We have also shown that Swifts seem to show no preference for a scoop-shaped concave over a simple flat-bottomed nest form.
However, it has been reported that, with any nest form, the Swifts do not bring in much nest material. This may not be surprising if the birds return to a ready-made nest. However, in the case of a flat-bottomed nest form, the eggs may roll around, may not get properly incubated and may be more likely to get knocked out. When inspecting nest boxes after the breeding season, it is not uncommon to find abandoned eggs on the floor of the box. It is possible that flat-bottomed nest forms have lower productivity.
However, it has been reported that, with any nest form, the Swifts do not bring in much nest material. This may not be surprising if the birds return to a ready-made nest. However, in the case of a flat-bottomed nest form, the eggs may roll around, may not get properly incubated and may be more likely to get knocked out. When inspecting nest boxes after the breeding season, it is not uncommon to find abandoned eggs on the floor of the box. It is possible that flat-bottomed nest forms have lower productivity.
So is there a way of keeping the advantages of nest forms without incurring potential disadvantages?
Up until now, we have made a lot of nest forms (1000s). The nest forms we make are cheap and simple: an 80mm diameter hole in a 100mm square of 11mm thick Stirling board. Of course this gives the birds a flat-bottomed nest space.
Can a better nest form shape that reduces egg loss be made at a reasonable cost?
We have measured a number of natural nests: A natural nest is a concave cup about 75 mm diameter with a vertical rim. The depth varies with the age of the nest. The birds often wedge their natural nest up against a wall or in a corner.
Up until now, we have made a lot of nest forms (1000s). The nest forms we make are cheap and simple: an 80mm diameter hole in a 100mm square of 11mm thick Stirling board. Of course this gives the birds a flat-bottomed nest space.
Can a better nest form shape that reduces egg loss be made at a reasonable cost?
We have designed a shape that attempts to emulate a natural nest. The concave part is 18 mm deep. A swift’s egg is about 16mm diameter.
Eggs will gravitate towards the centre. The vertical inside rim will help keep the eggs in. The 'steps' help any displaced chick to clamber back in.
Using this shape we have made a 3D-printed master from which we can make silicon rubber moulds.
Using a 50/50 mixture of Paster of Paris and sawdust, casting new nest forms is quick though it does take a number of hours before taking them out of the moulds. Demoulding is quick and easy. For a production run, one needs a large number of moulds.
The whole process is quicker and easier than making concave nest forms out of wood.
Moulded nest form in a Model 30
