Visual Differences Between Species

The 6 species of mousebirds are placed in 2 genera, Colius and Urocolius, which have several differences in visual appearance and skeletal. Within this site I will cover 3 of the 4 species that have been in The US. Of these I have only worked with 3 species: White-backed, Red-faced, Blue-naped and will use these species for illustrations. Click on the photos below for a larger view.

Urocolius: Blue-naped and Red-faced

Colius: White-backed, Speckled, White-head (not shown)

NOTE: I will note on the illustrations if a species is Uroclolius or Colius
1...Skeletal: The bones of the wing, pectoral girdle are more developed, and the legs and pelvic region of the are weaker, which makes the Urocolius better adapted to flying. Whereas the Colius are more adept at creeping, and scampering in foliage.
2...Wings: All mousebirds have 10 primary, and 10 secondary flight feathers. The Urocolius wings are shorter and wider which better adapts them for flight. Click on each photo for a larger view.
3...Tails: The Urocolius have a narrower tail consisting of 5 pairs of feathers. The Colius have 6 pairs of feathers (rectrices)
4...Bills: The Urocolius have a decurved upper mandible (20 degree downward curve), which as facial face surrounds the eyes in a diamond pattern in the same color as the upper mandible when mature. The Colius is straight. When young the upper mandible has a greenish cast which fades and disappears as the chick is ready to fledge.  Click on each photo for a larger view.
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5...Eyes From my experience all mousebirds when young have a brown iris and black pupil. The illustrations below show the changes to the eye color as the bird ages. 
Click on each photo for a larger view.
6...Eggs: The Urocolius lay patterned eggs and the Colius eggs are unmarked. Blue-Naped will be marked with maroon speckles and spots, and the red-faced will have reddish brown markings.
7...Chicks: The Urocolius chicks have very sparse white down which is seen in small tufts on the lower back, and a bulbous swelling towards the base of the bill, and pink tongues. The Colius chicks have a light coat of short, nappy dark grey down, and a bright yellow tongue.  Click on each photo for a larger view.
8...Crests: The shape varies between the species, as shown below.  Click on each photo for a larger view.
9...Feet: When chicks the feet of both genera are pale colored, and as they get to fledgling age the color comes in. The Colius have larger feet than the Urocolius. Their feet is a bright salmon red color. The urocolius feet deepen to a dark purple-red, and the toes are slightly thinner than the Colius.  Click on each photo for a larger view.
10...Monomorphic: From all my reading and research it is said that both sexes of all species look the same (monomorphic) but I am finding that this may not be entirely true. In working with the BN (blue-naped) I have noticed that at approx 12 days of age that some chicks will get a very pale/dilute blue patch on the back of the head and some don’t In having the chicks DNA sexed I’m learning that the males do show this patch at 9-12 days of age, and the females do not. I have a BN pair on eggs, and I will be watching the nape as the chicks feather out to see if this occurs again, and confirm my observations with sexing. I would love to hear from other breeders/keepers of BN to learn if they have observed the same thing.  Click on each photo for a larger view.
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