Fig 1.
Phenology of Snares penguins and Fiordland penguins, highlighting the post-moult non-breeding seasons.
As is typical of Eudyptes species, Snares penguins (purple) begin their non-breeding season at the end of April while Fiordland penguins (turquoise) begin their non-breeding season around 8 weeks before, at the end of February.
Fig 2.
Distribution of Fiordland and Snares penguins during the post-moult non-breeding season.
Coloured fill indicates 50% (core usage; darker) and 90% (peripheral distribution; paler) utilisation distributions for Fiordland penguins (turquoise) and Snares penguins (purple). The orange stars indicate the Fiordland breeding colonies along the New Zealand mainland coast of Southwestland and Fiordland and on Codfish Island off the south of New Zealand and the yellow star indicates the Snares Islands where Snares penguins breed. North of STF = North of the Sub-Tropical Front, SAFZ = Sub-Antarctic Frontal Zone, PFZ = Polar Frontal Zone and SACCFZ = Southern Antarctic Circumpolar Current Frontal Zone. Grey lines represent bathymetric contours with 1000 m interval.
Fig 3.
Usage of the different water masses by Fiordland penguins and Snares penguins during the non-breeding season.
Water masses are: North of STF = north of the Sub-Tropical Front, SAFZ = Sub-Antarctic Frontal Zone, PFZ = Polar Frontal Zone and SACCFZ = Southern Antarctic Circumpolar Current Frontal Zone.
Table 1.
Summary of track statistics (±SD) for Fiordland penguins and Snares penguins tracked during the post-moult dispersal period using light based geolocators.
Table 2.
Backwards elimination step-wise models of differences for trip characteristics between Fiordland penguins and Snares penguins tracked during the post-moult dispersal period.
Fig 4.
Monthly anomalies from trip speed for tracked Fiordland penguins and Snares penguins over the non-breeding season.
The Fiordland penguin migration takes place from February to July, while the Snares penguin migration takes place from April to September. Mean individual travelling speeds were 0.57 ± 0.4 m.s-1 and 0.63 ± 0.4 m.s-1 for Fiordland penguins and Snares penguins, respectively. Fiordland penguins had the slowest speeds during the months of April and May, and Snares penguins during the months of June and July.
Fig 5.
The core (50% UD) and peripheral (90% UD) non-breeding distributions for Snares (purple) and Fiordland (turquoise) penguins.
February (the month when the Fiordland penguins first set out) and September (when the Snares penguins return to their colonies) were excluded as they only represented one week of data each.
Fig 6.
Weekly Utilisation distribution overlapping statistics and area under the curve comparisons between observed and synchronous migrations.
Overlap indices for the core area (50% isopleth; dark grey) and the peripheral utilisation distributions (90% isopleth; light grey) for a) the observed and b) the synchronous migrations for Snares and Fiordland penguins during their non-breeding season presented with the relative percentage of time lapsed across the non-breeding season. The period of time in a) runs from the start of the Fiordland penguin migration (at the end of February) to the end of the Snares migration (which ends at the beginning of September). At the start of the observed migrations Fiordland penguins embark on their migrations. After 8 weeks, the Snares first start their migration (indicated by the arrow). The dark grey rectangle (a) represents the period when the Snares penguins would still be on their pre-moult trip (overlapping with the post-moult migration of the Fiordland penguins). During the synchronous migrations (b), Snares and Fiordland penguins were assumed to leave and return simultaneously.
Fig 7.
The synchronous core (50% UD) and peripheral (90% UD) non-breeding distributions for Snares (purple) and Fiordland (turquoise) penguins.
The start of the Fiordland penguins migration was shifted later in time by two months to coincide with the start of the Snares penguins migration (i.e. the Fiordland penguin distribution for March was shifted to May, etc.). February (the month when the Fiordland penguins first set out) and September were excluded as they only represented one week of data each.