THE CUCKOO. 55 



British Isles than on Continent ; shell always thick and heavy, 

 shape frequently blunt, texture also characteristic but colour and 

 markings vary widely, some being reddish, otheis bluish, greenish, 

 grey-brown more or less speckled, spotted or blotched with darker 

 shades. Small black spots are also nearly always present. Key's 

 average for 626 eggs is 22.4 x 16.5 mm. Max. : 25.5 X 17.8 and 

 25 X 18.1. Min. : 20 X 15.5 and 20.7 X 14.7. Breeding-season. 

 — Generally latter part of May and June, exceptionally early in 

 May or late in April, and early July. Incubation. — Period 12-13 

 days. The young Cuckoo ejects its companions from the nest, in 

 which it remains alone for about 20 days . 



Food. — Chiefly injurious insects ; caterpillars of many species, 

 especially hairy ones refused by most birds . Among those identified 

 are Pieris, Zeuzera, Spilosoma, Abraxas, Lasiocampa, Cosmotriche. 

 Also larvae of phytophagous hymenoptera (Nematns, Tenthredo, 

 etc.) ; larvae of diptera (Tipula, Syrphus, etc.) ; small coleoptera 

 and odonata (dragon-flies) ; while worms and eggs are also occa- 

 sionally taken and in a few cases birds' eggs have been found 

 in stomachs. Young are reared on diet which varies according 

 to fosterer, including larvae of lepidoptera, coleoptera, diptera, 

 orthoptera, etc., worms, small snails and even vegetable food. 



Distribution. — British Isles. — Summer -resident. Generally dis- 

 tributed, but scarce migrant in Shetlands, though occurs annually 

 in small numbers and exceptionally in larger numbers at Fair Isle 

 on spring migration. 



Migrations. — -British Isles. — Early arrivals of summer -residents 

 begin last three days March (early dates Mar. 10, 1884, Mar. 24, 

 Devon 1910, Mar. 26, Gloucester 1907, Yorks. 1910, Devon 1912, 

 Mar. 27, Sussex 1909) ; main arrival second week April, probably 

 accompanied by certain number of passage-migrants though 

 in most years numbers appear to be quite small ; there are 

 indications of a west coast route (Channel to Hebrides and 

 northern isles) being used by these, but very little of an east 

 coast route. Movement continues throughout May and in 

 northern isles to second week June. Adults begin to leave 

 early in July and stragglers are recorded up to last week Aug. 

 Juveniles leave during Aug. and first half Sept. with stragglers 

 up to end Sept. Passage -movements east and west coasts (Forth 

 and Sol way southwards) mid- July to mid-Sept. (Late dates 

 Stafis. Oct. 3, 1912, Suffolk Oct. 12, 1909, co. Down Nov. 26, 1900, 

 Wilts. Dec. 1, 1916, Cheshire Dec. 26, 1897 or 8). 



Distribution. — Abroad. — -Europe from within the Arctic Circle 

 to Pyrenees, Italy and south-east Europe, and a great part of Asia. 

 In winter in Africa south of Sahara and parts of south Asia. 

 Casual or on passage Canary Islands, Madeira and Fseroes. 

 Replaced by allied forms in parts of Asia, and in Iberian Peninsula 

 and north-west Africa. 



