ASPECTS OF REPRODUCTION AND PAIR BONDS IN FLORIDA SANDHILL CRANES

From 1980-98 we captured and uniquely marked more than 400 Florida sandhill cranes (Grus canadensis prafensis). Age ratios of the marked population, excluding juveniles, was 66% adult and 33% subadult, and the sex ratio was 49% male and 51% female. Average clutch size for 210 nests checked from 1983-97 was 1.78 ± 0.18 (SD) and frequency of l-egg clutches varied among years. Average post-fledging brood size from 1991 to 1997 was 1.27 ± 0.17 (SD), included a 3-chick brood. Average percent ofYOlmg from 2 study areas, 1991-97 was 11.9 ± 3.23 (SD). We observed renesting up to 3 times, even after chicks had been hatched and reared for up to 16 days. Re-pairing following death or divorce was documented and was particularly noteworthy in a female that oscillated between 2 males during 4 years of observation

AN INDIVIDUALIZED MARKING SCHEME FOR SANDHILL CRANES AND ITS USE TO DETERMINE FALL MIGRATION INTERVAL

A color-band based marking scheme was used for individually marking sa ndhill cranes in Florida. The band-loss rate was 2.8% per year between 1977 and 1988. Band loss was greatest on bands placed below the ankle joint and occurred most frequently during years 2 to 5. Color-marked individuals monitored during fall migration averaged 6.2 days (r=5-13 days) between the Jasper-Pulaski Fish and Wildlife area in northwestern Indiana and winlering areas in northern Florida

Timing of Molt in Florida Sandhill Cranes

We observed feather molt in Florida sandhill cranes (Grus canadensis pratensis) between 1978 and 1997. We report data from 4 feather groups: remiges, rectrices, wing coverts and contour feathers. In all feather groups, the median date of ecdysis preceded endysis by about 30 days. Endysis in adults was generally later than it was in first- or second-year subadults. Remiges grew at a rate of 4.72 ± 1.56 SD mm per day. We estimated that primary and secondary wing feathers were usually regenerated within 45 to 70 days

Interaction of Young Florida Sandhill Cranes with Their Parents

We studied the interactions of 46 Florida sandhill crane (Grus canadensis pratensis) chicks and their parents from hatching until the chicks left the family group. Our goal was to see if young remained closer to one parent than the other and if the distance between a chick and its parents increased as the young approached the age of independence. Using a population of individually marked adult pairs, we ranked the distance to and gender of the nearest parent during 233 30-minute observation periods. Between hatching and 180 days of age, chicks showed a greater tendency to be nearer the female than male parent. Before 265 days of age there was a greater probability that the chick would be within 5 m of its nearest parent. After 265 days of age the probability that a chick would be ≥ 20 m from its nearest parent increased. These 2 ages may represent developmental milestones that could have relevance for captive management and reintroduction strategies. By the end of the first stage (180 days), the benefits of being reared by their parents may have peaked for crane chicks and the end of the second stage (265 days) could be the optimal time for releasing captive-reared cranes into the wild

RESPONSE OF FLORIDA SANDHILL CRANES TO NEST INSPECTION

We observed the response of nesting Florida sandhill cranes (Grus canadensis pratensis) to 27 instances of nest inspection. The disturbed bird flew from the area 81% and walked 19% of the time. The median distance moved was 330 meters (range 28 to 480 meters). The median length of time the nest was left unattended following inspection was 50 min (range: 10 to 166 min). The median length of time that observers stayed at the nest was 16 min (range: 5 to 48 min). Ten of the nests inspected (40%) eventually failed to produce young. Statistical analysis was focused on the direction and strength of association between various predictors and 4 disturbance-related outcomes; flying vs. walking, distance moved, time-off-nest, and nest fate. A limited sample size precluded the use of more than 2 predictors simultaneously in any of the statistical models. We found that the farther into incubation the nest was (nest age) the greater the likelihood the incubating bird would fly from the nest (r2=0.28, P= 0.064). Greater time-in nest area was associated with a longer time-off-nest (r2=0.29, P= 0.008). Greater time-in nest area and longer time-off-nest were both univariantely associated with a greater probability of nest failure (r2=0.36, P=0.018 and r2=0.40, P=0.008 respectively). Four variables (time-in-area, time-off-nest, age of nest, whether the disturbed crane or its mate returned to the nest) considered in pair wise combinations were all significantly associated with probability of nest failure (r2 range: 0.46 to 0.72). Longer time-in-area and whether the disturbed bird was the returning bird had the strongest overall association with likely nest failure (r2=0.72, P=0.010). Although the nest failure rate of 44% in the experimental nests was greater than the failure rate of 26% for a concurrently collected sample of control nests, the 2 rates were not significantly different (P=0.353). Based on these results we would recommend that crane nests be inspected in 12-13 min or less. If possible, nest inspections should occur later rather than earlier in the incubation period, carried out in a manner that increases the likelihood that the disturbed bird will walk rather than fly from the nest area, and timed to increase the chance that the non-disturbed bird will be the returning bird

Survival and Sources of Mortality in Florida Sandhill Crane Chicks – Hatching to Fledging

Forty-five pairs of Florida sandhill cranes (Grus canadensis pratensis) were monitored during the nesting seasons from 1996 through 1999. Thirty-eight chicks were produced from 25 successful nests. Twenty-one of these survived to fledging age. Predation was the source of most (81%) of the mortality for which a cause was determined. Mammals were the primary predator. Average age at time of mortality was 27.2 days for the 17 chicks lost

INJURIES AND ABNORMALITIES OF SANDHILL CRANES CAPTURED IN FLORIDA

Observations of gross pathological abnormalities were made during handling of sandhill cranes (Grus canadensis) captured for banding in Florida. One hundred fifty-six of 1,331 (11.7%) cranes examined showed evidence of one or more anomalies that were the result of disease, congenital deformity, or injury. Most frequent were abnormalities of the legs and feet, followed by abnormalities of the bill. Injuries of the eyes, head, and neck were also noted. Many of these birds were observed subsequent to banding and survived for several years with their injuries, though some never succeeded in reproducing

THE USE OF RADIO TRANSMITTERS TO MONITOR SURVIVAL OF SANDHILL CRANE CHICKS

To determine cause of death of Florida sandhill crane (Grus canadensis pratensis) chicks, in 1996-99 we glued shorttenn transmitters on newly hatched chicks. At about 10 days of age, these were replaced with surgically implanted subcutaneous transmitters in the field. Chicks were then recaptured at 55 to 65 days of age for more pennanent transmitters. This combination of transmitter configurations allowed us to track individuals through their rapid-growth period