Table 2.

Estimated values of advancing contact angles (θ_adv) for water on the waxy preen oil coating that is present on a feather, critical angular location (ϑ_c), predicted breakthrough pressure for water droplets (P_b) and the corresponding transition mode are compiled for the uncoated wing feathers of the six bird species. The last two columns contain empirically observed diving depth and wing-spreading behaviour for the same bird species.

bird species	estimated CA θadv (°)	critical angular location ϑc (°)	predicted breakthrough pressure, Pb (kPa)	predicted transition mode	diving depth (m)	wing-spreading
African darter	112 ± 2	68	28	depinning	<5	Y
reed cormorant	118 ± 2	73	40	depinning	5–6a	Y
great cormorant	117 ± 6	62	19	depinning	4.7, <10b	Y
mallard	105 ± 3	57	13	sagging	dabbling	N
European shag	106 ± 3	58	12	sagging	33–35	Y
common shelduck	116 ± 2	61	13	sagging	dabbling	N

^aFrom neutral buoyancy experiments, not natural observation.

^bUsually < 10 m, but can dive to depths of 35 m [40]; wing-spreading: Y, predictably; N, never; dabbling, dabbling species, not primarily divers.