THE NORTHERN TREE-CREEPER. 217 



BREEDING-HABITS. Usually nests behind loose bark on the trunks 

 of trees, or behind ivy roots where they have become separated 

 from the stem. Also occasionally in crevices of buildings, in loose 

 stone-walls, or even in masses of dead leaves accumulating in trees. 

 Nest. Foundation of birch twigs, moss, roots, grass, etc., lined 

 feathers, bark and bits of wool, with a few twigs in the outer rim. 

 Eggs. Usually 6, occasionally 5 or 7 ; white with a zone of red- 

 brown spots at the big end, varying in intensity. The presence of 

 reddish- violet shell-marks distinguishes them from the eggs of the 

 Crested Tits. Average of 100 eggs, 15.5x12.1 mm. Breeding- 

 season. Latter part April and early May, also June. Incubation. 

 Lasts 15 days from laying last egg (W. Evans). Two broods 

 sometimes reared. 



FOOD. Almost entirely insects : coleoptera, orthoptera, larvse 

 of lepidoptera, diptera, and hymenoptera. Spiders, their eggs and 

 webs are also eaten ; and occasionally one or two seeds have been 

 found in stomachs. 



DISTRIBUTION. Confined to British Isles. Resident. Generally dis- 

 tributed in suitable localities, but only once recorded O. Hebrides 

 (Lewis, Oct., 1915, during gale) and very rarely seen in Shetlands 

 and Orkneys. 



88. Certhia familiaris familiaris L. THE NORTHERN 

 TREE-CREEPER. 



CERTHIA FAMILIARIS Linnaeus, Syst. Xat., ed. x, i, p. 118(1758 Europe. 

 Restricted typical locality : Sweden). 



DESCRIPTION. Adult male and female. Like C. f. brittanica, but 

 upper -parts considerably paler, pale streaks on head being white ; 

 pale portion of feathers of mantle and scapulars larger and whiter 

 and rest of feathers paler brown ; rump paler rufous ; inner 

 secondaries and pale markings on other secondaries, primaries and 

 wing-coverts buffish-white, much paler than in C. f. brittanica ; 

 eye-stripe pure white ; under-parts pure silvery-white with very 

 pale buff wash on belly, flanks, and under tail-coverts. Moults 

 as in C. f. brittanica. 



Measurements and structure. $ wing 63-67 mm., tail 61-66, 

 tarsus 14-16, bill from skull 14-16 (12 measured). $ wing 60-65, 

 bill from skull 13-16. Structure as in C. f. brittanica. 



FIELD-CHARACTERS. Its paler upper-parts and pure white under- 

 parts give it a very distinct appearance as compared to the British 

 form (H.F.W.). 



BREEDING-HABITS. Closely resemble those of the British race. 

 The paper-like outer bark of the birch is often used in nest-building. 



