LETTER TO THE EDITOR. 
251 
they are found breeding in the Valley of the Tay. Further, we would desire more 
proof and information of the record, vaguely given by Mr. W. Horn, of their 
presence in the North-west of Perthshire. We feel convinced, knowing Mr. Horn 
intimately, that his remarks refer not to summer habitation of these parts, but to 
autumn migration, i.e., during the shooting season. And, moreover, even if now 
the Marsh Tit be actually discovered breeding anywhere within the Tay Basin, I 
would still hold that there has appeared no past authentic proof of the fact. It is 
only natural to suppose that, if it has migrated south between Spey and Forth, 
intermediate areas may in time be occupied, but, as we have elsewhere indicated, 
we believe in the fact that expansions or extensions of range of many species are 
much more likely to take place along the lines of the exact routes of migration of 
many species in springy than along the lines merely of autumn or winter migra¬ 
tions, whether general or only local. We may add that the two phases of general 
and local movements, while closely allied to one another, nevertheless, especially 
in their initial stages, often show very different immediate results. Meanwhile, 
we require proofs. 
J. A Harvie-Brown. 
Note. —It may be seen we still use the term “within the watershed,” although this was 
criticised by no less an influential authority than the Ibis. We failed at the time, and still fail, 
to understand the force of the argument then used, nor do we think the term “watershed” can 
correctly have any other meaning than “water-parting”—a term proposed to be used instead in 
the same article (Ibis, July, i8g8, p. 440). We cannot, in fact, realize that there is any dubiety 
in the expression or meaning of “ watershed ” as used by us.—J. A. H.-B. 
