ALDREDGE, R.A.*; BOWMAN, R.; BOUGHTON, R.K.; SCHOECH, S.J.; BRIDGE, E.; Archbold Biol. Stn., FL; Archbold Biol. Stn., FL; Univ. of Memphis, TN; Univ. of Memphis, TN; Univ. of Memphis, TN: Increased ambient temperatures in an urban landscape affect hatching success of the threatened Florida scrub-jay Aphelocoma coerulescens

Ambient temperature has important physiological consequences on the viability of eggs. According to the egg viability hypothesis eggs exposed to ambient temperatures for prolonged periods prior to the onset of incubation have reduced hatchability. Data collected over two years show that daily ambient temperatures differ between a suburban and a wildland site in south central Florida. We studied the effects of these differences on the hatchability of eggs. We hypothesized that the suburban population would have decreased viability of earliest laid eggs within a clutch. We recorded clutch initiation date, number of laying days, clutch size, number of incubation days (days between last laid egg and first hatched egg), pre-incubation and total egg water loss, and pre-incubation embryonic development as potential factors affecting egg viability. Using logistic regression we found that the hatchability of entire clutches was affected only by site and the number of days of incubation. Specifically, first-laid eggs in the suburban population had lower viability than first-laid eggs in the wildlands, supporting the egg viability hypothesis. In addition, the mean number of incubation days was lower in the suburbs. Ambient daily temperature increased in both sites as the season progressed, and a negative relationship existed between the number of incubation days and the advancing season. This suggests that as ambient temperature increases, jays may respond by initiating incubation before the clutch is completed, thus decreasing the duration that un-incubated eggs are exposed to ambient temperatures. This may be a behavioral adaptation to reduce decreased viability of the first laid egg in warm environments.