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).