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).

Tom Stehn, USFWS biologist, Aransas National Wildlife Refuge and assocates recently completed another census of whooping cranes at Aransas. Stehn reports that, “The eighth aerial census of the 2008-09 crane season at Aransas was conducted February 24-25, 2009 with USFWS observer Tom Stehn in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas. Viewing conditions were very good for the survey, although strong winds made for a very choppy ride.”

Stehn advised that, “We found 238 whooping cranes, but time limitations required us to fly at
greater speeds making it likely a few whooping cranes were overlooked. Strong tail winds and full power gave us at one point a maximum recorded speed of 198 mph on our GPS.”

Whooping Crane Numbers
The estimated peak winter flock size remains at 232 adults + 38 juveniles = 270 total. However, the last two census flights have documented additional mortality that has occurred at Aransas. I estimate the current flock size to be 228 adults + 25 juveniles = 253, but this figure may change depending on future observations.

Mortality
Mortality this winter is currently estimated at 4 adults/subadults and 13 juveniles totaling 17 whooping cranes. This is a loss so far of 6.3% of the wintering population (17 out of 270). The all-time worst winter on record was 1990 when 11 out of 146 (7.5%) whooping cranes died at Aransas. In the last 20 years, the current winter ranks as the second worst in terms of mortality, but we still have one month to go. The 3rd worst winter in 1993 showed a 4.9% loss at Aransas (7 out of 143). Mortality in the 2008-09 winter (17 birds) must be added to the 34 whooping cranes that left Aransas in the spring of 2008 and failed to return in the fall. Thus, 51 whooping cranes have died in the last 12 months, or 19.2% of the flock of 266 present at Aransas in the spring, 2008.

Three dead whooping cranes have been picked up this winter; two were emaciated. The wing from a juvenile whooping crane was picked up by refuge staff in the North Pt. Pasture on February 13th. The remainder of the carcass was in the mouth of an alligator at a freshwater dugout. This chick from the North Dunham Point family had separated from its parents as observed by staff on January 29th and February 11th. It presumably was sick and/or emaciated, a factor that contributed to its separation and made the juvenile vulnerable to predation.

Migration
One juvenile whooping crane was confirmed on the Platte River in Nebraska on February 20th. This is presumably the juvenile that had over-wintered in Oklahoma and probably moved north with sandhill cranes.

Sightings near Aransas
Three whooping crane subadults continue to use farm fields south of Austwell. They were seen in a pond next to an agricultural field.

Habitat use
Management practices are aiding the cranes this winter. Cranes on the flight included 28 observed at man-made fresh water sources, 9 on burned uplands, 13 on unburned uplands mostly foraging for tubers where feral hogs have rooted up the earth, 18 at game feeders, 1 on a shell road, and 20 in open bay habitat. Some water is starting to move back into the coastal salt marshes, although much of San Jose Island remained as dry tidal flats. Salinities remain high, measured at 30 ppt in the refuge boat canal. The drought rated as “exceptional” shows no sign of ending in central and south Texas. Many counties have imposed prescribed burn bans due to the fire danger.

Blue crabs are still scarce due to the drought. The refuge is continuing its program of supplemental feeding using corn. A moderate response by the whooping cranes has been observed with 100 photographs taken by remote motion-activated cameras in the past week of whooping cranes at refuge feeders. Other animals eating the corn include feral hogs, deer, raccoons, grackles and sandhill cranes.

The USFWS used up to 2 airboats the week of February 23rd to pick up abandoned crab traps in the crane area. This was done in conjunction with a program organized by Texas Parks and Wildlife Department to pick up traps all along the Texas coast. Volunteers running private boats picked up many traps on February 21st.

This entry was posted on Tuesday, March 3rd, 2009 at 3:53 pm and is filed under Aransas Updates, Census Flights. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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