garden BIRDS
African Birdlife|January - February 2021
THE LONG & THE SHORT OF IT Abnormal weaver nest attachments
WESLEY GUSH

For the past three years I have observed the intriguing nests made by a male Southern Masked Weaver in our garden in northern Joburg.

Three years ago, the male built a long nest in a thorn tree and he’s done the same every year since then. In 2020 the first long nest (approximately 50 to 60 centimetres) appeared in a fever tree in the garden, but two weeks later a weaver built a long nest in the same thorn tree as in previous years.

I’m not sure if it’s the same bird every year. The first nest attachment was a medium length, about 40 centimetres, before the weaver tore the bottom off the nest chamber and extended the attachment until it was almost a metre long. He then finished it off with a proper nest chamber at the bottom. One day when he was building the nest, a second weaver perched near him with a blade of grass in his beak and then added it to the nest. I haven’t subsequently seen two birds at the nest.

The weaver left the extended nest for a few days, then set about shortening it by tearing off about 50 centimetres of the attachment and added the nest chamber at the end of what was now an approximately 30-centimetre-long attachment. He constructed a second long nest near the first one; he finished it, then tore off the bottom section and once again proceeded to lengthen it, this time to about 70 centimetres. A couple of days later he shortened this attachment too.

Not satisfied with his work, he then once again reduced the length of the original long nest and it now far more closely resembles a ‘normal’ weaver’s nest; he has shortened the attachment of the second nest as well.

Is this normal behaviour? Do you think it’s genetic and could it be the same bird, year after year? In previous years he didn’t extend and shorten the attachments multiple times, but this year he’s constantly modifying his nests. IZABELLA GATES

H. Dieter Oschadleus comments: The Southern Masked Weaver commonly breeds in Johannesburg gardens. Izabella has provided some fascinating observations on weaver nests with unusually long, broad attachments. Even more unusual is the fact that this pattern was repeated on a number of occasions. This certainly suggests that the same male was involved, even though the nest site changed to a different tree; individual males do sometimes change a nest site from one tree to another.

A long, broad attachment between the nest chamber and twig has occasionally been recorded previously (for example, see the photograph in Africa – Birds & Birding, 2007, 12(6): 8). However, this seems to be the first record where the nest-building behaviour was repeated for many nests and for several years. Weavers have a genetic imprint for nest building, but their ability to do this is greatly improved by learning and memory.

There are four clear stages in nest building by typical weavers and these are most likely genetically controlled: the initial attachment, the ring or stirrup, the nest chamber and the entrance (which may extend into a short or long tunnel). Each stage requires similar building techniques, except for the initial attachment, which requires the most adaptability because nest sites vary (nests may be attached to reeds, palm leaves or twigs that differ in shape). In the attachment building phase, weavers do not show repeatability in technique, but they do for the rest of the nest-building process.

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