Ground Tit

BirdCentral Asia

Jan 5

Written By Alexander Julius Jensen

Pseudopodoces humilis

A resident of the Tibetan Plateau, the ground tit lives above the treeline at elevations no lower than 3,000 metres (9,800 ft). It moves along the ground in unpredictable dashes and hops — said to resemble a bouncing rubber ball — and digs burrows for nesting and shelter.

Left to right; a yellow-cheeked tit (*Machlolophus spilonotus*), great tit (*Parus major*), and Eurasian blue tit (*Cyanistes caeruleus*).

Tits like trees.

I am referring, of course, to the family of birds called the Paridae — variably known as tits, titmice, and chickadees. These songbirds are woodland sprites. They forage in the trees; flitting from branch to branch, hanging upside-down like little acrobats to peck up insects and seeds. They hide in them; safe from ground predators in the canopy world and concealed from soaring sparrow hawks and owls in tangles of twigs and leaves. And they nest beneath their bark; excavating nest hollows in tree trunks and branches, where broods are safe inside wombs of wood. A tree is a larder, a shelter, and a nursery. All of the 60 or so species of tit rely, in some part, on trees. That is, all except one.

Treeless Heights

Trek up any tall mountain and you'll notice the trees begin to thin out. The forests give way to sparse groves, the groves to scattered and lonely trees, stunted and short, until there is little but low shrubbery clinging to windswept rocks. You've passed the 'treeline' — the boundary above which wood-trunked plants cannot grow. This line exists across both altitudes and latitudes; there are treelines at the northern and southern reaches of our planet as there are on every mountain tall enough to inspire awe. And just as the line varies, zigs and zags, across the Arctic north and the frozen south, the exact boundary is different for every range and mountain.¹

In parts of the Andes, forests can grow at elevations as high as 5,000 metres (16,400 ft), while the hardy birches of the Scandinavian Mountains disappear before reaching 1,000 metres (3,300 ft). Across the world's mightiest mountain range, the Himalayas, the treeline rises and falls between heights of 3,200 and 4,900 metres (10,500 - 16,000 ft). Generally, as the trees thin out with altitude, so does most other life. Few things live where trees cannot. You'll only find the hardiest creatures up here — hoofed mountaineers and ghostly snowcats. And a little bouncing bird.

The Odd Tit Out

The ground tit lives across the Tibetan Plateau, from northern India, across Nepal and Bhutan, and into western Sichuan and Gansu in China. Completely counter to its elfin relatives and their arboreal lifestyles, the ground tit avoids dense shrubbery and trees, often by living where trees don't grow at all — the average elevation of the Tibetan Plateau is 4,500 metres (14,760 ft) above sea level and the tit rarely descends below 3,000 m (9,800 ft). That is, in any given part of the plateau, it lives above the treeline, among highland pastures and alpine steppe, where its muted grey-brown plumage fades into the dry grasses and rocky outcrops.

It stands with impeccable posture. It moves unpredictably, making little use of its wings, flying low across the ground if at all, and much use of its long, strong legs. It travels in sprints and leaps — performing jumps that cover thrice its own body length — bouncing around like an animate and hyperactive rubber ball, whistling and "cheep-cheep-cheeping" all the while. One wonders where it finds enough energy in this cold and desolate place. The answer is in rocky crevices and holes in the ground, or in the yak dung which it probes with its decurved beak to find arthropod prey.

Underground Architect

The ground tit is friendly with its alpine neighbours, often hanging out alongside Himalayan marmots and pikas and, like other Paridae (tits), it is a cavity nester, just not in the traditional sense. Instead of excavating a hole in a (non-existent) tree, it digs one in the ground. However, it seems averse to borrowing an uninhabited burrow from any furry diggers (as other burrowing birds, like burrowing owls, often do) — perhaps it doesn't like the musky mammal smell, or more likely, the construction of the burrow doesn't meet its strict specifications. The ground tit digs its first burrow in spring; a simple, straight tunnel around 130 cm (51 in) long, terminating in an ovular chamber some 30 cm (12 in) beneath the ground. This little nook is turned into a nest with a lining of grasses and wool, and, inside, a clutch of pure white eggs is laid — to be tended by a monogamous mated pair and often one or more male helpers (these being young from the previous year, who were unlucky in love and couldn't find any mates).

Once its latest brood has left the nest, the ground tit begins construction on a second burrow. This one is similar to its first in most ways, aside from a conspicuous lack of eggs. This is its winter burrow — a shelter, not a nest. As it did for its spring burrow, the tit plans out construction like a little architect, adjusting the dimensions and location of its subterranean home in relation to the sun and wind. Typically, a burrow is oriented towards the sun and away from the prevailing wind, probably to maintain a more consistent internal temperature. The length of the tunnel — usually between 100 and 160 cm (39 - 63 in) long — acts like a kind of thermostat. Does the tit want its chamber to retain more heat? If so, it builds a longer tunnel. Does it want the sun to warm its chamber up faster? Then it builds a shorter tunnel. And to prevent a drafty chamber, especially during times of cold winter winds, the tit builds a smaller tunnel entrance. Clearly, no crude pika burrow will suffice for such an accomplished architect as the ground tit.

Hume's Ground-Jay

This alpine resident looks unlike any other tit — more jay than Paridae — which has, in the past, caused some confusion among ornithologists and taxonomists. Its "deceptive" appearance, as well as its strange habits, are no accident, but evolutionary adaptations to the high-altitude and cold, often arid, climate of the Tibetan Plateau.

Clockwise from left; an Iranian ground-jay (*Podoces pleskei*), Mongolian ground-jay (*Podoces hendersoni*), and Turkestan ground-jay (*Podoces panderi*).

Across central Asia live a group of birds known as ground-jays (in the genus Podoces). These are true corvids — part of the Corvidae family with crows, magpies, and other jays — but they aren't your typical corvids. They're specialists of high-altitude, semi-desert environments, where trees are few if present at all, and most food is foraged amidst boulders and shrubs or dug up from beneath the soil. As such, these jays are weak fliers but strong runners, that sprint along the ground on long legs, and jumpers, that hop from boulder to boulder, and their downcurved beaks are sharp-tipped shovels for churning up soil. Sound familiar?

For more than 100 years the ground tit was a ground-jay — Hume's ground-jay, to be specific.² It was considered a relative to the likes of the Mongolian and Xinjiang ground-jays, with their tan plumage and black-capped heads, and the Turkestan and Iranian ground-jays with their black chest "badges." Living in a remote region, alongside similar-looking, ground-dwelling birds, the ground tit was simply lumped in with the ground-jays.

But its position on the avian Tree of Life nagged at ornithologists throughout the 20th century. Several noticed its visual incongruity with the rest of the group, stating that "Pseudopodoces looks more like one of the larks (Alaudidae) than a crow," as well as its behavioural quirks, like the fact that "Pseudopodoces may also nest in its own excavations in earth banks, another non-corvid characteristic." A 1977 study comparing corvid anatomy to that of the ground tit (then Hume's ground-jay), concluded that it lacks certain features that all corvids share and, with some reservations, suggested it might belong with the starlings (in the family Sturnidae). Another study of corvid phylogeny in the 80s agreed that Hume's jay was no jay and no corvid at all, and proposed that it belonged to the large infraorder known as Passerida — which includes all the perching/songbirds (in the order Passeriformes), except for the corvids.

Finally, in the early 2000s, analyses of the chemical composition of the grounds tit's uropygial gland secretion,³ as well as several DNA sequences,⁴ placed this feathered enigma with the Paridae; the tits. Just like that, the ground tit — measuring around 19 centimetres (7.5 in) long — went from being the smallest covid to the largest tit. But, despite clear molecular evidence of its tit-ties, in appearance and behaviour, Pseudopodoces makes for just as atypical a tit as it did a corvid, if not even more so. Comparing the ground tits genome to two of its relatives, the great tit and yellow-cheeked tit, found that it diverged from them between 7.7 and 9.9 million years ago, and has been on its own evolutionary path since.

Along its path, it encountered the frigid temperatures and low-oxygen conditions of the Himalayas — no other tit lives in an environment so inhospitably high and cold — and the ground tit adapted accordingly, with "genes regulating energy metabolism, hypoxia response and skeletal development [that] evolve at higher rates in the ground tit than in two other [tit] species." It evolved traits that are common among high-altitude residents, from yaks to the native people of Tibet. Natural selection, always the thrifty economist, also pruned unneeded traits. Feather β-keratin genes, which contribute to forming the elasticity of feathers and are more abundant in flying birds and less so in flightless ones, are reduced in the ground tit, reflecting its ground-based lifestyle.

It was shaped by its environment into a form better suited to survive, just as the true ground-jays had been, with both bird groups arriving separately at similar solutions — a neat example of convergent evolution. Today, these various alpine birds sprint and hop around on long legs, having little use for wings in their treeless landscapes, and sport drab feathers that disappear against barren backdrops. They're separated into different families, but united, in place and in form, by life on the Tibetan Plateau.

A treeline situation in in SW New Zealand.¹

¹ The treeline not only varies from place to place, but it's also changing as the planet heats up. The following are a few quotes on the issue.

"Scientists from the Southern University of Science and Technology in Shenzhen, China, used remote sensing to map the highest points of patches of tree coverage on mountains. They found that 70% of mountain treelines had moved uphill between 2000 and 2010."

"On average, treelines moved upwards by 1.2 metres (4ft) a year, but the shift was greatest in tropical regions, with an average increase in elevation of 3.1 metres a year – and in all regions they found the rate of change was accelerating. In total, the researchers tracked almost 1m km (620,000 miles) of treeline across 243 mountain regions around the world." (The Guardian)

"In a review of treeline migration studies, Hansson et al. (2021) revealed that on 66 % of 477 treeline sites worldwide, forests have expanded into tundra biomes along elevational and latitudinal gradients." (Noordermeer, et al. 2023)

For an example of an outlier, a study carried out on the semi-arid Mediterranean island of Crete in Greece, "found no shift in the treeline over the past 70 years, despite an increase in temperature" but, as an explanation, posed that "the temporal lag in treeline response to warming could be explained by a combination of topographic and microclimatic factors, such as the absence of a shelter effect [from wind] and a decrease in moisture" and that "the lack of climate-mediated migration at the treeline should raise concerns about the threats posed by warming, such as drought damages, and wildfire, especially in the Mediterranean region." (Mirela Beloiu, et al. 2022)

² The ground tit, once Hume's ground-jay, was — and still is in its scientific name, Pseudopodoces humilis — named after Allan Octavian Hume, a notable British ornithologist that pioneered the study of Indian birds. Alongside the tit (which Hume described as a jay), he has a small aviary of bird species named after him; including Hume's wheatear, Hume's lark, Hume's treecreeper, Hume's leaf and bush warblers, Hume's boobook, as well as a pheasant named for his wife (simply called Mrs. Hume's pheasant).

A diagram and photo of a tit’s uropygial, or preen gland.

³ The uropygial gland, located at the base of a bird's tail, is also known as the preen or oil gland. The gland secretes an oily substance that a bird can spread over its feathers and skin to prevent bacterial infection and parasites, make its feathers waterproof, and maintain their brightness. The chemical composition of the gland's oily secretion is often a good indicator of relatedness between different groups of birds and, as such, has been used to determine the phylogeny (placement on the evolutionary family tree) of different bird species.

⁴ "The re-sequencing data of the two tit species [great tit and yellow-cheeked tit] mapped to 78–80% of the ground tit genome, and to only 9.7% of ground jay. The phylogenetic reconstruction clearly supports the grouping of the ground tit with the other two tit species."

From a 2013 study on the ground tit's high altitude adaptations: Qu, Y., Zhao, H., Han, N. et al. Ground tit genome reveals avian adaptation to living at high altitudes in the Tibetan plateau. Nat Commun 4, 2071 (2013).

**Where Does It Live?**

⛰️ Treeless steppes, grassy plains, rocky hills, yak pastures, and near human settlements.
📍 The Tibetan Plateau; from northern India, across Nepal and Bhutan, and into western Sichuan and Gansu in China.

‘Least Concern’ as of 12 June, 2014.

IUCN

Size // Small
Wingspan // N/A
Length // 19 - 20 cm (8 in)
Weight // 42·5 - 48·5 g (1.5 oz)
Activity: Diurnal ☀️
Lifestyle: Solitary / Pair 👤/👥
Lifespan: N/A
Diet: Omnivore (Insectivore)
Favorite Food: Insects and grubs from the soil 🐜
Class: Aves
Order: Passeriformes
Family: Paridae
Genus: Pseudopodoces
Species: P. humilis

The ground tit is the only tit (out of ~60 species in the family Paridae) whose distribution is limited to treeless terrain — living on the rocky steppes and grasslands of the Tibetan Plateau at elevations of 3,300 to 5,400 metres (10,800 - 17,700 ft).
It travels across the ground in sprints and hops — capable of flying but seldom doing so — and is able to jump up to three times its body length without using its wings
It searches for insects and their larvae between rocky crevices and uses its long, decurved beak to prod through yak dung in search of grubs.
The ground tit is a little architecture. It builds two burrows; one for nesting in spring and the second for overwintering. Both consist of a straight tunnel ending in an ovular chamber, but this simple design belies the bird's careful engineering.
Typically, a burrow is oriented towards the sun and away from the prevailing wind, likely to maintain a more consistent internal temperature. The length of the tunnel acts like a kind of thermostat; a shorter tunnel means the inside gets warmed faster by the sun, while a longer tunnel retains more heat. For its winter burrow, the entrance is built narrower to reduce any cold draft.
So specific is the ground tit about its burrow preferences, that it appears to only use burrows of its own construction — not utilizing the abandoned burrows of mammalian neighbours like the Himalayan pika.
For more than 100 years the ground tit was considered a ground-jay. So different was this bird from the rest of the Paridae family (tits, titmice, and chickadees), that it was grouped with the similar looking ground-jays in the Corvidae family (crows, magpies, and jays).
Only after DNA tests and chemical analyses of its preening oil did it go from being a jay to a member of the Paridae. And measuring around 19 centimetres (7.5 in) long, it went from the smallest corvid to the largest tit.