NEST FORM AND CONSTRUCTION IN CERTAIN WEST AFRICAN
Authors: CROOK JOHN HURRELL 
Published: April 2008

Ploceine nests are small globes with entrances at the side or below with or without some extension of the entrance in a spout or tube. An “initial ring” is first constructed and thereafter the male bird sits in this to carry out stitching and shaping. The form and dimensions of a nest are thus determined by the use of a fixed position and the distances to which the bird can reach up, out and around from it. The egg chamber develops first and the initial ring is thus the original entrance. Later construction involves the extension of the roof down over the front of the initial ring aperture to form porch, antechamber or funnel etc. (Construction in Amblyospiza albifront is aberrant.)

Four types of nest are characterised: “globular”, “kidney‐shaped”, “incomplete kidney‐shaped” and “retort‐shaped”. The latter may be subdivided into nests with a funnel entrance (Type A) and those with tubes (Type B).

Nest construction is described in detail for Quelea quelea and compared with that of Ploceus {Sitagra) cucullatus and other species. The stages are classified and stitching and shaping movements described. The differences between stitching movements correlate with successive stages of construction and the differences are regarded as due to different orientations of the same basic movements to the developing nest.

Proximate factors determining nest form are: the methods of attachment, the size of the bird, and the construction of much of the nest from a fixed position in the initial ring. Extension of the entrance is a function of the extent to which building continues after the completion of the egg chamber. It is thus in part an expression of the length of time spent building relative to the total duration of the breeding season.

In considering the ultimate factors responsible for the evolution of nest forms a correlation is noted between long breeding seasons, predominantly insect diet, nest siting in trees and long tubular entrances. Likewise there is a rough correlation between short breeding seasons (and/or rapid breeding) and globular or kidney‐shaped nests. A high speed of reproduction in a short breeding season seems correlated with a cessation of nest building at an earlier stage than where the breeding season is a long one. However, nests of a particular species often show characteristic features, which suggests that the nest of a species is the product of selection for its survival value in the habitat concerned. Nest form is thus considered not merely the expression of the speed of reproduction but in addition to be directly adapted to its site. The evidence for the four types of nest is discussed and the need for further study emphasised.

Building behaviour is discussed. The production of a properly developed nest requires constant repetition of the building sequences, especially at the fixed building position, and also building activity sufficiently sustained to produce roof and walls and shaping sufficient to mould the form of the nest. Low motivation results in aberrant shapes through the use of irregular building positions and inadequate shaping.