 5.4% of 316 offspring were not related to either putative parent and hatched from eggs that had been dumped by intraspecific brood parasites. 2011-01-06T18:10:50.862Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11128 Birds are a particularly good group with which to examine the importance of maternal effects, as parental contributions can be relatively easily quantified compared with other groups. There have undoubtedly been more studies on maternal effects in the Zebra Finch than any other single bird species. Studies of this species have examined the importance of maternal effects mediated through sex allocation, size, nutrients and hormones of of eggs, incubation behaviour and provisioning levels. A synthesis of all of this work illustrates some contrasting results (e.g. many high-profile results have failed to be replicated), some very common patterns (e.g. investment shifts through the laying sequence), and potentially interesting and complex interactions between traits (e.g. between sex of offspring and hormonal profiles of eggs). This extensive collection of work on the Zebra Finch provides useful general insight into the patterns of maternal investment in birds and the effects on offspring phenotype. However, we caution that the literature is probably littered with studies that have overemphasised the importance of some maternal effects and recent studies have highlighted analytical and logical flaws that have probably led to misplaced confidence in some of the findings reported to date. Finally, it is worth considering that the bulk of the literature is based on studies of captive domesticated birds and ecological and physiological data from individuals in the wild is currently lacking. The biological relevance of maternal effects documented in this model species is therefore unclear. 2011-01-06T18:10:26.750Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:10451 The Australian zebra finch, Taeniopygia guttata, is a widely used model organism, yet few studies have compared domesticated and wild birds with the aim of examining its relevance as an evolutionary model species. Domestic and wild broods hatch over approximately 4 and 2 days, respectively, which is important given that nestlings can fledge after as little as 12 days, although 16-18 days is common. We aimed to evaluate the extent to which the greater hatching asynchrony in domestic stock may effect reproductive success through greater variance in size hierarchies, variance in within-brood growth rates, and partial brood mortality. Therefore, by simultaneously controlling brood sizes and experimentally manipulating hatching intervals in both domesticated and wild birds, we investigated the consequences of hatching intervals for fledging success and nestling growth patterns, as well as trade-offs. Fledging success was similarly high in domestic and wild broods of either hatching pattern. Nonetheless, between-brood analyses revealed that domestic nestlings had significantly higher masses, larger skeletal characters, and longer wings than their wild counterparts, although wild nestlings had comparable wing lengths at the pre-fledging stage. Moreover, within-brood analyses revealed only negligible differences between domestic and wild nestlings, and larger effects of hatching order and hatching pattern. Therefore, despite significant differences in the hatching intervals, and the ultimate size achieved by nestlings, the domestication process does not appear to have significantly altered nestling growth trade-offs. The present study provides reassuring evidence that studies involving domesticated zebra finches, or other domesticated model organisms, may provide reasonable adaptive explanations in behavioural and evolutionary ecology. 2010-11-05T04:30:57.760Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:8399 Divergent selection pressures among populations can result not only in significant differentiation in morphology, physiology and behaviour, but also in how these traits are related to each other, thereby driving the processes of local adaptation and speciation. In the Australian zebra finch, we investigated whether domesticated stock, bred in captivity over tens of generations, differ in their response to a life-history manipulation, compared to birds taken directly from the wild. In a 'common aviary' experiment, we thereto experimentally manipulated the environmental conditions experienced by nestlings early in life by means of a brood size manipulation, and subsequently assessed its short- and long-term consequences on growth, ornamentation, immune function and reproduction. As expected, we found that early environmental conditions had a marked effect on both short- and long-term morphological and life-history traits in all birds. However, although there were pronounced differences between wild and domesticated birds with respect to the absolute expression of many of these traits, which are indicative of the different selection pressures wild and domesticated birds were exposed to in the recent past, manipulated rearing conditions affected morphology and ornamentation of wild and domesticated finches in a very similar way. This suggests that despite significant differentiation between wild and domesticated birds, selection has not altered the relationships among traits. Thus, life-history strategies and investment trade-offs may be relatively stable and not easily altered by selection. This is a reassuring finding in the light of the widespread use of domesticated birds in studies of life-history evolution and sexual selection, and suggests that adaptive explanations may be legitimate when referring to captive bird studies. 2010-06-04T14:21:02.963Z ]]>