Table 1.

Nanostructural measurements of barbules from belly feathers of members of grackles and allies. (All values are in nanometres, except where otherwise indicated.)

species	cortex thickness	outer melanin layer thickness	number of melanin granules	diameter of melanin granules	melanin density in outer layer (%)	melanin density in inner layer (%)
red-winged blackbird Agelaius phoeniceus	111.52±3.37	188.96±5.25a	1a	188.96±5.25a	70.24±7.53	44.73±2.50
scrub blackbird Dives warszewiczi	164.51±6.16	367.97±44.62	2.28±0.33	161.55±11.01	61.03±14.22	20.65±3.45
bobolink Dolichonyx oryzivorus	241.12±27.51	331.75±13.17	1a	331.75±13.17	55.37±7.69	43.55±2.33
bronzed cowbird Molothrus aeneus	82.38±2.37	223.61±7.28	1.89±0.07	118.38±3.24	76.91±4.54	35.65±4.20
brown-headed cowbird Molothrus ater	121.29±1.98	265.92±8.43	1.17±0.03	227.93±6.90	63.33±1.59	20.66±1.95
shiny cowbird Molothrus bonariensis	84.22±2.56	281.50±10.05	1.33±0.04	211.12±11.74	78.99±4.98	28.27±2.05
screaming cowbird Molothrus rufoaxillaris	117.06±3.97	229.39±6.32a	1a	229.39±6.32a	68.31±3.62	40.70±2.64
great-tailed grackle Quiscalus major	123.47±2.28	438.05±25.33	2.93±0.20	139.34±8.22	55.37±7.96	25.66±1.54
boat-tailed grackle Quiscalus mexicanus	111.94±5.48	391.05±20.01	2.90±0.12	134.84±10.02	48.52±5.13	17.82±3.98
giant cowbird Scaphidura oryzivora	61.14±1.21	274.18±8.94	1.08±0.01	253.70±4.03	80.45±9.58	34.21±2.71
western meaddowlark Sturnella neglecta	110.18±7.89	230.34±6.33	1a	230.34±6.33	70.33±6.53	42.33±2.20

^aClear outer melanin layers were not present in these species, and we therefore measured the diameter of the single outermost melanin granule at six points on the barbule.