Figure 1.
Examples of the migratory paths of Cory’s shearwaters to each wintering area (A) and stopovers locations (B).
Dots represent wintering locations (panel A): orange – Benguela and Agulhas currents; white – Brazilian current and central South Atlantic; light blue – northwest Atlantic (the positions of the birds that stayed on Canary current are not shown). Green dots (panel B) represent stopovers locations. Red star indicates the colony location.
Figure 2.
Relationship between departure date and mean (± SE) daily speed during the outward (A) and return (B) migrations.
Open symbols (panel A) represent birds that stopped over (n = 33) and closed symbols birds that did not make stopovers (n = 30). Grey line represents the predicted probability of stopover occurrence considering the departure date from the colony (secondary y-axis; significant negative effect of departure date on the probability of stopping over during the outward migration; slope of the logistic regression = −0.045±0.02; P = 0.03). None of the birds made stopovers during the return migration (panel B; n = 30).
Table 1.
Summary of the main activity patterns (means ± SE) of Cory’s shearwaters among the different stages of the non-breeding period.
Figure 3.
Frequency of individuals starting flight bouts during a 24 h period, in each stage of the non-breeding period.
Solid line represents the mean and dashed line the SE. Grey areas correspond to sunrise and sunset intervals (mean ± SD).
Figure 4.
Comparison of some behavioural parameters among stages of the non-breeding period and lunar phases.
O Mig – outward migration; R Mig – return migration; Stop: Stopovers; Wint – Wintering period; black circles – new moon; open circles – full moon; grey circles – lunar quarters (see methods). Means are presented ± SE.
Figure 5.
Variation in the flight activity patterns (means ± SE) along the latitude gradients crossed during the outward and return migrations.
Note that latitude values (x-axis) varies southwards first (outward migration), and northwards after the grey bar (that represents the winter area), thus mirroring the temporal order at which the birds crossed each latitude.
Table 2.
Comparison of the activity patterns (means ± SE) of Cory’s shearwaters between the pre-migratory phase of the wintering stage (a 15 days period before return migration: “-pre-migration”) and a period of equivalent duration 28 days before the former (“mid-winter”).
Figure 6.
Variation of the night flight index (NFI) along the migratory routes (A) and sea surface temperature in the Atlantic Ocean (B).
The NFI (panel A) reflects the amount of flight allocated to the night time, considering the relative duration of the night period (a value of 0 corresponds to a proportional allocation of the flight effort to the daylight and darkness; see methods); colours range from red (NFI = -1; i.e., flying exclusively during daylight) to blue (NFI = 1; i.e., flying exclusively during darkness). Colour gradient (panel B) reflects the sea surface temperature in the Atlantic Ocean during November 2007 and varies between blue (−2°C) and orange (30°C).