Results

Male Cory’s Shearwaters were consistent in their migratory strategy during the two tracked years – of the 75 males tracked in both years, none changed strategy. In total, 19 males remained predominantly in the Canary Current over the non-breeding season while 89 migrated to the South Atlantic.

Exploration

Annual cycle stage significantly influenced emergence into the novel environment – while 59% and 51% of individuals left the box when tested during incubation periods in 2016 and 2017 respectively, only 28% did during pre-laying 2017. The latency to leave the box was also determined by age, with a decrease in exploration in older birds (Table 2, Fig. 1).
Emergence was not repeatable over the whole dataset (R = 0.103, CI = 0 – 0.282, p = 0.212), nor when analysing only data collected during incubation (R = 0.08, CI = 0 – 0.229, p = 0.304). Mixed effect model results also suggest that individual emergence is not related to its migratory strategy (Table 3, n = 85 observations of 69 individuals).

Extraction score

Annual cycle stage and age had no influence on extraction score after controlling for migratory strategy (Table 2). Repeatability estimates suggest that Cory’s Shearwaters are consistent in their response on extraction, rarely switching from “reactive” to “unreactive” responses over the course of the two years (R = 0.646, CI = 0.253 – 0.711, p <0.0001). However, repeatability values are inflated due to the omission of behaviours that did not classify under the two extremes.
Migratory males were far more likely to have been reactive towards extraction from the nest than were resident males (Est = 4.03 ± 1.55, z = 2.61, p = 0.009, n = 175 observations of 85 individuals) (Fig. 2).