Main Research Proposal

Since the pilot study observed high territoriality of the bird species to its nesting site, in situ implementation approach of the mitigation method shall be applied. In situ in this case means within their feeding range of 1.6km from their nest. The alternative nesting structures will be placed at 10m from nested power line poles, far enough for electromagnetism to be substantially reduced, but not too far from the original nesting site that it would become ex situ. Electromagnetic exposure has altered the behavior, physiology, endocrine system, and the immune function of birds, which generally resulted in negative repercussions on their reproduction or development. The sociable weaver species that live intimately with powerlines may therefore be in significant danger, although the effects on the species in not well documented, if at all.

In the main study, I will test the effectivity of two alternative nesting structures: dummy powerline poles and dummy trees. Dummy poles are isolated powerline poles (i.e. without electricity transmission wires), and provide the same structural support as functional real powerline poles. In addition, due to the lack of electromagnetism around the dummy poles, the birds are expected to prefer these structures to functional powerline. Dummy trees are models of the main tree species that the bird naturally nests on i.e. Acacia erioloba. A previous study by showed that the gap in sociable weaver distribution in some areas of South Africa highly coincided with the extensive clearance of the Acacia veld. Furthermore, during the pilot study a lack of trees was observed in the area. Therefore, tree models of Acacia erioloba are also a good fit as alternative nesting sites for the bird if not a better alternative.

The study will still be conducted in the Mariental District in Namibia from April to September 2014.

Pilot Study Results

I previously blogged about the pilot study plans, find out here http://juliaschallenges.blogspot.com/2014/01/pilot-study.html

I conducted the pilot study in the Mariental District of Namibia on a 15km powerline section, totaling to 175 powerline poles, of which 12 had nests on them. Most of these twelve poles had more than one nest on them. The result of the pilot study indicated high site fidelity of the sociable weaver to its nesting: the colonies came back to their exact nesting pole after I continuously removed their nests twice a week for six weeks. I only observed one pole out of the 12 nested poles (8.33%) to be a new nest which did not exist before the beginning of the study, which could possibly mean that adjacent colonies diverged, or that a new colony of the species settled in. Neither of the two possibilities are unexpected since the study took place during the species’ breeding period, September to May, and the birds are therefore expected to construct more nests than at other times. The photo below shows vegetation along the pilot study site. Trees are only found around farm houses and none are a natural or suitable nesting choice for the sociable weaver.