Abstract
Parental care plays a key role in ontogeny, life-history trade-offs, sexual selection and intra-familial conflict. Studies focusing on understanding causes and consequences of variation in parental effort need to quantify parental behaviour accurately. The applied methods are, however, diverse even for a given species and type of parental effort, and rarely validated for accuracy. Here we focus on variability of parental behaviour from a methodological perspective to investigate the effect of different samplings on various estimates of parental effort. We used nest box cameras in a captive breeding population of zebra finches, Taeniopygia guttata, a widely used model system of sexual selection, intra-familial dynamics and parental care. We investigated diurnal and reproductive stage-dependent variation in parental effort (including incubation, brooding, nest attendance and number of feedings) based on 12h and 3h continuous video-recordings taken at various reproductive stages. We then investigated whether shorter (1h) sampling periods provided comparable estimates of overall parental effort and division of labour to those of longer (3h) sampling periods. Our study confirmed female-biased division of labour during incubation, and showed that the difference between female and male effort diminishes with advancing reproductive stage. We found individually consistent parental behaviours within given days of incubation and nestling provisioning. Furthermore, parental behaviour was consistent over the different stages of incubation, however, only female brooding was consistent over nestling provisioning. Parental effort during incubation did not predict parental effort during nestling provisioning. Our analyses revealed that 1h sampling may be influenced heavily by stochastic and diurnal variation. We suggest using a single longer sampling period (3h) may provide a consistent and accurate estimate for overall parental effort during incubation in zebra finches. Due to the large within-individual variation, we suggest repeated longer sampling over the reproductive stage may be necessary for accurate estimates of parental effort post-hatching.
Highlights
Parental care, in its widest sense, is an essential component of individual reproduction in most animal species
We investigated patterns of parental behaviour from a methodological perspective in standard laboratory conditions using a captive population of zebra finches, Taeniopygia guttata
We found division of labour to change within and between reproductive stages and to vary within a given day in our captive zebra finch population
Summary
In its widest sense (including pre-natal care such as for instance searching for a safe place to lay eggs in insects), is an essential component of individual reproduction in most animal species It can be provided by either or both parents in various forms and at different reproductive stages [1, 2]. We should aim at a trade-off that maximizes the return for observer effort [14] Another question that standardization does not address is whether a sample obtained by observing care at an arbitrarily chosen time and day of the reproductive stage is representative for other periods of the day or other days of the reproductive stage. An arbitrarily chosen time and duration of period may not yield valid conclusions regarding division of parental sex roles and total parental effort from many aspects
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