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Declining extra-pair paternity with laying order associated with initial incubation behavior, but independent of final clutch size in the blue tit.

Vedder O, Magrath MJ, Niehoff DL, van der Velde M, Komdeur J - Behav. Ecol. Sociobiol. (Print) (2011)

Bottom Line: Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction.Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring.This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species.

View Article: PubMed Central - PubMed

ABSTRACT
Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species.

No MeSH data available.


Average (±binomial SE) proportion of extra-pair offspring in relation to position in the laying order, for females that incubated less and more than average (0.81 h) on the first night after laying start. The solid trend line represents the model prediction for the average duration of incubation and the dashed lines represent the model predictions for 1 standard deviation (0.32 h) less and more than average incubation. Sample sizes for each position in the laying order are depicted for both below (n−) and above (n+) average incubation durations
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Fig4: Average (±binomial SE) proportion of extra-pair offspring in relation to position in the laying order, for females that incubated less and more than average (0.81 h) on the first night after laying start. The solid trend line represents the model prediction for the average duration of incubation and the dashed lines represent the model predictions for 1 standard deviation (0.32 h) less and more than average incubation. Sample sizes for each position in the laying order are depicted for both below (n−) and above (n+) average incubation durations

Mentions: Incubation on the first night after laying start was not affected by the experimental treatment (n = 37 control and 40 experimental nests, t = 1.05, df = 75, P = 0.30), which allowed us to combine all nests to test whether incubation duration at this stage predicted the likelihood of individual hatchlings being sired by an extra-pair male. Together with the effect of laying order (see also above), the likelihood of EPP was indeed strongly related to incubation on the first night (Fig. 4; laying order: χ2 = 23.71, df = 1, P < 0.001; incubation: χ2 = 7.57, df = 1, P = 0.006). Inclusion of the interaction term indicated that the likelihood of EPP declined more steeply with laying order when females incubated less on the first night (Fig. 4; laying order × incubation: χ2 = 12.64, df = 1, P < 0.001). Visual inspection of Fig. 4 suggests that this primarily reflected an increased likelihood of EPP among the first eggs in clutches of females that incubated less (Fig. 4). Nevertheless, when only clutches with mixed paternity were included in the analysis, there was still a highly significant interaction between laying order and first-night incubation on EPP (coefficient ± SE = 0.83 ± 0.24, χ2 = 12.13, df = 1, P < 0.001).Fig. 4


Declining extra-pair paternity with laying order associated with initial incubation behavior, but independent of final clutch size in the blue tit.

Vedder O, Magrath MJ, Niehoff DL, van der Velde M, Komdeur J - Behav. Ecol. Sociobiol. (Print) (2011)

Average (±binomial SE) proportion of extra-pair offspring in relation to position in the laying order, for females that incubated less and more than average (0.81 h) on the first night after laying start. The solid trend line represents the model prediction for the average duration of incubation and the dashed lines represent the model predictions for 1 standard deviation (0.32 h) less and more than average incubation. Sample sizes for each position in the laying order are depicted for both below (n−) and above (n+) average incubation durations
© Copyright Policy
Related In: Results  -  Collection

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Fig4: Average (±binomial SE) proportion of extra-pair offspring in relation to position in the laying order, for females that incubated less and more than average (0.81 h) on the first night after laying start. The solid trend line represents the model prediction for the average duration of incubation and the dashed lines represent the model predictions for 1 standard deviation (0.32 h) less and more than average incubation. Sample sizes for each position in the laying order are depicted for both below (n−) and above (n+) average incubation durations
Mentions: Incubation on the first night after laying start was not affected by the experimental treatment (n = 37 control and 40 experimental nests, t = 1.05, df = 75, P = 0.30), which allowed us to combine all nests to test whether incubation duration at this stage predicted the likelihood of individual hatchlings being sired by an extra-pair male. Together with the effect of laying order (see also above), the likelihood of EPP was indeed strongly related to incubation on the first night (Fig. 4; laying order: χ2 = 23.71, df = 1, P < 0.001; incubation: χ2 = 7.57, df = 1, P = 0.006). Inclusion of the interaction term indicated that the likelihood of EPP declined more steeply with laying order when females incubated less on the first night (Fig. 4; laying order × incubation: χ2 = 12.64, df = 1, P < 0.001). Visual inspection of Fig. 4 suggests that this primarily reflected an increased likelihood of EPP among the first eggs in clutches of females that incubated less (Fig. 4). Nevertheless, when only clutches with mixed paternity were included in the analysis, there was still a highly significant interaction between laying order and first-night incubation on EPP (coefficient ± SE = 0.83 ± 0.24, χ2 = 12.13, df = 1, P < 0.001).Fig. 4

Bottom Line: Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction.Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring.This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species.

View Article: PubMed Central - PubMed

ABSTRACT
Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species.

No MeSH data available.