Use calcium suet for eggshell formation

Calcium is an essential mineral for eggshell formation as well as bones formation and growth. Without sufficient calcium, eggshells can become thin and the eggs will break. Or young birds may develop deformities in their bones.

Female birds change their diets during nesting season to obtain calcium-rich nutrients. Seed and insects alone are insufficient. They provide only 10 percent of the calcium needed for egg laying.

Garden songbirds do not "store" extra calcium needed for egg laying. That would make the females too heavy and less maneuverable. So where do they get it? By gobbling up calcium within hours of egg laying.

One British study found that a female bird deposits 60 percent of the calcium needed for the eggshell within eight hours prior to laying. At this critical time, females must forage to collect huge quantities of calcium. They depend on calcium-rich nutrients naturally found in the soil, usually calcium carbonate. Fortunately that is found in many limestone-rich deposits in the Lehigh Valley area. But when acid rain saturates the soil, the amount of calcium may become insufficient.

Millipedes, worms and woodlice are part of birds' diets. The insects themselves don't provide all the necessary calcium needed for egg laying, but the soil in the insects' gut does. Some birds even consume shells of spent eggs from their own broods.

You can assist female birds in two ways.

First, you can add egg shells to your bird seed. Be sure to sterilize the shells. Rinse the eggshells first to clean off the raw egg. Place the washed shells on a cookie sheet in an oven heated to 250 degrees for about a half hour. This will eliminate the salmonella in the egg shells. Then crush the shells using a rolling pin and add the material to the bird seed.

Another way of providing calcium to female birds' diet is by offering them calcium-rich suet dough. "Calcium Delight" is available at The Bird House. The females can feast on the suet, taking up as much calcium as they need. Other ingredients include roasted peanuts, corn, rendered beef suet, oats and soy oil—which together provide plenty of fat and protein needed as energy right after egg-laying.

By offering calcium-rich suet dough, the fledglings and young birds can develop stronger bones to help them for long-distance migration in the fall.

Calcium Delight is a no-melt suet dough that comes in standard-sized suet feeders.