Proposals (209-211) to South American Classification Committee
Proposals for the taxonomic treatment of Red-legged Tinamou Crypturellus erythropus
209. Split Crypturellus columbianus from C. erythropus
210. Split Crypturellus idoneus from C. erythropus
211. Split Crypturellus saltuarius from C. erythropus
This set of proposals is made with a view to providing an SACC view for conservation decision-makers and others on a taxonomically complicated and controversial group. The three taxa Crypturellus (erythropus) columbianus, C. (e.) idoneus and C. (e.) saltuarius, particularly the first and third, have often been regarded as separate species. Two of them, C. (e.) columbianus and C. (e.) saltuarius, are currently classified as threatened species in many assessments. BirdLife International recently sought views from myself and others on whether to adopt the current SACC treatment for this group (which would result in these species being lumped) because the current SACC baseline treatment differs from that which they currently follow and because two of the taxa are threatened. As the matter has not been considered by the SACC, I suggested that it would be prudent to raise a series of SACC proposals dealing with these issues in advance of BirdLife changing its treatment. BirdLife will delay taking a decision on this issue pending outcome of this series of SACC proposals and will likely adopt the SACC consensus. I have also included here a proposal for C. (e.) idoneus here which, although not treated as separate by BirdLife International, has been treated as a separate species by some authors.
Recent taxonomic treatments:
The taxonomy of the red-legged medium-sized Crypturellus has been controversial for decades. Per the current SACC baseline comment, "species limits in this complex are poorly understood and weakly justified, and a thorough study, especially of voice, is badly needed" and "species-level taxonomy and allocation of subspecies to species has been exceptionally labile, perhaps more so than any other species complex in the New World".
Red-legged Tinamou C. erythropus is a widespread species of the lowlands of South America, found in forest and in some disturbed habitats. The races C. e. cursitans, C. e. margaritae and C. e. spencei, all of lowlands east or north of the Andes, have consistently been treated as being conspecific with the nominate form. However, three other taxa currently regarded as part of C. erythropus in the SACC baseline have often been regarded as separate species by many authors:
1. Colombian Tinamou C. (e.) columbianus, of the Nech’ lowlands of Colombia. Treated as separate by: e.g. Hellmayr & Conover 1942; Meyer de Schauensee, 1964 (within C. noctivagus but not C. erythropus) & 1970; Stotz et al., 1998; BirdLife International 2000; Salaman et al., 2001; Renjifo et al., 2002; Donegan et al., 2003; BirdLife International 2004).
2. Santa Marta Tinamou C. (e.) idoneus of the foothills of the Santa Marta mountains of Colombia and northern Perij‡ mountains of Colombia and Venezuela. Treated as separate by: e.g. Meyer de Schauensee 1970; Salaman et al., 2001; Donegan et al., 2003.
3. Magdalena Tinamou C. (e.) saltuarius of the Magdalena valley in Colombia (historically, western Perij‡ mountain foothills and possibly, lowlands of Serran’a de San Lucas and other sites in Colombia's Magdalena valley). Treated as separate by: e.g. Hellmayr & Conover 1942; Meyer de Schauensee, 1964 & 1970; Stotz et al., 1998; BirdLife International 2000, Salaman et al., 2001; Renjifo et al., 2002; Donegan et al., 2003; BirdLife International 2004.
Other authors (e.g. Hilty & Brown, 1986; Dunning, 1987; Schwarz & Lentino, 1984; Sibley & Monroe 1990; Cabot, 1992; Davies 2002; Bertelli et al., 2002; Hilty, 2003; Bertelli & Porzecanski 2004), tentatively lump all or some of these forms, though again almost always with comment.
Although sufficient taxonomic chaos could be considered to exist among these three taxa, the entire red-legged medium-sized Crypturellus group is a very difficult one and has been subject to multiple different treatments. Plagiarising the SACC baseline comment for this group (with some small editions): within subspecies included in the SACC baseline within C. erythropus, Meyer de Schauensee (1966) suggested that C. e. cursitans was actually a subspecies of C. duidae. Blake (1977) suggested that C. (e.) columbianus was possibly a distinct species (as treated by Hellmayr & Conover 1942) or "perhaps a very distinct Colombian isolate of ... C. boucardi." Meyer de Schauensee (1964 and 1970) considered C. (e.) saltuarius as a distinct species, and Blake (1977) suggested that saltuarius might be a subspecies of C. kerriae (but that kerriae might also be a subspecies of Middle American C. boucardi). The subspecies idoneus and spencei were treated as subspecies of Middle American C. cinnamomeus in early Peters. Thus, Sibley & Monroe (1990) noted that the taxa C. (e.) columbianus, C. (e.) idoneus, and C. (e.) saltuarius, treated here as subspecies of C. erythropus, may deserve species rank or may belong in other species, an approach adopted by Stotz et al. (1998) among others. The taxon C. atrocapillus garleppi, here treated as a subspecies of C. atrocapillus (following Blake 1977, 1979) was formerly considered a subspecies of C. noctivagus (e.g., Hellmayr & Conover 1942, Peters) and perhaps merits species rank (Cabot 1992). Sibley & Monroe (1990) considered C. kerriae and C. erythropus, along with Middle American C. boucardi, to form one superspecies, and C. duidae, C. noctivagus, and C. atrocapillus to form a separate superspecies. Bertelli et al.'s (2002) analysis of phenotypic characters indicated that C. boucardi and C. kerriae are sister species, but otherwise found little support for the monophyly of this complex.
No strong opinions have been voiced in any of the above publications as to the treatment of this group, other than as to the fact that more research is needed and that the problem is a complex and difficult one. Those that lump the taxa typically comment that the four taxa in question may well be separate species; those that split them typically comment that they may well be well-marked races of the same species. There is essentially no force of precedent for the taxonomic treatment (split vs. lump) for these taxa (save for the lumping of C. (e.) idoneus in C. erythropus).
The four taxa in question vary somewhat in plumage, principally head and underparts coloration, with C. (e.) columbianus showing additional differences. Most C. erythropus subspecies show a dusky or greyish crown, barred underparts and upperparts, a dark crown with lighter throat and a yellowish breast and belly. All have reddish legs. All are of a similar size, being considerably larger than Little Tinamou C. soui taxa with which this group is sympatric across much of its range. For reference, C. e. erythropus is illustrated in Hilty (2003)'s Birds of Venezuela. A plate of C. (e.) margaritae, which is probably the most morphologically distinctive of the core C. erythropus taxa, is available on the following link: http://www.geocities.com/faunavenezuela/macagua.htm
C. (e.) columbianus is probably the most morphologically distinctive of the taxa subject to this set of proposals. It has a rather different (darker) back coloration from the other forms and much reduced barring on the upperparts and underparts (Meyer de Schauensee 1964; Hilty & Brown, 1986; BirdLife International 2000, 2004). It has indeed been considered perhaps to be more closely related to Choc— Tinamou C. kerriae (Blake, 1977), C. noctivagus (Meyer de Schauensee, 1964) or C. boucardi (e.g. Hellmayr & Conover 1942) than to C. erythropus due to the lack of similarity between this form and C. erythropus taxa.
C. (e.) idoneus has a greyish brown crown but otherwise differs very little in plumage from C. (e.) spencei and C. (e.) cursitans. Indeed, among the Venezuelan forms, variation within some subspecies has been considered to be often as great as intrasubspecific variation (Hilty, 2003). Among the three taxa, this has most often been lumped with C. erythropus (Meyer de Schauensee 1964; Hilty & Brown, 1986; Schwarz & Lentino, 1984, Hilty, 2003) including by some authors who split the other two (e.g. Meyer de Schauensee, 1964; BirdLife International 2000; BirdLife International 2004).
The only C. (e.) saltuarius skin shows has a lighter belly than other forms, more greyish wash on the breast and darker crown (Wetmore, 1950; Meyer de Schau3nsee 1964; Hilty & Brown, 1986; Cabot, 1992; BirdLife International 2000 & 2004). A plate of C. (e.) saltuarius is available online at the following link: http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=32&m=0
The voices of C. erythropus in Venezuela have been subject to some study (Schwartz & Lentino, 1984). The calls are trisyllabic whistles, described variously as "whooo hooo-a", "soy sola", "whuu, whuu-whu?" (e.g. Schwartz & Lentino, 1984; Hilty, 2003). The voice of what is apparently C. saltuarius is also reported by local people to be a trisyllabic whistle "soy sola" (Donegan et al., 2003). The voices of C. (e.) idoneus is also a trisyllabic "whooo hooo-a" or "si-u-ri", similar to those of the other forms (Schwarz & Lentino 1984; Donegan et al., 2003). Other medium sized red-legged Crypturellus taxa currently treated as separate species also give calls consisting of trisyllabic whistles (e.g. Central American C. cinnamomeus and C. boucardi, per Howell & Webb, 1995). The little data that exists therefore suggests that at least C. (e.) idoneus and C. (e.) saltuarius have broadly similar vocalisations to C. erythropus taxa. Given the widespread use of trisyllabic whistles within this complex, one would be surprised were C. (e.) columbianus not also to have a similarly structured call. Clearly, transcriptions of trisyllabic whistles are somewhat removed from detailed sonogram analysis. Further, as other red-legged medium sized Crypturellus currently regarded as separate species on the SACC baseline share trisyllabic whistles, basing taxonomic decisions purely on (poorly understood) vocal characters could be criticised as being inconsistent. However, it is clear that no vocal data yet exists that would support strongly any split.
Molecular and morphological phylogenies
Bertelli et al. (1992)'s and Bertelli & Porzecanski (2004)'s recently published phylogenies (the latter using morphological and molecular data) include only C. e. erythropus and no C. (e.) saltuarius or C. (e.) columbianus data. However, unpublished analyses of morphological data using Bertelli et al. (1992)'s characters do not suggest paraphyly of a greater C. erythropus (S. Bertelli in litt.).
Is C. (e.) saltuarius a "dubious taxon"?
C. (e.) saltuarius is known from just one specimen, an immature bird. Its voice and adult plumage are not known. C. erythropus taxa show considerable individual variation (Hilty, 2003) some of which may be age-related (pers. comm.). The single C. (e.) saltuarius skin is therefore hardly substantial evidence for the existence of a taxon, be it a species or subspecies. The difference in morphology of a single skin is hardly strong evidence of reproductive isolation of the form. Recent work at the type locality revealed high levels of deforestation and very few recent reports of the taxon among local people (Donegan et al., 2003). C. erythropus spencei and C. (e.) idoneus are present on the eastern slope of the Perij‡ mountain range where C. (e.) saltuarius is said to have existed. The Andean ridgeline in this region is at its lowest (c. 1500m) and narrowest north of the Equator in this region. The fact that only one immature skin exists, this from a poorly known region but where other similar taxa exist close by, may mean that "dubious taxon" status would be a better treatment for C. (e.) saltuarius. However, various studies have consistently asserted the distinctiveness of the type specimen from these other forms (e.g. Wetmore 1950; Meyer de Schauensee 1964 & 1970; Blake 1977).
Some evidence for the existence of a medium-sized red-legged Crypturellus in the Magdalena Valley was recently presented by Mantilla & D’az (1992), citing written accounts of Fray Diego Garc’a on "Expedici—n Botanica" in the 1600s which would match an adult C. (e.) saltuarius. Further, recent lay reports of medium-sized red-legged tinamous exist from the foothills of Serran’a de San Lucas (Donegan et al., 2003), provide additional evidence that there is or was a "magdalena tinamou" of some description in the C. erythropus group. However, discussion of C. (e.) erythropus still lies somewhere on the boundary between ornithology and cryptozoology. It is even feasible that the Expedici—n Botanica records and San Lucas reports could refer instead to C. (e.) columbianus (Donegan et al., 2003), particularly given the propensity for Nech’/Choc— birds to extend in range into the humid part of the Magdalena valley (e.g. Stiles et al. 1999). The San Lucas region of Colombia is presently a highly dangerous region in which to conduct fieldwork - the participants on the only recent expedition to the region were detained for two weeks and could only survey secondary habitats in which no red-legged Crypturellus were found (Salaman et al., 2002). If the split of this taxon is sanctioned, I will raise a separate proposal dealing with the issue of whether to treat C. (e.) saltuarius as a "dubious taxon" so that this issue can be taken off the table in the discussions as to whether it and others should be treated as separate from C. erythropus. However, I would suggest that the case for C. (e.) saltuarius not being a "dubious taxon" is arguably less bad than the case for, e.g. Heliangelus zusii, which remains on the main list following a proposal for its removal.
C. (e.) saltuarius is treated as a species by BirdLife International (2000, 2004) (following Stotz et al. 1996), who classify it as Critically Endangered with a population of probably less than 50 individuals. It has previously been regarded as possibly extinct (Collar et al., 1992). C. (e.) columbianus is regarded as Endangered, restricted to the largely deforested Nech’ region. No recent records of this taxon exist (BirdLife International 2004). The global importance of the type locality for C. (e.) saltuarius has been stressed in multiple conservation priority setting initiatives (Stattersfield et al., 1997; BirdLife International 2000 & 2004; Renjifo et al., 2002; Alvarez, 2002). A greater (or lesser) C. erythropus would be non-threatened (Least Concern).
These proposals are difficult ones due to the lack of hard data. An interim decision on this issue (rather than a "let's wait and see" approach) is necessary for conservation priority setters due to the political instability in regions from where C. (e.) saltuarius and C. (e.) columbianus are found which shows no sign of abating in the near future and which deters fieldwork (see e.g. Alvarez, 2002; Salaman et al., 2001; Donegan et al., 2003).
Morphology of some of these forms (particularly C. (e.) columbianus) is rather distinct from that of the nominate C. erythropus group. However, the very little and tentative vocal data points to conspecific treatment perhaps being the more conservative approach.
Little Tinamou Crypturellus soui includes a number of morphologically distinctive forms with a similar voice and is currently treated as one species. The plumage differences here for C. (e.) columbianus in particular are greater than those among many C. soui races, at least to the human eye. Whatever the evidence one way or the other, a further question is whether the SACC baseline truly reflects the 'status quo' in modern ornithology, given the large number of recent publications that treat particularly C. (e.) saltuarius and C. (e.) columbianus as separate species (if we restrict the widely followed findings of Schwartz & Lentino to C. idoneus). If a split treatment is regarded as the status quo, the tables are somewhat reversed and the question rather becomes whether evidence exists to effect a lump.
Acknowledgements: Thanks to Stuart Butchart, Rob Clay and Sara Bertelli for comments on this proposal. The suggestions here are those of the author and not necessarily those of BirdLife International or any of the other persons mentioned.
Proposal 209: Split C. columbianus from C. erythropus.
C. (e.) columbianus is morphologically more different from C. erythropus than either C. (e.) saltuarius or C. (e.) idoneus and has been considered more closely related to each of C. kerriae, C. boucardi and C. noctivagus than C. erythropus in the past. C. (e.) columbianus, of all these three, probably has the best case for treatment as a separate species. The plumage differences between this taxon and others in the group, particularly C. (e.) columbianus' lack of underpart and upperpart barring and its darker plumage, are significant, broadly similar to that between other red-legged Crypturellus taxa treated as separate species, for example in Central America. Though the evidence and justification presented here are admittedly poorly supported and the relations between these forms are poorly understood, I would personally be more inclined towards a "YES" vote to split this taxon than the converse.
Proposal 210: Split C. idoneus from C. erythropus.
Vocal and morphological data point to C. idoneus not being distantly related from C. erythropus taxa. This split has much less force of precedent than the other two and recent studies suggest conspecific treatment is preferable. This is therefore probably the easiest proposal of the three. I would recommend a "NO" vote for this proposal, i.e. not to sanction the split.
Proposal 211: Split C. saltuarius from C. erythropus.
The little that we know of C. (e.) saltuarius suggests that it differs in more than just crown colour (cf. C. (e.) idoneus) from C. erythropus populations. However, such differences remain relatively small in the context of a very variable group. Indeed, C. (e.) margaritae presents comparable levels of dissimilarity to the other taxa as C. (e.) saltuarius, but is almost always treated as conspecific with C. erythropus. The plumage of just one immature skin is hardly a great deal of evidence on which to base a split evidenced on morphological considerations and tentative vocal data points to this form having a similar call to C. erythropus taxa. I would probably be inclined more towards a "NO" vote for the recognition of this controversial taxon as a species than the converse, though would not wish to discourage further research into the taxonomy and status of this taxon.
References (not including major reference works on SACC reference list):
çlvarez, M. D. (2002) Illicit crops and bird conservation priorities in Colombia. Conservation Biology 16(4): 1086-1096.
Bertelli S. & Porzecanski A.L. 2004. Tinamou (Tinamidae) systematics: a preliminary combined analysis of morphology and molecules. Ornitologia Neotropical (Suppl.) 2004. (available at http://www.arches.uga.edu/~perdiz/pdf/bertelli_&_porzecanski_2004.pdf)
Bertelli S., Giannini, N.P. & Goloboff, P.A. 2002. A phylogeny of the tinamous (Aves: Palaeognathiformes) based on integumentary characters. Syst. Biol. 51:959-979.
Donegan TM, Huertas BC & Brice–o, ER. 2003. Status of the Magdalena Tinamou Crypturellus saltuarius in the type locality and surrounding lower Magdalena Valley. Cotinga 19 (2003): 34-39.
Mantilla R., L. C. & D’az, P. S. (1992) Fray Diego Garc’a, su vida y su obra cient’fica en la Expedici—n Bot‡nica. Rev. Acad. Colombiana Cienc. Nat. F’sicas y Nat. 7: 242-243.
Renjifo, L. M., Franco Maya, A. M., Amaya-Espinel, J. D., Kattan, G. H. & L—pez-Lanus, B. (eds.) (2002) Libro rojo de aves de Colombia. Serie Libros Rojos de Especies Amenazadas de Colombia. Bogot‡: Instituto de Investigaci—n de Recursos Biol—gicos Alexander von Humboldt & Ministerio de Medio Ambiente.
Salaman, P. G. W., Cuadros, T., Jaramillo, J. G. & Weber, W. H. 2001. Checklist of the birds of Colombia. Medell’n: Sociedad Antioque–a de Ornitolog’a.
Salaman P.G.W., Donegan T.M. & Cuervo A.M. 2002. New distributional bird records from Serran’a de San Lucas and adjacent Central Cordillera of Colombia. Bull BOC 122(4): 285-304.
Schwartz P & Lentino M. 1984. Relaciones de los tinamidos Venezolanos del grupo Crypturellus noctivagus indicados por su voz (Aves: Tinamidae). Serie Informes Cient’ficos DGSIIA/IC/23, Ministerio del Ambiente y de Recursos Naturales Renovables, Caracas, Venezuela.
Stiles, F G, Rosselli, L & Boh—rquez, C I. 1999. New and noteworthy records of birds from the middle Magdalena valley of Colombia. Bull Brit. Onith. Club 119: 113-128.
Wetmore A. 1950. Proc. Biol. Soc. Wash. 63 at p.171.
Thomas Donegan, March 2006
Comments from Stiles: "On this group of proposals I shall vote NO. I feel that the forms columbianus, idoneus and saltuarius are best left as forms of erythropus until solid new data (ideally, genetic and vocal) clearly favors their being split. Although I have met none of these forms in life, I did examine series of skins of the first two and a set of photos of the type of the latter while in the US several years ago. My conclusions from this study were that all of the forms share a similar overall pattern and similar sexual dimorphism (the lone specimen of saltuarius being an immature male), differing mainly in intensity of coloration (which seems to follow Gloger`s rule: columbianus, from a wet area, is darker and more richly colored, with less contrasting black barring, than the pale, greyish idoneus with more contrasting black barring, from the dry-forested lowlands around the Santa Marta range of N Colombia). (Momotus motmots show a similar pattern of variation in N Colombia). Blake (1977) mentioned that Carriker's data on the Mallophaga of these birds also indicates close relationship. A further consideration is that the race spencei, of the wet Paria peninsula of Venezuela, is also darker than adjacent erythropus and in fact, bears a considerable resemblance to columbianus. If one lumps spencei into erythropus, I can see little justification for keeping columbianus separate. (Hilty (2003) states that individual variation in the Venezuelan races is a great as the differences between them; while at least idoneus and columbianus are quite distinct, the one specimen of saltuarius is closer to idoneus but somewhat darker (again in accordance with Gloger`s rule); only more specimens of this form will confirm its distinctness. Donegan is correct in noting that a description of what is presumably the adult male was made by Fray Diego Garc’a in 1793, but the difference in vocabulary, anatomical and color terms make comparisons difficult (for example, the generic term for brown in those days was "tabaco" - but did it refer to simply the dried leaves, cured leaves or smoked leaves?). Be this as it may, saltuarius is clearly a representative of the erythropus group. The differences in intensity and contrast of the dark barring is also not wholly convincing as basis for a split: for example, the change in C. undulatus from a strongly barred, contrasty bird in E Peru to a very weakly patterned one in E Colombia is at least as striking. Color differences as great or greater occur among the races of C. soui. In sum, the evidence from color and pattern of specimens does not seem to me sufficient to justify splitting these forms. Good recordings of columbianus, idoneus and saltuarius either do not exist or have never been analyzed.
Donegan`s final argument is that the three forms in question are all endangered to a greater or lesser degree, and according them species rank will facilitate obtaining funding for studying them. I sympathize with this argument, but disagree that conservation considerations should drive taxonomic decisions: this is putting the cart before the horse. One solution that we have been trying to implement in Colombia (as in the designation of IBAs) is to consider certain forms as "genetically significant populations" - specifically, distinctive subspecies which on present evidence are not species, but from their degrees of phenotypic distinctiveness probably include a significant degree of genetic variation with respect to the rest of the species - and these three tinamous are so considered. The challenge, of course, is convincing funding agencies that such populations are worth studying and saving.
Additional comments from Thomas Donegan: "Gary and I seem in agreement on two of the three proposals (lump C. e. saltuarius and C. e. idoneus with C. erythropus). I find the comparison with C. e. spencei convincing that the lump (and not the split) version of the status quo may also be better for C. e. columbianus. This does raise questions as to whether some other taxa in this group currently treated as separate species may not also be Gloger's rule variations on a theme, but this is not the subject of these proposals.
"In relation to Gary's other comments, could I please emphasise that the proposal does not suggest that a conservation cart should ever be put before a taxonomic horse. For clarity (if this was lacking?), comments on conservation status in the proposal are (i) to provide evidence of the status quo in ornithological publications (of which ornithological conservation publications form part) and (ii) to provide some context for the SACC as to the wider ramifications of the proposal and the reasons behind raising it. Although much criticised (including by me, in print), the wide use of only (BSC) species data in conservation assessments cannot be denied."
Comments from Robbins: "NO. Until there is a detailed analysis of vocalizations and genetic data I see no reason why any of the proposed splits in 209-211 should be made."
Comments from Silva: "NO. No change without any good data."
Comments from Nores (209): "NO. Aunque la propuesta hecha por Donegan me pareci— bien fundamentada y estuve a punto de votar por SI, el comentario de Stiles me hizo cambiar de idea. Este es un caso que casi corresponder’a emitir un "blank vote", pero dejemos eso para la elecci—n de pol’ticos."
Comments from Nores (210): "NO. Pienso que Donegan ha fundamentado bien que esta propuesta no es factible, y m‡s si uno vota por NO en la propuesta anterior."
Comments from Nores (211): "NO. Con los mismos comentarios que para la propuesta anterior, con el agregado de que existiendo solamente un ejemplar no parece apropiado hacer demasiadas conjeturas y m‡s en este grupo donde las especies son tan parecidas y variables."
Comments from Zimmer: "NO. Gary nicely summarizes several reasons for not making a change here, and, as reiterated by virtually everyone, the absence of any formal analysis or new data leaves us with no compelling reason for making the change."
Comments from Jaramillo: "NO - This is a complicated issue but I think that vocal (or molecular) data is needed to steer this situation to a firmer decision than we can at this point. The issue of Gloger's rule is very important given that these are ground dwelling, and ground nesting creatures. It is precisely in these species where color matching to substrate is expected, and the cryptic coloration that tinamous tend to have clarifies that this is no insignificant point."
Comments from Pacheco: "NO. Diante dos dados expostos e a espera de novos dados, voto com a maioria."
Additional comments from Thomas Donegan: "Miguel Lentino recently kindly provided me with a copy of the difficult-to-obtain article that he and Paul Schwarz authored re Crypturellus vocalisations. A summary of this was provided in Hilty's Venezuela book (relied upon in the above proposal).
"The article evidences some small vocal differences between idoneus and the other erythropus taxa, which the authors conclude are better treated as not sufficient to evidence species rank. A discussion of morphological variation in the other taxa relevant to this set of proposals is also included in the Schwarz & Lentino article, with not dissimilar conclusions from the proposals above read together with Gary Stiles' comments.
"Jeff Thompson has kindly put a scan of the article on the Tinamou Research Group website: http://gallus.forestry.uga.edu/trg/pdf/SchwarzLentino1984.pdf."