All over the backyard, a persistent squawking and chirping alerts us to the presence of newly fledged young birds. In fact, the noise of these youngsters has entirely replaced the melodic singing of breeding adults. Weaning is a difficult process as any parent knows, because the youngsters understand that the best way to get something is to annoy the parent until they finally give in (sound familiar?). Some examples I have seen in the past couple of weeks:
This is what happens to some of the local birds when cowbirds are in the area.Cowbirds are infamous as nest parasites, and lay their eggs in the nests of several different species of small birds. This isn’t as easy as it sounds because they have to find the nests of suitable species, determine the incubation stage of that nest, and deposit one egg, at will, while parents are off the nest. If they lay the egg too early, the parents might abandon the nest with a strange egg in it; if they lay the egg too late, their own egg might not get sufficient incubation time for full development. Having found an appropriate nest, then they have to quickly lay their egg in it. For comparison, it takes a hen more than 1/2 hour to get her egg out.
Why do they do it? Brown-headed Cowbirds once followed bison herds across the prairie, moving nomadically with the herds and feeding on the insects flushed by many hooves and the seed heads of prairie grasses. Nesting in one spot was thus impossible with such a nomadic lifestyle, and “egg-dumping” in other species’ nests became advantageous.