MERLIN 93 



parts of Scandinavia and Finland, an old nest in a birch or pine is 

 frequently used, although beyond the tree limit, only cliff and ground 

 sites are available. It seems to be an almost invariable rule that a 

 nest on the ground should command a good view of the adjacent 

 country. 



Eggs. — The commonest number of eggs in England is four, and five 

 are quite exceptional. Farther north the proportion of fives seems to 

 increase, and in the Orkneys and Iceland they are common enough. 

 The six set has occurred in Scotland at least nine or ten times and 

 probably oftener, while seven occur in Sweden in lemming years and 

 have also been recorded from Finland. Six have also been recorded 

 from Iceland. Second layings may consist of only three eggs, but 

 E. R. Paton (1917) says that it is also found in first layings at times, 

 and J. A. W. Bond confirms this. 



In color they show less variation than the kestrel's eggs, and they 

 are sometimes rather elongated in shape, but normally almost oval, 

 the creamy ground being often quite concealed by red-brown stippling 

 and spots. It is rare to find a really richly and boldly marked clutch, 

 and the most remarkable varieties are those in which most of the 

 coloring matter is absent and a good deal of the creamy ground is 

 visible. One remarkable set has three eggs almost white, while the 

 fourth is clouded with red-brown. Other varieties show patches of 

 violet shell marks, while some sets have a very attractive violet bloom, 

 and others are of a pale yellowish type, approaching that of the hobby 

 (F. subbuteo). All the eggs are rather dull, and those from the moors 

 near industrial centers become much contaminated by soot in the air. 



Measurements of 100 British eggs average 39.95 by 31.27 milli- 

 meters; the eggs showing the four extremes measure 42.4 by 32, 41.4 

 by 33.8, 37 by 29.1, and 40.3 by 29 millimeters. Fourteen Icelandic 

 eggs average 40.9 by 31.9 millimeters; the eggs showing the four 

 extremes measure 42.3 by 32.8, 41 by 33.2, and 38.9 by 30.2 milli- 

 meters. 



Young. — The eggs are laid at 48-hour intervals, i. e., every second 

 day, and Paton (1917) states that in a clutch of three it begins with 

 the third egg ; other observers are of the opinion also that it begins on 

 the completion of the set. Both sexes take a share in incubation, but 

 there seems to be a consensus of opinion that the female takes the 

 greater share of the work. Rowan (1921-22), however, states that in 

 one case where he watched at night the male was incubating all the 

 time. During brooding the hunting is done by the male, the hen 

 generally keeping to the neighborhood of the nest, while she preens 

 and sleeps during her mate's spell of brooding. 



The incubation period is estimated by Rosenius at 25 days ; Edmond- 

 son states that it is not less than 26 days, while Rowan says that three 



