Although they are present further south, the arrival of some of the usual migrant birds in this area appears to be somewhat delayed. The season seems otherwise normal and the breeding of resident species is in full swing.
Nesting materials required by birds have been mentioned in the past but there is one important aspect that we frequently overlook. With the dry conditions there is a limited supply of mud in many localities. The availability of suitable mud is vital for the successful breeding of numerous species of insects and birds that use this material in nest building.
Mud Building Insects
It would take too long to list all the species that use mud. The termites that live in the soil have access to moisture and make their own mud. Certain wasps and bees collect water with which to make mud but the majority of species rely on a source of ready-made mud, without which they cannot build and breed. The limitation of certain species affects predation on pest species in a significant ripple effect.
Some of the more familiar mud builders are the mud wasps, often considered a nuisance when they plaster their homes on our newly painted walls. These species consistently prey on hoards of caterpillars and other soft 'insects'. They usually seal this paralysed prey within their mud nests for consumption by their developing young.
Many species make mud nests on trees and rocks out in the veld. The mud balls of the solitary bees, attached to tree branches, are a common sight in our area. Although the original mud constructions are impervious to most predators, cuckoo wasps, with the protection of very hard ectoskeletons, have no problem drilling holes through which to enter the sealed chambers full of food.
With a host of other parasitic species, they lay their eggs on existing food supplies. Many other species take over plundered or abandoned nests and add their own architectural requirements. Like certain species of termite, those Hymenoptera that build in exposed locations habitually combine plant material and resin with the mud to make their nests more weather-resistant.
Mud Building Birds
Certain birds such as hammerkops and some species of thrush use mud to seal or strengthen their nests. The bird species most commonly associated with mud building are many of our swallows. The mud building swallows, among other species in this group and including the swifts, are some of the most useful birds in their control of flying insects. Many of them use human constructions, and often dwelling houses, on which to build their nests.
Most of the bridges and culverts along our roads have at least one pair of some species of swallow nesting in them. Resident birds can often be seen on trees or telephone lines within the vicinity. Pairs of birds will return to their nest site year after year and become very conditioned to close proximity of human activity.
It is heart-breaking to see a pair of swallows, having chosen a suitable nest site, searching vainly for a source of mud with which to build. After a while they will abandon the prospects and move elsewhere.
It is also sad to find that a completed nest has collapsed with the destruction of eggs or young after all the hard work that went into nest building. Each little mouthful of mud reflects so much effort by the birds. Where there is only sandy mud the birds will attempt to build with only limited hope of success.
Assistance To Mud Builders
Folks trying to attract bird life to their areas will ensure that there is a sufficient supply of building material in the form of spider web, fine grass and other requirements. Think also of the mud builders and provide a source of mud in the form of a small, permanent pool in soft clay soil. Such a pool should be in an open area, visible and accessible to swallows, which cannot take off very easily.
The approaches to the pool should be clear and some termite mound (without destroying a working termitaria) or other clay soil will ensure good building material that will bind and hold a nest in place.
The pool does not need to be larger than half a metre across but should be kept permanently wet by means of a dripping pipe - or regular filling. Apart from becoming a popular birdbath, such a pool will provide you with a fascinating source of enjoyment as you observe the insect and bird traffic. Have a go and let us know of any success.