Comparison of Hatching Failure in a Wildland and Suburban Population of the Florida Scrub-Jay (<em>Aphelocoma coerulescens</em>)
Egg hatchability has been correlated with many factors, including clutch size, presence of helpers, timing of breeding and predation risk. Hatching failure is higher in a suburban population of Florida Scrub-Jays than in a wildland population, but the reasons for this pattern are unclear. An analysi...
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| Format: | Others |
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Scholar Commons
2005
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| Online Access: | https://scholarcommons.usf.edu/etd/736 https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1735&context=etd |
| Summary: | Egg hatchability has been correlated with many factors, including clutch size, presence of helpers, timing of breeding and predation risk. Hatching failure is higher in a suburban population of Florida Scrub-Jays than in a wildland population, but the reasons for this pattern are unclear. An analysis of long-term demographic data on scrub-jays in both habitats revealed the factors that best explained variation in hatching failure, and an experiment tested whether two potential site factors, ambient temperature and predation risk, could increase hatching failure in the suburbs.
Although a global model was best supported by the data for occurrence of partial hatching failure (PHF), clutch size and site were the most significant parameters in this model, which is consistent with the analysis of rates of PHF. I further examined two potential site differences, ambient temperature and predation risk, which might increase PHF in the suburbs.
Human activity may increase the perception of predation risk, thus suburban jays may take fewer, longer off-bouts or make fewer incubation feedings to decrease this perceived risk. These behavioral changes may increase nest temperature, thus increase embryo mortality. I placed thermocouples and video cameras at nests during incubation to gauge both ambient and nest temperature and behavior of scrub-jays at each site. I predicted higher ambient temperatures in the suburbs, because suburban areas often serve as heat islands. I also predicted fewer, longer off-bouts and fewer feedings in the suburbs and where human activity was increased experimentally. Ambient temperatures were higher in the suburbs as a result of higher daily minimums rather than higher maximums. Furthermore, females exposed to increased human activity took fewer but not longer off-bouts than suburban or wildland controls; therefore, they increased their nest attentiveness. |
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