On June 2, I received a letter from Jean Booth, who lives in Muncy, stating that she has a virtual wildlife preserve on the property, where she has lived for the past 55 years. Jean wrote that she faithfully monitors the nests that a phoebe has been building for many years on a ledge of her front porch. This year Jean noticed that a robin was the first bird in the nest to hatch. |
Fast forward to June 12th when I received a second letter from Jean, relating that, after seeing a photograph of a cowbird on the internet, she now realizes that the larger bird was not a robin but a cowbird. She also wrote that although the cowbird left the nest, it continues to follow the adult phoebes, begging for more food. Jean also mentioned that the cowbird grew faster and left the nest before the phoebes.
When a female lays her eggs in another bird’s nest, it is known as
cuckoldry (a man whose wife is unfaithful to him). The word is a variant of the Old French word cucuault, which comes from cucu “cuckoo,” from the analogy that other birds’ nests are invaded by cuckoos.
Most birds that parasite other birds’ nests have very short egg
incubation periods and rapid nestling growth, which gives the parasitic nestling a head start on growth over its nest mates, allowing them to out compete for food and attention. In some cases where the host nestlings are smaller than the parasitic nestling, the host nestlings will end up starving to death.
There are instances when the host bird rejects the parasitic egg. Some birds have adapted a defense to protect their own eggs. If able to distinguish which eggs are not theirs, the host bird, such as a robin, will either roll the egg out of the nest or puncture the egg with its beak. The host bird could also realize that there are too many eggs in the nest and destroy the parasitic egg; however, some parasitic birds will remove a host’s egg and lay an egg of their own in the nest, thus
tricking the host bird.
Some parasitic young will eliminate all nest mates shortly after
hatching, by either ejecting them from the nest or killing them with the sharp mandible hooks that fall off in a few days.
There is some evidence that the cowbird could somehow change the egg coloration, mimicking a number of their hosts eggs. The cowbird has been known to have 221 host nests but only a few have been successful in 144 of the species. The cowbird will produce an average of forty eggs during a year, so they can take advantage of all the available nests during that period. They are often compared to a chicken, which keeps producing eggs for two months.
The cowbird’s tradeoff for this nest cuckoldry is only three percent of cowbird eggs will survive to adulthood, in spite of the advantages of hatching a day earlier than other eggs in the nest and the tendency to get more food.
Brood parasites not only occur in birds, but are also found among insects and fishes. There are many different types of cuckoo bees, which lay their eggs in the nest cells of other bees. This is referred to as kleptoparasites because the immature stages are never fed by the adult host (Kleptomania is an uncontrolled impulse to steal and comes from two Greek two words: kleptein, meaning to steal and mania, meaning madness).
There are also cuckoo wasps, which are kleptoparasites, laying their eggs in nests of potter and mud dauber wasps. Some species of paper wasps have lost the ability to build their own nests and rely on host species to raise their brood.
A cuckoo bumblebee (the subgenus Psithyrus) kills the queen in a colony; replaces it and then uses the host workers to feed her brood. A parasitic butterfly (Phengaris rebeli) parasites the nest of the ant (Myrmica schencki) and tricks the ants to raise her young. She does this by releasing a chemical that confuses the host ants into believing that the larvae actually belong to the ants. The ants will take the larvae back to their nest to raise.
We think of nature as being peaceful; however, there are many that are fighting battles to survive.