sandee@sun16.scri.fsu.edu (Daan Sandee) (09/14/90)
In article <1201@cluster.cs.su.oz.au> andrewt@cluster.cs.su.oz (Andrew Taylor) writes: >In article <675@sun13.scri.fsu.edu> sandee@sun16.scri.fsu.edu (Daan Sandee) >writes: >> [useful info about the Atitlan Grebe] >>It was definitely flightless. > >I had a vague memory of being told by someone they had seen one fly but maybe >my memory is faulty. I checked Seabirds of the World which I think said >"almost" flightless. I see I have to back up my statements by citing my authorities. A. LaBastille, "Ecology & Management of the Atitlan Grebe, Lake Atitlan, Guatemala", Wildlife Monographs No. 37, 1974. [For the purists : there is a diacritical sign on the last a in 'Atitlan', indicating the stress is on the last syllable.] LaBastille specifically notes that previous reports have surmised that it could fly, but refutes this based on (a) direct observation, including reports from local inhabitants (b) thorough examination of physiology (wing size and pectoral muscles). > >> ... the A.O.U. uses interbreeding as the criterium for species determination, > >It seems to me this only helps in the easy case. If the ranges of two >populations overlap but they never interbreed then you call them separate >species. Correct. I wasn't complaining about their criterium - I was merely using it. LaBastille again : no interbreeding at all was observed between Atitlan Grebe (Podylimbus gigas) and the sympatric population of Pied-billed Grebe (P.podiceps). As with the flightlessness or otherwise, earlier opinions to the contrary by other scientists are not based on evidence, or based on other criteria than interbreeding. >But what does the A.O.U do if the ranges don't overlap (common >in Australia) and surely it doesn't declare two populations to be >the same species just because interbreeding has been recorded? > >Andrew David Mark has already answered that question (thanks, David). Daan Sandee sandee@sun16.scri.fsu.edu Supercomputer Computations Research Institute Florida State University, Tallahassee, FL 32306-4052 (904) 644-7045
mjm@oliven.olivetti.com (Michael Mammoser) (09/15/90)
In article <687@sun13.scri.fsu.edu>, sandee@sun16.scri.fsu.edu (Daan Sandee) writes: > > I see I have to back up my statements by citing my authorities. > A. LaBastille, "Ecology & Management of the Atitlan Grebe, Lake Atitlan, > Guatemala", Wildlife Monographs No. 37, 1974. > [For the purists : there is a diacritical sign on the last a in 'Atitlan', > indicating the stress is on the last syllable.] > LaBastille specifically notes that previous reports have surmised that it > could fly, but refutes this based on > (a) direct observation, including reports from local inhabitants > (b) thorough examination of physiology (wing size and pectoral muscles). I read that it was a "weak flyer", though this was a general literary reference and not a specific study paper. However, I was wondering how one goes about verifying flightlessness through direct observation. This would seem to be quite tricky. For instance, I have directly observed thousands of Pied Billed Grebes, but can't recall ever seeing one fly. What conclusions can I draw from this? :-) Mike
sandee@sun16.scri.fsu.edu (Daan Sandee) (09/15/90)
In article <49409@olivea.atc.olivetti.com> mjm@oliven.olivetti.com (Michael Mammoser) writes: >In article <687@sun13.scri.fsu.edu>, sandee@sun16.scri.fsu.edu (Daan Sandee) writes: > > LaBastille specifically notes that previous reports have surmised that it > > could fly, but refutes this based on > > (a) direct observation, including reports from local inhabitants > > (b) thorough examination of physiology (wing size and pectoral muscles). > > I read that it was a "weak flyer", though this was a general >literary reference and not a specific study paper. However, I was >wondering how one goes about verifying flightlessness through direct >observation. This would seem to be quite tricky. For instance, I have >directly observed thousands of Pied Billed Grebes, but can't recall >ever seeing one fly. What conclusions can I draw from this? :-) > >Mike You're absolutely right. Direct observation can only provide negative evidence of flightlessness, which is inconclusive. Hence LaBastille spends several pages in her monograph on the bird's physiology with respect to its flying potential, and concludes that it most probably could not fly. As for Pied-billed Grebe : I can't remember ever having seen one fly, either. Though people who have seriously studied the bird no doubt have. There is circumstantial evidence of its flying capacity : it's a partially migratory bird, and even if there are no banding records, its seasonal appearances and disappearances suggest migration ; unless you assume, as scientists in centuries past did, that it hibernates in the mud, or gets turned into a barnacle, or something. And I do suppose it migrates by air - it doesn't walk, or swim the rivers, or something. (I'm not being sarcastic. Just making a thorough scientific investigation.:-)) Daan Sandee sandee@sun16.scri.fsu.edu Supercomputer Computations Research Institute Florida State University, Tallahassee, FL 32306-4052 (904) 644-7045
wander@csa2.lbl.gov (ADRIAN WANDER) (09/15/90)
In article <689@sun13.scri.fsu.edu>, sandee@sun16.scri.fsu.edu (Daan Sandee) writes... >In article <49409@olivea.atc.olivetti.com> mjm@oliven.olivetti.com (Michael Mammoser) writes: >>In article <687@sun13.scri.fsu.edu>, sandee@sun16.scri.fsu.edu (Daan Sandee) writes: >> > LaBastille specifically notes that previous reports have surmised that it >> > could fly, but refutes this based on >> > (a) direct observation, including reports from local inhabitants >> > (b) thorough examination of physiology (wing size and pectoral muscles). >> >> I read that it was a "weak flyer", though this was a general >>literary reference and not a specific study paper. However, I was >>wondering how one goes about verifying flightlessness through direct >>observation. This would seem to be quite tricky. For instance, I have >>directly observed thousands of Pied Billed Grebes, but can't recall >>ever seeing one fly. What conclusions can I draw from this? :-) >> >>Mike > >You're absolutely right. Direct observation can only provide negative evidence >of flightlessness, which is inconclusive. Hence LaBastille spends several pages >in her monograph on the bird's physiology with respect to its flying potential, >and concludes that it most probably could not fly. >As for Pied-billed Grebe : I can't remember ever having seen one fly, either. >Though people who have seriously studied the bird no doubt have. >There is circumstantial evidence of its flying capacity : it's a partially >migratory bird, and even if there are no banding records, its seasonal >appearances and disappearances suggest migration ; unless you assume, as >scientists in centuries past did, that it hibernates in the mud, or gets >turned into a barnacle, or something. And I do suppose it migrates by air - >it doesn't walk, or swim the rivers, or something. >(I'm not being sarcastic. Just making a thorough scientific investigation.:-)) > >Daan Sandee sandee@sun16.scri.fsu.edu >Supercomputer Computations Research Institute >Florida State University, Tallahassee, FL 32306-4052 (904) 644-7045