USGS USGS Patuxent Wildlife Research Center


Breeding Season Preparations - 2007

It is that time of year again when our Crane Crew begins the process of gearing up for a new and exciting Whooping Crane breeding season.  A lot of thoughtful planning and physical labor on the part of the crew is required to motivate these rare birds to do their seemingly uncomplicated jobs -- laying the eggs.  However, chickens they are not!

We have found that experienced breeding crane pairs are somewhat predictable based on their egg laying and fertility histories (extreme environmental phenomena aside).  Using this behavioral information, combined with genetic profiles, the crane flock manager creates an annual breeding plan for each pair of endangered birds.  This plan includes estimates for the onset (first day) of egg laying, the quantity of eggs to expect per season, artificial insemination recommendations, and identifying egg breakage risks and solutions.  The crew thoughtfully evaluates each mated pair of Whooper and surrogate Sandhill Cranes and assigns a rating for their incubation qualities.  Only excellent pairs may incubate endangered eggs.  Very poor pairs (such as egg breakers) may require immediate intervention to save valuable eggs, which in turn would be given to proven surrogate incubators for safe keeping. 

To provide each crane pair with a safe and healthy environment, we use a practice called annual pen rotation.  Just like farmers who rotate crops to condition the soil, we rotate crane pens every year to allow the soil to be cleansed of waste and potentially undesirable parasites.  This practice also provides the opportunity for maintenance and repairs while alternate pens are empty.  Each new breeding pen is scrupulously inspected and repairs are made to fences, waterers, sheds, top nets and shelters as needed.  In addition, feed shed floors are replenished with fresh sand, fresh gravel is laid down to ensure proper drainage around water cups, vines and other unwanted vegetation are removed and shade trees are pruned.  

Once the cranes are situated in their freshly prepared pens, they are given plenty of straw to build nests.  They are fed a specially designed pellet diet to support reproductive health for several weeks before breeding starts.  Additional supplements such as ground oyster shells are provided to maintain calcium in laying females and support healthy egg shell production.  Treats like smelt (small fish) are given to birds for enrichment, especially during or after times of disturbance.

Although we have not explored the influence of romantic ballads and candle lit dinners on our mating pairs, we do employ some other strategies for proper crane breeding ambiance.  In particular, we do what we can to create an environment, here in Maryland, similar to that experienced by wild Whooping Cranes at their breeding grounds in the Northwest Territories of Canada. The area is so far north that day length increases much more rapidly throughout the spring than it does here, up to nearly twenty-four hours of sunlight per day by summer.

Research has shown that seasonal changes of day length have physiological and behavioral effects on animals, such as stimulating the production of hormones associated with reproduction.  So, Patuxent scientists calculated the correlation between temperature changes and relative photo-periods (day length) at the Whooper’s natural breeding grounds.  It is still pretty cold up there during early spring.  Therefore, we begin lengthening the photo period of our cranes using artificial light beginning in mid-February.  The lights are adjusted weekly to extend day length at a rate similar to that in the far north. 

We have done our best to prepare the cranes for the breeding season.  We have altered diets, fixed up pens, provided nesting material and given the birds more light.  Now the start of egg season is up to them.  We patiently wait, expecting our first Whooping Crane egg sometime very soon.

Artificial lights over whooping crane pens. Photo by Charlie Shafer, USGS Patuxent Wildlife Research Center.

Artificial lights over whooping crane pens. Photo by Dan Sprague, USGS Patuxent Wildlife Research Center.

Jane Chandler and Dan Sprague performing artificial insemination on a Whooping Crane. Photo by Charlie Shafer, USGS Patuxent Wildlife Research Center.

Jane Chandler and Dan Sprague performing artificial insemination on a Whooping Crane. Photo by Charlie Shafer, USGS Patuxent Wildlife Research Center.

Nest of a surrogate Sandhill Crane pair. Photo by Dan Sprague, USGS Patuxent Wildlife Research Center.

Nest of a surrogate Sandhill Crane pair. Photo by Dan Sprague, USGS Patuxent Wildlife Research Center.