Proposal (75) to South American Classification Committee
Separate Pterodroma sandwichensis from P. phaeopygia
(i.e., Hawaiian from Galapagos [Dark-rumped] Petrel)
Tomkins and
Milne (1991) presented information suggesting that the Galapagos and Hawaiian
populations of Dark-rumped Petrel might be distinct at the species (rather than
subspecies) level. Galapagos birds are 16% larger, but Hawaiian birds lay eggs
that are 18% larger. (Presumably Hawaiian females make louder squeals during egg-laying.) Black markings on the white forehead are
variable (sometimes lacking) in Galapagos birds but are lacking in Hawaiian
birds. Hawaiian birds have a short, well-defined nesting period, but Galapagos
birds have an extended, almost-always nesting period (but there are several
island colonies). And, sonograms of the two populations are said to be very
different. However, Tomkins and Milne (1991: 12) show sonograms, and Simons
(1985:236) show sonograms, but I find them impossible to compare. There is no
evidence (but there is speculation) that they occur together in non-breeding
times. This 1991 paper was apparently convincing enough that Sibley and Monroe
split the species in 1993. [Why Burt did not do that for the Check-list
is another continuing mystery. He kept them as groups.] They used the names
Hawaiian Petrel and Galapagos Petrel, maintaining Dark-rumped for the
combination.
Browne et
al. (1997) summarized the above and did allozyme electrophoresis on blood from
members of the two populations (no voucher specimens). They found one fixed
allelic difference between them, out of 13 loci. They say this
"supports" their recent elevation to species status by S&M. This
paper also summarizes morphological differences and mentions vocal differences.
One of the
coauthors of Browne et al. (1997) was also a coauthor of the BNA account on Pterodroma
phaeopygia (Simons and Hodges 1998). The Condor article was submitted in
Dec. 1996, accepted April 1997, and in the August issue. The BNA account was
submitted in Jan. 1997, published in 1998. Thus, work on the two papers was
simultaneous. However, the BNA account makes NO mention of the genetic work,
and the possible specific status of the two forms was downplayed. That is very
interesting.
Pratt and
Pratt (2001) recognize sandwichensis at the species level.
Recommendation: I think
we should split these populations into species.
References
Browne, R.
A. et al. 1997. Condor 99:812-815.
Pratt and
Pratt. 200l. SAB on Hawaii
Sibley and
Monroe 1993. Supplement
Simons, T.
R. 1985. Condor 87:229-245. Re Hawaiian birds
Simons and
Hodges. 1998. BNA 345
Tompkins,
R. J., and B. J. Milne. 1991. Notornis 38: 1-35.
Richard C. Banks
Addendum
from Remsen: No one on AOU CLC, including Dick, was impressed one way or
another on the evidence either way on this one, but in the end, we decided
unenthusiastically to go with the split because there seemed to be less
evidence for considering them the same species than for considering them
separate (and recognizing that the original lump of the two was probably based
on "data-free" opinion.) We fearfully assumed that the described
differences in voices are OK, and we were impressed with the differences in
reproductive biology between them.
Ridgway
described sandwichensis as distinct species. Of interest is that Jouanin
& Mougin (1979) ("Peters") considered sandwichensis a
"doubtfully distinct" species, and this was
repeated by Carboneras (1992) ("HBW"); this influenced
Dickinson (2003) to recognize them only as subspecies (and that's the genesis
of SACC's current classification).
[I haven't
checked to see if more recent data have been published -- please chime in if
you know of some.]
References:
CARBONERAS,
C. 1992b. Family Procellariidae (petrels and shearwaters). Pp. 216-257 in
"Handbook of the Birds of the World, Vol. 1" (J. del Hoyo et al.,
eds.). Lynx Edicions, Barcelona.
JOUANIN,
C., AND J.-L. MOUGIN. 1979. Order Procellariiformes. Pp. 48-121 in "Check-list
of birds of the World, Vol. 1, Second Edition" (Mayr, E. & G. W.
Cottrell, eds.). Museum of Comparative Zoology, Cambridge, Massachusetts.
________________________________________________________________________________________
Comments
from Robbins: "[YES]. I did not appreciate how weak the data are for this
split, but given that it is suggestive and everyone has been splitting these I
guess we should follow. Thus, I vote "yes" for recognizing them as
two species."
Comments
from Stiles: "This is one I'd love to abstain on, but if passing the
buck isn't to be allowed, I will most reluctantly vote YES, largely because the
AOU checklist committee did so (and as "hijito", it might not be good
to flout "Papa's" decisions, however off-base we might consider them
- and I do think this was not one of their wiser decisions). I am decidedly
skeptical about using genetic analysis to decide species-level questions,
especially if sampling was not dense, and the breeding-season argument cuts
both ways - there are a number of cases of seabird populations on different
islands differing in breeding seasonality - Sooty Tern comes to mind). A more
thorough statistical analysis of both vocalizations and measurements would also
help."
Comments
from Zimmer: "YES, although the evidence is weak."
Comments
from Jaramillo: "YES. I think that Procellariiformes will give Scytalopus
a run for their money in the end. This is a not a group that tends towards
divergence in plumage pattern, and my guess is that many taxa currently
classified as subspecies are probably good and very well differentiated
species. Admittedly this is a gut feeling more than anything, but as soon as
more vocal data are available, and when a careful molecular analysis is
performed on the group we may end up being surprised at the results. I will
stop there and just say that I am comfortable with this split."
Comments
from Nores: "YES. Acepto
reconocer a Pterodroma sandwichensis como especie.
Aunque cabe reconocer que la evidencia es liviana y el trabajo genético que ser
fuerte, tiene la contradicción (o falta de aceptación del coautor) indicada por
Richard."