986 TREE-CREEPER 
from observation, and a considerable mass of material is commonly 
used to stuff up the opening partly and give a sure foundation for 
the tiny cup, in which are laid from six to nine eggs of a trans- 
lucent white, spotted or blotched with rust-colour. The Tree- 
Creeper inhabits almost the whole of Europe as well as Algeria, 
and has been traced across Asia to Japan. It is now recognized 
as an inhabitant of the greater part of North America, though for 
a time examples from that part of the world, which differed slightly 
in the tinge of the plumage, were accounted specifically distinct 
(cf. Ridgway, Proc. U. S. Nat. Mus. 1882, pp. 111-116). It there- 
fore occupies an area not exceeded in extent by that of many 
Passerine birds; and is one of the strongest witnesses to the in- 
separability of the Holarctic Fauna. 
Allied to Certhia, but wanting its lengthened and stiff tail- 
feathers, is the genus Tichodroma, the single member of which is 
the Wall-Creeper, 7. muraria, of the Alps and some other moun- 
tainous parts of Europe and Asia, and occasionally seen by the 
fortunate visitor to Switzerland fluttering like a big butterfly 
against the face of a rock, conspicuous from the scarlet-crimson of 
its wing-coverts and its white-spotted primaries. Its bright hue 
is hardly visible when the bird is at rest, and it then presents a 
dingy appearance of grey and black. It is a species of wide range, 
extending from Spain to China; and, though but seldom leaving 
its cliffs, it has wandered even so far as England.! 
The genus Certhia as founded by Linneus contained 25 species, 
all of which, except the two above mentioned, have now been 
shewn to belong elsewhere; and for a long while so many others 
were referred to it that it became a most heterogeneous company. 
At present so few are the forms left in the Family Certhide 
that systematists (¢f. Gadow, Cat. B. Br. Mus. viii. pp. 322-340) 
are not wanting to unite it with the Sctidw (NUTHATCH), for the 
two groups, however much their extreme members may differ, are 
linked by forms which still exist, and little violence is done to the 
imagination by drawing upon the past for others to complete the 
series of descendants from a common and not very remote ancestor, 
one that was possibly the ancestor of the WRENS as well. Two 
things, however, have especially to be noticed here. The Certhiide 
have not the least affinity to the Picidx (WOODPECKER), but are 
strictly Passerine, and also that the Australian genus Climacteris 
may possibly not belong to them. 
1 Merrett (Pinax, p. 177) in 1667 included it as a British bird, and the 
correspondence between Marsham and Gilbert White (Proc. Norf. and Norw. 
Nat. Soc. ii. p. 180) proves that an example was shot in Norfolk, 30th October 
1792 (cf. Stevenson and Southwell, B. Worf. iii. p. 380, pl. v.), while another is 
reported (Zoologist, ser. 2, p. 4839) to have been killed in Lancashire, 8ti 
May 1872. Its reputed occurrence in Abyssinia seems doubtfal. 
