LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 15 



northern Siberia nesting *' in dry spots in swamps." Eussell (1898) 

 at the mouth of the Mackenzie, says that "the nest was simply a 

 level bit of dry moss on the tundra a few yards from the water's 

 edge.'' 



Eggs. — Only two eggs are laid and one brood hatched. Nelson 

 (1887) says the eggs are laid in northern Alaska by June 5. The 

 egg is ovate in shape, of a dull olive varying to green, gray or brown 

 ground color, with spots, blotches, and lines of a sepia, drab, dark 

 chocolate, and umber-vinaceous color. These markings are some- 

 times distributed with great uniformity over the whole egg or gath- 

 ered as a wreath about the larger end. The measurements of 50 

 eggs in various collections average 57 by 41 millimeters; the eggs 

 showing the four extrenies measure 61 by 41, 58 by 43, 51 by 40.5, 

 and 56 by 38 millimeters. 



Plumages. — [Author's note: I have never seen a small specimen 

 of the downy young of the parasitic jaeger, but a half -grown young 

 in my collection, which is still more than half downy, has the down 

 of the upper parts uniform "• natal brown," paler on the head and 

 neck, and shading off to " drab-gray " on the under parts. There is 

 no indication of any mottling anywhere. The ju venal plumage is 

 well advanced on the wings and scapulars, where it evidently appears 

 first; the feathers are appearing through the down all over the 

 breast and belly and on the upper part of the back ; the tail feathers 

 are bursting their sheaths. 



The sequence of plumages to maturity is practically the same, in 

 both phases, as in the pomarine jaeger, except that the parasitic 

 jaeger normally acquires its fully adult plumage when a little over 

 2 years old. The first-year plumage is heavily barred above and 

 below with rufous edgings, which fade and wear away during the 

 fall and winter. The second-year plumage is less heavily barred, 

 with narrower and whitish edgings above, with much more white in 

 the underparts, with heavily barred under tail-coverts, with some- 

 what elongated central rectrices and sometimes with a suggestion of 

 the golden color. At the second postnuptial molt, when the bird 

 is from 25 to 27 months old, the fully adult plumage is assumed 

 with no mottling or barring anywhere, with the dusky under tail- 

 coverts and crissum and with the elongated central rectrices. 



During this m.olt the upper body plumage is completed first, and 

 the last signs of immaturity to disappear are the barred feathers of 

 the chest and flanks. The postnuptial molt of both adults and 

 young is complete and occurs in August, September, and October, 

 the wings being molted in October. There is probably an incom- 

 plete prenuptial molt also, but material is lacking to show it satis- 

 factorily. Fall adults in fresh plumage have the chin, throat, and 



