3 The New York Years (1931–1953)

46 2 The Budding Scientist
Erwin Stresemann emphasized that extant birds provide a number of borderline
cases between species and subspecies and that the taxonomic rank of geographically
separated (allopatric) taxa as subspecies or species is to be determined by
inference on the basis of several auxiliary criteria (Stresemann 1921: 66):
(1) Similarity or dissimilarity in morphological and other biological characteristics
(ecological requirements, voice, etc.),
(2) overlap or nonoverlap of individual variation in several characteristics,
(3) comparison with other congeneric forms that are in contact and either hybridize
(subspecies) or overlap their ranges without hybridization (species).
Stresemann had established some ties between ornithology and genetics through
a series of publications. Based on the work of Seebohm, Berlepsch, Hartert, Kleinschmidt,
Hellmayr and their extensive discussions of the species problem, he had
initiated a theoretical broadening of the Seebohm-Hartert tradition in the direction
of the “new systematics.” This conceptual modernization was continued by
Bernhard Rensch and, in particular, Ernst Mayr (pp. 204–206).
During the late 1920s Mayr also reviewed several publications for Stresemann’s
Ornithologische Monatsberichte.Muchofhissparetimehedevotedtobirdexcursions
around Berlin discovering, e.g., that the Willow Tit (Parus montanus)wasfar
more common in Brandenburg than recorded in bird books; probably it had been
often confused with its sibling species, the widespread Marsh Tit (P. palustris).
A report of his observations on this species appeared in the Journal für Ornithologie
(1928). He also published notes on the nesting of the Chaffinch (1926a) and the
House Martin (1926c), on the occurrence of the Waxwing (1926g), the calls of the
Bittern (1927c), on snake skins as nest material (1927d) and he often accompanied
Gottfried Schiermann (1881–1946), whose population studies at that time were
pioneer efforts continued in Germany only many years later.
Mayr reported: “My best friend in Berlin, except of course for Stresemann, was
Gottfried Schiermann, a superb field ornithologist. I met him through Stresemann
andthroughthemeetingsoftheDOG.SchiermannwassomucholderthanI,
he could have been my father. He had no academic background but had been an
ardent egg collector in his younger years. The bird censuses and ecological studies
he published in the 1920s and 30s are pioneering. I loved to go in the field with
him because he was such an acute observer. One day, just going through the woods
together, he discovered 54 occupied bird nests. This included such difficult to find
nests as that of the Wood Warbler (Phylloscopus sibilatrix). He was a specialist in
finding the nests of birds of prey, most of whom use abandoned crows nests as their
first foundation. Hence, in suitable woods he mapped in winter all the old crow
nests and old hawk nests and then checked them systematically during the season
foroccupancybyhawks.Ioncemadeamemorabletripwithhimtothelower
Spreewald where he showed me nesting Black Storks, and woodland White Storks,
as well as many other exciting things. (We were nearly eaten up by the mosquitoes).
He took me out to the nesting place of the Rohrschwirl (Savi’s Warbler, Locustella
luscinioides), where I was lucky enough to find a nest of this species (Fig. 2.2).