ABOVE: Africa’s Ploceus weavers are named after the intricate nests that the males weave – certainly one of the most complex structures built by any creature. This video shows some (shaky handheld) footage of a male Southern Masked Weaver P. velatus that decided a palm tree in my garden is the perfect place to establish a new colony. Some introductory weaver biology above, and more detailed stuff below.
ABOVE: A ‘thumbnail’ image from my book Chamberlain’s LBJs, showing a female Southern Masked Weaver inspecting a newly built nest, with the male architect hanging below the nest, with his wings partly spread and vibrating, while delivering his extremely complex ‘swizzling’ medley. The male at the top is just starting a new nest: the first step is to get the main supporting ring in place.
Weavers of the genus Ploceus are probably some of Africa’s most remarkable but most under-appreciated birds. This is largely because they are so common, noisy and conspicuous, including in urban environments, that people take them for granted. Nevertheless the breeding males are stunningly attractive, with bright yellow or orange plumage, often adorned with black or chestnut-brown masks. Females and non-breeding males, on the other hand, can be very challenging to identify. Weavers have remarkably complex display songs (called ‘swizzling’) that accompanies energetic visual displays that the males perform while hanging under their nests. Indeed, a weaver’s nest is the very epicentre of its entire life. Nests are much more than just a shell to protect the eggs and young. They are arenas for males to strut their stuff in order to outcompete rivals and impress potential mates, and they are bold visual advertisements that reflect their builder’s skill and health. Most weavers fall into one of two categories. Monogamous weavers (i.e. one male, one female) are mostly sedentary in wooded habitats, and are mainly insectivorous. Conversely, polygamous weavers (i.e. one male, many females) are more nomadic and are partly granivorous. In the polygamous species, such as Southern Masked Weaver, the competition for females can be intense. In the latter species, particularly successful males may attract 2-3 females simultaneously up to 12 females successively throughout a summer breeding season. But this also comes at a price, namely investing a huge amount of energy (and in fact spending most of your waking hours) doing what weavers do best: weaving!
In the last few days a male Southern Masked Weaver, Ploceus velatus, has decided that he is going to attempt to establish a new breeding colony in my garden. He chose a high, horizontal frond of a smallish palm tree for one of his nests, with an adjacent nest about halfway up a poplar tree in the neighbour’s yard. There are accounts of males building up to 52 nests in a season – typically discerning female weavers will come to inspect the nest once it is complete, judging it by its strength and freshness. During her inspection, the male does his utmost to win her affections by energetic singing near the nest or while danging below it. Males also strip off foliage in the surrounding branches. This is often said to be a counter-measure against predatory snakes, but is probably more likely an attempt to make the nest more visible to females. If the female deems the male’s nest acceptable, she will proceed with ‘interior decorating’ i.e. adding nest lining in the form of leaf strips, grass and heads and sometimes feathers. In effect, adding a woman’s touch and making the nest shell more cosy. The male will also contribute a short entrance tunnel to a breeding nest.
However, if the female reject his nest, the male will immediately rip it apart and start over. And that is the focus of this blog post. One afternoon I happened to notice a large amount of grass lying on our lawn. Looking up, I saw a torrent of grass stalks ‘raining’ down from above. The culprit, of course, was a Masked Weaver ripping his nest apart with abandon! I took the opportunity to collect the nesting material and spent a monotonous few hours counting and analyzing it. Here are the results.
…a torrent of grass stalks ‘raining’ down from above. The culprit, of course, was a Masked Weaver ripping his nest apart with abandon!
The destruction was over in only a few minutes. All in all, the shredded nesting material filled up one plastic shopping bag. The vast majority of the material consisted of narrow strips of plant fibre, ranging in width from about 6 mm broad strips, to hair-like filamentous strands. The majority of the fibres were probably around 2 mm broad though. The length of the strips varied tremendously, with the longest pieces in the order of 40-50 cm. These are almost certainly stripped from long palm leaves, in a process which I’ve witnessed countless times before. Using its beak the bird neatly snips a section of palm leaf, and then simply grips it in its bill and starts flying away. This causes the strand to rip neatly along the length of the leaf, with an audible ripping sound. The majority of the strips were about 5-15 cm in length. However, a lot of them were probably snipped into shorter lengths when the male deconstructed his nest.
In addition to the palm leave strands, there were also what appeared to be rips from broad-bladed grasses. Another major nest material component was short, clumps of conifer needles, almost certainly from a streetside pine tree about 30 m away. By the way, most nest material is apparently collected within 50 m of the nest. Leaves of Acacia (now Vachellia) trees were also in evidence, and roughly in the same proportion as the pine needles.
ABOVE: The vast majority (approximately 80%) of the nest was constructed with long, thin plant fibres. These are probably mostly shredded strips of palm leaves, ripped from the many palm trees in close proximity of the nest. Some of them might even have come from the very same branch that the nest was suspended from: as can be seen in the video above, the last 75 cm of the branch was stripped of all leaves by the bird.
ABOVE: At the top one clump of short pine needles can be seen. Such pliable but strong material was much favoured in the nest construction. Below this is an example of a particularly broad strip ( about 8 mm broad). The next strip is typical width; note also the split ends, which is a features of a great many of the fibres used in the nest. Lastly, thin hair-like filaments may play an important role in binding everything together, and was often knotted or tangled.
ABOVE: Acacia-type leaves (heap on left) were commonly used in the nest, in about the same proportion as pine needles (heap on right). While the pine needles were still soft and pliable several days after the nest was demolished, the fine Acacia leaves were by then dry and mostly disintegrated.
ABOVE: Various other leaves were also used in the nest, but only in small amounts. In particular, the leaves at the far right were frequently encountered. These have a velvety texture and are covered in short fluffy hairs, which may aid in binding the nesting material together.
ABOVE: The weaver manages to bend and manipulate the pliable plant fibres into complicated knots, some examples of which are shown here. It is amazing to think that it accomplishes this using only its bill.
So. How many strips, leaves and needles are required to construct a weaver’s nest? The answer to this is complicated by the fact that the bird almost certainly snipped or shredded some of the longer strands into shorter ones when destroying its nest. However, I counted a total of…wait for it…1161 items. These are as follows:
- Fibres: 848
- Pine needles: 146
- Acacia leaves: 101
- Velvet leaves: 48
- Misc. leaves: 15
- Grass seeds: 3
What a privilege it is to be ale to witness such incredible physical dedication, intelligence and architectural talent in your very own backyard! If you have weavers at your place, or if you ever come across a bustling colony, why not document it? Undoubtedly the best way to do so is through the Animal Demography Unit’s PHOWN project (PHOtos of Weaver Nests). This citizen science project tracks and monitors the variation in weaver colony sizes and breeding effort, which is an indicator of various underlying environmental issues [i.e. perhaps weavers will start breeding earlier in spring due to climate change?]. Although many weavers remain common to abundant, even in transformed habitats, there are also many threatened species. Documenting their breeding through PHOWN will help scientists and conservationists protect these remarkable birds. Currently the project has already documented more than 8 million individual nests from 90 species in 37 countries with the help of 363 volunteers. Read more and get involved here.
Dieter Oschadleus and I once spent an evening on Robben Island picking a Cape Weaver nest apart and counting the different materials. This was a long time ago and I cannot remember the final tally, but also think it was north of 1000 individual items.
Thanks for your comment David. It really is amazing the amount of effort these guys put into their constructs.