Physiological adjustments to high foraging effort negatively affect fecundity but not final reproductive output in captive zebra finches

Yap, Kang Nian; Powers, Donald R.; Vermette, Melissa L.; Tsai, Olivia; Williams, Tony

doi:10.1242/jeb.235820

Cited by 6 publications

(4 citation statements)

References 63 publications

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“…Egg production in terms of egg number and mass was significantly lower under warm compared to cold ambient temperature (Figures 1B,C), which is consistent with previous findings revealing decreased egg size and mass (Williams and Cooch, 1996;Schaper and Visser, 2013) with increasing ambient temperatures (but see Griffith et al, 2020). In addition, breeding zebra finches showed decreased egg mass and clutch size when exposed to a high foraging cost feeder similar to the one we implemented (Yap et al, 2021). Here, we suggest that reduced clutch size and egg mass in the warm conditions resulted from a combination of both warm temperature and elevated foraging costs.…”

Section: Discussionsupporting

confidence: 91%

Manipulation of Heat Dissipation Capacity Affects Avian Reproductive Performance and Output

et al. 2022

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Animal life requires hard work but the ability to endure such workload appears to be limited. Heat dissipation limit (HDL) hypothesis proposes that the capacity to dissipate the excess of body heat during hard work may limit sustained energy use. Experimental facilitations of heat loss rate via feather-clipping in free-living birds seem to support HDL hypothesis but testing of HDL through laboratory experiments under controlled conditions is not reported. We employed a two-factorial experimental design to test HDL hypothesis by manipulating the capacity to dissipate heat through exposure of captive zebra finches (Taeniopygia guttata) to a cold and warm ambient temperature (14°C and 25°C), and through manipulation of the insulating layer of feathers around the brood patch in females (clipped and unclipped). To simulate foraging costs encountered in the wild we induced foraging effort by employing a feeding system that necessitated hovering to access food, which increased energetic costs of reproduction despite ad libitum conditions in captivity. We quantified the outcome of reproductive performance at the level of both parents, females, and offspring. Thermal limitations due to warm temperature appeared at the beginning of reproduction for both parents with lower egg-laying success, smaller clutch size and lower egg mass, compared to the cold. After hatching, females with an enhanced ability to dissipate heat through feather-clipping revealed higher body mass compared to unclipped females, and these clipped females also raised heavier and bigger nestlings. Higher levels for oxidative stress in plasma of females were detected prior to reproduction in warm conditions than in the cold. However, oxidative stress biomarkers of mothers were neither affected by temperature nor by feather-clipping during the reproductive activities. We document upregulation of antioxidant capacity during reproduction that seems to prevent increased levels of oxidative stress possibly due to the cost of female body condition and offspring growth. Our study on reproduction under laboratory-controlled conditions corroborates evidence in line with the HDL hypothesis. The link between temperature-constrained sustained performance and reproductive output in terms of quality and quantity is of particular interest in light of the current climate change, and illustrates the emerging risks to avian populations.

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Section: Discussionsupporting

confidence: 91%

Manipulation of Heat Dissipation Capacity Affects Avian Reproductive Performance and Output

et al. 2022

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“…Interestingly, despite finding sex-specific effects of energy management strategies, no sex-specific effects were found in physiological metrics in our companion study (Yap et al, 2021). In that study, we found increases in haematocrit, haemoglobin concentration and oxidative stress in response to HF treatment in both sexes.…”

Section: Discussioncontrasting

confidence: 72%

“…In that study, we found increases in haematocrit, haemoglobin concentration and oxidative stress in response to HF treatment in both sexes. However, when birds were bred in low foraging effort common garden condition following HF treatment, measures of fecundity and final reproductive output were similar between both groups (Yap et al, 2021). Taken together, findings from both the current study and the companion study suggest that daily energy expenditure and physiological metrics such as haematology and oxidative stress are at least somewhat uncoupled, as evident from the sex-specific effect and lack thereof in DEE and physiology, respectively.…”

Section: Discussionsupporting

confidence: 54%

Sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction in captive zebra finches

Yap

Powers

Vermette

et al. 2021

Journal of Experimental Biology

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Free-living animals often engage in behaviour that involve high rates of workload and result in high daily energy expenditure (DEE), such as reproduction. However, the evidence for elevated DEE accompanying reproduction remain equivocal. In fact, many studies have found no difference in DEE between reproducing vs. non-reproducing females. One of the hypotheses explaining the lack of difference is the concept of energetic ceiling. However, it is unclear whether the lack of increases in energy expenditure is due to the existence of an energetic ceiling and/or compensation by males during parental care. To investigate whether an energetic ceiling exists we experimentally manipulated foraging effort in captive zebra finches, Taeniopygia guttata, creating two groups with high- and low foraging effort followed by both groups breeding in a low foraging effort common garden condition. DEE was measured in both sexes throughout the experiment. Our findings showed sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction. Specifically, males and females responded differently to high foraging effort treatment and subsequently to chick rearing in terms of energy expenditure. Our results also suggested that there appears to be an energetic ceiling in females and that energetic costs incurred prior to reproduction can be carried over into subsequent stages of reproduction in a sex-specific manner.

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“…Thus, the mechanism through which food availability affects reproductive success is largely an open question; in particular to what extent this effect can be attributed to direct effects, as opposed to the array of potential indirect effects. Prior studies addressed this question by either manipulating the time (Lemon 1991 ; Wiersma and Verhulst 2005 ) or the effort required per unit food (Simons et al 2014 ; Yap et al 2021 ) and found reduced food availability to decrease reproductive success, mainly by decreasing laying intervals. In our study, we used a technique we developed to mimic natural variation in food availability, by manipulating the effort required per unit food, i.e.…”

Section: Introductionmentioning

confidence: 99%

Experimentally manipulated food availability affects offspring quality but not quantity in zebra finch meso-populations

et al. 2022

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Food availability modulates survival, reproduction and thereby population size. In addition to direct effects, food availability has indirect effects through density of conspecifics and predators. We tested the prediction that food availability in isolation affects reproductive success by experimentally manipulating food availability continuously for 3 years in zebra finches (Taeniopygia guttata) housed in outdoor aviaries. To this end, we applied a technique that mimics natural variation in food availability: increasing the effort required per food reward without affecting diet. Lower food availability resulted in a slight delay of start of laying and fewer clutches per season, but did not affect clutch size or number of offspring reared per annum. However, increasing foraging costs substantially reduced offspring growth. Thus, food availability in isolation did not impact the quantity of offspring reared, at the expense of offspring quality. Growth declined strongly with brood size, and we interpret the lack of response with respect to offspring number as an adaptation to environments with low predictability, at the time of egg laying, of food availability during the period of peak food demand, typically weeks later. Manipulated natal brood size of the parents did not affect reproductive success. Individuals that were more successful reproducers were more likely to survive to the next breeding season, as frequently found in natural populations. We conclude that the causal mechanisms underlying associations between food availability and reproductive success in natural conditions may be more complex than usually assumed. Experiments in semi-natural meso-populations can contribute to further unravelling these mechanisms.

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Physiological adjustments to high foraging effort negatively affect fecundity but not final reproductive output in captive zebra finches

Cited by 6 publications

References 63 publications

Manipulation of Heat Dissipation Capacity Affects Avian Reproductive Performance and Output

Manipulation of Heat Dissipation Capacity Affects Avian Reproductive Performance and Output

Sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction in captive zebra finches

Experimentally manipulated food availability affects offspring quality but not quantity in zebra finch meso-populations

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