Last year the decision was made by the Florida Fish and Wildlife Conservation Commission (FWC) to discontinue the release of whooping cranes into Florida’s non-migratory flock. The FWC accepted the recommendation from the multi-agency International Whooping Crane Recovery Team.
The team created the release program 15 years ago in an effort to establish a self-sustaining, non-migratory whooping crane population in Florida. Naturally occurring whooping crane populations in the southeastern United States disappeared by the 1930s.
Scientists decided to stop releasing cranes into the non-migratory flock for a variety of reasons, including problems with survival and reproduction, both of which have been complicated by drought. Additional considerations included shorter-than-expected life spans, scarcity of birds for release, project costs and the loss of habitat from development. The team felt that project resources and birds produced in captivity could be better used for other whooping crane releases as well as to maintain the captive flock.
Marty Folk, whooping crane project leader with the Florida Fish and Wildlife Conservation Commission continues to monitor the population and has provided an update report concerning the 2009 Breeding Season.
Marty reports that, “Conditions have been very dry in Florida for several years. Attached is an image we recently took of a small lake in Lake County. The area outlined in green is the normal shoreline. All marshes in this area are completely dry. The drought continues but despite that, we now have an active nest. This pair’s marsh holds water only because of a hydrological connection to a large lake. As you know, the goal of this project now has shifted to an emphasis on increasing our knowledge of the problems, especially regarding reproduction and survival. Toward that end, we are monitoring the nest intensively by employing video surveillance. There’s a chance we might see several other nest attempts this year, but we don’t expect more than 3 nests from the population’s 11 pairs. The current population consists of 11 males and 18 females.”
Marty continues, “Drought is an obvious problem for breeding, but even in wet years some pairs failed to hatch eggs, so we are looking at incubation behavior to see if some pairs don’t incubate ‘properly’. We are computerizing a back-log of surveillance video that will allow us to look for problems with behavior by comparing successful vs. unsuccessful pairs. Thus far we have computerized >800 hours (that’s not a typo-800 hours) of incubation behavior and still have a lot to go.”
Marty advises that in addition to long-term drought, other major problems include survival of individual whoopers. Marty explains that, “Male Florida whooping cranes are not living as long as they should; the general rule is that they die by age 10. Females are doing better and 9 birds are >9 years of age (the 2 oldest are turning 16 this spring).However, for both males and females, we don’t have good data on what happens to them when they “disappear”. Some birds, at time of disappearance, did not have functioning transmitters and so could not be tracked. Even for birds with functioning transmitters, if a carcass is not retrieved within 24 hours of death, scavenging and decomposition make it very difficult to determine cause of death. Others likely dispersed beyond a reasonable tracking distance and were never seen again.”
Florida wildlife officials are attempting to get a better understanding of the problems by intensive monitoring. Marty describes, “When we plot dates of mortality/disappearance by age, we see that most older cranes die/go missing from March-June. With that knowledge, we’ve begun an intensive monitoring schedule that involves checking high-priority (older) birds on a daily basis. We’ve not monitored this intensively since the early days of the project; our normal schedule has been 2-3 checks/week. Our hope is to recover downed birds asap so that necropsies can provide the best possible data.”
Marty concludes that, “We do know that perhaps one reason males don’t survive as well as females is that they are more prone to power line collisions, and may be more prone in general to other traumatic events and also predation. We speculate that it is associated with the males’ role in defending a territory, and also the males’ general tendency to lead the group. So now we are collecting behavioral data on who leads flocks of whooping cranes, both in flight and on the ground, to look for trends.”
The Florida whooping crane team has been flying roughly one day/week to track migratory whooping cranes this winter. From the ground they have also been able to monitor 4 migratory birds in Polk County (the ultra-light led whoopers).