Eggshell Porosity in Relation to Brood Hatching Patterns in House Wrens (Troglodytes aedon)
Submission Type
Event
Expected Graduation Date
2014
Location
Center for Natural Sciences, Illinois Wesleyan University
Start Date
4-12-2014 9:00 AM
End Date
4-12-2014 10:00 AM
Disciplines
Biology
Abstract
In bird species, the eggs of a clutch may hatch asynchronously over several days, which results in offspring that differ considerably in size shortly after hatching due to the growth advantage of earlier hatched siblings. As a result, the last-hatched nestlings may be outcompeted for food by older siblings and die of starvation. In contrast, if the eggs of a clutch hatch synchronously (i.e., within a day of one another), siblings are similar in size. Maternal incubation can influence brood hatching patterns in that commencement of incubation prior to laying the penultimate egg results in an asynchronously hatched brood, whereas delaying incubation until the penultimate or ultimate egg is laid results in a synchronously hatched brood. Variation in eggshell porosity (i.e., total eggshell pore area ÷ eggshell thickness) may also explain differences in developmental rates and hatching spans among siblings. Eggshell pores permit gas exchange to/from the developing embryo, and higher rates of gas exchange may accelerate rates of development. In this study, we assessed within- and among-clutch variation in eggshell porosity by determining the number of pores, pore diameter, and eggshell thickness in a population of House Wrens (Troglodytes aedon). We then compared those data to the commencement of incubation by females. We found that females that initiated full incubation before laying all of their eggs produced eggshells with more pores and slightly greater porosity, on average, than females that delayed incubation until clutch completion.
Eggshell Porosity in Relation to Brood Hatching Patterns in House Wrens (Troglodytes aedon)
Center for Natural Sciences, Illinois Wesleyan University
In bird species, the eggs of a clutch may hatch asynchronously over several days, which results in offspring that differ considerably in size shortly after hatching due to the growth advantage of earlier hatched siblings. As a result, the last-hatched nestlings may be outcompeted for food by older siblings and die of starvation. In contrast, if the eggs of a clutch hatch synchronously (i.e., within a day of one another), siblings are similar in size. Maternal incubation can influence brood hatching patterns in that commencement of incubation prior to laying the penultimate egg results in an asynchronously hatched brood, whereas delaying incubation until the penultimate or ultimate egg is laid results in a synchronously hatched brood. Variation in eggshell porosity (i.e., total eggshell pore area ÷ eggshell thickness) may also explain differences in developmental rates and hatching spans among siblings. Eggshell pores permit gas exchange to/from the developing embryo, and higher rates of gas exchange may accelerate rates of development. In this study, we assessed within- and among-clutch variation in eggshell porosity by determining the number of pores, pore diameter, and eggshell thickness in a population of House Wrens (Troglodytes aedon). We then compared those data to the commencement of incubation by females. We found that females that initiated full incubation before laying all of their eggs produced eggshells with more pores and slightly greater porosity, on average, than females that delayed incubation until clutch completion.