Discovering a bird’s nest is perhaps one of my favourite moments in birding. A bird’s nest is the very centre of its existence, and gives you an intimate insight into the most private and guarded part of its life. My friend Michael Mason recently experienced this special connection when he spent time at the nest of a pair of Cape Penduline Tits in the strandveld near Silverboomstrand. Michael simply couldn’t tear himself away and ended up taking thousands of images over several days.
Penduline Tit nests are nothing short of miraculous. And this is perhaps even more impressive considering that they are among the smallest of all our birds, weighing less than a R5 coin. The ‘penduline’ part of the name comes from the Eurasian Penduline Tit, Remiz pendulinus, in which the nest hangs from an extended connection, like a pendulum or pendant. The nest is more firmly attached to its supporting twigs at the nest’s roof in our Cape or Southern Penduline Tit, Anthoscopus minutus (‘tiny flower-looker’),
The nest structure is a hollow, upright oval that measures about 6-8 cm in diameter and 13-15 cm high (put your fingertips together and make a ball). The interior chamber is about 5-6 cm in diameter and 9-11 cm deep (could almost hold a can of Coke) and is accessed via a 2 cm wide spout that is 2-6 cm long and angled slightly downwards. The nest is remarkably strong and weatherproof, with outer walls up to 20 mm thick. If extrapolated to human proportions, this would be about 40 cm thick!
ABOVE: This particular nest was situated on the outer edge of a thorny Putterlickia pyracantha bush, about 1.3 m above the ground.
In open, scrubby habitats the nest is usually quite low down: about 1-3 m up in a thorny shrub, small tree or occasionally simply on a wire fence. In thornveld habitats nests are among the upper branches, as high as 7 m above the ground. They are not particularly well hidden and are sometimes completely exposed and conspicuous due to their pale colour. Instead of camouflage the birds rely on a different anti-predator strategy: an ingenious ‘false entrance’.
Upon first glance the nest has an obvious large entrance hole along one side. But should a snake, monkey or avian predator come calling, they might be disappointed to find that the nest is empty. In reality, this blatant entrance is a dummy or distraction – the real entrance is accessed via a narrow tube that can be sealed shut.
ABOVE: Diagram showing the false and real entrances.
Upon arrival at the nest, the bird perches on or hangs from the lip of the ‘false entrance’. It then pulls the entrance spout open with its foot and bill to gain access to the nest. However, the entrance is only briefly left open. When the bird exits the nest the spout’s mouth closes automatically or is ‘zipped’ close with the bill, or pushed up with the head. Even when the bird is inside the nest, it usually closes the entrance spout from the inside.
If ever you find an old penduline tit nest, be sure to touch it – there is nothing quite like it. It is simultaneously durable and soft. It feels a bit like sheep’s wool but denser. The secret to achieving this unique felt-like texture is twofold: material and method. One of the primary nesting materials is cobwebs, including those of sociable spiders. Spider webs are known for their tensile strength and also help bind everything together.
ABOVE: Eriocephalus africanus is frequently incorporated into the nest. In late winter the bush produces gorgeous white ray florets ringing the central purplish red disc florets (top image). Shortly after flowering the plant forms fluffy, hairy white fruits that look like cotton – this is what the penduline tits have been waiting for (middle image). The plant is often one of the dominant species in a particular area: in the lowermost picture the fluffy white seed-heads indeed resemble a light coating of snow. Penduline Tits do not have to go far to find perfect nesting material!
To this the birds add fluffy, feathery plant down, such as that of the 34 species of Eriocephalus bushes (Kapokbossie or Wild Rosemary). Indeed, this is also where the birds’ Afrikaans name, Kapokvoël, comes from (kapok refers to light snow). Finally, mammal hair makes for excellent insulation, whether this be fur from hares, pelts of Angora goats or wool from sheep. Generally nests have a whitish colour, but in regions with lots of Karakul sheep the nests may be almost black, or have patches of brown and black wool.
In terms of methodology, the birds have a special trick: they repeatedly pull the material out of the nest wall, tease it, and jab it back in. This gives the nest its unique firm, felted, interlocked texture.
ABOVE: Both sexes (and often 1-2 helpers) assist in feeding the chicks. Likewise nest-building and incubation duties are also shared. Michael suspects that there were three birds involved in this breeding team. Sexes are alike in Cape Penduline Tits.
Both sexes contribute to building the nest, finishing the job in 20-35 days (average about 26 days). If however, the nest is destroyed by a storm or predator, they will replace it in only 13-20 (average 16) days. Nests may also be destroyed by sunbirds and canaries, perhaps in an attempt to steal the soft material for lining their own nests. Nest material continues to be added throughout the incubation phase.
Cape Penduline Tits lay 4-7 eggs (average about 4.5 eggs; a high total for a passerine) at daily intervals. The eggs are plain white and absolutely tiny: 14.1 x 9.8 mm. That’s just barely bigger than a Tic Tac! Hold your fingers apart…closer…there you go. Incubation is shared by both sexes and after about 15 days, a tiny hatchling will emerge. But not all the eggs will hatch. In one study of 29 nests, only 64 out of 114 eggs (56%) hatched. Of these, 49 chicks (43% of the original eggs) survived until they left the nest. Rather heartbreaking stats, but not atypical of small birds.
ABOVE: Note how sturdy the feet are, giving the bird remarkable dexterity – for example, they often hold food items in one foot like a parrot. The sort of half-hanging posture shown by this bird is typical. I’ve also seen them ‘sit’ with their bums resting on a twig to free up the feet. The bill also has an unusual shape: a symmetrical cone tapering to a needle-fine tip: like tweezers for manipulating small items.
Feeding all these hungry and rapidly growing nestlings is a full-time job. So much so, that the breeding pair may enlist the assistance of 1-2 helpers. These are likely grown offspring from a previous brood. When the chicks are little, each member of the parenting team delivers food at a rate of about 5 items per hour. But as the chicks and their appetite grow, this rate increases: one group of 3 adults delivered more than 30 snacks per hour.
The chicks fledge at about 16-22 days. But, if environmental conditions are still good, the breeding pair may give it another go. A new set of eggs may be laid only a month after the young from the first clutch fledged. As such, the fledgelings from the first brood may roost alongside the eggs/chicks of the second brood in the nest at night. Talk about a tight-knit family!
ABOVE: Penduline tits have rather coarse plumage, including a little tuft of black-and-white ‘grizzling’ on the forehead that identifies the Cape Penduline Tit. Here the bird is halfway inside the ‘false entrance’ while the (closed) entrance spout hangs over its head. The exterior of the nest is usually not decorated but may collect windblown debris over time. Sometimes the birds add a few spider egg capsules for decoration.
ABOVE: This sequence shows the parent arriving at the nest and opening the entrance spout. In the first image it is hanging by its right foot from the lip of the false-entrance, while its left foot reaches high up to grasp the spout. In the middle image the spout has been pulled open and the bird is preparing to enter. The spout is is only about 2 cm in diameter, which is a tight squeeze even for a bird as tiny as a penduline tit!
ABOVE: Here one wing wing is held open for additional balance, while the tail props the bird against the nest wall. The spout is being pulled open with the left foot. I wonder if it’s always the left foot?
ABOVE: Nope. It seems the right foot can also be used. It’s a bit baffling to me how the birds’ claws don’t become entangled in the fine threads of the nest.
ABOVE: Michael says that whenever the birds saw him looking at them, or heard a burst of camera shutters, they would immediately pretend to be very busy in side the ‘false entrance’ hollow. He got the impression that this was deliberate deception, sort of like a lapwing pretending to be incubating eggs in some other random spot to send predators on a wild goose chase. Very interesting!
ABOVE: When leaving the nest care is taken to close the entrance spout securely. When the bird exits the nest the spout’s mouth closes automatically or is ‘zipped’ close with the bill, or pushed up with the head. Even when the bird is inside the nest, it usually closes the entrance spout from the inside. Here the bird is pushing the opening closed with its head.
ABOVE: Another sequence showing how the bird uses its head to push the entrance spout closed.