robin nestlingrobin nestlings

June 10, 2019

Babies are everywhere around the farmyard.   Bird babies of all colors and sizes fight over who should get first use of the bathing facilities at the little pond.   Rabbit babies are living under the deck and visit my flower garden at their doorstep.   Kestrel babies squawk constantly, complaining they are on the verge of starvation while making so much noise it must be extremely difficult for the harried parents to catch a mouse or sparrow that has not been warned of their presence.  Fawns are beginning to follow their parents as they feed and can’t resist gambling about, chasing each other.  Tadpoles of all sizes line up along the edge of the little pond, while toads and grey tree frogs still sing and presumably continue to lay eggs. Caterpillars are appearing, along with holes in the leaves of all sorts of plants.

Most wild babies have to grow up quickly as the great majority end up as meals for other species, and the faster they become proficient at moving around and caring for themselves, the more likely they are to survive. Two weeks is a common length of time for the average songbird to grow from a blind, naked mite to a fully feathered creature capable of flying about (although most do depend upon their parents to teach them how to find food for another couple of weeks). Rabbits can care for themselves by the time they are a few weeks old and a little brown bat can fly when only 18 days old.

If a species is going to sustain itself, each breeding female must replace herself with another breeding female before she dies. (The survival of any one male is less significant as most take many mates during their lifetimes.) The numbers are amazing. Take American robins as an instance. In order for robins to continue to arrive each spring and nest in our apple trees, each pair will have two or sometimes three broods each year. Each brood contains three to five eggs, so a female could produce from six to fifteen young each year and therefore up to thirty babies in the two years she usually lives, and considerably more should she survive longer. If she and her mate only need to replace themselves, what happens to all those extra offspring?

A coyote pair has an average of six young each year, although it may be as few as two and as many as a dozen. They can expect to live 6-8 years, according to the DNR statistics, and if so, will probably have had at least 30 pups and possibly as many as a hundred.

Consider the cottontail: a female that survives long enough to leave its nest can expect to live about a year, although some have been known to live four or five years. She will have three or four litters each year with three to eight young per litter, although a few up to l0 have been reported. Therefore, she would probably have had at least 25 young and possibly many more. Farther south, cottontails may breed year round with as many as 7 litters a year. We should be overrun!

The female Monarch butterfly lays about 400 eggs during her six or eight months of life, and it has been estimated that our common toad produces close to 5000 eggs. It is not known how long these amphibians live in the wild laying long strings of eggs each spring and filling many a puddle and pond with their tadpoles, but they have been known to subsist for more than 30 years in captivity. 

One of the most prolific breeders of all the mammals is the meadow vole, a small, common rodent that lives in grassy fields and marshes and is a close relative of our deer mouse and that pesky house mouse. It is a short stubby rodent with a rounded face, small eyes, short fur, and a very short tail. There are 4 species of voles in Wisconsin but only the meadow vole occurs in any numbers. It lives above ground, creating little round tunnels in grassy vegetation and eating foliage and seeds and sometimes tender tree bark, and can cause severe damage, especially during winter when it is active under the snow.

Female voles can have 10 litters per year if conditions are favorable, and if one assumes an average litter contains six offspring, the numbers are staggering. Voles are born naked and blind but they are fully furred after 10 days, and reach sexual maturity at 5-7 weeks. The arithmetic becomes complicated, but if a single female bears litters of six babies in March and April and her female pups begin their own litters just two months after birth that would then reach breeding age in another two months, by the end of the season her total offspring could top 1000 new rodents.

Some of these various babies are killed in accidents and a fair percentage are struck down by disease, but the great majority become part of the wild food chain. They are preyed upon by hawks, owls, foxes, domestic cats and dogs, snakes, crows, herons, shrews, skunks, bullfrogs, snapping turtles, largemouth bass, and raccoons.   Nature can be cruel to an individual, but the ultimate goal is survival of each species, and barring major problems this usually is accomplished, and the babies are certainly cute.