Cold Spring

by Stan Tekiela
© NatureSmart

May 13, 2005

This has been a bad spring for the birds. The extreme cold and several weeks of soaking rain is taking a major toll on many of our early nesting song birds such as the Eastern Bluebird and Black-capped Chickadee. Both of these birds lay eggs very early in spring and under normal weather conditions (if there is such a thing as normal weather) the young would have hatched and would be ready to leave the nest by now, but that is not what I am finding.

I just got back from two days of photographing and while I was out I was checking on a dozen or so nests that I am scoped out this spring. Without actually counting the exact numbers, I would guess there has been about an 80 percent mortality rate. In other words, 8 out of 10 nests that I have been monitoring over the last couple weeks contained dead baby birds. In most cases, 4 out of 5 young were already dead.

Now many things can contribute to the death of a young bird but I have my suspicions that the cold wet weather is the culprit. Cold wet weather affects the birds in several ways. First and the most obvious are the temperatures. Most baby song birds have no ability to regulate their body temperature for the first 3 to 5 days of life. This is a very vulnerable time of life. They are born naked and helpless. The only way they can keep warm is by snuggling with their nest mates and by the parents sitting on them in a process called brooding.

Most song bird parents have a bare patch of skin on their bellies called a brood patch. The brood patch is covered by the long contour feathers of the body so you won’t see the brood patch by just casually looking at a bird. If you move the body feathers to the side you can see the patch. The brood patch becomes engorged with blood vessels just prior to incubation of the eggs to greater enable heat transfer from the parent to the eggs. After the eggs hatch the brood patch is used to keep the hatchlings warm, especially at night.

Most young songbirds such as chickadees and bluebirds are fed only insects. This high protein diet allows the baby birds to grow amazingly fast. Now normally it’s not a problem for the parents to feed their young and keep them warm during a short cold snap but when the weather is cold and wet for nearly two weeks like it has been around the upper Midwest (about the length of time it takes for a baby chickadee to emerge from the egg and fledge) it’s a different story.

Not only does the cold weather make it hard to keep the babies warm, but the insect population is nearly non-existent. As you know, most insects are not active during cold weather which means foraging parents must look longer and further away from the nest to find enough food to keep their babies alive. The more time it takes for the parents to find food the longer they are "off" their babies and the young birds start to slowly cool down. Once the body core temperature starts to cool down the digestive system starts to slow down. Once the digestive system slows down the vigor in which they feed is reduced so when the parents due come back to feed the young they are often too cold and weak to lift their heads and beg for food. It’s a tragic cycle.

In addition the quality of food is poor when the weather is cold because the large juicy insects are no where to be found. The parents are forced to bring back smaller less substantial insects for their young.

The wet weather also contributes to respiratory disorders in many bird species. The young developing lungs of a baby bird don’t handle the excess moisture in the air very well and the young die of respiratory complications such as pneumonia.

So you may be asking yourself, what I can do to help my resident birds. Try offering them some meal worms. My bluebirds and chickadees love them and will eat as many as I put out for them. It is as simple as putting 20 or so meal worms in a slick sided plastic margarine tub so they can’t crawl out. Place the container with the meal worms near the nest site or near one of their favorite perches. Since both of these species are cavity nesters you can simply put the container with the meal worms directly on the bird’s house. You will be amazed how quickly they will find it and snatch up your offerings. Until next time…