We monitored the survival, dispersal, and home-range establishment of captive-bred, reintroduced puaiohi Myadestes palmeri, a critically endangered thrush endemic to the island of Kauai. Fourteen captive-bred, juvenile birds were released from hacktowers in January-February 1999 and monitored for 8-10 weeks using radiotelemetry. All 14 birds (100%) survived to 56 days post-release. Two birds (14.3%) dispersed greater than 3 km from release site within 1 day of release. The remaining birds settled within 1 week and established either temporary home-ranges (mean area=7.9 AE 12.0 ha, range 0.4-31.9) or breeding home-ranges (mean area 1.2 AE0.34 ha, range 0.8-1.6). Temporary home ranges were abandonded by the beginning of the breeding season, and ultimately 6 of the 14 birds (43%) established breeding home ranges in the release area. The high survival rate bodes well for establishing additional populations through captive breeding and release; however, the 57% dispersal rate out of the target area means that several releases of birds may be necessary in order to repopulate a given drainage. Furthermore, observed dispersal and gene flow between the reintroduced and wild populations have important implications for management of the captive flock. Published by Elsevier Science Ltd.
The currrent California condor (Gymnogyps californianus) recovery plan entails increasing the reproductive rate via replacement‐clutch manipulation of eggs. During the period from 1983 to 1985, 15 eggs were removed from wild nesting pairs for artificial incubation. The eggs were incubated at a dry bulb temperature of 36.4°C in modified forced‐air Lyon Electric incubators. The incubation humidity was adjusted for individual eggs based on weight loss data (water = weight), 25.6–30.0°C wet bulb (41.0–63.0% Relative Humidity (RH)). The chicks were hatched initially under forced‐air conditions of 36.1°C dry bulb, 31.1–01.7°C wet bulb (70.0–73.0% RH). In 1984, hatching parameters were changed to still‐air conditions, 36.1°C dry bulb (top of the egg), 35.0°C dry bulb (bottom of the egg), 31.1–31.7°C wet bulb (70.0‐73.0% RH). Tactile and auditory stimulation was utilized during the pip‐to‐hatch interval. From among 15 eggs collected, 13 hatched, and 12 condor chicks were raised successfully (hatchability: 86.7%; survivability: 92.3%).
The Peregrine Fund, Boise, IdahoCalifornia condors are one of the most endangered species native to the mainland United States and are subject of intense effort regarding captive breeding and reintroduction. We analyzed 20 years of California condor egg records from the wild and from three captive propagation facilities for fertility, hatchability, and chick survivability, along with changes in egg size due to multiple clutching. Overall annual mean percent of fertile eggs was 80.2%, hatchability was 87.3%, and chick survivability to Z60 days was 95.5%. One egg-laying site had a significantly lower fertility rate (P r 0.0001) than the other sites, which was probably due to pair incompatibility rather than any physiological factors. Egg volume of the first egg was significantly greater than both the second (t ¼ 6.73, P ¼ 0.0001) and third egg (t ¼ 6.62, P r 0.0001) of the season, while the second egg had a significantly greater volume (t ¼ 3.20, P ¼ 0.0084) than the third egg. Chicks from the second egg (t ¼ 3.24, P ¼ 0.029) and third egg (t ¼ 7.94, P ¼ 0.0014) of the season were significantly smaller than chicks from the first egg of the season. The decrease in egg measures and chick hatch weight due to multiple clutching did not affect hatchability or chick survivability. There were significant positive relationships (Po0.0001) between fresh egg weight and chick hatch weight and between egg volume and chick hatch weight, as well as between fresh egg weight and egg volume. In spite of the decrease in fresh egg weight, egg volume and chick hatch weights, due to egg removal to stimulate double and sometimes triple clutching, the captive propagation program has been
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