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!
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.
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.
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.
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.
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!
