Several species of birds have build nests in the constructed wetland (about three meters by one meter) that treats the sewage of three houses in Mikocheni. The constructed wetland uses matete (Phragmeites reeds), which was once the most common plant
in the former Msasani wetland (now 99% disappeared to make room for big houses, apartments, and shops).
Range changes in birds are usually due to land-use changes which may be induced by human beings or by climate change. If birds in general, and weavers in particular, are able to adapt to land or habitat changes depends on the specificity of their needs and demographic parameters. African Golden Weavers (Kwera tumbodahabu) Spectacled Weavers (Kwera miwani), and Zanzibar Red Bishop Birds (Kweche) all tried to build their nests in the constructed wetland.
In the last few months Spectacled Weavers have built six nests elsewhere the garden, but I am not sure they are productive. The Blackheaded Weaver started to build a nest in a nearby mpingo tree but quit. The only birds now nesting in the constructed wetland are Zanzibar Red Bishops (Euplectes nigroventris). They are the smallest of the world’s 117 species of weaver birds and found only in Kenya, Mozambique and Tanzania.
Bishop Birds had not been seen for some months in the garden and then suddenly a male was back at the constructed wetland building nests in late October. He built several. I took a photo on 19 November of a female inspecting one of the nests that was rejected. She was subsequently proved correct when the reeds it was tied to were pushed down during the massive rains in late December; the nest ended upside down. A nest was finally accepted a few weeks later. This nest survived the heavy rains.
In 22 December two eggs were in the nest. On 25 December I have a photo of the female at the nest, facing in for a long time. She was probably watching the chicks hatching, as soon afterwards I found pieces of light blue eggshell nearby. She had taken them out of the nest and threw them away. The next photos I have were taken on January 7th, the day that the last fledgling left the nest. It was just luck. I was standing near the wetlands watching the nest for action.
Until they moved I did not know that one of the fledglings and the mother were outside the nest in the reeds near me. I went to get my camera and they were still there when I returned. For two successive seasons the Zanzibar Red Bishop birds have successfully bred in the constructed wetlands. I can now say with a bit of confidence that this small constructed wetland is adequate habitat for one pair of Bishop Birds to annually raise young to adulthood.
They may be able to raise two broods per year in the constructed wetland. The first group fledged in March 2011 and the second in January 2012. While the young ones on the second group were growing, a male was already building another nest about two feet away on some strong young reeds rising tall with new growth. The male is so astoundingly bright I thought he was doing it as
a way to detract attention from the mother feeding the young. Perhaps it was for that reason.
And if so, it may have worked since the fledglings matured safely. A very few days later this new nest had a female sitting in it. If she were the mother of the last fledglings, or a new female I cannot tell. But she is sitting snugly in the nest, facing out the entrance. She is sitting in there more hours every day; surely there are eggs underneath her. If all goes well, those eggs will hatch after about two weeks and the chicks will fledge a couple of weeks later, in February.