Extant from deep time

This post is about Mousebirds, an ancient group of small arboreal birds which could be considered “living fossils” being survivors of a lineage that was massively more diverse in the late Paleogene and Miocene ages. These birds are unrelated to anything else alive today. They are morphologically unique and were proposed as a separate Order of birds as long ago as 1872.

“There is a popular misconception that natural selection is synonymous with evolution. If a species isn’t adapting by obvious changes over time then it isn’t evolving. Are external morphological changes the only evidence of evolution? Physical fossil analysis suggests so but there is plenty of evidence that this is not true, DNA analysis for starters!”

Mousebirds are classified in the order Coliiformes because these birds look like mice when they creep along tree branches. In this order there is only one family, Colliidae. This family comprises two genera. The skeletons of the two genera are different, and Urocolius Mousebirds are stronger fliers, while Colius Mousebirds spend most of their time ‘creeping’ through the vegetation, like small rodents, giving rise to their family name.

Genus Colius
• Speckled Mousebird, Colius striatus
• White-headed Mousebird, Colius leucocephalus
• Red-backed Mousebird, Colius castanotus
• White-backed Mousebird, Colius colius
Genus Urocolius– from Eastern and Southern Africa
• Blue-naped Mousebird, Urocolius macrourus
• Red-faced Mousebird, Urocolius indicus

Mousebirds is the only Order which is restricted to sub-Saharan Africa. They are very adaptable, and can be found in forest edges, thickets, gardens, orchards, strandveld, riverine woodland and alien tree plantations, usually foraging in the mid to upper canopy of trees. They feed on a wide variety of plant matter – often fruit, but also flowers, nectar, leaves, buds and dead bark. These birds have adapted to man-made habitats, and are even considered a ‘pest’ in some places because they eat so much fruit.

Three species of Mousebird found in southern Africa. The White-backed Mousebird is found in South Africa and Namibia, the Speckled Mousebird is found in South Africa and Mozambique and the Red-faced Mousebird is found throughout southern Africa.

Speckled Mousebird- Colius striatus

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The four species of Colius Mousebirds are essentially allopatric (a scientific name for geographic isolation) in distribution, without any significant overlap. Where there is a little range overlap, they separate out by habitat.

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Like Swifts, Mousebirds are pamprodactylous meaning their two outer toes are reversible, so all four toes can be directed forward at will. Being able to rotate all four toes to face forward enables them to feed upside down, hold food with their feet, and perch with their legs positioned at strange angles. Their feet are large, and their legs widely spaced, so Mousebirds do not perch like most other species and tend to rest their abdomens on their perch.

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Both sexes have erectile crests on their heads. Their plumage is usually a dull grey or brown and unremarkable. Mousebirds do though have very long tail feathers and unusual mannerisms. They have a habit of perching with the body vertically suspended between the widely splayed feet, held apart at chest level.

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Their beaks look “finch-like” though they are not seed eaters as they do not have a developed crop. They are arboreal and scurry along tree branches like rodents, in search of berries, fruit and buds. Between the lower jaw and the base of the skull is a supplementary joint, much like a snake, which enables Mousebirds to swallow large bits of food. The upper bill acts as a plow, furrowing sections of the fruit, and the lower mandible acts as a scoop. They drink water by sucking it into the mouth, similar to pigeons and doves.

“Nature teems with consciousness—with intelligence—an insight shared by shamans and indigenous people long before modern humans used our “intelligence” to disengage from the rest of the natural world.”

 Red-faced Mousebird-Urocolius indicus

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The Colius and Urocolius genus differ substantially in skeletal and other aspects. In the Urocolius genus, the bones of the wing and pectoral girdle are relatively more robust, and those of the legs and pelvic girdle relatively weaker, than those of Colius. This reflects the relative locomotory capacities of the two genera, Urocolius being stronger fliers and Colius more adept at creeping.

Mousebirds are essentially frugivorous (fruit-eating) birds. They spend most of their time in the dense foliage of trees and shrubs, through which they move rapidly and with surprising agility, continually demonstrating their acrobatic prowess. They scurry rapidly lengthwise along horizontal branch surfaces, supporting themselves with the tarsi, tail and beak. I would normally not show a bird with placed food but wanted to show their surprising agility.

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Contour feathers cover the Mousebird’s body almost uniformly, and have loose distal barbs owing to an incomplete development of barbules, This feather feature is thought to be an adaptation allowing them to move easily through dense scrub. This is also what gives them their hair-like appearance of their body feathers.

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I hope this short discussion around Mousebirds has shown you an intriguing view of the lineage, depth and adaption in just this one piece of nature’s jigsaw puzzle which you would not normally give a second thought. This is yet another example of the idea that there are libraries of knowledge yet to be learned from nature with her wonderful tapestry woven together in ways we have yet to fathom.

” It is the marriage of the soul with nature that makes the intellect fruitful, and gives birth to imagination”

– Henry David Thoreau

Explore, seek to understand, marvel at its interconnectedness and let it be.

Have fun

Mike

One thought on “Extant from deep time

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