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Avian Incubation Patterns Reflect Temporal Changes in Developing Clutches.

Cooper CB, Voss MA - PLoS ONE (2013)

Bottom Line: One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance.We found that the rate of heat loss from eggs increased with embryo age.Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature.

View Article: PubMed Central - PubMed

Affiliation: Bird Population Studies, Cornell Lab of Ornithology, Ithaca, New York, United States of America.

ABSTRACT
Incubation conditions for eggs influence offspring quality and reproductive success. One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance. Age related changes in embryo thermal tolerance would thus be expected to shape parental incubation behavior. We use data from unmanipulated Black-capped Chickadee (Poecile atricapillus) nests to examine the temporal dynamics of incubation, testing the prediction that increased heat flux from eggs as embryos age influences female incubation behavior and/or physiology to minimize temperature fluctuations. We found that the rate of heat loss from eggs increased with embryo age. Females responded to increased egg cooling rates by altering incubation rhythms (more frequent, shorter on- and off- bouts), but not brood patch temperature. Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature. Our findings highlight the need to view full incubation as more than a static rhythm; rather, it is a temporally dynamic and finely adjustable parental behavior. Furthermore, from a methodological perspective, intra- and inter-specific comparisons of incubation rhythms and average egg temperatures should control for the stage of incubation.

No MeSH data available.


Related in: MedlinePlus

Schematic of egg temperatures resulting from off-bouts/on-bout combinations.Increased frequency of off-bouts from the nest, coupled with a decrease in time on the nest per incubation on-bout, can elevate minimum egg temperature and reduce temperature variations. The key to this counterintuitive result is that incubation on-bouts are not decreased to the same extent as incubation off-bouts. When on-bouts are considered cumulative over the course of a day, nest attentiveness increases in spite of the decreased time on the nest during individual incubation on-bouts. This pattern has the advantage of decreasing temperature variation while simultaneously limiting low egg temperatures.
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pone-0065521-g003: Schematic of egg temperatures resulting from off-bouts/on-bout combinations.Increased frequency of off-bouts from the nest, coupled with a decrease in time on the nest per incubation on-bout, can elevate minimum egg temperature and reduce temperature variations. The key to this counterintuitive result is that incubation on-bouts are not decreased to the same extent as incubation off-bouts. When on-bouts are considered cumulative over the course of a day, nest attentiveness increases in spite of the decreased time on the nest during individual incubation on-bouts. This pattern has the advantage of decreasing temperature variation while simultaneously limiting low egg temperatures.

Mentions: Females achieved higher nest attendance through a 2.9-fold reduction in the duration of their off-bouts (GLMM: F = 3.31, df = 9 and 119, P = 0.001), a 1.0-fold increase in the number of off-bouts per day (GLMM: F = 3.22, df = 9 and 119, P<0.002), and a 1.1-fold decrease in the mean on-bout duration (GLMM: F = 2.31, df = 9 and 119, P = 0.02). The increased off-bout frequency, accompanied by a reduction in off-bout duration 2.7-times the simultaneous reduction in on-bout duration, resulted in increased daily attentiveness as the incubation period progressed (GLMM: F = 1.45, df = 51 and 119, P = 0.01; represented in schematic Fig. 3.).


Avian Incubation Patterns Reflect Temporal Changes in Developing Clutches.

Cooper CB, Voss MA - PLoS ONE (2013)

Schematic of egg temperatures resulting from off-bouts/on-bout combinations.Increased frequency of off-bouts from the nest, coupled with a decrease in time on the nest per incubation on-bout, can elevate minimum egg temperature and reduce temperature variations. The key to this counterintuitive result is that incubation on-bouts are not decreased to the same extent as incubation off-bouts. When on-bouts are considered cumulative over the course of a day, nest attentiveness increases in spite of the decreased time on the nest during individual incubation on-bouts. This pattern has the advantage of decreasing temperature variation while simultaneously limiting low egg temperatures.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3686773&req=5

pone-0065521-g003: Schematic of egg temperatures resulting from off-bouts/on-bout combinations.Increased frequency of off-bouts from the nest, coupled with a decrease in time on the nest per incubation on-bout, can elevate minimum egg temperature and reduce temperature variations. The key to this counterintuitive result is that incubation on-bouts are not decreased to the same extent as incubation off-bouts. When on-bouts are considered cumulative over the course of a day, nest attentiveness increases in spite of the decreased time on the nest during individual incubation on-bouts. This pattern has the advantage of decreasing temperature variation while simultaneously limiting low egg temperatures.
Mentions: Females achieved higher nest attendance through a 2.9-fold reduction in the duration of their off-bouts (GLMM: F = 3.31, df = 9 and 119, P = 0.001), a 1.0-fold increase in the number of off-bouts per day (GLMM: F = 3.22, df = 9 and 119, P<0.002), and a 1.1-fold decrease in the mean on-bout duration (GLMM: F = 2.31, df = 9 and 119, P = 0.02). The increased off-bout frequency, accompanied by a reduction in off-bout duration 2.7-times the simultaneous reduction in on-bout duration, resulted in increased daily attentiveness as the incubation period progressed (GLMM: F = 1.45, df = 51 and 119, P = 0.01; represented in schematic Fig. 3.).

Bottom Line: One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance.We found that the rate of heat loss from eggs increased with embryo age.Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature.

View Article: PubMed Central - PubMed

Affiliation: Bird Population Studies, Cornell Lab of Ornithology, Ithaca, New York, United States of America.

ABSTRACT
Incubation conditions for eggs influence offspring quality and reproductive success. One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance. Age related changes in embryo thermal tolerance would thus be expected to shape parental incubation behavior. We use data from unmanipulated Black-capped Chickadee (Poecile atricapillus) nests to examine the temporal dynamics of incubation, testing the prediction that increased heat flux from eggs as embryos age influences female incubation behavior and/or physiology to minimize temperature fluctuations. We found that the rate of heat loss from eggs increased with embryo age. Females responded to increased egg cooling rates by altering incubation rhythms (more frequent, shorter on- and off- bouts), but not brood patch temperature. Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature. Our findings highlight the need to view full incubation as more than a static rhythm; rather, it is a temporally dynamic and finely adjustable parental behavior. Furthermore, from a methodological perspective, intra- and inter-specific comparisons of incubation rhythms and average egg temperatures should control for the stage of incubation.

No MeSH data available.


Related in: MedlinePlus