Morphometric , Karyotypic , and Laparoscopic Techniques for Determining Sex in Bald Eagles

Willow ptarmigan (Lagopus lagopus lagopus) were censused in late summer for 4 years and broods classified as first, renest, or null (empty) broods. From brood frequencies and clutch size data, estimates were made of egg production, hatching success, survival of young, and contribution to production of each class. Loss of first clutches (N = 231) averaged 27%, and renesting compensated for 43% of the eggs lost. Clutch loss and survival of chicks were similar for both classes. Adults composed 18% (N = 462), first nest chicks 70% (N = 1,792), and renest chicks 12% (N = 299) of the late summer population. Renest chicks compensated for an estimated 45% of the first nest chicks lost due to first clutch destruction. Production from renests was close to the maximum possible during this period of high production and rapid population increase. J. WILDL. MANAGE. 49(3):599-604 Many single-brooded species respond to nest destruction by laying repeat or renest clutches. Renesting has been documented for most members of the Tetraonidae (Angelstam 1979, Parker 1981, Storaas et al. 1982), the ring-necked pheasant (Phasianus colchicus) (Seubert 1952, Warnock and Joselyn 1964, Gates 1966, Dumke and Pils 1979), and probably occurs among all galliforms. Errington (1942) derived an equation from which the contribution of renestings to brood production could be calculated, but for a hypothetical species. In this study, estimates are made of the success of the first and renest clutches, survival of young from first and renest broods, and the contribution of both classes to production, based on quantitative information about eggs and young from intitial and repeat layings.