Table 2.

Durations, distances, and travel speeds for different segments of the annual migration circuit of arctic terns

Segment	Mean dates	Duration (days)	Mean distance (km)	Min‐max distance (km)	Mean speed (km/day)
Breeding area – N Atlantic	15 July to 29 July	14	3,560		254
N Atlantic – Equator	29 July to 12 August	14	7,110		508
Equator – South Africa	12 August to 6 September	25	4,290		172
South Africa – Antarctica	6 September to 7 November	62	10,880	7,750–16,400	175
Antarctica, E to W	7 November to 13 March	126	7,890	5,450–10,990	63
Antarctica – N Atlantic	13 March to 10 April	28	12,710		454
N Atlantic – breeding area	10 April to 26 April	16	4,460		279
Total nonbreeding migration circuit	15 July to 26 April	285	50,900	45,330–59,520	179

Durations are estimated from mean dates given in Table 1. Mean distances have been schematically calculated along loxodromes between mean locations as given in note below table (see also Table 1). Distances have also been estimated for the two journeys with shortest (ind. D) and longest (ind. E2) segments in the Indian Ocean and Antarctica (Table 1). Locations used for schematic distance calculations: Breeding area – N Atlantic (56N, 14.5E–43N, 31W), N Atlantic – Equator (43N, 31W–0N, 13W–0N, 5E), Equator – S Africa (0N, 5E–36S, 20E), S Africa – Antarctica (36S, 20E–40S, 100E–65S, 141E), Antarctica (65S, 141E–65S, 27W), Antarctica – N Atlantic (65S, 27W–30S, 5E–34N, 34W), and N Atlantic – breeding area (34N, 34W–56N, 14.5E). Locations for minimum distance: S Africa – Antarctica (36S, 20E–40S, 75E–65S, 89E), Antarctica (65S, 89E–65S, 27W). Locations for maximum distance: S Africa – Antarctica (36S, 20E–40S, 160E–65S, 207E), and Antarctica (65S, 207E–65S, 27W).