Table 1.

Biometrics and gliding airspeeds for individual vultures. Birds showed inter-individual differences in airspeeds (Va) through the glide (F = 214.110410,4, p < 0.001) and their median airspeeds were greater than their Vbg, calculated from the following biometric data: wing loading (in kg m−2) (WL), aspect ratio (AR) and mass (kg) (M). The theoretical minimum sink (Vms) and best glide speeds (Vbg) are given for reference, as are the numbers and durations of inter-thermal glides (ITGs) performed by the bird that were defined as uninformed (S1) and informed (S2).

vulture (age)biometricsITG (s)theoretical optimaVa (m s−1)Va regression
G. fulvus
adult (18)
WL: 7.77
AR: 6.61
M: 7.7
44.8 ± 9.2
(N = 4)
S1 = 4, S2 = 0
Vbg: 14.4 m s−1
Vms: 9.20 m s−1
14.86 ± 1.49Embedded Image
G. fulvus
immature (3)
WL: 7.28
AR: 6.88
M: 7.14
98.0 ± 42.0
(N = 8)
S1 = 4, S2 = 3
Vbg: 13.8 m s−1
Vms: 8.80 m s−1
16.30 ± 2.58Embedded Image
G. fulvus
immature (4)
WL: 7.06
AR: 6.73
M: 7.2
67.1 ± 50.6
(N = 6)
S1 = 5, S2 = 1
Vbg: 13.7 m s−1
Vms: 8.70 m s−1
15.11 ± 2.57Embedded Image
G. himalayensis
adult (19)
WL: 7.18
AR: 6.95
M: 8.1
77.0 ± 50.8
(N = 10)
S1 = 6, S2 = 4
Vbg: 13.8 m s−1
Vms: 8.70 m s−1
16.34 ± 2.80Embedded Image
G. himalayensis
immature (4)
WL: 6.63
AR: 5.98
M: 8.45
62.7 ± 38.6
(N = 8)
S1 = 5, S2 = 3
Vbg: 13.8 m s−1
Vms: 8.70 m s−1
16.56 ± 3.47Embedded Image