trance (3 nests all) 6 in (15 cm); number of eggs 

 or young 1 to 3 (av. 2 eggs or young per nest). 

 Eggs glossy white, shell very thick for size of eggs, 

 which averaged 1.53 x 1.19 in (3.88 x 3.02 cm) 

 (Thayer 1906). 



A single egg hatched in captivity after 

 28 days of incubation (Lint 1966 in Forshaw 

 1973). Captive young were brooded by the fe- 

 male for the first 11 days after hatching; young 

 left nest 59 days after hatching (Dyson 1969 in 

 Forshaw 1973). At the Arizona-Sonora Desert 

 Museum, 2 pairs have bred successfully, 1 pair in 

 2 successive years. They began nesting in July, 

 but may start later. A clutch is usually 2 eggs 

 (Charles Hanson pers. comm. 1977). 



No nests with eggs or young of R. p. terrisi 

 have been reported. At La Mesa de las Tablas, 

 Coahuilain a flight of 91 parrots, pairs were always 

 in evidence, but many of the pairs seemed to be 

 accompanied by offspring, most often 2, some- 

 times only 1 and once 3. The groups of 3, 4, and 

 5 birds were about as frequent as unaccompanied 

 pairs, indicating that breeding success was good 

 (Ridgley WWF Report). 



MANAGEMENT AND CONSERVATION 



Ideas that have been presented are: To set 

 aside and protect adequate areas of mature ever- 

 green mountain forest in both the Sierra Madre 

 Occidental and Sierra Madre Oriental (Vincent 

 1966). Preservation of the rapidly disappearing 

 mature high mountain forests is the only obvious 

 method to preserve the species (Ridgley WWF 

 Report;King 1977). 



The species is Hsted in Appendix 1 of 1973 

 Convention on International Trade of Endangered 

 Species of Wild Fauna and Flora. It is protected 

 by law in Mexico, but the law is unenforceable in 

 practice because of the remoteness of the areas 

 where birds still occur. In 1976, 76 Thick-billed 

 Parrots {R. p. pachyrhyncha) were in captivity in 

 24 collections; of these, 10 (13%) were bred in 

 captivity (Olney 1976 in King 1977 ms.). Captive 

 rearing might be a means of aiding the survival of 

 the species until adequate wild populations are 

 assured. 



PREPARER'S COMMENTS 



It would appear that both subspecies of the 

 thick-billed parrot are endangered because of the 



steady eUmination of the high mountain conifer- 

 ous forests of northern Mexico, on which the 

 birds are completely dependent because of their 

 specialized feeding and nesting requirements: 

 large trees for nesting and pine seeds for nutrition 

 adequate for reproduction. There would seem to 

 be no remedy for this except the prompt setting 

 aside of a number of very large tracts of such 

 habitat where the parrots still occur, and exclud- 

 ing lumbering in those tracts. It is essential to 

 have a number of different areas because of the 

 periodic failure of pine cone crops in a particular 

 area. Much further investigation of nesting behav- 

 ior is needed, particularly to determine the im- 

 portance of cliff nest sites as compared with holes 

 in dead trees. 



AUTHORITIES 



Robert S. Ridgley 

 Department of Zoology 

 Duke University 

 Durham, North Carolina 27706 



John W. Hardy 

 Florida State Museum 

 University of Florida 

 Gainesville, Florida 32611 



Robert W. Dickerman 

 Department of Microbiology 

 Cornell University Medical College 

 1300 York Avenue 

 New York, New York 10021 



L. Irby Davis 

 2502 Keating Lane 

 Austin, Texas 78703 



Warren B. King 



871 Dolly Madison Blvd. 



McLean, Virginia 22101 



Charles A. Ely 

 Department of Zoology 

 Fort Hayes Kansas State College 

 Hayes, Kansas 67602 



Joe T. Marshall 



National Fish and Wildlife Laboratory 

 National Museum of Natural History 

 Washington, D.C. 20560 



Charles L. Hanson 

 Arizona-Sonora Desert Museum 

 Tucson, Arizona 



