Protocol

Conditioning costume-reared Sandhill Cranes and Whooping Cranes to follow an ultralight aircraft in migration

Developed by Operation Migration

Introduction:

Since its inception, Operation Migration (OM) has been improving a technique it first developed in 1988 to teach migratory routes to endangered, precocial birds (i.e., birds that are able to move about soon after hatching). To date, the OM team has conducted or participated in eight migration studies with three species. The latest studies have focused on teaching Sandhill Cranes to follow ultralight aircraft in migration, yet remain wild enough to be released.

Operation Migration, the U.S. Fish and Wildlife Service, the Wisconsin Department of Natural Resources and the Whooping Crane Recovery Team will use these techniques (and others) in an attempt to re-introduce a wild, migratory flock of Whooping cranes back to Eastern North America. This combined effort will require the talents and expertise of many individuals and is based on the research contributions of numerous agencies.

Drawing from our experiences, Operation Migration developed the following protocol for costume rearing, flight conditioning, migration and subsequent release of Sandhill Cranes and Whooping Cranes as required in Phase I and II of the reintroduction project.

Protocol:

The first Whooping Cranes reintroduced into an Eastern habitat will not have the benefit of wild cranes to teach them wild behaviour; particularly human avoidance.  Therefore, Operation Migration believes that to produce wild birds that will avoid humans but will also follow an ultralight, every effort should be made to reduce human contact during the training period.  Human contact is defined as the presence of the human form including costumed handlers, the sounds of human activity including voices and the presence of man-made environments and equipage.

This rationale may be used as an argument to support the decision to raise birds in the field as opposed to a propagation facility, however, both options have benefits.   If the Recovery Team prefers the security of an established rearing center, some thought should be given to creating a more natural environment in the enclosure used to raise birds for this release.  This could involve using foliage to disguise walls and fences and the use of recorded marsh sounds to mask the noise of human activity.  In the early stages, it is also important to introduce adult role models or taxidermic brood mounts to the young colts.  Using puppet heads extensively for food and water training can reinforce the natural experience and add a control and communication element to later training sessions.

Notes on rearing facilities:

In the past, Operation Migration has benefited from the assistance of the USGS Patuxent Wildlife Research Center.  Birds for two studies were raised at Patuxent until pre-fledge age, before being transported to Ontario.  They have also raised birds for studies conducted by Dr. Ellis (trucking) and Kent Clegg (ultralight).  Patuxent staff initiated many of the innovations that led to the successful conclusion of our experiments and many of these are highlighted in this protocol.  They have raised more birds for release than any other propagation center and are the only facility to prepare birds for ultralight migration studies. They can also provide adequate isolation in which to condition pre-fledge birds to the aircraft.  Use of Patuxent to raise the birds guarantees a high survival rate and makes use of the expertise they have accumulated.

Flight Conditioning:

By far, the most human contact time necessary will be when we encourage the birds to follow an aircraft.  To minimize this time, it is essential to begin conditioning the birds to the aircraft as early as possible.  While the eggs are still in the incubator and after the chicks have pipped, a recording of the aircraft engine should be played regularly until the birds are moved to the rearing pen.

The Cosmos aircraft used by OM has a removable wing allowing the “trike” to be driven like a powered tricycle.  As soon as the chicks are old enough to venture outdoors, the aircraft should be started and run directly outside and in view of the pen area.  This familiarizes the young birds with the sights and sounds of the real aircraft, including its loudness and the feel of the wind from the prop-wash.

In earlier studies, OM made the mistake of having young chicks follow costumed handlers to a distant field for taxi training with the aircraft.  Inadvertently, the birds were taught to follow the handlers and not the aircraft.  To correct this error, it is important to minimize the number of times a chick is led by a walking handler.

At 2 to 3 days of age, the birds should be taken on daily walks with the aircraft.   Chicks should be carried or led by a costumed handler out of the propagation building, a minimal distance, to the waiting aircraft and thereafter, led by the handler in the aircraft.  Mealworms can be used to entice the chicks and a puppet head on an extension arm can be used to help control them. These “trike-walks” need only cover a short distance and the length can be extended as the chicks mature. This can also be used as an opportunity for social integration, however, the handler must be cautious of prop strikes that could result as the chicks try to avoid attacks from flock mates.  Later, as their endurance increases, the group can be led to a pond and allowed to forage near the aircraft.

Often a young chick, carried outside, will be so nervous that it is difficult to control its movements. To overcome this situation, Patuxent Wildlife Research Center staff built a circular pen thirty-feet in diameter and two-feet high. This allowed the handler to taxi around the outside of the enclosure while the chick followed from the inside, protected by the fence from mishap.  A second, smaller pen was erected in the center of the circle and birds that would not follow were placed in this area to watch the training. This form of abandonment conditioning has encouraged even reluctant chicks to eventually follow the aircraft.

As the birds mature and begin to socialize, they should be housed separately in groups of 4 to 6 individuals. This cohort size is easier to handle and are less independent than larger groups, making them more reliant on the handlers and more likely to follow the aircraft. Establishing the dominance of the aircraft as leader of the flight is an important part of conditioning the birds to follow.  If this can be accomplished early in the season the human contact time can be greatly reduced.

Later, as they begin to follow the ultralight in flight, they can be integrated into larger groups based on the dominance structure, culminating in one cohesive flock just prior to migration.

During all stages of flight conditioning the handlers must decide whether the benefits derived from the training outweigh the disadvantages of additional contact time. The birds’ behaviour must be used as a measure of this desired balance. As an example, if the pre-fledge chicks are eager to run after the aircraft then it is not necessary to continue training simply to reinforce the lesson.

Pens and Enclosures

Birds from the OM 1997 experiment were overly tame and landed in a number of schoolyards on their return migration. This led to the speculation that they may have been attracted by to schoolyards because of the similarity to the Patuxent Wildlife Research Center.  High chain link fences, large areas of cut grass and institutional looking buildings may have seemed familiar to the birds. In Canada, the birds were also housed in pens made of chain link fence. To reduce this possible connection, OM constructed pens for the 1998 study that were covered in heavy camouflage fabric. These panels also acted as a visual barrier allowing the handlers to control what the birds could see. Cut trees were placed in and around the top netted pen and all feeders and water containers were painted natural earth tones. The rear of the enclosure was built of open fence panels to allow a view of a wetland and all human paraphernalia was removed.

This type of pen may or may not be of benefit for the aforementioned problem, however it does provide the birds with a more natural environment and makes them more wary of all things human.

During fledging it is imperative that the holding pen be positioned adjacent to a field from which the aircraft can operate. When the birds are released for early morning training sessions they will immediately take-off.  If the aircraft is running and waiting outside the pen door, the pilot can take the lead on even the short flights that are typical of fledgling. If, however, the birds are kept in a large pen overnight they will fly at their own discretion and will not be as eager to follow the aircraft.

As the birds mature, they begin to establish their dominance structure. This order of leadership is an important factor to be considered during flight conditioning.  As they begin to follow the aircraft, the more aggressive individuals will lead the formation and each successive bird, all the way down to the most subservient, will find its own position in the pattern.  Once this is accomplished, all of the birds will follow the aircraft as a cohesive flock, content with the sequence and willing to follow the bird ahead.  Training flights that take place before this order is set invariably become leadership struggles and the flock will often break up into several uncontrollable units.

This dominance structure in the air starts with a “pecking order” on the ground and its development can be assisted by allowing the birds to forage on their own. If the flock is confined to a small pen, less assertive birds cannot escape the aggressions of larger ones and are often injured.  Releasing the birds to forage on their own allows them space and time to set their order and allows subservient birds room to escape aggression. It also provides a more natural environment.  It would be possible to minimize predation during these periods by monitoring the birds from a blind and/or constructing a five-acre release pen protected by an electric fence. It is important, however, to pen the birds at night in a smaller, top-netted enclosure for protection and to control their release for flight training.  Often, it is difficult to return the birds to the holding pen in the evening.  With practice (and careful observation) it is possible to strike a balance between providing adequate nourishment and controlled food withholding so the birds will move into the pen on their own to gain access to their feeders. This method avoids unnecessary handling of the birds.

Migration:

During migration the problems of isolation rearing become more evident.  The additional people involved in the ground crew and interest from the media and by-standers make the management of the flock’s experiences more difficult.  Having pre-arranged landing sites with alternates available, and the cooperation of the owners is imperative. To add an additional element of control to the first Whooping Crane migration study it may be wise to have two ground crews that “leap frog” ahead of the flight team to ensure that the landing sites are secure before the birds and aircraft arrive.  Operation Migration uses panels from the holding pen to construct a temporary enclosure while on migration. This provides housing for the birds in a system with which they are familiar and eliminates the need of introducing new, man-made materials.  Approximately 50% of the panels for this enclosure are visual barrier partitions and the other half are built of open fence panels.  This allows the ground crew to position the pens to obscure an undesirable view of buildings or other human environs.

Wintering Site:
In 1998, OM constructed a 250 X 150 ft. release pen at the wintering site.  This open topped enclosure was protected by three strands of electric fence wire and erected mostly in water 3 to 18 inches deep. It is important that this pen be as large as possible so the birds can forage unaware that they are contained. Because of the electric fence, ground predators cannot crawl under the barrier and are forced to jump over it.  The resulting “splash” as they land acts as a warning to the birds inside. The water area also taught our flock to water roost.  During OM’s last study, this type of pen protected the flock from the large number of bobcats that lived in the area, however it did not afford protection from airborne predators.  The portable travel pen was set up in the center of the release pen to hold the birds at night.  The flock was released during the day and led on early morning local flights to familiarize them with the area.  These forays always terminated back at their pen.   After two weeks the portable pen was removed, leaving the feeding station.   This allowed the birds to fly free.  They were encouraged to stay in the area by means of an ample food supply; the presence of a costumed dummy and daily visits by a costumed handler.