Keeping out the Cuckoos

The nefarious Deiderick Cuckoo

Southern Masked Weaver with nest

Really, when you think about the animal world, there are no "villains" or "heroes". Animals do what they need to do to survive. Sometimes (think hyena) that means stealing food, killing other animals, or (as in the cuckoo's case) making someone else raise their young. I don't think it's possible to be entirely impartial in some of these cases, personally. So, let me lay before you the case of the piratical cuckoo and the ridiculously skillful Southern Masked Weaver and you tell me what you think:

The masked weaver bird, a resident of Africa, is in the Finch family. Its bill, sort of like a Leatherman, can be used for many things: cracking open seeds, catching bugs, cutting through tough-skinned fruits, and...you guessed it, weaving! The male weaver bird uses soft, pliable grasses or leaves to build an elaborate spherical nest with an underside entrance. First, he strips all the leaves off a branch so snakes can't sneak up on him. Then, he starts by weaving a circle. Next he works downward to create the proper shape. Finally, the male hangs below the nest and sings to attract females.

Females get to pick and choose among a throng of potential mates, inspecting the quality of each one's work before they commit. If the female approves she "furnishes" the nest, lining it with soft feathers and grasses and just tweaking the fung shui, adding that special "je ne sais quoi". She will then mate with the chosen builder, and raise the family alone. (The male, after mating, immediately sets out to build another nest and troll for more females, leaving her to attend to the details of parenting.)

Why would a bird use precious time and energy to build such an elaborate nest?
Enter stage left, the Deiderick CUCKOO (evil entrance tune: dun dun duuuuunnnnnn!)
As a "nest parasite" the Cuckoo would love to lay its eggs in some unsuspecting weaver's nest. Then, after the cuckoo babies hatch, they push the weaver's chicks out of the nest (infanticide! oh, ahem...I mean they're narrowing the competition for resources...) and start crying loudly for food, which the weavers will exhaust themselves to bring for the growing monster, or uh fledgling.

Ya ya, the cuckoos are just doing their thing.

Fortunately, weavers are not entirely defenseless! They build their intricate woven homes with entrance holes just small enough to deter cuckoos. Some even add long entrance tubes to stop the cuckoos from sneaking in. Eggshell pigments may also be a means for weavers to pick out foreign eggs: because egg colors vary from female to female among weavers, cuckoos' eggs usually don't match weavers' and the weavers will evict the eggs they don't recognize. (Why they don't know their own chicks is another story...)